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Dairy fat is one of the most complex natural fats because of its fatty acid (FA) composition. Ruminant dairy fat contains more than 400 different FA varying in carbon chain length, and degree, position and configuration of unsaturation. The following article reviews the different methods available to analyze FA (both total and free) in milk and dairy products. The most widely used methodology for separating and analyzing dairy FA is gas chromatography, coupled to a flame ionization detector (CG-FID). Alternatively, gas chromatography coupled to a mass spectrometer (GC-MS) is also used. After lipid extraction, total FA (TFA) are commonly converted into their methyl esters (fatty acid methyl esters, FAME) prior to chromatographic analysis. In contrast, free FA (FFA) can be analyzed after conversion to FAME or directly as FFA after extraction from the product. One of the key questions when analyzing FAME from TFA is the selection of a proper column for separating them, which depends mainly on the objective of the analysis. Quantification is best achieved by the internal standard method. Recently, near-infrared spectroscopy (NIRS), Raman spectroscopy (RS) and nuclear magnetic resonance (NMR) have been reported as promising techniques to analyze FA in milk and dairy products.

Objective: In India, there is a rise in non-communicable diseases due to diets deficient in vitamin B12, low in docosahexaenoic acid (DHA) and increased consumption of westernized diet. The present study aims to examine the effect of maternal high fat diet (HFD) in absence of vitamin B12 on pregnancy outcome and tissue fatty acid composition in dams.Methods: Pregnant Wistar rats were assigned to following diets: Control (C), HFD, High fat diet supplemented with omega-3 fatty acids (HFDO), 4) High fat diet deficient in vitamin B12 (HFBD), High fat deficient in vitamin B12 supplemented with omega-3 fatty acids (HFBDO).Results: There was no effect on pregnancy outcome as a consequence of different dietary treatments. The levels of DHA in HFBD group were lower (p < 0.05 for both) in placenta as compared to both control and HFD groups, which were improved by omega-3 fatty acid supplementation.Conclusion: This data suggests that maternal HFD (using dairy fat) did not adversely affect pregnancy outcome. However, maternal HFBD reduced levels of placental DHA. This may have implications for reduced fetal brain growth and development. [ABSTRACT FROM AUTHOR]

Aims/hypothesis: Previously, we demonstrated that myristic acid (14:0) increases levels of diacylglycerol kinase (DGK) δ, a key enzyme involved in type 2 diabetes exacerbation, and enhances glucose uptake in C2C12 myotube cells. Moreover, results from a population-based cohort study suggest that consumption of high-fat dairy products, which contain high amounts of myristic acid, is associated with a lower risk of developing type 2 diabetes. Taken together, we hypothesised that intake of myristic acid reduces type 2 diabetes risk in vivo. The aim of this study was to examine the glucose-lowering effect of myristic acid in Nagoya-Shibata-Yasuda (NSY) mice, a spontaneous model for studying obesity-related type 2 diabetes. Methods: Male NSY mice were orally administered vehicle ( n = 9), 300 mg/kg of myristic acid ( n = 14) or 300 mg/kg of palmitic acid (16:0) ( n = 9) every other day from 4 weeks of age. Glucose and insulin tolerance tests were performed at weeks 18, 24 and 30, and weeks 20 and 26, respectively. DGKδ levels were measured in skeletal muscle from 32-36-week-old NSY mice via western blot. Results: Chronic oral administration of myristic acid ameliorated glucose tolerance (24-28% decrease in blood glucose levels during glucose tolerance tests) and reduced insulin-responsive blood glucose levels (~20% decrease) in male NSY mice compared with vehicle and palmitic acid groups at 24-30 weeks of age (the age at which the severity of type 2 diabetes is exacerbated in NSY mice). Myristic acid also attenuated the increase in body weight seen in NSY mice. Furthermore, the fatty acid increased DGKδ levels (~1.6-fold) in skeletal muscle of NSY mice. Conclusions/interpretation: These results suggest that the chronic oral administration of myristic acid improves hyperglycaemia by decreasing insulin-responsive glucose levels and reducing body weight, and that the fatty acid accounts for the diabetes protective properties of high-fat dairy products. Myristic acid is a potential candidate for the prevention and treatment of type 2 diabetes mellitus and its related diseases. [ABSTRACT FROM AUTHOR]

Dietary recommendations to decrease the risk of cardiovascular disease (CVD) have focused on reducing intake of saturated fatty acids (SFA) for more than 50 years. While the 2015-2020 Dietary Guidelines for Americans advise substituting both monounsaturated and polyunsaturated fatty acids for SFA, evidence supports other nutrient substitutions that will also reduce CVD risk. For example, replacing SFA with whole grains, but not refined carbohydrates, reduces CVD risk. Replacing SFA with protein, especially plant protein, may also reduce CVD risk. While dairy fat (milk, cheese) is associated with a slightly lower CVD risk compared to meat, dairy fat results in a significantly greater CVD risk relative to unsaturated fatty acids. As research continues, we will refine our understanding of dietary patterns associated with lower CVD risk. [ABSTRACT FROM AUTHOR]

Dososahexaenoate (DHA) is highly concentrated in mammalian nervous and visual systems and its deficiency during gestation, lactation and early life, could have dramatic impacts on brain functions and mental health. Achieving an appropriate DHA status in the neonatal brain is an important goal of neonatal nutrition. We evaluated how a-linolenic acid (ALA) provided by different dietary fat matrices improved DHA content in the brains of both young male and female rats. Young rats born from dams fed during gestation and lactation with a low ALA diet (0.4% of fatty acids) were subjected for 6 weeks after weaning to an anhydrous dairy fat blend-based diet that provided 1.5% ALA or to a palm oil blend-based diet that provided the same ALA level: either 1.5% ALA or 1.5% ALA and 0.12% DHA with 0.4% arachidonic acid (ARA). With each diet the n-6/ n-3 ratio was similar (10) to follow the values generally recommended for infant formula. Fatty acids analysis in whole brain showed that 1.5% ALA dairy fat blend was superior to both 1.5% ALA palm-oil blends, supplemented or not with dietary DHA, for increasing brain DHA. Females compared to males had significantly higher brain DHA with the 1.5% ALA palm-blend diet, but the dietary supplementation with DHA smoothed the differences by a specific increase of males DHA brain. In conclusion, dairy fat blend enriched with ALA appear to be an interesting strategy for achieving optimal DHA levels in the brain of post-weaning rats. Inclusion of dairy fat in infant formulas should be reconsidered.

Epidemiological studies suggest that chronic consumption of trans MUFA may alter muscle insulin sensitivity. The major sources of dietary trans MUFA (dairy fat vs. industrially hydrogenated oils) have different isomeric profiles and thus probably different metabolic consequences. These effects may involve alterations in muscle mitochondrial oxidative capacity, which may in turn promote insulin resistance if fatty acid oxidation is reduced. We report that in Wistar rats, an 8 week diet enriched (4% of energy intake) in either dairy, industrial, or control MUFA did not alter insulin and glucose responses to an intraperitoneal glucose tolerance test (1g/kg). In C2C12 myotubes, vaccenic and elaidic acids did not modify insulin sensitivity compared with oleic acid. Furthermore, the ex vivo total, mitochondrial and peroxisomal oxidation rates of [1-14C]oleic, vaccenic, and elaidic acids were similar in soleus and tibialis anterior rat muscle. Finally, an 8 week diet enriched in either dairy or industrial trans MUFA did not alter mitochondrial oxidative capacity in these two muscles compared with control MUFA but did induce a specific reduction in soleus mitochondrial ATP and superoxide anion production (P < 0.01 vs. control). In conclusion, dietary trans MUFA of dairy or industrial origin have similar effects and do not impair muscle mitochondrial capacity and insulin sensitivity.

Background: Few prospective studies have examined dairy fat in relation to cardiovascular disease (CVD). Objective: We aimed to evaluate the association between dairy fat and incident CVD in US adults. Design: We followed 43,652 men in the Health Professionals Follow- Up Study (1986-2010), 87,907 women in the Nurses' Health Study (1980-2012), and 90,675 women in the Nurses' Health Study II (1991-2011). Dairy fat and other fat intakes were assessed every 4 y with the use of validated food-frequency questionnaires. Results: During 5,158,337 person-years of follow-up, we documented 14,815 incident CVD cases including 8974 coronary heart disease cases (nonfatal myocardial infarction or fatal coronary disease) and 5841 stroke cases. In multivariate analyses, compared with an equivalent amount of energy from carbohydrates (excluding fruit and vegetables), dairy fat intake was not significantly related to risk of total CVD (for a 5% increase in energy from dairy fat, the RR was 1.02; 95% CI: 0.98, 1.05), coronary heart disease (RR: 1.03; 95% CI: 0.98, 1.09), or stroke (RR: 0.99; 95% CI: 0.93, 1.05) (P > 0.05 for all). In models in which we estimated the effects of exchanging different fat sources, the replacement of 5% of energy intake from dairy fat with equivalent energy intake from polyunsaturated fatty acid (PUFA) or vegetable fat was associated with 24% (RR: 0.76; 95% CI: 0.71, 0.81) and 10% (RR: 0.90; 95% CI: 0.87, 0.93) lower risk of CVD, respectively, whereas the 5% energy intake substitution of other animal fat with dairy fat was associated with 6% increased CVD risk (RR: 1.06; 95% CI: 1.02, 1.09). Conclusions: The replacement of animal fats, including dairy fat, with vegetable sources of fats and PUFAs may reduce risk of CVD. Whether the food matrix may modify the effect of dairy fat on health outcomes warrants further investigation. [ABSTRACT FROM AUTHOR]

A dairy wastewater treatment system composed of the 1st segment (no aeration) equipped with a facility for the destruction of milk fat particles, four successive aerobic treatment segments with activated sludge and a final sludge settlement segment was developed. The activated sludge is circulated through the six segments by settling sediments (activated sludge) in the 6th segment and sending the sediments beck to the 1st and 2nd segments. Microbiota was examined using samples from the non-aerated 1st and aerated 2nd segments obtained from two farms using the same system in summer or winter. Principal component analysis showed that the change in microbiota from the 1st to 2nd segments concomitant with effective wastewater treatment is affected by the concentrations of activated sludge and organic matter (biological oxygen demand [BOD]), and dissolved oxygen (DO) content. Microbiota from five segments (1st and four successive aerobic segments) in one location was also examined. Although the activated sludge is circulating throughout all the segments, microbiota fluctuation was observed. The observed successive changes in microbiota reflected the changes in the concentrations of organic matter and other physicochemical conditions (such as DO), suggesting that the microbiota is flexibly changeable depending on the environmental condition in the segments. The genera Dechloromonas , Zoogloea and Leptothrix are frequently observed in this wastewater treatment system throughout the analyses of microbiota in this study. [ABSTRACT FROM AUTHOR]

Dietary cis-9, trans-11 (c9t11) conjugated linoleic acid (CLA) fed at 0.5 % w/w was previously shown to attenuate inflammation in the murine collagen-induced (CA) arthritis model, and growing evidence implicates c9t11-CLA as a major anti-inflammatory component of dairy fat. To understand c9t11-CLA's contribution to dairy fat's anti-inflammatory action, the minimum amount of dietary c9t11-CLA needed to reduce inflammation must be determined. This study had two objectives: (1) determine the minimum dietary anti-inflammatory c9t11-CLA intake level in the CA model, and (2) compare this to anti-inflammatory effects of dairy fat (non-enriched, naturally c9t11-CLA-enriched, or c9t11-CLA-supplemented). Mice received the following dietary fat treatments (w/w) post arthritis onset: corn oil (6 % CO), 0.125, 0.25, 0.375, and 0.5 % c9t11-CLA, control butter (6 % CB), c9t11-enriched butter (6 % EB), or c9t11-CLA-supplemented butter (6 % SB, containing 0.2 % c9t11-CLA). Paw arthritic severity and pad swelling were scored and measured, respectively, over an 84-day study period. All c9t11-CLA and butter diets decreased the arthritic score (25-51 %, P < 0.01) and paw swelling (8-11 %, P < 0.01). Throughout the study, plasma tumor necrosis factor (TNFα) was elevated in CO-fed arthritic mice compared to non-arthritic (NA) mice but was reduced in 0.5 % c9t11-CLA- and EB-fed mice. Interleukin-1β and IL-6 were increased in arthritic CO-fed mice compared to NA mice but were reduced in 0.5 % c9t11-CLA- and EB-fed mice through day 42. In conclusion, 0.125 % c9t11-CLA reduced clinical arthritis as effectively as higher doses, and decreased arthritis in CB-fed mice suggested that the minimal anti-inflammatory levels of c9t11-CLA might be below 0.125 %. [ABSTRACT FROM AUTHOR]

Reduced fat dairy products are generally recommended for adults and children over the age of two years. However, emerging evidence suggests that dairy fat may not have detrimental health effects. We aimed to investigate prospective associations between consumption of regular versus reduced fat dairy products and cardiometabolic risk factors from early to late adolescence. In the West Australian Raine Study, dairy intake was assessed using semi-quantitative food frequency questionnaires in 860 adolescents at 14 and 17-year follow-ups; 582 of these also had blood biochemistry at both points. Using generalized estimating equations, we examined associations with cardiometabolic risk factors. Models incorporated reduced fat and regular fat dairy together (in serves/day) and were adjusted for a range of factors including overall dietary pattern. In boys, there was a mean reduction in diastolic blood pressure of 0.66 mmHg (95% CI 0.23-1.09) per serve of reduced fat dairy and an independent, additional reduction of 0.47 mmHg (95% CI 0.04-0.90) per serve of regular fat dairy. Each additional serve of reduced fat dairy was associated with a 2% reduction in HDL-cholesterol (95% CI 0.97-0.995) and a 2% increase in total: HDL-cholesterol ratio (95% CI 1.002-1.03); these associations were not observed with regular fat products. In girls, there were no significant independent associations observed in fully adjusted models. Although regular fat dairy was associated with a slightly better cholesterol profile in boys, overall, intakes of both regular fat and reduced fat dairy products were associated with similar cardiometabolic associations in adolescents. [ABSTRACT FROM AUTHOR]

Metabolic syndrome is a worldwide health issue. Previous research has revealed that low-birth weight (LBW) swine fed a high-fat (HF) diet were susceptible to insulin resistance (IR) and developed a preferential intestinal lipid absorption, hypertriglyceridemia, and muscle steatosis. We hypothesized that fatty acid transporters such as CD36, FATP4, and FABP2 could potentially explain the development of these conditions. In addition, dairy-derived fatty acids have been shown to be valid biomarkers to assess dairy intake, which can be utilized to investigate muscle lipid deposition in LBW swine. The overall aim of this study was to delineate molecular transport candidates responsible for intestinal lipid absorption and muscle lipid deposition in LBW swine; and secondly to determine what dietary fatty acids might accumulate preferentially in pork muscle when consuming dairy products. At 5 weeks of age, normal birth weight (NBW) and LBW piglets were randomly assigned to three experimental diets: 1-chow diet, 2-HF diet, or 3-isocaloric HF diet supplemented with full fat dairy products. At 12 weeks of age, piglets were euthanized, and carcass, fasting plasma, biceps femoris and jejunum mucosal scrapings were collected. Results showed that HF-fed LBW swine exhibited early signs of IR (fasting glucose, P < 0.05; fasting insulin, P = 0.091; HOMA-IR, P = 0.086) compared with NBW-Chow, which were attenuated with increased dairy intake. Muscle samples from HF-fed LBW swine contained significantly more triglyceride compared to Chow-fed NBW swine (P < 0.05). Increased dairy intake significantly increased myristic acid (C14:0) and DPA (C22:5n3) relative to HF feeding alone (P < 0.05). All HF-fed LBW swine (regardless of dairy intake) exhibited an upregulation of CD36 expression (but not FABP2) compared with NBW littermates in both the small intestine and muscle (P < 0.05). Interestingly, increased dairy intake significantly increased the Canadian Lean Yield percentage in LBW swine fed an HF diet (P < 0.05). Findings from this study provide evidence on the mechanistic pathway of intestinal and muscle lipid metabolism in an innovative LBW swine model. We have also revealed that increasing dairy intake can enhance the incorporation of dietary long-chain polyunsaturated fatty acids into pork, as well as increasing the predicted lean yield of the carcass., (© The Author(s) 2023. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Reduced phospholipase A (PLA) activity has been reported in blood cells and in postmortem brains of patients with Alzheimer disease (AD), and there is evidence that conjugated linoleic acid (CLA) modulates the activity of PLA groups in non-brain tissues. As CLA isomers were shown to be actively incorporated and metabolized in the brains of rats, we hypothesized that feeding a diet naturally enriched in CLA would affect the activity and expression of Pla-encoding genes in rat brain tissue, with possible implications for memory. To test this hypothesis, Wistar rats were trained for the inhibitory avoidance task and fed a commercial diet (control) or experimental diets containing either low CLA- or CLA-enriched butter for 4 weeks. After this period, the rats were tested for memory retrieval and killed for tissue collection. Hippocampal expression of 19 Pla genes was evaluated by qPCR, and activities of PLA groups (cPLA, iPLA and sPLA) were determined by radioenzymatic assay. Rats fed the high CLA diet had increased hippocampal mRNA levels for specific PLA isoforms ( iPla g6γ; cPla g4a, sPla g3, sPla g1b, and sPla g12a) and higher enzymatic activity of all PLA groups as compared to those fed the control and the low CLA diet. The increment in PLA activities correlated significantly with memory enhancement, as assessed by increased latency in the step-down inhibitory avoidance task after 4 weeks of treatment ( r = 0.69 for iPLA, P < 0.001; r = 0.81 for cPLA, P < 0.001; and r = 0.69 for sPLA, P < 0.001). In face of the previous reports showing reduced PLA activity in AD brains, the present findings suggest that dairy products enriched in cis-9, trans-11 CLA may be useful in the treatment of this disease. [ABSTRACT FROM AUTHOR]

Previous work has demonstrated that elevated maternal lipid intake (particularly from dairy products) is associated with increased lipids and altered fatty acid profile in milk produced by healthy lactating women. To investigate our primary hypothesis that a maternal diet rich in full-fat dairy products would simultaneously increase milk lipid percent and expression of genes related to the uptake and/or de novo biosynthesis of milk lipids, we provided 15 lactating women with diets enriched in full-fat or nonfat dairy products for 14 days each in a randomized, crossover study with a 2-week washout period. Milk fat (%) was lower when women consumed the low-fat compared with the full-fat dairy diet (2.41% ± 0.31% vs 3.35% ± 0.28%, respectively; P < .05); concentrations of more than 20 fatty acids also differed. However, neither conservatively evaluated microarray data nor quantitative real-time polymerase chain reaction analysis uncovered any treatment effects on expression of genes related to lipid synthesis or uptake. These data suggest that alteration in gene expression in the lactating human mammary gland is likely not the primary mechanism by which consumption of a high-fat diet affects milk fat percent in healthy, lactating women. [ABSTRACT FROM AUTHOR]

Background/Aims: Biomarkers can provide objective measures of dietary exposure, but their relationship with dietary intake in different populations needs to be characterized. This study aimed to determine the association between C14:0, C15:0 and C17:0 and children's dairy fat intake, and to ascertain whether these fatty acids can be used as biomarkers for detecting change in dairy fat intake. Methods: Data from a randomized controlled trial (114 healthy children of 4-13 years of age) was used. The intervention was a replacement of regular-fat dairy foods with reduced-fat or low-fat items. Serum fatty acid composition was measured and dairy intake was assessed via 3 × 24-hour diet recalls at baseline and at 12 weeks (the end of the intervention). Correlation analysis was used to evaluate the relationship between dietary intake and fatty acids at baseline and at week 12, and for the change in biomarkers and diet between these time points. Results: Total dairy fat intake correlated with C14:0, C15:0 and C17:0 at baseline (n = 114; r = 0.24; r = 0.42; r = 0.25 respectively, all p < 0.05), but not at week 12. The change in the total amount of dairy fat (g/day) after 12 weeks was associated with a change in serum C15:0 (n = 59; r = 0.27; p = 0.04). Conclusions: C15:0 is a useful biomarker of dairy fat intake in children and can detect short-term changes in the absolute intake of dairy fat. © 2014 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Background: Previous observational studies of self-reported dairy product consumption and stroke risk have reported mixed findings. Few studies have used circulating biomarkers that provide objective measures of dairy fat intake. Objectives: We tested the hypothesis that the circulating biomarkers of dairy fat, pentadecanoic acid (15:0), heptadecanoic acid (17:0), and trans palmitoleate (trans 16:1n-7), were associated with lower incidence of stroke, especially ischemic stroke. Secondarily, we evaluated 14:0, which is obtained from dairy products and beef, and also endogenously synthesized. Design: In participants from 2 large US cohorts (the Health Professionals Follow-Up Study: 51,529 men; the Nurses' Health Study: 121,700 women) with stored blood samples in 1993-1994 (n = 18,225) and 1989-1990 (n = 32,826), respectively, we prospectively identified 594 incident stroke cases (median follow-up: 8.3 y) and matched them 1:1 to risk-set-sampled control subjects by age, sex, race, and smoking. Total plasma and red blood cell (RBC) fatty acids were measured by using gas-liquid chromatography. Covariates were assessed by using validated questionnaires. Stroke events and subtypes were adjudicated by using medical records or other supporting documentation. We used conditional logistic regression to estimate associations of fatty acids with incident stroke, and cohort-specific findings were combined by inverse-variance weights. Results: After adjustment for demographic characteristics, lifestyle, cardiovascular disease risk factors, diet, and other circulating fatty acids, no significant associations with total stroke were seen for plasma 15:0 (pooled HR for highest compared with lowest quartiles: 0.85; 95% CI: 0.54, 1.33), 17:0 (0.99; 0.67, 1.49), trans 16:1 n-7 (0.89; 0.55, 1.45), or 14:0 (1.05; 0.62, 1.78). Results were similar for ischemic and hemorrhagic stroke subtypes, for RBC fatty acids, and in several different sensitivity analyses. Conclusion: In 2 large prospective cohorts, circulating biomarkers of dairy fat were not significantly associated with stroke. [ABSTRACT FROM AUTHOR]

Because research focusing on dairy food consumption and the risk for obesity is inconsistent and only a few studies have even examined specific dairy products, in regard to type of food and fat content, in relation to obesity risk, this cross-sectional study investigated whether dairy food consumption is associated with the prevalence of global and abdominal obesity. Data were analyzed from 1352 participants in the Observation of Cardiovascular Risk Factors in Luxembourg survey. We hypothesized that higher total dairy food consumption would be independently associated with reduced prevalence of obesity. A validated food frequency questionnaire was used to measure intakes of dairy foods. Odds for global obesity (body mass index ≥30 kg/m 2 ) and abdominal obesity (waist circumference >102 cm for men and >88 cm for women) were determined based on total dairy food intake as well as intakes of individual low- and whole-fat dairy products (milk, yogurt, and cheese). Total dairy food intake was inversely associated with the likelihood of global obesity (odds ratio [OR], 0.51; 95% confidence interval [CI], 0.30-0.89; P < .05) and abdominal obesity (OR, 0.51; 95% CI, 0.32-0.83; P < .01). Participants in the highest tertile of whole-fat dairy intakes (milk, cheese, yogurt) had significantly lower odds for being obese (global obesity: OR, 0.45; 95% CI, 0.29-0.72; P < .01; abdominal obesity: OR, 0.35; 95% CI, 0.23-0.54; P < .001), compared with those in the lowest intake tertile, after full adjustment for demographic, lifestyle, dietary, and cardiovascular risk factor variables. Increasing consumption of dairy foods may have the potential to lower the prevalence of global and abdominal obesity. [ABSTRACT FROM AUTHOR]

Intake of dairy fat has long been considered as a risk factor for CVD. Pasture and dietary lipid supplementation have been reported to be reliable strategies in ruminant nutrition, in order to increase the content of α-linolenic acid (ALA), conjugated linoleic acid (CLA) and vaccenic acid (VA), and decrease SFA in milk fat. In the present study, we aimed at verifying whether consumption of a sheep cheese, naturally enriched in ALA, CLA and VA, would modify the plasma lipid and endocannabinoid profiles in mildly hypercholesterolaemic subjects. A total of forty-two adult volunteers (nineteen males and twenty-three females) with diagnosed mildly hypercholesterolaemia (total cholesterol 5·68–7·49 mmol/l) were randomly assigned to eat 90 g/d of a control or enriched cheese for 3 weeks, with a cross-over after 3 weeks of washout. Plasma lipids, endocannabinoids, adipokines and inflammatory markers were measured. The intake of enriched cheese significantly increased the plasma concentrations of CLA, VA, the n-3 fatty acids ALA and EPA, and more remarkably decreased that of the endocannabinoid anandamide. LDL-cholesterol decreased significantly (7 %). No changes were detected in the levels of inflammatory markers; however, a significant correlation was found between the plasma levels of anandamide and leptin. The control cheese modified none of the parameters measured. The results obtained do not support the view that intake of dairy fat is detrimental to hypercholesterolaemic subjects. Indeed, they show that a naturally enriched cheese possesses beneficial properties, since it ameliorates the plasma lipid profile, and more remarkably reduces endocannabinoid biosynthesis. [ABSTRACT FROM PUBLISHER]

Purpose: To comprehensively review the data on the relationship between the consumption of dairy fat and high-fat dairy foods, obesity, and cardiometabolic disease. Methods: We have conducted a systematic literature review of observational studies on the relationship between dairy fat and high-fat dairy foods, obesity, and cardiometabolic disease. We have integrated these findings with data from controlled studies showing effects of several minor dairy fatty acids on adiposity and cardiometabolic risk factors, and data on how bovine feeding practices influence the composition of dairy fat. Results: In 11 of 16 studies, high-fat dairy intake was inversely associated with measures of adiposity. Studies examining the relationship between high-fat dairy consumption and metabolic health reported either an inverse or no association. Studies investigating the connection between high-fat dairy intake and diabetes or cardiovascular disease incidence were inconsistent. We discuss factors that may have contributed to the variability between studies, including differences in (1) the potential for residual confounding; (2) the types of high-fat dairy foods consumed; and (3) bovine feeding practices (pasture- vs. grain-based) known to influence the composition of dairy fat. Conclusions: The observational evidence does not support the hypothesis that dairy fat or high-fat dairy foods contribute to obesity or cardiometabolic risk, and suggests that high-fat dairy consumption within typical dietary patterns is inversely associated with obesity risk. Although not conclusive, these findings may provide a rationale for future research into the bioactive properties of dairy fat and the impact of bovine feeding practices on the health effects of dairy fat. [ABSTRACT FROM AUTHOR]

Abstract: Achieving an appropriate DHA status in the neonatal brain is an important goal of neonatal nutrition. We evaluated how alpha-linolenic acid (ALA), provided for six weeks after weaning by different dietary fat matrix, improved brain DHA content of young male rats born from deficient-dams. The level of ALA achieved was based on the fat composition of usual infant vegetable formula. A palm oil-blend diet thus providing 1.5%ALA was compared to dairy fat-blend-based diets that provided either 1.5%ALA or 2.3%ALA, or a rapeseed oil diet providing 8.3%ALA (n−6/n−3 ratio were, respectively 10,10,5,2.5). The 1.5%ALA-dairy-fat-blend was superior to 1.5%ALA-palm-oil-blend to restore values of brain DHA, while the 2.3%ALA-dairy-fat-blend exhibited a further increase and reached the values obtained with pure rapeseed diet (8.3%ALA). Dairy-fat-blends enriched with ALA appear to be an interesting strategy for achieving optimal DHA levels in the brain of post-weaning rats. Providing dairy fat as well as a reduction of the LA/ALA ratio should be reconsidered to design infant formula. [Copyright &y& Elsevier]

Metabolic impairments associated with type 2 diabetes, including insulin resistance and loss of glycaemic control, disproportionately impact the elderly. Lifestyle interventions, such as manipulation of dietary fat quality (i.e. fatty acid (FA) composition), have been shown to favourably modulate metabolic health. Yet, whether or not chronic consumption of beneficial FAs can protect against metabolic derangements and disease risk during ageing is not well defined. We sought to evaluate whether long-term dietary supplementation of fish-, dairy- or echium-derived FAs to the average FA profile in a U.S. American diet may offset metabolic impairments in males and females during ageing. One-month-old CD-1 ® mice were fed isoenergetic, high-fat (40 %) diets with the fat content composed of either 100 % control fat blend (CO) or 70 % CO with 30 % fish oil, dairy fat or echium oil for 13 months. Every 3 months, parameters of glucose homoeostasis were evaluated via glucose and insulin tolerance tests. Glucose tolerance improved in males consuming a diet supplemented with fish oil or echium oil as ageing progressed, but not in females. Yet, females were more metabolically protected than males regardless of age. Additionally, Spearman correlations were performed between indices of glucose homoeostasis and previously reported measurements of diet-derived FA content in tissues and colonic bacterial composition, which also revealed sex-specific associations. This study provides evidence that long-term dietary fat quality influences risk factors of metabolic diseases during ageing in a sex-dependent manner; thus, sex is a critical factor to be considered in future dietary strategies to mitigate type 2 diabetes risk.

The "fat hypothesis of coronary heart disease", according to which saturated fatty acids (SFA) increase the concentration of low-density lipoprotein-cholesterol (LDL-C) and consequently increase the risk for cardiovascular diseases, influenced the nutritional recommendations over the last 60 years, initially in the USA and later also in Europe. Over the years there accumulated a growing body of evidence from epidemiology and controlled clinical studies that the consumption of SFA per se was not associated with an increased cardiovascular risk and the limitation of consumption of SFA did not show a preventive effect. The focus on the SFA content negated the biologically heterogeneous and sometimes biologically favorable effects of various SFAs. In addition, it was neglected that SFAs in foodstuffs are bound in a variety of complex matrices, which are composed of dozens of nutrients with different structures and concomitant substances and therefore each triggers different biological responses and metabolic effects. Accordingly, such nutrient-based recommendations are principally not very productive and also difficult to realize. In addition, LDL‑C is not a suitable marker to assess the effect of lifestyle interventions, such as nutrition or physical activity, on the global cardiovascular risk., (© 2021. The Author(s).)

Abstract: Achieving an appropriate docosahexaenoic acid (DHA) status in the neonatal brain is an important goal of neonatal nutrition. We evaluated how different dietary fat matrices improved DHA content in the brains of both male and female rats. Forty rats of each gender were born from dams fed over gestation and lactation with a low α-linolenic acid (ALA) diet (0.4% of fatty acids) and subjected for 6 weeks after weaning to a palm oil blend-based diet (10% by weight) that provided either 1.5% ALA or 1.5% ALA and 0.12% DHA with 0.4% arachidonic acid or to an anhydrous dairy fat blend that provided 1.5% or 2.3% ALA. Fatty acids in the plasma, red blood cells (RBCs) and whole brain were determined by gas chromatography. The 1.5% ALA dairy fat was superior to both the 1.5% ALA palm oil blends for increasing brain DHA (14.4% increase, P<.05), and the 2.3% ALA dairy blend exhibited a further increase that could be ascribed to both an ALA increase and n-6/n-3 ratio decrease. Females had significantly higher brain DHA due to a gender-to-diet interaction, with dairy fats attenuating the gender effect. Brain DHA was predicted with a better accuracy by some plasma and RBC fatty acids when used in combination (R 2 of 0.6) than when used individually (R 2=0.47 for RBC n-3 docosapentaenoic acid at best). In conclusion, dairy fat blends enriched with ALA appear to be an interesting strategy for achieving optimal DHA levels in the brain of postweaning rats. Human applications are worth considering. [Copyright &y& Elsevier]

There is clinical and observational evidence to suggest that saturated fatty acids (SFA) increase cardiovascular disease risk compared with polyunsaturated fatty acids from vegetable oils. Replacing SFA intake has thus been a public health target, but the role of individual SFA in metabolic disease is still incompletely understood. Observational data indicate that all SFA may not necessarily be detrimental. The cholesterol-raising effect of SFA differs among individual SFA and possibly also with regard to cardiovascular and metabolic risk factors. The impact of dietary SFA on cardiovascular disease remains somewhat controversial, possibly due to such individual differences. In this article, we will also separately discuss the effects of dairy SFA, including biomarkers, as a means to elucidate these relationships between fatty acids, foodstuffs and cardiometabolic disease. [ABSTRACT FROM AUTHOR]

To determine socio-economic differences from 1994 to 2004 in the use of butter and milk in Pitkäranta in the Republic of Karelia, Russia and North Karelia, Finland. Health behaviour surveys in Pitkäranta ( n = 3,599) and North Karelia ( n = 3,652) in 1994, 1996, 1998, 2000 and 2004. A clear overall decrease occurred in the use of butter in cooking in Pitkäranta from 1994 to 2004. In both areas, subjects with lower education used butter in cooking and drank fat-containing milk more often. Regarding butter on bread, the educational patterns in the two areas were opposite: in Pitkäranta, subjects with lower education used butter less often but in North Karelia, they used butter on bread more often. Practically, no changes in socio-economic differences from 1994 to 2004 were observed in either area. The socio-economic differences in the use of dairy fat were stable in both areas but larger in North Karelia than in Pitkäranta. Our results support earlier assumptions of a weaker role of education as a determinant of health in Russia than in the western societies. [ABSTRACT FROM AUTHOR]

Abstract: The acute oral toxicity of a trans-10 C18:1-rich milk fat (T10, 20% of total FA), and a trans-11 C18:1+ cis-9 trans-11 C18:2-rich milk fat (T11-CLA, 14% and 4.8% of total FA, respectively) was studied in rats receiving a single oral dose of 2000mg/kg body weight (BW). T10 and T11-CLA milk fats were well tolerated; no adverse effects or mortality were observed during the 2-week observation period. Two weeks following a single oral dose of 2000mg/kg BW of T10 and T11-CLA milk fats there were no changes in haematological and serum chemistry parameters (excepting plasma lipid) organ weights, gross pathology or histopathology. In rats treated with T10 milk fat a significant increase of triglycerides was observed. In contrast, in rats treated with T11-CLA milk fat significantly decreased triglycerides were detected. It was concluded that dairy fats rich in T10 and T11-CLA have a low order of acute toxicity, the oral lethal dose (DL50) for male and female rats are in excess of 2000mg/kg BW. Our results suggest that the T10 milk fat treatment tended to increase triglycerides concentrations, whereas the T11-CLA milk fat treatment tended to reduce it. [Copyright &y& Elsevier]

The objective of this study was to review the pediatric literature on the relationship between dairy, milk fat, and body weight to ascertain whether it supports current recommendations to limit dairy fat in children and adolescents. With only a few exceptions, pediatric crosssectional and prospective studies from across the globe have demonstrated significant negative associations between dairy or milk intake and body mass index or body fat. Four studies have looked specifically at the fat content of milk, and none have implicated whole or 2% milk as being more weight inducing than lower fat milk. The pediatric literature on dairy provides no support to the notion that skim milk is more protective against excessive weight gain than whole milk and in fact raises the possibility that the very opposite may be the case. Hypotheses are suggested to explain this. [ABSTRACT FROM PUBLISHER]

Fatty acids have been classified into “good” or “bad” groups according to their degree of unsaturation or whether they are “animal fat” or “vegetable fat”. Today, it appears that the effects of fatty acids are complex and vary greatly according to the dose and the nature of the molecule. Monounsaturated fatty acids are still considered as having a “neutral” status, but any benefits may be related to the chemical environment of the source food or the associated overall food pattern. Controversy surrounds omega-6 polyunsaturated fatty acids, because even though they lower LDL cholesterol levels, excessive intakes do not appear to be correlated with cardiovascular benefit. The omega-3 fatty acids are known to exert cardiovascular protective effects. Dairy fat and its cardiovascular impact are being evaluated. This review examines the existing literature on the relationships between the different fatty acids and cardiovascular disease. [ABSTRACT FROM AUTHOR]

The role of dairy fat in the aetiology of myocardial infarction (MI) is controversial. The aim of this study was to evaluate the association between intake of dairy fat and dairy products, and risk of a first acute MI. A total of 111 MI patients with a first acute MI and 107 population controls (men and women, age 45-75 years) were studied. Diet was assessed using a 180-item food frequency questionnaire. The MI cases had higher intake of total fat, but lower intake of saturated fat and dairy fat than the control persons. No effect of dairy fat or saturated fat on the odds ratio for MI was observed, however. A significant inverse trend in odds of MI for intake of cheese was observed, but the trend was no longer significant after adjustment for smoking. The results suggest that intake of fat from dairy products may not be associated with increased risk of having a first MI. The healthy control persons had a diet that differed from the diet of the MI patients in many aspects, and dairy products were a part of this diet. This may have protected them from having a first MI. [ABSTRACT FROM AUTHOR]

Epidemiological data suggest that a diet rich in animal foods may be associated with an increased risk of several cancers, including cancers of the prostate, colorectum and breast, but the possible mechanism is unclear. It is hypothesised that phytanic acid, a C20 branched-chain fatty acid found predominantly in foods from ruminant animals, may be involved in early cancer development because it has been shown to up regulate activity of α-methylacyl-coenzyme A racemase, an enzyme commonly found to be over-expressed in tumour cells compared with normal tissue. However, little is known about the distribution of plasma phytanic acid concentrations or its dietary determinants in the general population. The primary aim of the present cross-sectional study was to determine circulating phytanic acid concentrations among ninety-six meat-eating, lacto-ovo-vegetarian and vegan women, aged 20–69 years, recruited into the Oxford component of the European Prospective Investigation into Cancer and Nutrition (EPIC-Oxford). Meat-eaters had, on average, a 6.7-fold higher geometric mean plasma phytanic acid concentration than the vegans (5·77 v. 0·86 μmol/l; P < 0·0001) and a 47 % higher mean concentration than the vegetarians (5·77 v. 3·93 μmol/l; P = 0·016). The strongest determinant of plasma phytanic acid concentration appeared to be dairy fat intake (r 0·68; P < 0·0001); phytanic acid levels were not associated with age or other lifestyle factors. These data show that a diet high in fat from dairy products is associated with increased plasma phytanic acid concentration, which may play a role in cancer development. [ABSTRACT FROM PUBLISHER]

Postprandial chylomicrons are potent ultimate acceptors of cell membrane cholesterol and are believed to accelerate reverse cholesterol transport (RCT). We compared the effects of meals rich in polyunsaturated fat (PUFA) and either high (605 mg) or low (151 mg) in cholesterol and a meal rich in dairy fat (DF) in the form of cream on net in vitro transport of red blood cell (RBC) membrane cholesterol to 4 and 6 h postprandial plasma in eight normotriglyceridemic (NTG-H) and eight hypertriglyceridemic (HTG-H) men with mild to moderate hypercholesterolemia. In HTG-H men, cell cholesterol accumulation in 6-h postprandial plasma was significantly ( P = 0.02) less after the PUFA-HC meal compared with the other meals. The significant ( P < 0.001) increase in cell plus endogenous cholesterol accumulation in the triglyceride-rich lipoprotein (TRL) fraction of 4 h postprandial plasma incubated with RBC was significantly ( P = 0.007) higher after the PUFA-HC meal compared with DF meal in HTG-H men. In NTG-H men, cholesterol accumulation in plasma and plasma lipoproteins in the presence and absence of RBC was not significantly affected by the type of meal ingested. These data suggest that addition of large amounts of cholesterol to a PUFA meal may impair diffusion-mediated transport of cell membrane cholesterol to postprandial plasma and that replacing DF with PUFA in a meal increases postprandial lipemia and may potentially increase cholesterol accumulation in atherogenic postprandial TRL in HTG-H men. [ABSTRACT FROM AUTHOR]

The objective was to evaluate different levels of sunflower oil (SFO) in dairy rations to increase vaccenic (trans-11-18:1) and rumenic acids (cis-9, trans-11-18:2) in milk fat, and assess the content and composition of other trans-octadecenoic (trans-18:1) and conjugated linoleic acids (CLA) isomers. Eighty lactating Holstein cows were fed control diets for 4 wk and then placed on 4 diets for 38 d; milk fat was analyzed after 10 and 38 d. The treatments were: control, 1.5% SFO plus 0.5% fish oil (FO), 3% SFO plus 0.5% FO, and 4.5% SFO plus 0.5% FO. The forage-to-concentrate ratio was 50:50 and consisted of barley/alfalfa/hay silage and corn/barley grain concentrate. There were no differences in milk production. Supplementation of SFO/FO reduced milk fat compared with respective pretreatment periods, but milk protein and lactose levels were not affected. There was a linear decrease in all short- and medium-chain saturated fatty acids (SFA) in milk fat after 10 d (25.5, 24.1, 20.2, and 16.7%) and a corresponding linear increase in total trans-18:1 (5.2, 9.1, 14.1, and 21.3%) and total CLA (0.7, 1.9, 2.4, and 3.9%). The other FA in milk fat were not affected. Separation of trans-18:1 isomers was achieved by combination of gas chromatography (GC; 100-m highly polar capillary column) and prior separation of trans FA by silver ion-thin layer chromatography followed by GC. The CLA isomers were resolved by a combination of GC and silver ion-HPLC. The trans-11- and trans-10-18:1 isomers accounted for ∼50% of the total trans-18:1 increase when SFO/FO diets were fed. On continued feeding to 38 d, trans-11-18:1 increased with 1.5% SFO/FO, stayed the same with 3%, and declined with 4.5% SFO/FO. Rumenic acid showed a similar pattern on continued feeding as trans-11-18:2; levels increased to 0.43, 1.5, 1.9, and 3.4% at 10 d and to 0.42, 2.15, 2.09, and 2.78% at 38 d. Rumenic acid was the major CLA isomer in all 4 diets: 66, 77, 78 and 85%. The CLA isomers trans-7,cis-9-, trans-9, cis-11-, trans-10,cis-12-, trans-11,trans-13-, and trans-9,trans-11-/trans-10,trans-12-18:2 also increased from 0.18 (control) to 0.52% (4.5% SFO/FO). Milk fat produced from 3% SFO/FO appeared most promising: trans-11-18:1 and cis-9,trans-11-18:2 increased 4.5-fold, total SFA reduced 18%, and moderate levels of trans-10-18:1 (3.2%), other trans-18:1 (6.6%) and CLA isomers (0.5%) were observed, and that composition remained unchanged to 38 d. The 4.5% SFO/FO diet produced higher levels of trans- 11-18:1 and cis-9, trans-11-18:2, a 28% reduction in SFA, and similar levels of other trans-18:1 (9.2%) and CLA isomers (0.52%), but the higher levels of trans-11-18:1 and cis-9,trans-11-18:2 were not sustained. A stable milk fat quality was achieved by feeding moderate amounts of SFO (3% of DM) in the presence of 0.5% FO that had 4% vaccenic and 2% rumenic acids. [ABSTRACT FROM AUTHOR]

Abstract: Diet is important in the prevention and treatment of the metabolic syndrome, a cluster of metabolic risk markers, leading to type 2 diabetes and coronary heart disease (CHD). The aim of this review is to summarize recent findings from human studies on the effects of dairy products in this area. Epidemiological studies suggest a beneficial relationship between the consumption of low-fat dairy products and type 2 diabetes. For CHD, relationships are less consistent. These associations, however, do not prove causality, which can only be demonstrated by intervention studies. Several intervention trials have indeed shown positive effects on metabolic risk markers, of which dairy products were a part. The contribution of dairy products to the effects observed, however, is not known. Another important question is if dairy products contain a bioactive component that can explain these findings. In this respect, it is not likely that effects observed can be attributed to conjugated linoleic acid (CLA). [Copyright &y& Elsevier]

Ovary cancer risk in relation to consumption of dairy products was investigated using a self-administered questionnaire on dietary habits and other risk factors for cancer, which was completed in 1986 by 62 573 postmenopausal women participating in the Netherlands Cohort Study. Follow-up for cancer was implemented by annual record linkage with the Netherlands Cancer Registry and a nationwide pathology registry. After 11.3 years of follow-up, data of 252 incident epithelial ovarian cancer cases and 2216 subcohort members were available for analysis. No association was seen between consumption of milk, yoghurt, cheese or fermented dairy products and ovarian cancer risk. The multivariable adjusted relative risk of epithelial ovarian cancer for women in the highest compared to the lowest quintile of intake of lactose or dairy fat was 0.93 (95% confidence interval (CI)=0.60-1.45; P(trend)=0.32) and 1.53 (95% CI=1.00-2.36; P(trend)=0.11), respectively. Lactose or dairy fat intakes were not associated with serous ovarian cancer risk. Our results do not support an association between consumption of dairy products or lactose intake and ovarian cancer. [ABSTRACT FROM AUTHOR]

Background:There is a need for biomarkers of dietary saturated fatty acids, because several diseases have been related to intake of these fatty acids.Objective:To examine the relation between intake of dairy fat and the proportion of pentadecanoic (15:0) and heptadecanoic (17:0) acid in serum and adipose tissue.Design:Healthy men aged 21–55 y provided serum (n=110) and adipose tissue samples (n=107) and completed both 14 days weighed records (WR) and a 180-item food frequency questionnaire (FFQ). The proportions of 15:0 and 17:0 acid in serum and adipose tissue as measured by gas liquid chromatography were evaluated as biomarkers for fat intake from dairy products using Pearsons correlation coefficient and the method of triads.Results:The strongest correlation coefficients were observed between total intake of dairy fat estimated from WR and relative content of 15:0 in adipose tissue (0.52, 95% CI: 0.37, 0.65) and total serum (0.43, 95% CI 0.26, 0.57). A consistent inverse association was observed between the intake of milk fat and relative serum content of 17:0. The validity coefficients observed for the intake of dairy fat estimated from weighed records, the 180-item FFQ and by the relative content of 15:0 in serum and adipose tissue were 0.94 (95% CI: 0.68, 1.00), 0.50 (95% CI: 0.29, 0.67), 0.49 (95% CI: 0.32, 0.67) and 0.56 (95% CI: 0.28, 0.82), respectively.Conclusion:Relative content of 15:0 in serum and adipose tissue may be a useful biomarker for the intake of total dairy fat, whereas FFQs and WRs may provide better estimates of the intake of fat from milk.European Journal of Clinical Nutrition (2005) 59, 1417–1422. doi:10.1038/sj.ejcn.1602256; published online 24 August 2005 [ABSTRACT FROM AUTHOR]

The relative contents of the fatty acids 14: 0, 15: 0 and 17: 0 in serum and adipose tissue may be used as biological markers of dairy fat intake. However, the determinants of these fatty acids are not fully understood. This study investigates the relationship between these fatty acids and the intake of macronutrients and physical activity in a cross-sectional study of 301 healthy men aged 61???64 years. Dietary intake was assessed using a pre-coded 7 d food record, and physical activity during the previous year was recorded in an interview. Under-reporters of energy intake were identified by the Goldberg cut-off. Fatty acid composition was determined in serum phospholipids (PL) and subcutaneous adipose tissue (AT) from the upper buttock. The relative content of each of 14: 0, 15: 0 and 17: 0 in PL and AT was positively associated with the intake of dairy fat. In addition, all three fatty acids were inversely correlated with alcohol intake, R ranging from ???0??28 to ???0??53 (P<0??001). The results were not markedly affected when under-reporters (n 88) were excluded from the analyses. In both PL and AT, the relative content of the fatty acids was approximately 5% higher in a group of high physical activity compared with a group of low physical activity, although significant trends were only seen for 14: 0 in PL and 17: 0 in AT. The findings suggest that adjustments should be made for alcohol intake when the fatty acids 14: 0, 15: 0 and 17: 0 are applied as markers for dairy fat intake. [ABSTRACT FROM PUBLISHER]

OBJECTIVE:: This study evaluates the association between abdominal obesity and the intake of dairy fat and calcium using information from dietary data and the relative content of the fatty acids 14:0, 15:0, and 17?:?0 in serum phospholipids (PL) and adipose tissue (AT), which are suggested biological markers for dairy fat intake. This study also explores how the associations were affected when under-reporters (URs) were separated from the analyses. DESIGN:: Cross-sectional study. SUBJECTS:: In all, 301 healthy 63-y-old men with different degrees of fasting-insulin concentrations. METHODS:: Sagittal abdominal obesity (SAD), dietary intake assessed by a 7-day food registration, and the fatty acid composition in serum PL and AT were measured. URs (n=88) and non-under-reporters (non-URs, n=213) were identified by Goldberg's equation, which compares energy intake with energy expenditure, both expressed as multiples of the basal metabolic rate. RESULTS:: The intake of dairy fat, expressed as g/100?g fat, was inversely correlated with SAD; however, this association was only observed in the URs (r=-0.36, P=0.001) and not in the non-URs (r=-0.04, P=0.59). The intake of calcium was inversely correlated with SAD in both groups, although the association was weaker in the non-URs. The intake of dairy fat was related to the relative content of the fatty acids 14:0, 15:0, and 17?:?0 in serum PL and AT (r ranging between 0.32 and 0.55). When these fatty acids were correlated to SAD, inverse associations were seen except for 14:0 in PL (r ranging between-0.17 and-0.29. CONCLUSION:: If there is a true inverse association between the intake of dairy fat and SAD, it remains to explain why this association was not seen in the non-URs. The data gave some indications of an inverse association between SAD and the intake of calcium. The diverse findings observed when the URs and non-URs were separated highlight the question of how to use and interpret dietary data in URs when diet-disease relationships are investigated.International Journal of Obesity (2004) 28, 1427-1434. doi:10.1038/sj.ijo.0802769 Published online 24 August 2004 [ABSTRACT FROM AUTHOR]

Background: We recently showed that trans-10,cis-12 (t10,c12) conjugated linoleic acid (CLA) causes insulin resistance in obese men. However, metabolic effects of the c9,t11 CLA isomer are still unknown in obese men. Because c9,t11 CLA is the predominant CLAisomer in foods and is included in dietary weight-loss products, it is important to conduct randomized controlled studies that use c9,t11 CLA preparations. Objective: We investigated the effects of c9,t11 CLA supplementation on insulin sensitivity, body composition, and lipid peroxidation in a group at high risk for cardiovascular disease. Design: In a randomized, double-blind, placebo-controlled study, 25 abdominally obese men received 3 g c9,t11 CLA/d or placebo (olive oil). Before and after 3 mo of supplementation, we assessed insulin sensitivity (hyperinsulinemic euglycemic clamp), lipid metabolism, body composition, and urinary 8-iso-prostaglandin F2α (a major F2-isoprostane) and 15-keto-dihydro-prostaglandin F2α, markers of in vivo oxidative stress and inflammation, respectively. Results: All subjects completed the study. Compared with placebo, c9,t11 CLA decreased insulin sensitivity by 15% (P < 0.05) and increased 8-iso-prostaglandin F2α and 15-keto-dihydroprostaglandin F2α excretion by 50% (P<0.01) and 15% (P<0.05), respectively. The decreased insulin sensitivity was independent of changes in serum lipids, glycemia, body mass index, and body fat but was abolished after adjustment for changes in 8-iso-prostaglandin F2α concentrations. There were no differences between groups in body composition. Conclusions: A CLA preparation containing the purified c9,t11 CLAisomer increased insulin resistance and lipid peroxidation compared with placebo in obese men. Because c9,t11 CLA occurs in commercial supplements as well as in the diet, the present results should be confirmed in larger studies that also include women. [ABSTRACT FROM AUTHOR]