Search

In North America, there is increasing public health awareness of the importance of adequate vitamin D intake to the maintenance of optimal vitamin D status and overall health. Experts now define this as circulating levels of 25-hydroxyvitamin D of 75-80 nmol/L. This serum level and high levels of dietary intake have been associated with significantly reduced risk of chronic diseases, such as osteoporosis, cardiovascular disease, diabetes, and some cancers. All of these diseases are more prevalent in the elderly of all races, and some are more prevalent and of greater severity among blacks than whites. Our objective is to review recent actions to increase public awareness of the health importance of maintaining optimal circulating 25(OH)D and potential strategies to increase vitamin D intake. Clinicians and educators are encouraged to promote improved vitamin D intake and status, particularly among the elderly and blacks. This will largely depend on combined efforts to judiciously fortify our food supply and to develop individual supplementation protocols for supplements or controlled use of UV light exposure to maintain optimal serum 25(OH)D, especially in high-risk groups. Growing evidence supports a low risk of toxicity with vitamin D use in fortification or supplementation, despite its past reputation of potential toxicity in excess. The cost to fortify food or supplements with vitamin D is relatively inexpensive compared with developing drugs used to treat or prevent chronic diseases; moreover, there is significant potential for broad health benefits in the reduced risk and prevention of multiple chronic diseases. [ABSTRACT FROM AUTHOR]

From its inaugural value in 1941, the Recommended Dietary Allowance (RDA) for adults for vitamin D has remained close to 400 IU (10 microg) level. This original recommended intake was based on the observation that the amount of vitamin D activity in a teaspoon of cod liver oil was sufficient to prevent rickets in infants. Since that time until 1997, determination of vitamin D requirements and status was more conjecture than science. In 1997, when the recommended intake level of vitamin D was set as an adequate intake value rather than an RDA, much has been learned about metabolism of vitamin D. The circulating metabolite 25-hydroxyvitamin D is the major static indicator of vitamin D status. Using its response to diet in the absence of sun exposure, a dose-response study suggests a mean requirement of at least 500 IU (12.5 microg) from which an RDA could be set. Other factors may need adjustment, such as sun exposure and body fat. However, functional indicators of status are needed. The role of vitamin D in calcium metabolism (i.e., calciotropic functions) is better understood; bone turnover and parathyroid hormone are potential indicators. Vitamin D has noncalciotropic functions arising from extrarenal synthesis of the active metabolite 1,25 dihydroxyvitamin D involving cell proliferation and immunity, from which function indicators of status may be derived. Despite gaps in our knowledge, there are data from which new dietary reference intake values for vitamin D may be set. [ABSTRACT FROM AUTHOR]

Global high prevalence of vitamin D insufficiency and re-emergence of rickets and the growing scientific evidence linking low circulating 25-hydroxyvitamin D to increased risk of osteoporosis, diabetes, cancer, and autoimmune disorders have stimulated recommendations to increase sunlight (UVB) exposure as a source of vitamin D. However, concern over increased risk of melanoma with unprotected UVB exposure has led to the alternative recommendation that sufficient vitamin D should be supplied through dietary sources alone. Here, we examine the adequacy of vitamin D intake worldwide and evaluate the ability of current fortification policies and supplement use practices among various countries to meet this recommendation. It is evident from our review that vitamin D intake is often too low to sustain healthy circulating levels of 25-hydroxyvitamin D in countries without mandatory staple food fortification, such as with milk and margarine. Even in countries that do fortify, vitamin D intakes are low in some groups due to their unique dietary patterns, such as low milk consumption, vegetarian diet, limited use of dietary supplements, or loss of traditional high fish intakes. Our global review indicates that dietary supplement use may contribute 6-47% of the average vitamin D intake in some countries. Recent studies demonstrate safety and efficacy of community-based vitamin D supplementation trials and food staple fortification introduced in countries without fortification policies. Reliance on the world food supply as an alternative to UVB exposure will necessitate greater availability of fortified food staples, dietary supplement use, and/or change in dietary patterns to consume more fish. [ABSTRACT FROM AUTHOR]

The development of bone mass during the growing years is an important determinant for risk of osteoporosis in later life. Adequate dietary intake during the growth period may be critical in reaching bone growth potential. The Saskatchewan Bone Mineral Accrual Study (BMAS) is a longitudinal study of bone growth in Caucasian children. We have calculated the times of maximal peak bone mineral content (BMC) velocity to be 14.0 +/- 1.0 y in boys and 12.5 +/- 0.9 y in girls; bone growth is maximal approximately 6 mo after peak height velocity. In the 2 y of peak skeletal growth, adolescents accumulate over 25% of adult bone. BMAS data may provide biological data on calcium requirements through application of calcium accrual values to factorial calculations of requirement. As well, our data are beginning to reveal how dietary patterns may influence attainment of bone mass during the adolescent growth spurt. Replacing milk intake by soft drinks appears to be detrimental to bone gain by girls, but not boys. Fruit and vegetable intake, providing alkalinity to bones and/or acting as a marker of a healthy diet, appears to influence BMC in adolescent girls, but not boys. The reason why these dietary factors appear to be more influential in girls than in boys may be that BMAS girls are consuming less than their requirement for calcium, while boys are above their threshold. Specific dietary and nutrient recommendations for adolescents are needed in order to ensure optimal bone growth and consolidation during this important life stage. [ABSTRACT FROM AUTHOR]

Discusses the relationships of caffeine, urinary calcium, calcium metabolism and the bone. Increased urinary excretion of calcium, magnesium, sodium and chloride after oral doses of caffeine; Hypercalciuric effect's blockage by adenosine receptor agonists; Review of risks of osteoporosis after caffeine; Older women's failure to compensate.

The article overviews the proceedings of the 2005 Experimental Biology Symposium titled "Optimizing Vitamin D Intake for Populations with Special Needs: Barriers to Effective Food Fortification and Supplementation." The symposium examines the reasons why there are many barriers in the provisions of enough vitamin D foods in compliance of the newly emerging recommendations about vitamin D nutrition. In addition, it also canvasses on the current upper intake level of vitamin D. Concerns on darkly pigmented skin which blocks cutaneous Vitamin D synthesis is also examined.

Presents an overview of the proceedings from Experimental Biology 2004 Symposium: Vitamin D Insufficiency: A Significant Risk Factor in Chronic Diseases and Potential Disease-Specific Biomarkers of Vitamin D Sufficiency. Need to reevaluate current dietary reference intakes for Vitamin D; Inability of the food supply to provide adequate Vitamin D in the absence of sunlight; Diet supplementation in infancy to prevent type 1 diabetes.

There is a need to increase the options for vitamin D fortification. We have developed a method to fortify hard cheese with vitamin D. Our aim was to characterize the bioavailability of vitamin D from fortified cheeses. Eighty adults were randomized to weekly servings of fortified cheddar cheese (DC) (34 g; n = 20); fortified low-fat cheese (DLF) (41 g; n = 10); liquid vitamin D supplement (1 mL), taken with food (DS+) In = 201 or without food (DS-) (n = 10); placebo cheddar cheese In = 101; or placebo supplement In = 10). The treatments contained 28,000 lU cholecalciferol (vitamin D3), equivalent to 4000 lU (100 μg/d). The primary outcome was the comparison of vitamin D bioavailability, as measured by the serum 25-hydroxyvitamin D [25(OH)D] response, between fortified cheeses and supplement. In the placebo groups, initial 25(OH)D, 55.0 ± 25.3 nmol/L, declined over the 8-wk winter protocol, to 50.7 ± 24.2 nmol/L (P = 0.046). In the vitamin D-treated groups, the mean increases in 25(OH)D over 8 wk were: 65.3 ± 24.1 (DC), 69.4 ± 21.7 (DLF), 59.3 ± 23.3 (DS+), and 59.3 ± 19.6 nmol/L (DS-); these changes differed from the placebo groups IP < 0.0001) but not from one another (P= 0.62). Compared with baseline, serum parathyroid hormone decreased with both fortification (P= 0.003) and supplementation (P= 0.012). These data demonstrate that vitamin D is equally bioavailable from fortified hard cheeses and supplements, making cheese suitable for vitamin D fortification. [ABSTRACT FROM AUTHOR]

Background: In light of the publications (2008-2014) linking calcium intake, mainly from supplements, to the elevated risk of cardiovascular events, there is a need to determine if there have been any changes in usual intakes of calcium among Canadians.Objective: We aimed to examine changes in dietary and total usual intake of calcium among Canadians aged ≥1 y over the period 2004-2015.Methods: We used nutrition data from 2 nationally representative surveys conducted in 2004 and 2015 (CCHS 2004 Cycle 2.2 and CCHS-Nutrition 2015). This study included all the Canadians across 10 provinces, and the analyses were performed across different age/sex groups. We used the National Cancer Institute (NCI) method to estimate the usual intake of calcium and the prevalence of calcium inadequacy. Multiple logistic regression was performed to assess the relation between supplement uses and sociodemographic variables.Results: From 2004 to 2015, the usual intake of calcium from food sources significantly decreased in calcium supplement nonusers (from 872 ± 18.2 mg/d to 754 ± 18.0 mg/d), but not in calcium supplement users. The contribution of calcium from the Milk and alternatives food group significantly decreased by 7.5% and 6.1% in calcium supplement users and nonusers, respectively. The prevalence of calcium supplement use significantly decreased from 2004 to 2015 in the Canadian population, from 27.5% to 22.0%. During this time, the percentage contribution of calcium from supplemental sources significantly decreased among Canadians, especially women. The prevalence of calcium inadequacy increased from 58.0% to 68.0% in supplement nonusers; however, among users of calcium supplements, the prevalence of calcium inadequacy remained at ∼31%.Conclusions: Calcium intake from both food and supplemental sources decreased in the Canadian population over an 11-y period, which must be addressed by policy-makers in their efforts to decrease the high prevalence of calcium inadequacy. [ABSTRACT FROM AUTHOR]

Background: Evidence is lacking to determine whether there have been any changes in dietary or total usual intakes of vitamin D among Canadians, in the light of recent evidence of beneficial health effects beyond bone.Objective: We aimed to examine trends in dietary and total usual intake of vitamin D among Canadians aged ≥1 y.Methods: This study used nationally representative nutrition data from the Canadian Community Health Survey Cycle 2.2 (CCHS 2004) and CCHS Nutrition in 2015. Dietary intake data were collected with use of two 24-h dietary recalls and dietary supplement use was determined by questionnaire. The National Cancer Institute method was used to estimate the usual intake of vitamin D as well as the prevalence of vitamin D inadequacy among Canadians aged ≥1 y.Results: From 2004 to 2015, the usual intake of vitamin D from food significantly decreased (P < 0.05) by 1 μg/d only in vitamin D supplement nonusers. The contribution of Milk and Alternatives food group (i.e., fluid milk, fortified soy beverages, powdered milk, and other milk alternatives) to dietary vitamin D intake significantly decreased (P < 0.05) in both supplement users (by 7.1%) and nonusers (by 5.8%). Prevalence of vitamin D supplement use and percentage contribution of vitamin D from supplemental sources significantly increased (P < 0.05) by 5.0% and 14.9%, respectively, from 2004 to 2015. Total usual intake of vitamin D (food + supplement) significantly increased (P < 0.05) from 15.1 ± 0.3 μg/d in 2004 to 31.5 ± 1.8 μg/d in 2015 in vitamin D supplement users. In contrast to vitamin D supplement nonusers, the prevalence of vitamin D inadequacy significantly decreased (P < 0.05) from 20.6% to 14.1% among users of vitamin D supplements.Conclusions: The prevalence of vitamin D supplement use and the percentage contribution of vitamin D from supplemental sources has increased in the Canadian population over an 11-y period. [ABSTRACT FROM AUTHOR]

Previous research indicates that circulating vitamin D levels are low in many otherwise healthy adults and that there is considerable seasonal variation in 25-hydroxyvitamin D 125(OH)D] concentrations at high latitudes. We examined seasonal variation in 25(OH)D levels in a sample of young adults of diverse ancestry living in the Greater Toronto Area. Three hundred and fifty-one 1351) healthy young adults completed both a fall and winter visit during this study. The study was conducted over 2 y )y 1: fall 2007 to winter 2008 andy 2: fall 2008 to winter 2009). At both visits, each participants serum 25(OH)D concentration was measured. Information was also obtained on skin pigmentation (measured via reflectometer), vitamin D intake, and extent of sun exposure. Overall, the serum 25(OH)D concentration was 54.4 ± 1.3 nmol/L in the fall and 38.4 ± 1.1 nmol/L in the winter. Concentrations differed among ancestral groups at both visits (P < 0.001), with South Asians and East Asians having substantially lower concentrations than Europeans. Skin pigmentation 1r2 = 0.14; p < 0.001), supplemental vitamin D intake (r2 = 0.09; P< 0.0011, sun exposure (r2= 0.04; P< 0.001), and study year )r2 = 0.02; P= 0.0171 were predictors of fall 25(OH)D concentrations. During the wintertime, serum 25(OH)D concentrations were associated with concentrations taken in the fall (r2 = 0.45; P < 0.001), supplemental (r2 = 0.15; P < 0.001) and dietary vitamin D intake (r2 = 0.06; P < 0.001), and with study year = 0.02; P = 0.009). Our study confirms that serum 25(OH)D concentrations undergo strong seasonal variation at high latitudes and are influenced by vitamin D intake, skin pigmentation, and sun exposure. [ABSTRACT FROM AUTHOR]

The effect of dietary protein on bone mass measures at different life stages is controversial. We investigated the influence of protein intake on bone mass measures in young adults, considering the influence of calcium intake through adolescence. Subjects were 133 young adults (59 males, 74 females) who were participating in the Saskatchewan Pediatric Bone Mineral Accrual Study (1991-1997, 2003-2006). At adulthood, their mean age was 23 y. We assessed dietary intake via serial 24-h recalls carried out at least once yearly. Total body (TB) bone mineral content (BMC) and TB bone mineral density (BMD) were assessed annually using Dual energy X-ray absorptiometry. We determined TB-BMC net gain from the age of peak height velocity (PHV) to early adulthood. We analyzed data from all subjects and subsets based on sex and calcium intake using multiple regression. TB-BMC significantly increased from age at PHV to early adulthood by 41% in males and 37% in females. Height, weight, physical activity, and sex were significant predictors of TB-BMC, TB-BMC net gain, and TB-BMD among all subjects. Protein intake predicted TB-BMC net gain in all subjects (beta = 0.11; P = 0.015). In females at peri-adolescence or early adulthood with adequate calcium intake (>1000 mg/d), protein intake positively predicted TB-BMC, TB-BMC net gain, and TB-BMD (P < 0.05). Our results indicate that when calcium intake is adequate, protein intake has a beneficial effect on the bone mass of young adult females. Protein, in the absence of sufficient calcium, does not confer as much benefit to bone. [ABSTRACT FROM AUTHOR]

New Zealand children, particularly those of Māori and Pacific ethnicity, may be at risk for low vitamin D status because of low vitamin D intakes, the country's latitude (35-46 degrees S), and skin color. The aim of this study was to determine 25-hydroxyvitamin D concentrations and their determinants in a national sample of New Zealand children aged 5-14 y. The 2002 National Children's Nutrition Survey was designed to survey New Zealand children, including oversampling of Māori and Pacific children to allow ethnic-specific analyses. A 2-stage recruitment process occurred using a random selection of schools, and children within each school. Serum 25-hydroxyvitamin D concentration [mean (99% CI) nmol/L] in Māori children (n = 456) was 43 (38,49), in Pacific (n = 646) 36 (31,42), and in New Zealand European and Others (NZEO) (n = 483) 53 (47,59). Among Māori, Pacific, and NZEO, the prevalence (%, 99% CI) of serum 25-hydroxyvitamin D deficiency (<17.5 nmol/L) was 5 (2,12), 8 (5,14), and 3 (1,7), respectively. The prevalence of insufficiency (<37.5 nmol/L) was 41 (29,53), 59 (42,75), and 25 (15,35), respectively. Multiple regression analysis found that 25-hydroxyvitamin D concentrations were lower in winter than summer [adjusted mean difference (99% CI) nmol/L; 15 (8,22)], lower in girls than boys [5 (1,10)], and lower in obese children than in those of "normal" weight [6 (1,11)]. Relative to NZEO, 25-hydroxyvitamin D concentrations were lower in Māori [9 (3,15)] and Pacific children [16 (10,22)]. Ethnicity and season are major determinants of serum 25-hydroxyvitamin D. There is a high prevalence of vitamin D insufficiency in New Zealand children, which may or may not contribute to increased risk of osteoporosis and other chronic disease. There is a pressing need for more convincing evidence concerning the health risks associated with the low vitamin D status in New Zealand children. [ABSTRACT FROM AUTHOR]