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Background: Riboflavin is required to generate the active form of vitamin B-6 (pyridoxal 5'-phosphate; PLP) in tissues, but the relevance of this metabolic interaction for nutritional status of vitamin B-6 is unclear because riboflavin biomarkers are rarely measured in human studies.Objectives: The purpose of this study was to identify the determinants of biomarkers of vitamin B-6 and riboflavin status and to examine the relationship between these nutrients in healthy adults.Methods: Multiple linear regression was performed on observational data in 407 healthy adults aged 18-92 y who did not use B-vitamin supplements. Vitamin B-6 status was assessed by plasma PLP concentrations and erythrocyte glutathione reductase activation coefficient (EGRac) was used as a functional indicator of riboflavin status.Results: Dietary intakes of vitamin B-6 and riboflavin were below the average requirements in 10% and 29% of participants, respectively. Suboptimal status of vitamin B-6 (PLP ≤30.0 nmol/L) was more prevalent in adults aged ≥60 y than in younger participants (i.e., 14% compared with 5%), whereas a high proportion (i.e., overall 37%) of both age groups had deficient riboflavin status (EGRac ≥1.40). In multiple regression analysis, EGRac (P = 0.019) was a significant determinant of plasma PLP, along with dietary vitamin B-6 intake (P = 0.003), age (P < 0.001), BMI (kg/m2) (P = 0.031), and methylenetetrahydrofolate reductase gene (MTHFR) genotype (P < 0.001). Significant determinants of EGRac were dietary riboflavin intake (P < 0.001), age (P < 0.001) and MTHFR genotype (P = 0.020). Plasma PLP showed a stepwise decrease across riboflavin status categories from optimal (EGRac ≤1.26) to low (EGRac 1.27-1.39) to deficient status (P = 0.001), independent of dietary vitamin B-6 intake.Conclusions: The findings are consistent with the known metabolic dependency of vitamin B-6 on riboflavin status and indicate that riboflavin may be the limiting nutrient, particularly in older people, for maintaining adequate vitamin B-6 status. [ABSTRACT FROM AUTHOR]

Background: Cross-sectional studies indicate an age-related decline in vitamin B6 status. Because longitudinal studies are lacking, the present study investigates the long-term association between age and vitamin B6 status in older adults by considering potential confounding factors.Methods: The study population consists of 249 women and 111 men aged ≥ 60 years, who had at least three follow-ups between 1996 and 2014 with complete data records on relevant parameters. Vitamin B6 status was assessed by serum pyridoxal 5'-phosphate (PLP) concentrations measured by high-performance liquid chromatography. Linear mixed models were used to analyze the influence of age, sex, body composition, supplements, diet, lifestyle, and serum creatinine on PLP concentrations.Results: At baseline, 37% of the subjects showed PLP concentrations < 30 nmol/L and more than half failed to meet the recommended dietary intake. Longitudinal analyses revealed that age, use of supplements and protein intake were positive determinants of PLP concentrations, whereas body fat showed a negative impact. No influence of sex, dietary vitamin B6 intake, lifestyle factors or serum creatinine on PLP concentrations was found.Conclusion: The present study provides no evidence that in the course of aging PLP concentrations decline between 60 and 90 years. However, age-related changes in body composition, such as an increased ratio of fat mass to fat-free mass may negatively affect vitamin B6 status. [ABSTRACT FROM AUTHOR]

Background: Considering the suggested link between vitamin D insufficiency and several chronic diseases, attention should be given to approaches for improving vitamin D status. Elderly subjects are regarded as a high-risk group for developing an insufficient vitamin D status. Socioeconomic, dietary, lifestyle and environmental factors are considered as influencing factors, whereupon sex differences in predictors of vitamin D status are rarely investigated. The purpose of this study is to identify the main predictors of serum 25-hydroxyvitamin D3 [25(OH)D3] concentrations in elderly subjects by taking into account potential sex differences. Methods: This is a cross-sectional study in 162 independently living German elderly aged 66 to 96 years. Serum 25(OH)D3 concentrations were assessed by an electrochemiluminescence immunoassay. Multiple regression analyses were performed to identify predictors of 25(OH)D3 concentrations stratified by sex. Results: Median 25(OH)D3 concentration was 64 nmol/L and none of the subjects had 25(OH)D3 concentrations < 25 nmol/L. In women, intact parathyroid hormone (iPTH) (β = -0.323), % total body fat (β = -0.208), time spent outdoors (β = 0.328), month of blood sampling (β = 0.229) and intake of vitamin D supplements (β = 0.172) were the predominant predictors of 25(OH)D3, whereas in men, iPTH (β = -0.254), smoking (β = -0.282), physical activity (β = 0.336) and monthly household net income (β = 0.302) predicted 25 (OH)D3 concentrations. The final regression models accounted for 30% and 32% of the variance in 25(OH)D3 concentrations in women and men, respectively. Conclusion: The findings indicate that 25(OH)D3 concentrations are influenced by body composition, month of blood sampling, economic factors, lifestyle, supplement intake and iPTH, but may not be associated with age, sex, dietary factors, kidney function and presence of selected chronic diseases in community-dwelling elderly. Furthermore, our results provide evidence for sex-specific determinants of the vitamin D status, which ought to be considered for preventive strategies. [ABSTRACT FROM AUTHOR]

Women show higher vitamin C plasma concentrations than men, but the reasons for this observation still require elucidation. The objective of the present study was to investigate whether sex differences in vitamin C plasma concentrations are present in elderly subjects and whether these differences are due to sex-specific lifestyles, total antioxidant status (TAOS) and/or body composition. Fasting plasma concentrations of vitamin C were assessed by photometric detection in a cross-sectional study of 181 women and eighty-nine men aged 62–92 years. Body composition was determined by bioelectrical impedance analysis. Vitamin C intake was assessed with a 3 d estimated dietary record. Stepwise multiple regression analyses were performed to investigate whether sex is an independent predictor of vitamin C plasma concentrations by controlling for age, vitamin C intake, lifestyle factors, TAOS and body composition. Women showed higher vitamin C plasma concentrations than men (76 v. 62 μmol/l, P< 0·0001). In the multiple regression analysis, male sex was a negative predictor of vitamin C plasma concentrations (β = − 0·214), as long as absolute fat-free mass (FFM) was not considered as a confounder. When absolute FFM was included, sex was no longer a predictor of vitamin C plasma concentrations, whereas absolute FFM (β = − 0·216), physical activity level (β = 0·165), intake of vitamin C supplements (β = 0·164), age (β = 0·147) and smoking (β = − 0·125) affected vitamin C plasma concentrations. The results indicate that a higher absolute FFM, and thus a higher distribution volume of vitamin C, contributes to lower vitamin C plasma concentrations in men than women. [ABSTRACT FROM PUBLISHER]

Background: Considering the suggested link between vitamin D insufficiency and several chronic diseases, attention should be given to approaches for improving vitamin D status. Elderly subjects are regarded as a high-risk group for developing an insufficient vitamin D status. Socioeconomic, dietary, lifestyle and environmental factors are considered as influencing factors, whereupon sex differences in predictors of vitamin D status are rarely investigated. The purpose of this study is to identify the main predictors of serum 25-hydroxyvitamin D3 [25(OH)D3] concentrations in elderly subjects by taking into account potential sex differences. Methods: This is a cross-sectional study in 162 independently living German elderly aged 66 to 96 years. Serum 25(OH)D3 concentrations were assessed by an electrochemiluminescence immunoassay. Multiple regression analyses were performed to identify predictors of 25(OH)D3 concentrations stratified by sex. Results: Median 25(OH)D3 concentration was 64 nmol/L and none of the subjects had 25(OH)D3 concentrations < 25 nmol/L. In women, intact parathyroid hormone (iPTH) (β = −0.323), % total body fat (β = −0.208), time spent outdoors (β = 0.328), month of blood sampling (β = 0.229) and intake of vitamin D supplements (β = 0.172) were the predominant predictors of 25(OH)D3, whereas in men, iPTH (β = −0.254), smoking (β = −0.282), physical activity (β = 0.336) and monthly household net income (β = 0.302) predicted 25 (OH)D3 concentrations. The final regression models accounted for 30% and 32% of the variance in 25(OH)D3 concentrations in women and men, respectively. Conclusion: The findings indicate that 25(OH)D3 concentrations are influenced by body composition, month of blood sampling, economic factors, lifestyle, supplement intake and iPTH, but may not be associated with age, sex, dietary factors, kidney function and presence of selected chronic diseases in community-dwelling elderly. Furthermore, our results provide evidence for sex-specific determinants of the vitamin D status, which ought to be considered for preventive strategies. [ABSTRACT FROM AUTHOR]

Background: Emerging evidence indicates that there is an association between vitamin D and obesity. The aim of this study was to investigate whether the level of serum 25-hydroxyvitamin D3 [25(OH)D3] in the elderly is influenced by parameters of anthropometry and body composition independent of potential confounding lifestyle factors and the level of serum intact parathyroid hormone (iPTH). Methods: Cross-sectional data of 131 independently living participants (90 women, 41 men; aged 66-96 years) of the longitudinal study on nutrition and health status in senior citizens of Giessen, Germany were analysed. Concentrations of 25(OH)D3 and iPTH were ascertained by an electrochemiluminescence immunoassay. Body composition was measured by a bioelectrical impedance analysis. We performed univariate and multiple regression analyses to examine the influence of body composition on 25(OH)D3 with adjustments for age, iPTH and lifestyle factors. Results: In univariate regression analyses, 25(OH)D3 was associated with body mass index (BMI), hip circumference and total body fat (TBF) in women, but not in men. Using multiple regression analyses, TBF was shown to be a negative predictor of 25(OH)D3 levels in women even after controlling for age, lifestyle and iPTH (β = -0.247; P = 0.016), whereas the associations between BMI, hip circumference and 25(OH)D3 lost statistical significance after adjusting for iPTH. In men, 25(OH)D3 was not affected by anthropometric or body composition variables. Conclusions: The results indicate that 25(OH)D3 levels are affected by TBF, especially in elderly women, independent of lifestyle factors and iPTH. [ABSTRACT FROM AUTHOR]