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Population level data on how older individuals living at high latitudes achieve optimal vitamin D status are not fully explored. Our objective was to examine the intake of vitamin D among healthy older individuals with 25-hydroxyvitamin D [25(OH)D] concentrations > or =75 nmol/L and to describe current sources of dietary vitamin D. We conducted a population-based, cross-sectional study of 404 healthy men and women aged 69 to 83 y randomly selected from the NuAge longitudinal study in Québec, Canada. Dietary intakes were assessed by 6 24-h recalls. We examined the contribution of foods and vitamin/mineral supplements to vitamin D intake. Serum 25(OH)D was assessed by RIA. We assessed smoking status, season of 25(OH)D measurement, physical activity, and anthropometric and sociodemographic variables. Vitamin D status was distributed as follows: 7% (<37.5 nmol/L), 48% (37.5-74.9 nmol/L), and 45% (> or = 75 nmol/L). Vitamin D intake from supplements varied across the 3 vitamin D status groups: 0.5, 4.1, and 8.9 microg/d, respectively (P < 0.0001). Adding food sources, these total intakes were 4.6, 8.7, and 14.1 microg/d, respectively. In multivariate analysis, vitamin D from foods and supplements and by season was associated with vitamin D status. These healthy, community-dwelling older men and women with 25(OH)D concentrations >75 nmol/L had mean intakes of 14.1 microg/d from food and supplements. Supplement use is an important contributor to achieve a minimal target of 25(OH)D concentration > or = 75 nmol/L. [ABSTRACT FROM AUTHOR]

Day-to-day variability in dietary intake makes it difficult to measure accurately the "usual" intake of foods and nutrients. The objectives of the present study were to estimate within- and between-subject variability for foods and nutrients by adjusted and unadjusted models and to assess the number of days required to assess nutrient and food group intakes accurately by two different methods. Adult men and women aged 18-65 y (n = 1543) in the Food Habits of Canadians Study provided a 24-h recall. A repeat interview was conducted in a subsample to estimate components of variability. Within- and between-subject variability were determined by mixed model procedure (crude and adjusted for age, gender, education, smoking, family size and season). The number of days required to obtain various degrees of accuracy was ascertained by two methods, one that uses the variance ratio for groups and one that considers within-subject variability alone for individuals. Variance ratios were higher using the adjusted compared with the unadjusted method (e.g., for men, energy 1.07 vs. 0.49). More days were required to reflect usual intake with accuracy using the adjusted model (energy 5 vs. 2 d), indicating the need to control for confounders to obtain reliable estimates of intakes. [ABSTRACT FROM AUTHOR]

Discusses implications of daily variability on measurements of usual food and nutrient intakes. Assessment of the number of days required to assess nutrient and food group intakes; Study subjects and methods; Need to control for confounders to obtain reliable estimates of intakes.

Background: Endogenous reactive oxygen species appear to contribute to aging and cancer and dietary antioxidants, present in fruit and vegetables, counteract these effects. Objective: The objective was to examine the association between intracellular glutathione, ascorbate (vitamin C), and alpa-tocopherol (vitamin E) in human lymphocytes. Design: The study group consisted of 240 healthy nonsmoking volunteers with an approximately equal number of male and female subjects subdivided into 3 age groups: 18-39, 40-59, and >/=60 y). Glutathione, glutathione disulfide, ascorbate, and alpha-tocopherol were measured in lymphocytes by HPLC. Results: The average concentration of antioxidants in lymphocytes was 27 +/- 8 nmol/mg protein for glutathione, 21 +/- 8 nmol/mg protein for ascorbate, and 0.4 +/- 0.2 nmol/mg protein for alpha-tocopherol. There was a strong positive correlation between glutathione and ascorbate (r = 0.62, P < 0.001). No correlation was observed for glutathione and ascorbate with alpha-tocopherol. The concentration of glutathione in lymphocytes was inversely correlated with age (r = -0.19, P < 0.01), as was that of ascorbate (r = -0.22, P < 0.01), with 10-20% lower values in elderly than in young and elderly subjects. The concentrations of glutathione in lymphocytes were as much as 25% higher and those of ascorbate were as much as 38% higher during the summer than during the winter. The seasonal variation of ascorbate in lymphocytes was described by a linear function for age and a periodic sine function for season. Conclusion: Glutathione and ascorbate are directly correlated in human lymphocytes. Copyright © 2000 American Society for Clinical Nutrition [ABSTRACT FROM AUTHOR]