Vitamin D Supplementation Does Not Impact Resting Metabolic Rate, Body Composition and Strength in Vitamin D Sufficient Physically Active Adults.

Supplementation with the most efficient form of Vitamin D (VitD3) results in improvements in energy metabolism, muscle mass and strength in VitD deficient individuals. Whether similar outcomes occur in VitD sufficient individuals' remains to be elucidated. The aim of this study is to determine the effect of VitD3 supplementation on resting metabolic rate (RMR), body composition and strength in VitD sufficient physically active young adults. Participants completed pre-supplementation testing before being matched for sunlight exposure and randomly allocated in a counterbalanced manner to the VitD3 or placebo group. Following 12 weeks of 50 IU/kg body-mass VitD3 supplementation, participants repeated the pre-supplementation testing. Thirty-one adults completed the study (19 females and 12 males; mean ± standard deviation (SD); age = 26.6 ± 4.9 years; BMI = 24.2 ± 4.1 kg·m2). The VitD group increased serum total 25(OH)D by 30 nmol/L while the placebo group decreased total serum concentration by 21 nmol/L, reaching 123 (51) and 53 (42.2) nmol/L, respectively. There were no significant changes in muscle strength or power, resting metabolic rate and body composition over the 12-week period. Physically active young adults that are VitD sufficient have demonstrated that no additional physiological effects of achieving supraphysiological serum total 25(OH)D concentrations after VitD3 supplementation.

Mechanisms of vitamin D action in skeletal muscle.

Vitamin D receptor expression and associated function have been reported in various muscle models, including C2C12, L6 cell lines and primary human skeletal muscle cells. It is believed that 1,25-hydroxyvitamin D3 (1,25(OH)2D3), the active form of vitamin D, has a direct regulatory role in skeletal muscle function, where it participates in myogenesis, cell proliferation, differentiation, regulation of protein synthesis and mitochondrial metabolism through activation of various cellular signalling cascades, including the mitogen-activated protein kinase pathway(s). It has also been suggested that 1,25(OH)2D3 and its associated receptor have genomic targets, resulting in regulation of gene expression, as well as non-genomic functions that can alter cellular behaviour through binding and modification of targets not directly associated with transcriptional regulation. The molecular mechanisms of vitamin D signalling, however, have not been fully clarified. Vitamin D inadequacy or deficiency is associated with muscle fibre atrophy, increased risk of chronic musculoskeletal pain, sarcopenia and associated falls, and may also decrease RMR. The main purpose of the present review is to describe the molecular role of vitamin D in skeletal muscle tissue function and metabolism, specifically in relation to proliferation, differentiation and protein synthesis processes. In addition, the present review also includes discussion of possible genomic and non-genomic pathways of vitamin D action.

Dietary intake in high-level swimmers. A 32-week prospective cohort study

AIMS: To determine whether high-level swimmers present adequate energy and macronutrient intake during each training phase of the season. METHODS: A 32-week prospective cohort study was conducted with 18 elite swimmers (10 men, 20±2 years; 8 women, 20±3 years) from a competitive swimming club. This period comprised two training macrocycles, each one divided in four training phases: general, mixed, specific and competition. Dietary intake, estimated energy expenditure and daily energy requirements were assessed in every training phase. Body composition was evaluated five times throughout the season. Energy and macronutrient consumption were compared with the energy expenditure and the literature recommendations, respectively. RESULTS: Athletes maintained a relatively constant dietary intake throughout the season, regardless the different needs of each training phase. The balance between energy consumption and expenditure was negative in all training phases (p=0.02; d between 1.5-6.2) for women, while men did so in half of phases (p<0.01; d between 0.3-4.1). Swimmers had higher protein intake than recommendations in 73% of the evaluations, while carbohydrate and lipids intake were lower than recommendations in 76% and 69% of the evaluations, respectively. CONCLUSION: Athletes did not meet the energy demands and specific macronutrient requirements of each training phase of the competitive season.(AU)

Reproducibility and validity of a quantitative FFQ designed for patients with type 2 diabetes mellitus from southern Brazil.

OBJECTIVE: To evaluate the reproducibility and validity of a previously constructed FFQ to assess the usual diet of patients with type 2 diabetes mellitus (T2DM). DESIGN: Cross-sectional survey using two quantitative FFQ (1-month interval) supported by a food photograph portfolio, a 3 d weighed diet record (WDR) and urinary N output measurement (as a biomarker of protein intake). SETTING: Group of Nutrition in Endocrinology, southern Brazil. SUBJECTS: Out-patients with T2DM. RESULTS: From a total of 104 eligible T2DM patients, eighty-eight were included in the evaluation of FFQ reproducibility and seventy-two provided data for the validity study. The intakes estimated from the two FFQ did not differ (P > 0·05) and the correlation coefficients were significant (P < 0·01) for energy and nutrients, ranging from 0·451 (soluble fibre) to 0·936 (PUFA). Regarding the validity evaluation, data from the FFQ were higher than those from the WDR for total (28·3%), soluble (27·4%) and insoluble fibres (29·1%), and SFA (13·5%), MUFA (11·1 %) and total lipids (9·2%; all P < 0·05). There were significant correlation coefficients between the FFQ and WDR for most nutrients, when adjusted for energy intake and de-attenuated. Also, the Bland-Altman plots between the FFQ and WDR for energy and macronutrient intakes showed that the FFQ may be used as alternative method to the WDR. The validity coefficient (using the method of triads) for the FFQ protein intake was 0·522 (95% CI 0·414, 0·597). CONCLUSIONS: This quantitative FFQ was valid and precise to assess the usual diet of patients with T2DM, according to its validity and reproducibility.