Four months vitamin D supplementation to vitamin D insufficient individuals does not improve muscular strength: A randomized controlled trial

Linear and Nonlinear Associations Between Vitamin D and Grip Strength: A Mendelian Randomization Study in UK Biobank

BACKGROUND

Low vitamin D status is a widespread phenomenon. Similarly, muscle weakness, often indicated by low grip strength, is another public health concern; however, the vitamin D-grip strength relationship is equivocal. It is important to understand whether variation in vitamin D status causally influences muscle strength to elucidate whether supplementation may help prevent/treat muscle weakness.

METHODS

UK Biobank participants, aged 37-73 years, with valid data on Vitamin D status (circulating 25-hydroxyvitamin D [25(OH)D] concentration) and maximum grip strength were included (N = 368,890). We examined sex-specific cross-sectional associations between 25(OH)D and grip strength. Using Mendelian randomization (MR), we estimated the strength of the 25(OH)D-grip strength associations using genetic instruments for 25(OH)D as our exposure. Crucially, because potential effects of vitamin D supplementation on strength could vary by underlying 25(OH)D status, we allowed for nonlinear relationships between 25(OH)D and strength in all analyses.

RESULTS

Mean (SD) of 25(OH)D was 50 (21) nmol/L in males and females. In cross-sectional analyses, there was evidence of nonlinear associations between 25(OH)D and strength, for example, compared to males with 50 nmol/L circulating 25(OH)D, males with 75 nmol/L had 0.36 kg (0.31,0.40) stronger grip; males with 25 nmol/L had 1.01 kg (95% confidence interval [CI]: 0.93, 1.08) weaker grip. In MR analyses, linear and nonlinear models fitted the data similarly well, for example, 25 nmol/L higher circulating 25(OH)D in males was associated with 0.25 kg (-0.05, 0.55) greater grip (regardless of initial 25(OH)D status). Results were similar, albeit weaker, for females.

CONCLUSIONS

Using two different methods to triangulate evidence, our findings suggest moderate to small causal links between circulating 25(OH)D and grip strength.

Vitamin D deficiency associations with metabolic, bone turnover and adverse general health markers in community free living adults

BACKGROUND

Although there is some evidence that vitamin D deficiency is highly prevalent in the Middle East, however its health impact is still not clear. The aim of this study was to assess the prevalence, causes and health implications of vitamin D deficiency in local United Arab Emirates (UAE) citizens.

METHODS

A cross-sectional study was conducted on community free living adults living in the city of Al Ain, UAE. Following informed written consent eligible subject's blood and urine samples were taken for measurements of vitamin D [25(OH)D], metabolic and bone turnover markers. Clinical assessment that includes general and self-rated health, muscle health, and physical activity were also performed.

RESULTS

A total of 648 subjects (491 female) were included in this analysis. Their mean (SD) age was 38 (12) years. Mean 25(OH)D was 24 ng/ml (range: 4-67) with 286 (44%) subjects found to have vitamin D deficiency (< 20 ng/ml), 234 (36%) subjects have insufficiency (20-32 ng/ml) and 128 (20%) subjects have optimal concentrations (> 32 ng/ml). 25(OH)D concentrations were significantly higher in local indigenous UAE subjects compared to other Arab expatriates (p = 0.071). Although there were no statistically significant differences in clinical markers between groups, however, utra-sensitive C-reactive protein (us-CRP), parathyroid hormone (PTH), body mass index (BMI) and the bone markers U-PYD and PYD/CR were higher in vitamin D deficient older subjects aged ≥50 years and female subjects younger than 50 years respectively compared to those with insufficiency or optimal concentrations (p value < 0.05. Multiple logistic regression analysis revealed significant and independent association between 25(OH)D status and age and sex (p < 0.05).

CONCLUSION

Older subjects with vitamin D deficiency have increased BMI, inflammation and PTH compared with those with insufficiency or optimal concentrations. Co-existence of obesity and vitamin D deficiency may have increased adverse health effects.

Vitamin D and Muscle Health: A Systematic Review and Meta-analysis of Randomized Placebo-Controlled Trials

The objective of this study was to investigate the effects of vitamin D supplementation versus placebo on muscle health. For this systematic review and trial-level meta-analysis of placebo-controlled trials, a systematic search of randomized controlled trials published until October 2020 was performed in Medline, Embase, and Google Scholar. We included studies in humans (except athletes) on supplementation with vitamin D2 or D3 versus placebo, regardless of administration form (daily, bolus, and duration) with or without calcium co-supplementation. The predefined endpoints were physical performance reported as timed up and go test (TUG; seconds), chair rising test (seconds), 6-minute walking distance (m), and Short Physical Performance Battery (SPPB; points). Furthermore, endpoints were maximum muscle strength (Newton) measured at handgrip, elbow flexion, elbow extension, knee flexion, and knee extension, as well as muscle (lean tissue) mass (kg). Falls were not included in the analysis. Cochrane Review Manager (version 5.4.1.) calculating mean difference (MD) using a random effect model was used. In total, 54 randomized controlled trials involving 8747 individuals were included. Vitamin D versus placebo was associated with a significantly longer time spent performing the TUG (MD 0.15 [95% confidence interval (CI) 0.03 to 0.26] seconds, N = 19 studies, I²  = 0%, n = 5223 participants) and a significant lower maximum knee flexion strength (MD -3.3 [-6.63 to -0.03] Newton, N = 12 studies, I²  = 0%, n = 765 participants). Total score in the SPPB showed a tendency toward worsening in response to vitamin D compared with placebo (MD -0.18 [-0.37 to 0.01] points, N = 8 studies, I²  = 0%, n = 856 participants). Other measures of muscle health did not show between-group differences. In subgroup analyses, including studies with low vitamin D levels, effects of vitamin D supplementation did not differ from placebo. Available evidence does not support a beneficial effect of vitamin D supplementation on muscle health. Vitamin D may have adverse effects on muscle health, which needs to be considered when recommending vitamin D supplementation. © 2021 American Society for Bone and Mineral Research (ASBMR).

Micronutrients and sarcopenia: current perspectives

Sarcopenia, a skeletal muscle disorder that is characterised by loss of muscle strength and mass, is common in older populations and associated with poorer health outcomes. Although the individual and economic costs of sarcopenia are widely recognised, current understanding of its pathophysiology is incomplete, limiting efforts to translate research evidence into effective preventive and treatment strategies. While nutrition is a key field of sarcopenia research, the role of differences in habitual diets, and the effectiveness of dietary change as a prevention or treatment strategy, is uncertain. There is a growing evidence base that links low micronutrient intakes to sarcopenia risk and/or its components (low muscle strength and mass, impaired physical performance), although there remain many gaps in understanding. There is some consistency in findings across studies highlighting potential roles for antioxidant nutrients, B vitamins and magnesium; however, the evidence is largely observational and from cross-sectional studies, often describing associations with different muscle outcomes. As low intakes of some micronutrients are common in older populations, there is a need for new research, particularly from well-characterised prospective cohorts, to improve the understanding of their role and importance in the aetiology of sarcopenia and to generate the evidence needed to inform dietary guidelines to promote muscle health.

Vitamin D Supplementation and Impact on Skeletal Muscle Function in Cell and Animal Models and an Aging Population: What Do We Know So Far?

Aging is associated with impairment in skeletal muscle mass and contractile function, predisposing to fat mass gain, insulin resistance and diabetes. The impact of Vitamin D (VitD) supplementation on skeletal muscle mass and function in older adults is still controversial. The aim of this review was to summarize data from randomized clinical trials, animal dietary intervention and cell studies in order to clarify current knowledge on the effects of VitD on skeletal muscle as reported for these three types of experiments. A structured research of the literature in Medline via PubMed was conducted and a total of 43 articles were analysed (cells n = 18, animals n = 13 and humans n = 13). The results as described by these key studies demonstrate, overall, at cell and animal levels, that VitD treatments had positive effects on the development of muscle fibres in cells in culture, skeletal muscle force and hypertrophy. Vitamin D supplementation appears to regulate not only lipid and mitochondrial muscle metabolism but also to have a direct effect on glucose metabolism and insulin driven signalling. However, considering the human perspective, results revealed a predominance of null effects of the vitamin on muscle in the ageing population, but experimental design may have influenced the study outcome in humans. Well-designed long duration double-blinded trials, standardised VitD dosing regimen, larger sample sized studies and standardised measurements may be helpful tools to accurately determine results and compare to those observed in cells and animal dietary intervention models.

Population vitamin D supplementation in UK adults: too much of nothing?

Topics for DTB review articles are selected by DTB's editorial board to provide concise overviews of medicines and other treatments to help patients get the best care. Articles include a summary of key points and a brief overview for patients. Articles may also have a series of multiple choice CME questions.

Vitamin D status and supplementation impacts on skeletal muscle function: comparisons between young athletes and older adults

PURPOSE OF REVIEW

The present narrative review analyzes emerging research implicating vitamin D status and supplementation with skeletal muscle homeostasis and functions in two distinct segments of the adult population: young athletes and older adults.

RECENT FINDINGS

Vitamin D deficiency compromises multiple indices of muscle function in young athletes and older adults. A variety of vitamin D3 (cholecalciferol) supplementation regimens may transition young athletes and older adults from deficient or inadequate to adequate vitamin D status. Vitamin D supplementation, used to treat a vitamin D deficiency, but not necessarily an inadequacy, promotes muscle anabolism in older adults. For both young athletes and older adults, vitamin D supplementation, which transitions them from inadequate to adequate vitamin D status, may not beneficially affect measures of muscle strength and power, or physical performance. Also, when vitamin D status is adequate, vitamin D supplementation to further increase serum 25(OH)D concentrations does not seem to confer additional benefits to muscle strength and power and physical performance.

SUMMARY

The impacts of vitamin D status and supplementation on skeletal muscle homeostasis and functions seem comparable in young athletes who strive to maximize physical performance and older adults who seek to attenuate muscle mass and physical performance declines.