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

Area of Science:

• Nutritional science
• Human physiology
• Epidemiology

Background:

• Low vitamin D status is a prevalent global health issue.
• Muscle weakness, often measured by grip strength, is another significant public health concern.
• The relationship between vitamin D levels and muscle strength remains unclear, necessitating further investigation.

Purpose of the Study:

• To investigate the causal relationship between vitamin D status and muscle strength (grip strength).
• To determine if maintaining adequate vitamin D levels could help prevent or treat muscle weakness.
• To explore potential sex-specific associations and nonlinear effects.

Main Methods:

• Utilized data from 368,890 UK Biobank participants (aged 37-73 years).
• Assessed associations between circulating 25-hydroxyvitamin D [25(OH)D] and maximum grip strength.
• Employed Mendelian randomization (MR) and cross-sectional analyses, allowing for nonlinear relationships.

Main Results:

• Cross-sectional analyses revealed nonlinear associations between 25(OH)D and grip strength in both sexes.
• Higher 25(OH)D levels were associated with stronger grip strength, particularly at lower concentrations.
• Mendelian randomization analyses indicated moderate to small causal links between 25(OH)D and grip strength, with similar patterns observed in males and females.

Conclusions:

• Findings suggest a moderate to small causal effect of circulating 25(OH)D on grip strength.
• The results support the hypothesis that vitamin D status influences muscle strength.
• Further research into vitamin D supplementation for muscle weakness prevention/treatment is warranted.