Vitamin D and muscular strength

Vitamin D is known as the ‘sunshine vitamin’ as we depend on sunlight to synthesise 90% of our requirement, the remainder coming from dietary sources, primarily fish. But in the absence of sunshine do we get enough vitamin D to maintain optimal muscle function?

The prevalence of vitamin D insufficiency in UK adults has been estimated at 87% and this has been associated with suboptimal muscle function. Vitamin D is vital for musculoskeletal health and exerts its action on the tissue receptors of skeletal muscle to influence its function and performance. Following oral vitamin D supplementation, several recent studies have shown that vitamin D levels correlate with muscle strength, highlighting the need for individuals to attain and maintain a sufficient concentration that will prevent muscular decline. 

Should you take a vitamin D supplement?

The UK recommended nutrient intake for dietary vitamin D intake is 400IU/day but most of us do not achieve this and when skin absorption is not possible, individuals may require supplementation. Vitamin D status varies widely so it is important to test your status via your GP, particularly during winter.

Symptoms of vitamin D deficiency include tiredness, aches and pains, bone pain, weakness and frequent infections. In the event of being vitamin D deficient this will need to be corrected, and following vitamin D repletion, a maintenance dose may be required.

One study conducted on healthy Irish adults calculated that in those who avoided sunshine, the total vitamin D intake (from all sources) required to maintain a sufficient level of vitamin D during winter was 1,120 IU/d. With a growing evidence base emphasising the significance of vitamin D in human physiology, supplementation is an attractive option to avoid a state of insufficiency. However, individuals should supplement only as directed by a Registered Nutritional Therapist or health professional.