This review of vitamin D supplementation in athletes highlights the lack of good evidence for the widespread use of vitamin D in football players and provides guidelines for an individualised approach to supplementation.1
Vitamin D supplementation has become increasingly popular over the past few years, with reported benefits to athletes including improvements in bone and muscle health and a reduced infection risk. The authors of this paper highlight that while large trials have demonstrated the benefits of vitamin D in non-athletic patients, it remains unclear whether there is a measurable difference for many young, trained athletes. They also suggest that there may be some health and performance risks associated with consuming too much vitamin D.
Blanket supplementation with vitamin D has become quite common in some clubs. This review suggests that players are only supplemented if they are deficient in vitamin D levels – as there is no gain in elevating vitamin D above sufficient levels. It also highlights the cost associated with systematic screening of serum 25(OH)D (as a measure of vitamin D status) and that this marker may not give a good correlation with bone and muscle health. Furthermore, there are large variations of vitamin D levels found amongst athletes with dietary, lifestyle, clothing and sunlight exposure all influencing this marker. Skin colour also has a major influence. This variability further limits the value of testing.
As a result of these factors, targeting treatment based on the player’s individual risk for deficiency may be more useful in the ‘real world’. The authors present a decision tree to help guide the most effective use of vitamin D in athletes. They suggest that vitamin D status is tested for players who have sunlight exposure that is limited to < 20 minutes per day (arms and legs) and/or for players who reside < 30°or > 60°north. If the player has low serum 25(OH)D, or if testing is not available, they should be prescribed 2000-4000 IU vitamin D3/day. In all other situations it is unlikely that supplementation is required.
As with other supplements it is very important to consider what impact prescribing vitamin D might have on the athlete and their obligation to the WADA code. Choosing a reputable brand that has been produced as a ‘pharmaceutical’ or has been batch tested is advisable.
1. Owens DJ, Allison R, Close GL. Vitamin D and the Athlete: Current Perspectives and New Challenges. Sports Med (2018) 48 (Suppl 1): S3-S16.