Vitamins are essential micro-nutrients obtained from the diet and environment which are vital in a multitude of processes within the body. These include energy metabolism, oxygen transport, bone health and immune function. Vitamin supplementation is common in athletes, but is it necessary, and is there any evidence that it improves performance?

Many studies taking place during the 1980’s showed that in general, athletes met the recommended daily dose of vitamin intake through their diet, but with increased activity is this recommended dose sufficient?

Vitamins

B Vitamins 

B complex vitamins (B6, B12, riboflavin, thiamine, folate, niacin, pantothenic acid and biotin) have roles in energy metabolism and oxygen transport. Studies have shown with biochemical analysis that up to 40% of athletes may be deficient in B vitamins. In one study, the majority of female college athletes were deficient in vitamins B6, B12 and folate.

B vitamin supplementation in athletes receiving adequate dietary intake with no biochemical deficiency has no beneficial effect on performance.

Supplementation in individuals who are deficient will improve biochemical status. Whether this then causes an improvement in athletic performance is less clear. Studies have shown dramatic decreases in physical performance capacity in subjects consuming a B vitamin deplete diet, with subsequent improvements in performance when an adequate diet was reintroduced. (2)

Elsewhere however, supplementation has been shown to replace deficiencies but with no improvement in performance. (1)

Over supplementation can be detrimental to athletic performance. Niacin supplementation may influence fat metabolism, blocking the release of free fatty acids and increasing reliance on carbohydrate utilization. This may lead to early depletion of muscle glycogen. Some research has indicated that excess niacin supplementation actually impairs aerobic endurance performance. (3)

Vitamin E

Vitamin E acts mainly as an antioxidant. Supplementation has been shown to have some immune-enhancing effects in the frail elderly but no benefit in young, healthy humans. One study showed vitamin E supplementation actually increased upper respiratory tract symptoms (coughs and colds) under high exertion. High doses may be pro-oxidative.

Vitamin C

A Cochrane review, which is the highest form of evidence, demonstrated that regular ingestion of vitamin C had no effect on common cold incidence (how many colds) in the ordinary population. However, regular supplementation had a modest but consistent effect in reducing the duration of common cold symptoms. In five trials with 598 participants exposed to short periods of extreme physical stress (including marathon runners and skiers) vitamin C halved the common cold risk. There was no benefit if supplementation was started after the onset of symptoms. (4)

Vitamin C, similarly to E acts as an antioxidant. The production of reactive oxygen species (ROS) during exercise may actually mediate some beneficial training adaptations. There is widely varying evidence as to whether vitamin C supplementation actually improves or may hinder athletic performance. (5)

Vitamin D

Vitamin D metabolism is complex and requires exposure to sunlight for the conversion to its active form. It has effects on bone and mineral metabolism and immunity.

Deficiency varies widely depending on geographical location and type of sport (outdoor vs indoor). Athletes appear to be at a similar risk of vitamin D deficiency to the normal population. (6)

(7)

Close et al. examined young, UK based athletes (n = 30), and the effects of vitamin D supplementation on muscle performance (1rm bench press, leg press and vertical jump height). Subjects were assigned to a placebo, 20,000 IU/week or 40,000 IU/week of vitamin D for 12 weeks. Muscle performance and vitamin D levels were measured at 6 and 12 weeks, revealing that 6 weeks of supplementation was enough to correct vitamin D deficiency, however, it was not enough to obtain optimal vitamin D levels >40 ng/mL. No significant improvements in muscle performance were observed after 6 or 12 weeks.

A larger (n = 61 athletes, n = 31 healthy control subjects) UK based vitamin D supplementation trial demonstrated a higher mean vitamin D level as a result of 5000 IU/day of vitamin D3 for eight weeks. The supplementation group also displayed significant improvements in 10-meter sprint times and vertical jump (with no improvements in 1-rm bench and squat tests) compared to placebo. (6)

There are no studies available that have examined the effect of vitamin D on aerobic or endurance athletic performance.

Vitamin D deficiency has been associated with increased upper respiratory symptoms. The IAOC recommends 1000 IU/day D3 autumn-spring to maintain sufficiency. (8)

Conclusions

• The best source of vitamins is a balanced and varied diet
• Athletes may require higher intake of vitamins compared to sedentary people, demonstrated by reaching the RDA but still displaying biochemical deficiencies
• Supplementation where no deficiency is present does not improve performance
• Supplementation with B vitamins and vitamin D may have a beneficial effect on athletic performance if a deficiency is present
• Over supplementation, particularly with vitamin E and Niacin may be detrimental to athletic performance
• Vitamin C is effective in prevention and shortening of common cold symptoms when taken regularly, but it’s effect on athletic performance may be unfavourable

References

1. https://www.ncbi.nlm.nih.gov/pubmed/3829589
2. https://www.thieme-connect.com/products/ejournals/pdf/10.1055/s-2008-1025942.pdf
3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2129136/
4. https://www.cochrane.org/CD000980/ARI_vitamin-c-for-preventing-and-treating-the-common-cold
5. https://www.ncbi.nlm.nih.gov/pubmed/22777327
6. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3725481
7. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3725481/table/nutrients-05-01856-t002/?report=objectonly
8. https://bjsm.bmj.com/content/bjsports/52/7/439.full.pdf