Vitamin D – How Much Should I Take

Posted 13th November 2015 by Professor Graeme Close, Researcher at Liverpool John Moores University & Leading Sports Nutritionist

Vitamin D is one of the most important nutrients anyone should have an abundance of, mainly due to the vast amount of health benefits it can provide such as improving muscle function, bone health, immune health and cardiovascular function. The sporting community have become increasingly interested in vitamin D with many athletes now advised to include a daily vitamin D supplement into their diets. The reason for this increased interest is because of the number of key findings that has considerably advanced the field.

Vitamin D Deficiency

There is a growing amount of evidence, including a study I published in 2012 (Close et al., 2012), to suggest that many athletes are vitamin D deficient, especially during the winter months. Other reports around the world have shown similar results, suggesting that vitamin D deficiency and insufficiency is widespread among athletic communities. Although the consequences of such deficiencies are still unclear, impaired muscle function and reduced regenerative capacity, impaired immune function, poor bone health and impaired cardiovascular function have all been associated with vitamin D deficient athletes. All these factors can have a detrimental impact on performance, so making sure you have a daily source of vitamin D is essential.

Sources of Vitamin D

Vitamin D synthesis, the process which vitamin D goes through for it to be effective within the body, is activated through the reaction with the skins’ dermis and ultraviolet B radiation forming vitamin D3. Skin pigmentation can have an impact on the effectiveness of vitamin D synthesis as melanin competes with this process for UVB radiation. This means that those with darker skin require exposure for longer or to a stronger source of UVB radiation to reach the same levels as those with lighter skin.

An alternative route to obtaining vitamin D is through the diet. Foods that provide vitamin D include oily fish, eggs, fortified breakfast cereals, mushrooms and powdered milk, however large scale investigations identified that less than 2% of individuals meet the recommended daily allowance from foods. In addition, unlike vitamin D synthesis that solely produces vitamin D3, dietary intakes provide both vitamin D2 and vitamin D3. There is a huge difference in effectiveness between these two sources, quite simply vitamin D3 is 87% more potent in overcoming a deficiency and is the body’s naturally preferred form.

Vitamin D Supplements

Supplementation is an incredibly effective way of providing the necessary levels of vitamin D, however similarly to foods, supplements can come in the vitamin D2 or vitamin D3 form, so it is important to make sure to choose a supplement that contains vitamin D3. There is a lot of debate between governing bodies and authors, however in a previous study I have shown that 5000 IU per day over an 8 week period can overcome a deficiency and maintain sufficient levels of vitamin D (Close and Russell, et al., 2013). However, it is vitally important to remember that vitamin D synthesis via UVB exposure still occurs. The US Institute of Medicine have set the tolerable upper intake at 4000 IU, the same as the guidance set by the European Food Safety Authority, so it is recommended that you choose a supplement with a maximum dose of 4000 IU per day and do not exceed this recommended dose until further evidence and studies have been carried out, and where possible seek advice from a SENr practitioner.

Vitamin D and the Athlete

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