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Is Vitamin D deficiency holding you back from making the most out of your training?


Evidence of deficiency- A recent study that I was apart of was compiled from data collected over the last decade (2010-2020) of nutrient intakes from metabolomic testing (in this case urine and blood) and anecdotal reporting from a range of athletes including cross-fitters, bodybuilders, gym goers and power lifters indicated large scale deficiency in multiple micronutrients, one major one being vitamin D.

In my experience and own view is athletes hate nothing more than to be compared with the average population and resent anything that links them to those normal folks, yet the nutrient deficiencies seen in the athlete research echoes the nutritional status in the general public’s 2019 National Diet and Nutrition Survey (NDNS).

So, this maybe the nugget of information to propel your nutritional health to the next level and ensure you’re not one of the ‘average’ populations!

What’s more the reviews only analysed the minimal nutrient guidelines by the Department of Health (UK) and Office of Disease prevention and health Promotions (USA); therefore, this demonstrated that most micronutrients were only being met the bare minimum. This leaves the view that many athletes are in a further deficit, due to the increased demands of their training. Over the coming blogs the main nutrients will be addressed starting with vitamin D.

Vitamin D

There is a wealth of evidence, (both practical, lab based, bro-science and actual science!) suggesting that there is a substantial increased demand for vitamin D for all people but even more so in athletes- yes you!! Vitamin D has had a lot of airtime recently (and rightly so) with over 60 studies released in 2020 with the connection of vitamin D supplementation with enhancing the bodies immunity, and the enhancing recovery from COVID-19.

Whilst vitamin D does not itself directly enhance sports performance, it is key for the essential mediation and signaling of endocrine, cellular and enzymic functions, which in turn increase performance and aid recovery.

Figure 1: Photo by

What is vitamin D?

Vitamin D is the most commonly deficient vitamin across the western world. This little gem is not actually a vitamin at all, but a prohormone- but we will not dwell on the minor intricacies right now. Vitamin D is a fat-soluble vitamin and therefore best to take with salmon, nuts, or your Omega-3 supplement. Vitamin D is responsible for initiating multiple biological pathways to maintain optimal health. These pathways include the reduction of fatigue, hormonal transport (essential for testosterone production), control of blood glucose, reduces the risk of disease, calcium & phosphorus regulations, reduced risk of some cancers, reduces chronic pain, strengthens the immune system, aids nutrient uptake in the intestine, strengthen muscle contraction and reduced incidence of depression. As you can see it’s pretty impressive!!

Sun exposure is the bodies preferred version of vitamin D uptake (who does not love some sun seeking), however due to the lifestyle of many exposure to the sun is often inadequate to meet the daily recommendations, add to it the travel restrictions due to COVID and we are left with old blighties very measly offering of vitamin D.  Thankfully, the sunshine is not the only Vitamin D that the body can uptake; it can also be found in small amounts of food but often not in high enough quantities to meet the body’s needs. Therefore, vitamin D is one of the few vitamins that health professionals actively encourage supplementation.

Figure 2: Photo by NBC News

Naturally occurring vitamin D is mainly found in animal and marine products and even then, it is only found in small quantities. Fortified cereals, spreads and milk alternatives contain the highest quantities of vitamin D.

Table 1; Quantity of vitamin D in common food sources.

Mackerel 25ug
Salmon 13ug
Sardines 4.8ug
Plain yogurt 1.7ug
Tuna 1.7ug
Beef 1.4ug
Egg yolk 1ug
Milk (semi skimmed) 0.025ug

Vitamin D and mineral interaction

Nutrients that support the uptake of vitamin D are calcium, magnesium and phosphorous. Vitamin D regulates the levels of calcium within the body; this is the reason vitamin D and Calcium are essential for bone health, as they work in tandem. Calcium is also essential for muscle contraction, therefore without sufficient vitamin D the muscle can feel weak, unresponsive and result in poor quality workouts.

As a knock-on effect, the levels of Calcium within the body determine the level of phosphorous; the second most abundant mineral of the body. Phosphorus is essential for optimal bone health, required to enable the kidneys to excrete toxins, integral for the formation of DNA, maintaining optimal serum pH for cell, nerve, and muscle function. Those suffering from magnesium deficiency are very likely to be deficient in vitamin D, because magnesium regulates the critical enzymes required for vitamin D uptake.

Vitamin D and immunity

The effect on the immune system is of particular interest to the athlete as the increase strain can often leave the body vulnerable to virus and colds. There is considerable scientific evidence that 1,25-dihydroxyvitamin D has a variety of effects on immune system function, which may enhance innate immunity and inhibit the development of autoimmunity. Vitamin D had been evident in inhibiting cell mutation to reduce the risk of various cancers such as prostate, colon and breast due to vitamin D limiting free radical mutations.

Excess body fat inhibits vitamin D uptake

Maybe not so relevant to athletes or bodybuilders (unless you have veered a bit off track this season) but it must be noted that those who are obese are at higher risk of vitamin D deficiency. This is due to the vitamin D being up taken by and held in the fat stores resulting in it being less bio available.

How much vitamin D?

The UK revised the daily recommended intake to 10ug per day, yet many argue that this is still very low, with condition such as rickets that had been believed to be a condition of the past has become a real health concern within some demographics of the UK and western world. Countries such as USA, Australia and Denmark have revised recommendations to 15-20ug in general populations and 25ug for individuals with visible signs of deficiency.

The ISSN recommends that athletes of all sports consume a minimum of 25ug to 500ug per/day; though there is multiple studies suggesting that those prone to deficiency should supplement up to 1000ug per day; considerably more than that recommended by the UK department of health.

Overdose can potentially occur from prolonged high doses of >10,000iu per day; whilst not impossible it would be very hard to reach that level accidentally. Symptoms of overdose include nausea, vomiting, weakness, hypercalcaemia (high levels of Calcium).

Figure 3: Photo by Bangor University

I would recommend a varied diet with a combination of a decent supplement plan. CNP Pro Vital and Omega +, this will support the nutrient levels of both vitamin D and omega3 (to be covered next!), but also aid vitamin D uptake as Vitamin D is a fat-soluble vitamin and therefore must have fat present to be uptake.

Pro Vital + 380ug
Pro Omega+ 5ug
CNP Multi-Vit 5ug
Test Xtr 2000iu

25ug = 1000iu of Vitamin D

Natalie Rouse.
Nutritional Research Scientist
Bsc(hons), MRes, MSc RNutr