VITAMIN D Pandemic

In April 2020, the NHS issued a statement, based on recommendations from Public Health England (PHE), that we should all consider taking 400iU per day of vitamin D as a supplement, to keep our bones and muscles healthy.

Why is vitamin D so important for our health? and why and how, should we follow this recommendation?

What is the function of vitamin D?

Vitamin D has two main functions but a whole host of others: - 

• Calcium and phosphorus. Vitamin D is integral in calcium and phosphorus metabolism, to maintain healthy bones, teeth, and muscles.. Vitamin D facilitates the absorption of calcium and phosphorus from food in the intestines, through the gut wall and into the bloodstream. This is why you need to take in enough vitamin D in your diet. If your vitamin D levels are too low, this reduces the absorption of calcium from the gut, by up to 90%.
• Fighting infection. Vitamin D plays an important role in defending your body against infection. It helps maintain the barrier function of your skin and mucosal surfaces. It also stimulates the cellular immune response and activates the body’s defence mechanisms to destroy bacteria and viruses. It may not be a coincidence that most respiratory infections, including seasonal flu, are much more common in the winter months when days are short and dark, and vitamin D levels tend to be lowered??  

Low levels Of Vitamin D – Health Risks

In recent years, medical evidence has been accumulating which suggests that low levels of vitamin D are associated with increased mortality and poor health. 

There is a recognized association between low vitamin D levels, and cardiovascular disease, cancer, and death. Also, other medical studies have shown a link between vitamin D deficiency, and heart failure, high blood pressure, and diabetes. Vitamin D supplementation was shown to cause a significant reduction in all-cause mortality. All-cause mortality is the death rate from all causes of death for a population in a given time period.

However, symptoms of vitamin D deficiency in adults for example poor bone health and immune deficiencies are ignored in most cases. Patients with vitamin D deficiency have musculoskeletal pains that are often misdiagnosed as fibromyalgia, chronic fatigue syndrome and myositis. One study showed that 93% of the patients who presented common clinical symptoms of non-specific musculoskeletal pain had vitamin D deficiency. Clinically in physiotherapy practice, we have noted that those with stress fractures, bone and muscle pain, nerve related pain that DON’T respond well or at all to physiotherapy compared to similar clinical patterns e.g., same symptoms in other people, all have low vitamin D when referred to their GP for blood tests. 

Research has also shown links with vitamin D deficiency and depression. Statistically, people with low vitamin D were at a much greater risk of depression. Vitamin D receptors have been found in the same areas of the brain associated with depression. If you notice that your mood is low and your motivation levels to run have reduced then it may be worth considering whether your vitamin D levels are low? This is a paradox because if your vitamin D levels are low you are maybe less motivated to get out in the sun to train which means you are then more at risk of feeling more depressed. Read on to find out the strong relationship between vitamin D levels and the sun. 

Vitamin D and Athletes

In relation to athletes, vitamin D deficiency within the global athletic population also follows the same patterns. Different studies present 32% deficiency and up to to 80% insufficiency meaning 32% already deficient and up to 80% borderline. In addition a large analysis that grouped together 23 studies composed of 2313 athletes found that 56% had insufficient levels of vitamin D. 

Vitamin D is important in bone health, but recent research also points out its essential role in “extra skeletal” functions, including skeletal muscle growth, immune responses, cardiovascular and lung functions and inflammation, all of which influence athletic performance.

In relation to vitamin D supplementation in athletes with deficiency, several studies have shown that this increases muscle strength, reduces injury rates and improves sports performance.

• Vitamin D influences muscle growth and particularly in fast-twitch fibers (type II). On the flip side, muscle biopsies of individuals with muscle wasting diseases were highly correlated with vitamin D deficiency and significant improvements were found after supplementation. 
• Research has detected an association between vitamin D and sudden cardiac death in athletes, finding a strong relationship between severe vitamin D deficiency and sudden cardiac death. 
• The deficiency of this vitamin is generally widespread in the athletic population with an increase in morbidities associated with it, and the appearance of osteomalacia and osteoporosis (bone fractures). Vitamin D is essential in bone growth, bone density and bone remodelling. When vitamin D levels decrease below normal limits, the parathyroid hormone increases bone resorption to meet the body’s demands for calcium. This means that low levels of vitamin D lead to an increase in bone turnover with an added risk of bone injury such as stress fractures, which are very common in athletes. In addition when we look at the running research and stress fractures (see articles on bone stress injury for an in depth review) we know that running is very poor at improving bone strength. 
• The insufficiency of vitamin D in athletes is associated with a higher frequency of diseases, including common colds, influenza and gastroenteritis. In athletes, the incidence of respiratory diseases is higher (especially at the elite level), suggesting that low levels of vitamin D may favour the vulnerability of these professionals to upper respiratory tract infections, while individuals with higher levels of vitamin D show a lower propensity to them.
• The amount of vitamin D has shown to be related to how quick skeletal muscle strength is restored after an acute bout of intense exercise. Lower levels showed a slower response, therefore adequate levels of vitamin D are important for recovering quickly from training. 
• A few studies have shown positive links between vitamin D supplementation in run speed, jump height, isometric strength and significant reductions in injury risk compared with control groups of participants that did not receive vitamin D supplementation over 6 and 8 week periods. Other studies however have not found the same effects. 

How Do We Maintain Healthy Levels Of Vitamin D? 

Vitamin D – ‘the sun vitamin’ – also known as cholecalciferol –  is one of 13 ‘essential vitamins’. Essential vitamins are those which are vital for your body to function properly.

There are two forms of vitamin D –

• Vitamin D2 is ingested in your diet. It’s found in oily fish, for example, mackerel, salmon, and herring. Also, in egg yolks, red meat, liver, some fat spreads, and fortified breakfast cereals. Dietary intake of vitamin D2  is especially important because human beings cannot synthesise this in the body.
• Vitamin D3 is produced in your skin when this is exposed to sunlight – UVB radiation. This is important to note. 

To remain in good health, your body needs adequate levels of both vitamin D2 and D3, however, vitamin D2 seems to yield less cholecalciferol than an equal amount of vitamin D3. This is due to the way the liver metabolises (processes and uses) the two sources. It is therefore recommended to supplement with D3 rather than just D2. 

Vitamin D Deficiency – Who Is At Risk?

Vitamin D deficiency affects a staggering 50% of the population. This means more than one billion people are affected around the world. Most of us are unaware of the ‘hypovitaminosis D pandemic.’

But why should this be? There are a number of reasons and this is mainly to do with our exposure to the sun and our concerns over skin cancer. 

Firstly, it is not possible to achieve sufficient levels of vitamin D through diet alone. 

More people now work indoors for longer hours, meaning there is less exposure to sunlight. Vitamin D deficiency is more common in the winter when the days are shorter and darker. In the winter there is very little UVB, and most vitamin D will be coming from the diet (or as now recommended, supplementation). 

Fair-skinned people are recommended to go outside without sunscreen, for 15-20 minutes per day, in spring and summer, to avoid vitamin D deficiency all year. Use of above 30-SPF sunscreens reduces the production of vitamin D in the skin by more than 95%.

The NHS recommendations are: - 

“Most people can make enough vitamin D from being out in the sun daily for short periods with their forearms, hands or lower legs uncovered and without sunscreen from late March or early April to the end of September, especially from 11am to 3pm”

Ask yourself how many times this situation occurs for you??? 

“University of Manchester research shows that, although public awareness of vitamin D is good, behaviour is largely driven by concerns about sunburn and skin cancer. The University’s research shows that a ‘little and often’ approach to sunlight exposure in the UK can provide sufficient vitamin D and avoid vitamin D deficiency”

Other reasons:

• Obesity is known to significantly impair the production of vitamin D3 when the skin is exposed to UVB and we know we have an obesity epidemic in the UK.
• Fat malabsorption syndromes for example coeliac disease, lactose intolerance and cystic fibrosis – result in an inability to absorb vitamin D from the gut. The same problem occurs after bariatric surgery.
• Chronic kidney disease is also associated with vitamin D deficiency as the kidney loses its ability to convert vitamin D to its active form.
• Primary hyperparathyroidism – an overactive parathyroid gland results in an increased breakdown of vitamin D.
• Vegans- as they avoid eggs, meat and fish.

What is an Adequate amount of Vitamin D? 

An adequate blood level of vitamin D is ≥30 ng/ml (75 nmol/L).

However, there may be additional benefits if you have levels between 90 -100 nmol/L (36-40 ng/mL) in particular for athletes. 

How Do I Supplement With Vitamin D And Is It Safe?

Taking vitamin D supplements are safe so long as you stick to the recommended adult dose of 400 IU (10 μg) per day which achieves blood levels of 30ng/ml. This amount is under scrutiny however as many authorities deem this to be far too low. Given that most Vitamin D supplements are in daily doses of between 1000 to 2000IU and the upper limit of safe levels is a maximum of 4000 IU daily, for athletes then it may be sensible to stick to 1000 to 2000IU per day depending on your own general health, and sensible skin exposed sunshine amount. 

There is generally no need to have blood tests if you want to take a vitamin D supplement. However, it is possible if you have specific health concerns,  to see your GP before commencing supplementation. 

 For best results take vitamin D once a day, with a meal, because it is a fat-soluble vitamin. If you take it on an empty stomach it is unlikely to be absorbed.

Side-effects of vitamin D

The most worrying possible side effect from high doses of vitamin D is hypercalcaemia (high blood levels of calcium). However, hypercalcaemia only occurs when blood levels of vitamin D are very high. You are most unlikely to get this if you take extra vitamin D at the recommended dose.

References 

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