The Truth About Vitamin D

Vitamin D deficiency remains a worldwide public health problem, affecting large proportions of the population in developed and the developing countries. Many people hope to protect themselves from various diseases by taking vitamin D – including Covid-19. In fact, countless studies have shown such connections. But things are not that simple.

Vitamin D is a best-selling dietary supplement. It is mainly offered in combination with calcium. Both together can strengthen the bone structure and thus offer protection against osteoporosis.

But vitamin D fulfils far more tasks in the body: it is involved in the release of hormones and neurotransmitters and thus in a wide variety of metabolic processes, blood pressure regulation and nerve and muscle function.

Vitamin D

Low vitamin D levels, high risk of disease

This suggests the reverse conclusion that low vitamin D levels could increase the risk of various diseases. And indeed, countless large observational studies have shown a connection.

In adults, vitamin D deficiency can cause osteomalacia, muscle weakness and increased risk of fracture. Although the strongest evidence for the effect of vitamin D deficiency is related to skeletal disorders, low concentrations of vitamin D are also associated with several non-skeletal disorders including cardiovascular diseases, several types of cancer, neurodegenerative diseases, disorders of glucose metabolism, and a possible role in the recently emerging pandemic of COVID-19.

Recently, the information that people with low vitamin D levels also suffered more severe courses of Covid-19 caused a sensation. So, could vitamin D be an omnipotent patron saint in pill form?

The extreme consequences of vitamin D deficiency, such as rickets in children and osteomalacia in adults, have been almost eliminated in some developed countries through adequate diet, food fortification, and the encouragement of moderate sunlight exposure.

Paradoxically, populations in the Middle East and North Africa (MENA) region have some of the lowest serum 25-hydroxy-vitamin D [25(OH)D] concentrations worldwide, despite the abundance of sunshine throughout the year. Given the remarkably high percentage of working migrants, known as ‘expatriates’, the United Arab Emirates is one of the most culturally diverse countries. Expatriates account for almost 80% of the UAE’s total population. According to the International Osteoporosis Federation, up to 90% of the UAE population suffers from this deficiency. At the International Conference on Vitamin D Deficiency and Human Health held in Abu Dhabi in March, experts said that almost 70-80 per cent of pregnant women in the UAE also suffer from this deficiency.

The real problem is a sedentary lifestyle

Vitamin D has several benefits — from strengthening your bones, muscles and teeth to potentially helping maintain strong immunity. The best part is your body can make its own Vitamin D, naturally synthesised while you soak in the sun! However, in this age of urbanisation and sedentary lifestyles, we may not get the required daily sunlight exposure.

People with low vitamin D levels are usually not in top shape overall. For example, those who move little have a higher risk of heart disease and diabetes – and are often out and about in the sun less often.

“Of course, they also have correspondingly low vitamin D levels,” says the resident endocrinologist with a practice in Bad Reichenhall. Sunlight is required as a catalyst so that the vitamin can form in the skin. The body produces 90 percent of the vitamin D it needs itself.

Likewise, old people are usually less in the fresh air. “In addition, their skin is less able to produce vitamin D anyway,” explains the endocrinologist. Overweight people, on the other hand, need more of the fat-soluble sun vitamin overall, since larger amounts are stored in the fatty tissue, so that less is available for the current metabolism.

A low vitamin D level is therefore usually not the cause of health problems, but develops in parallel.

Studies on men and women who have genetically low vitamin D levels were also illuminating in this context. They are not more likely to develop cardiovascular diseases or diabetes than the rest of the population.

Vitamin D regulates the immune system

Vitamin D has a decisive influence on bone metabolism, but it also plays a major role in other processes in the body – for example in defence reactions of the immune system. For example, the vitamin is important for the work of various immune cells. It has an antimicrobial effect against bacteria, fungi and enveloped viruses such as coronaviruses. In addition, vitamin D inhibits the production of inflammatory messenger substances and increases the production of anti-inflammatory cytokines.

This could explain why the vitamin can have a beneficial effect on autoimmune diseases, among other things: it has a positive effect on the course of rheumatoid arthritis and could possibly delay the onset of type 1 diabetes. In the orchestra of various factors, vitamin D probably plays a subordinate role, says the endocrinologist, but: “For people who have a predisposition to autoimmune diseases, it could be worthwhile to compensate for low levels of vitamin D.”

The positive influence of the vitamin on the course of Covid-19 could also be explained by immune regulation. Because in many cases it is not the virus itself that dramatically worsens the course of the disease, but the violent immune reaction. “Vitamin D can downregulate excessive immune reactions again,” says Scharla. But vitamin D alone will not get the pandemic under control.

With normal vitamin D levels, vitamin pills are useless

If you have a sufficient supply of vitamin D, an additional dose in pill form will not help. In the worst case, it can even be harmful. Because too much vitamin D increases the calcium level in the body.

Taking dietary supplements without a specific deficiency is not a good idea anyway. “We already know that from vitamin E,” reports the endocrinologist. Years ago, large studies had shown that the consumption of appropriate dietary supplements shortens life instead of lengthening it.

Protection mechanism against overdose

Therefore, a lot does not bring much – in fact, it can even be problematic. “An overdose is counterproductive,” explains the doctor. “The body has its own protective mechanism against overdose for many biological systems – this also applies to the vitamin D system.”

In the event of an overdose, the body automatically counteracts it. It downregulates the active form of vitamin D, calcitriol. “Then the likelihood of broken bones increases”. And according to the Robert Koch Institute (RKI), this, in turn, can cause side effects such as abdominal cramps, vomiting or even kidney damage and potentially fatal cardiac arrhythmias. Since vitamin D is stored in the body, in addition to acute overdosing, creeping overdosing through nutritional supplements is possible, warns the RKI.

Do not dose too high!

Anyone who actually needs to compensate for a vitamin D deficiency should therefore take vitamin D every day instead of relying on high doses on individual days. “The daily dose should be 1000, 2000, a maximum of 3000 units, but not more than that,” says Scharla. Exceptions are people whose absorption of the vitamin is disturbed, for example due to chronic inflammatory gastrointestinal diseases.

Struggling for the target value

The goal is not too much and not too little vitamin D. But exactly how high the target value in the blood should be is more difficult to determine than one might think. “The dissent starts with the normal value,” says the doctor. The specialist societies have currently agreed on a value of 50 nmol/l for 25-hydroxyvitamin D – the storage form of vitamin D. Although less is not considered a real deficiency, it is classified as insufficiency.

However, this value reflects the actual individual vitamin supply only insufficiently. Here, too, the human genetic make-up plays a role. For example, it influences the sensitivity of the vitamin D receptors on the body cells. “If they are very sensitive, lower vitamin D levels are sufficient for the supply,” explains Scharla.

Other values ​​provide a more precise picture of the vitamin D balance – for example, the level of the so-called parathyroid hormone, which regulates calcium metabolism, or that of alkaline phosphatase. They show how the metabolic situation actually is. But these values ​​are rarely determined.

And that is only rarely necessary: ​​”In general, healthy adults under the age of 60 with normal lifestyle habits rarely have a biologically relevant vitamin D deficiency,” explains the doctor. Even if the level can be lower at the end of winter, this usually has no physical consequences. In spring, the stores of the fat-soluble vitamin fill up again.

Who is really at risk of shortage?

The actual risk of developing a vitamin D deficiency therefore only exists in healthy people from a certain age, as well as in younger people who, for whatever reason, are unable to spend enough time in the sunlight.

Problems converting vitamin D from food or sunshine can set you up for a deficiency. Factors that increase your risk include:

  • Age 50 or older
  • Dark skin
  • A northern home
  • Overweight, obese, gastric bypass surgery
  • Milk allergy or lactose intolerance
  • Diseases that reduce nutrient absorption in the gut, such as Crohn’s disease or celiac
  • Being institutionalized
  • Taking certain medications such as seizure meds

Using sunscreen can interfere with getting vitamin D, but abandoning sunscreen can significantly increase your risk for skin cancer. So, it’s worth looking for other sources of vitamin D in place of prolonged, unprotected exposure to the sun.


As we find ourselves in the midst of a global health crisis with the coronavirus pandemic, paying closer attention to the natural chemistry of our bodies is more important than ever. There is compelling evidence to suggest that having the optimal levels of Vitamin D can help to ward off and fight infections. It is also clear that the human body is far more complicated than just requiring one panacea type vitamin. Ensuring the correct levels of all vitamins and minerals is also important other things that we can do to ensure our bodies are in the best condition to deal with Covid-19. A good diet combined with regular exercise, albeit very simple are perhaps the best things we can do to support our health and well-being, with the so called “sunshine” vitamin providing that little extra boost that we all need

Unfortunately, the usage of vitamin D is one of the most common problems dealt with in daily practice due to which the Dubai Health Authority introduced protocols to manage its use in primary and secondary care for infants, children and adults. This has further led to a few health insurers to only cover Vitamin D deficiency tests for those suspected of having ailments such as osteoporosis, rickets, kidney disorders or previous history of vitamin D deficiency on their Health Insurance plans.