The Truth About Vitamin D

Many people believe that taking vitamin D, including Covid-19, will prevent them from a variety of ailments.

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Vitamin D is one of the most popular dietary supplements. It is most commonly used with calcium. Together, they can help to strengthen bone structure and so protect against osteoporosis.

Vitamin D, on the other hand, is involved in the release of hormones and neurotransmitters, and hence in a range of metabolic processes, blood pressure management, nerve and muscle function, and so on.

Low vitamin D levels are linked to an increased risk of disease.
This leads to the conclusion that low vitamin D levels may raise the risk of a variety of diseases. Indeed, numerous large observational studies have found a link, for example, between various cardiovascular illnesses, various types of cancer, diabetes, and depression.

The recent discovery that patients with low vitamin D levels also had more severe Covid-19 symptoms generated quite a stir. So, in pill form, might vitamin D be an all-powerful patron saint?

“Study results almost always disappointing”

Unfortunately it’s not that easy. “A statistical association does not yet prove a causal connection,” explains Dr. Stephan Scharla from the German Society for Endocrinology in conversation with NetDoktor. For this purpose, so-called controlled intervention studies are necessary. Group A receives vitamin D for a longer period of time, group B a placebo. At the end of the study, physicians and participants learn who received what. And then it’s counted.

“The results were almost always disappointing,” reports the doctor. For example, those who had taken vitamin D developed coronary heart disease, heart failure, depression or type 2 diabetes about as often as participants who did not take vitamin D.

The reason for this is that people with low vitamin D levels are frequently unhealthy in general. People who do not walk much, for example, have a higher risk of heart disease and diabetes, and are less likely to be outside in the sun.

“Of course, they have correspondingly low vitamin D levels,” explains a Bad Reichenhall-based resident endocrinologist. Sunlight acts as a catalyst, allowing the vitamin to develop in the skin. The human body manufactures 90% of the vitamin D it requires.

Similarly, elderly folks spend less time outside. “Plus, their skin is already less able to synthesize vitamin D,” the endocrinologist explains. Overweight people, on the other hand, require more of the fat-soluble vitamin in general because more of it is stored in fatty tissue, leaving less available for current metabolism.

Low vitamin D levels are so rarely the cause of health problems, but rather develop in tandem with them.

In this context, studies on men and women with low vitamin D levels due to genetics were especially fascinating. They are no more prone than the general population to suffer cardiovascular disease or diabetes.

The immune system is regulated by vitamin D.
Aside from bone production, vitamin D appears to have a significant impact on another critical health factor: the immune system. “Vitamin D is undeniably an immune system regulator. It affects the function of many immune cells, such as regulatory T cells, as well as cytokine release,” Scharla explains. The latter are inflammatory messenger molecules that cause inflammation.

This could explain why the vitamin is useful for inflammatory disorders, such as rheumatoid arthritis, and could perhaps postpone the formation of type 1 diabetes. According to the endocrinologist, vitamin D probably plays a minor role in the orchestra of different factors, but “for persons who have a predisposition to autoimmune illnesses, it could be worthwhile to compensate for low vitamin D levels.”

Immune modulation could potentially explain the vitamin’s beneficial effect on the course of Covid-19. Because it is often the violent immune response, not the virus, that substantially worsens the course of the disease. “Vitamin D can re-regulate overactive immunological responses,” Scharla explains. However, vitamin D alone will not be enough to stop the epidemic.
With normal vitamin D levels, vitamin pills are useless
However, all of these positive effects only occur in people whose vitamin D levels are actually too low. If you are already sufficiently supplied, an additional gift cannot help you.

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.

“Die Wahrheit Über Vitamin D – NetDoktor.” NetDoktor,, 13 May 2022,



4th Professional Medical Student. Karachi Medical and Dental College.

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