During the pandemic there has been a lot to do about healthy living, diets, BMIs and the risk of severe COVID-19. It makes sense that healthy living is, well, healthy. It also makes sense that the healthier you are, you could be more resistant to disease. The latter holds true up to a certain extent.
If your body is in decent shape, it can better manage an insult such as an infectious disease. This works on two levels.
-Excess weight is associated with increased inflammatory conditions, detrimental effects on your cardiovascular system, and therefore more pressure on other systems such as lungs and kidneys. This hampers a robust immune response, which itself puts extra pressure on your system. This may result in heart and lung failure. This does not have to be acute; it can have delayed effects. Furthermore, little exercise and overweight are strongly associated with poor diets.
- If you have a healthy lifestyle, you have some reserves of all the essential nutrients that you will need to combat a pathogen. Make no mistake, an immune response is resource heavy. To mount a response involves many cell types, some of which need to go through rapid cell division multiple times, and the activity of many enzymes. Enzymes function best with the help of small molecules such as metals. Think about your oxygen transport, which requires iron. Similarly, an immune response requires substantial amounts of essential nutrients, from metals to vitamines.
A less healthy lifestyle is a double whammy, you put more strain on your systems and your level of essential nutrients is often lower. This can result in increased disease severity, long-term detrimental effects and less robust defenses. The latter in turn enhances the former.
Like metals, many vitamins play a role in enzymatic reactions. They play the role of catalysts, making the enzymatic reaction much more efficient, or are sometimes even essential to make the reaction go. Vitamins are organic substances present in lesser amounts that we often do not make ourselves but obtain from our environment. Via our diet as well as via the exposure to sunlight. Once in our system, a vitamin may trigger chemical reactions or is often critical in speeding these reactions up. Vitamins themselves do not provide us with energy.
Vitamins have a special place in our minds and derive their name from the fact that they are essential for life. Their insufficiency causes disease.
It makes sense that if you have too few of certain vitamins, this may contribute to the susceptibility to disease, such as from infection. This is logical reasoning. However, two more things should be noted. The vitamins are used in the reactions they catalyze, and thus their levels will reduce with heavy need. Secondly, there are levels of vitamins (and metals, etc.), that are sufficient. More does not mean more benefits, sometimes it even means detrimental effects. Also here, too much of a good thing means an excessive amount that can become overwhelming or harmful, rather than helpful.
A prime example of this misunderstanding of vitamins and their role in physiology was seen during the COVID-19 pandemic. Vitamin D was soon targeted as important, with some data that seemed to back this up. On the basis of this, some argued that vitamin D could be a cure for COVID-19. However, what does the data say?
The data does show that many with severe COVID-19 had reduced vitamin D levels compared with those not suffering from severe COVID-19. You could think this suggests that low vitamin D may predispose for severe COVID-19. But, this is correlation. Drownings happen predominantly when the sale of ice-cream is high. Would stopping the sales of ice-cream prevent drownings?
The answer lays in the use of vitamin D during an immune response. Those suffering with severe COVID-19 have depleted much of their vitamin D stores. The level of vitamin D is not a deterministic variable to get (severe) COVID-19.
But, it could still be argued that supplementing vitamin D when you have COVID-19, may be beneficial. Indeed it could, and to test if that is the case, scientists performed research to address this question. The answer is very clear, no, it does not help to supplement with vitamin D. Here are some large and well-designed clinical trials during the covid-19 pandemic, and commentaries:
As always, there will be some studies, often smaller, that may hint at an effect. Here it is important to understand the size of the study, the confounders that may be introduced in the study, the type of study performed (and the journal it is published it may provide some clues), and the role chance can play. It is important to have extensive knowledge of the subject, the literature and science in general, before drawing conclusions, especially if they go against the consensus.
The conclusions are to, where possible, live a healthy life with exercise and add variety to your diet with fruits and vegetables. This is an important base and can reduce risks and severity of disease. Similarly, some vitamin D supplementation, such as depending on sun exposure, skin pigmentation, age, may be warranted. But, vitamin D will not itself protect you from an infectious disease or its outcome. That is a much more complex matter and interplay between the pathogen and your genes.