The arrival of the pandemic caused by SARS-CoV-2 is the event of a generation. Given the magnitude, the speed and the uncertainty with which everything is happening, it is normal to feel impotence or the need to prepare as well as possible.
In the midst of all these events, there have been several recommendations for “strengthening the immune system”, in order to prepare our body to fight the virus, if we are one of those infected. Most of these recommendations are useless. That is what I come to clarify.
The most effective measures to boost the immune system are inexpensive and affordable.
The most important thing to do is to stop smoking. Tobacco greatly increases the likelihood of respiratory infections, both in adults (1,2,3, 4) and children (1, 2, 3, 4, 5). Not only are they more likely to be infected, but the prognosis is worse for smokers (1, 2, 3, 4).
The arrival of SARS-CoV2 is one more, among hundreds of reasons, to stop smoking.
The practice of regular physical activity seems to help decrease the likelihood of infections and improve the prognosis when we have respiratory infections (1, 2). However, it is not possible to draw more assertive conclusions because the existing evidence is of poor quality (1, 2)
There is doubt in the scientific community whether intense physical activity will not lead to an increased risk of infections. Although the doubt persists, the latest data indicate that, even people who exercise high intensity physical activity, the risk of having infections is lower than in the sedentary population.
Obesity seems to be an important risk factor for the increased risk of infections, both in children (1) and adults (1,2,3,4). Maintaining a good weight is not just a matter of aesthetics, it is a matter of health.
Lack of sleep appears to increase susceptibility to infectious diseases (1, 2), like this like shift work (possibly associated with the disruption of sleep habits). It's needed more research before we can reach more definitive conclusions, but improving sleep habits is an inexpensive measure that has other short and long term benefits.
Most publications on social networks that promote falsehoods tend to advise the consumption of a series of products for "strengthening the immune system". To date, there is no supplement that improves the functioning of the immune system.
Vitamin C. The myth of Vitamin C and its effects in the treatment of flu and constipation is perpetuated since the time of Linus Pauling. There is no evidence that Vitamin C prevents common constipation unless, eventually, in people who do a lot of physical activity. There is a possibility that Vitamin C can reduce the duration of a cold by 8-14%. That is, in a constipation that lasts 7 days, it would last for 6.3 days. There is no evidence that Vitamin C prevents pneumonia, influenza and much less Covid-19. In fact, taking antioxidants in general, such as Vitamin C, E, A, Beta-Carotene and Selenium) seems to be associated with higher overall mortality (1, 2), without any proven benefit, except in very specific circumstances.
D vitamin. Due to a meta-analysis published in 2017, Vitamin D jumped into the spotlight with regard to reducing the risk of respiratory infections with taking this vitamin. The problem is that this meta-analysis, which was supposed to be of high quality, has immense methodological problems. Assuming that the meta-analysis was good, there was only a minimal reduction in the absolute number of infectious diseases and this advantage was only present in people with less than 10 ng / mL of vitamin D in their blood. That is, with very low levels of vitamin D. But the meta-analysis was not good, with unclear methods of inclusion and exclusion of studies for analysis and the inclusion of dubious studies carried out in Iran. When the meta-analysis was limited to studies with large and better quality samples, no positive effect of vitamin D supplementation was found. Therefore, vitamin D supplementation will hardly help.
Chinese herbs. The Chinese Government has taken advantage of the pandemic to, in an incomprehensible way, continue to advertise the uselessness that Traditional Chinese Medicine represents. He did the same in 2003, showing the effectiveness of Traditional Chinese Medicine in the treatment of SARS. It was concluded, ten years later, that the promoted herbs were useless. Currently, we even witness the publication of fraudulent studies in an attempt to validate the usefulness of herbs in the treatment of this infection. Proof that China continues to put its economic interests ahead of scientific truth. And it was also thanks to Chinese greed that SARS-CoV2 appeared.
During the coming times we will see a lot of noise and misinformation about SARS-CoV2 and the disease caused by this virus, Covid-19. Avoiding the sharing of false information and looking for reliable information on institutional websites is also a basic hygiene and life-saving measure.
If someone says they can “boost the immune system” using supplements or other unorthodox measures, check to see if those statements have any factual basis. Assume you don't even have evidence to the contrary.