Yes, I know “Covid-19” is the name of the disease, not the virus, but it’s easier to say than “SARS-CoV-2”.
Over the past 10 days, I’ve been addicted to the MedCram channel on YouTube, on which Dr. Roger Seheult (internist and pulmonologist, name is pronounced “SHOE-uhlt”) presents clear explanations of interesting research related to Covid-19. One of the most actionable things I have learned from his terrific videos is that there are some science-based things you can do to strengthen your immune defenses against the SARS-CoV-2 virus. In the overall media frenzy, I don’t see a lot of people talking about them, so I’ve decided to compile a list for the benefit of my readers, with some additional tidbits of information and links to scientific sources.
Get at least 7 hours of sleep every night
In one of his videos, Dr. Seheult talks about a study in which a group of subjects was restricted to 4 hours of sleep for 6 nights. On the fourth night, they were given an influenza vaccine (which looks like a virus to the immune system). After the six short nights, they slept normally for 7 nights. Then the researchers measured how many antibodies their bodies had produced. It turned out that the average antibody levels were less than half of those in the control group (which had no sleep restrictions).
This result seems to indicate that if you don’t sleep well, you will have a delayed response to a viral infection. This means that the virus will be able to replicate and spread all over your lungs, liver and other organs, killing your cells by the billion. When that happens, your body will normally turn up your immune response to 11, but by then the damage may be too severe or you can die from the intense immune reaction itself.
Another, larger study cited in the video had patients report their sleep duration for 14 days. Then the researchers attempted to infect them with a rhinovirus, which is one the viruses that cause the common cold, by putting the virus into their noses. The results showed that those subjects who had slept, on average, less than 7 hours a night, were 3 times as likely to develop a cold than those who slept more than 7 hours.
Get enough vitamin D
In this video, Dr. Seheult discusses a large meta-analysis based on multiple randomized controlled trials (ranging from 2 weeks to 12 months in duration). This analysis found that vitamin D3 supplementation reduced the risk of respiratory infection. However, it is important to note that lower doses (< 20μg / day) cut the risk by 20%, intermediate doses (20–50 μg / day) only by 10%, and doses over 50 μg / day had basically no effect.
If you live in the North, at the end of winter your vitamin D levels will likely be at their lowest, so make sure you take vitamin D3 (it’s more efficient than D2) and that you don’t overdo it. The cheapest source of vitamin D3 I’ve found is cod liver oil. I take a teaspoon every other day. Consult the label on the bottle to work out what dosage corresponds to less than 20μg / day.
Get enough zinc
There is some evidence that zinc supplementation can shorten the duration of the common cold. In vitro studies (reported in this video) show that if you put zinc ions inside human cells, that inhibits the replication of RNA viruses, including the SARS coronavirus (a close relative of the 2019 coronavirus).
This doesn’t mean that you should pop zinc tablets like tic-tacs – ingesting more zinc will not necessarily increase the concentration of zinc inside your cells. However, if you are deficient in zinc, your cells will probably also have little zinc in them. So it’s probably a good idea to make sure you are not deficient. I’m currently taking something close to 50% of the recommended daily allowance (8 mg / day for women, 11 mg / day for men). Note that zinc sulfate or chelated zinc are better absorbed than zinc oxide.
Quercetin (long shot)
I’d like to state up front that this one has by far the weakest evidence behind it, but since Dr. Seheult mentioned it, I thought I would include it. Quercetin is a plant polyphenol found in foods such as capers, dill, red onions, kale, and some berries. There is in vitro evidence that quercetin can act as a zinc ionophore, which is a fancy way to say that it brings zinc into cells. Note the “in vitro”: it works in isolated cells in a Petri dish, but nobody has tested what happens to quercetin in a living person’s blood. The liver and kidneys might remove it, or it might not end up in your cells for a thousand reasons. If in vitro results simply translated into in vivo results, we would have cured cancer a thousand times over.
To lend the whole quercetin idea a little more support, I found an additional study, in which mice were given large doses of quercetin and then exposed to the Ebola virus (an RNA virus like SARS-CoV-2). Quercetin dramatically improved the survival of infected mice. However, it can’t be stressed enough that treatments which work in mice very often don’t work in humans. (In the words of Dr Peter Hotez: Mice lie.)
(Paragraph added 20.03.2020) Indeed, in a randomized trial in which subjects received 500 mg or 1000 mg of quercetin per day over 12 weeks, there was no significant improvement in susceptibility to respiratory infections. The only subgroup which showed a statistically significant difference (8.1 vs 5.6 sick days over 12 weeks) was people over 40 who rated themselves as physically fit and received the larger 1000 mg dose. The authors speculate that this is due to the way quercetin is metabolized in the liver. So, quercetin does not look like a miracle supplement, but perhaps worth a try if you are fit and over 40.