There is a thought-provoking article by Lance Welton at vDare.com, Welton taking the line that there are racial differences in the susceptibility to Covid-19 infection, with East Asian being at risk, Africans and White Europeans less so. In his latest piece he speculates about one hypothesis explaining this, being a genetically based proficiency in maintaining vitamin C levels in the blood:
https://vdare.com/articles/coronavirus-and-vitamin-c-is-this-why-israel-closed-its-borders?scroll_to_paragraph=6
“This has been explored in detail by the health journalist Bill Sardi [Health Inheritance: Asians Have Lower Vitamin C Blood Levels; More Prone To Coronavirus & Other Infections, LewRockwell.com, March 7, 2020].
Maintaining healthy Vitamin C levels is extremely important. Vitamin C is an anti-oxidant, crucial because oxidization results in damage to cells and, so, a reduced ability to fight off infection. It is also crucial in repairing cells and maintaining a strong immune system. Vitamin C is obtained from certain kinds of fruit (most obviously oranges) and some vegetables, such as broccoli. People who don’t get enough of it are prone to cancer, heart problems, brain degeneration and, in extreme cases, scurvy. However, maintaining Vitamin C in the blood isn’t solely a matter of diet. Genetics plays its part as well. Some people can maintain a high level of Vitamin C without eating that much fruit at all. It depends on the form of Haptoglobin which they carry: Hp 1-1, Hp 2-1, or Hp 2-2. Haptoglobin (HAPTO-G) is a protein in the blood that binds to haemoglobin, this being the red protein in blood cells that carries oxygen and iron. Haptoglobin destroys excess iron, limits the amount of (potentially damaging) unbound iron, and reduces the amount of iron lost in the kidneys. Hp 2-2 doesn’t bind as well as the other two. The result of this is excess iron in the blood. This excess iron oxidates—rusts—in response to oxygen, setting off a process that also causes the Vitamin C to oxidate. This reduces the efficacy of the Vitamin C, causing the person with this form of HAPTO-G to have a less effective immune system.