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Comment by thaumasiotes | Hacker News Reader

> About 45% of the US population has Vitamin D deficiency. It's higher among some populations (elderly as they are more likely to be home-bound, African American as darker skin inhibits UV absorption

I believe Vitamin D deficiency is defined by reference to a single level which is assumed to be valid for everyone. In reality, the level at which a deficiency is experienced almost certainly varies both on an individual basis and between racial groups. We say African Americans have higher rates of Vitamin D deficiency, but this is based on the assumption that their average levels of Vitamin D should equal those of European whites, not on an assessment of when they experience problems.

The better measure of Vitamin D deficiency would be "are there signs of rickets?", but somehow that never gets used.

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Of course some believe that Vitamin D is a substance only required to prevent rickets, while others have assigned it all kinds of different roles so they would be unlikely to accept absence of rickets as a standard.

> Of course some believe that Vitamin D is a substance only required to prevent rickets, while others have assigned it all kinds of different roles

The phrasing there is a little weird. Conceptually you wouldn't expect Vitamin D to have the function "preventing rickets", in the same way that the function of Vitamin C is not "preventing scurvy". Vitamin C does several things, and the different failures of those different things manifest as different symptoms of scurvy. Scurvy is what happens when you don't have enough Vitamin C, as rickets is what happens when you don't have enough Vitamin D.

Rickets is one of the things that can happen if you don't have enough Vitamin D. Other less obvious things can happen as well.

Migraines and autoimmune issues are related heavily to Vit D.

> [...] the function of Vitamin C is not "preventing scurvy"

Ironically, its scientific name, "ascorbic acid" means precisely that: no-scurvy (a-scorbic) acid

The thing to keep in mind here is most illnesses deplete the body of Vitamin D during their course.

So you would actually need more data on whether these people were deficient before they got sick with COVID.

Exactly, and they don't get much sunlight while in a hospital

> We say African Americans have higher rates of Vitamin D deficiency, but this is based on the assumption that their average levels of Vitamin D should equal those of European whites, not on an assessment of when they experience problems.

Couldn't you just survey average vitamin D levels in native West African populations, and compare it with African Americans?

Even if there was a difference in the requirements between native Africans and native Europeans, many African Americans also have varying levels of European heritage that would complicate the picture.

Off the top of my head, I'm not familiar with Vit D surveys in West Africa, but there have been some in East Africa. From these, it looks like lifestyle and diet are probably the biggest determinants of Vit D levels. For example, the pastoral Masai have phenomenally high levels of Vit D, while a related tribe of agriculturalists have significantly lower levels, with similar sun exposure. Another survey of young healthy urban participants in Nairobi found similarly low to mid levels of Vit D. Among South Indian rural farm workers, who have complexions comparable to the African subjects and similar levels of sun exposure had much less levels of Vit D. It was speculated that phytates in their diet impacted Vit D levels.

So are you claiming that there is something biologically different about the different races that means their normal biochemistry differs between one another?

> are you claiming that there is something biologically different about the different races that means their normal biochemistry differs between one another?

Yes, genetic variations meaningful to e.g. certain drug responses [1] correlate with race.

Fair question which, if asked without malice, doesn’t deserve a downvote.

[1] https://pubmed.ncbi.nlm.nih.gov/17329986/

Advice about healthy sun exposure to ensure adequate Vitamin D production generally notes that more exposure is required if you have Melanin in your skin (i.e darker skin).

https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-...

"If you have dark skin – for example you have an African, African-Caribbean or south Asian background – you may also not get enough vitamin D from sunlight."

That is already being studied between genders [0] as there are drugs that interact differently between men and women.

Even though the racial aspect of it can be taken a bit to the eugenics side by bad actors I believe that more studies should be performed to assess if there are or not significant physiological differences to account for during medical development.

[0] https://medicine.yale.edu/news-article/11874/

Why wouldn’t there be variation depending on the genes and the phenotype of a population, which can be correlated with skin color? Talking about « races » on the other hand is not neutral.

Population groups, not races.

Skin colour is a poor dividing line between populations, though maybe on this vitamin D issue it might be more reasonable. There is no "black race." There are populations of various African origins, a much more complex and messier situation that the category "race" obscures. There is statistically more genetic diversity _within_ Africa than in the entire human population outside of Africa, so drawing a cline based on some "black" or "African" or "Negroid" basket of traits is fully 19th century quackery.

EDIT Put another way: "race" is a cultural category, with little biological meaning. The key question here is vitamin D responses in southern-adapted vs. northern lattitude adapted population groups.

"Race" is a fairly modern concept that bares little if any association with actual biology.

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