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Comment by progne | Hacker News Reader

  Immune function analysis displayed significantly lower phagocytosis of monocytes and granulocytes in an older vegetarian population (vs. older nonvegetarians (P < 0.05, P < 0.001). Similar effect of diet was observed as decreased phagocytic activity of granulocytes in younger vegetarians. Regardless of age, respiratory burst of phagocytic cells was also significantly decreased in women vegetarians versus nonvegetarians (P < 0.05, P < 0.001). Older vegetarians revealed significantly suppressed proliferative response of T-lymphocytes to mitogens (P < 0.001).

  In conclusion, our data indicate that a vegetarian diet might have a possible impact on human immune response.

https://journals.lww.com/epidem/fulltext/2007/09001/The_Effe...

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The opposite was also discovered (dairy increases cancer risk): https://pubmed.ncbi.nlm.nih.gov/34788365/

I find these studies to be deeply flawed. It is a multivariate situation and we cannot control/observe more than one variable mostly and still end up mistaking these correlations to be causation.

It could well be that it is not diary or meat but the amount of glucose/fructose one eats which really affects this. We must go back to molecular level proofs rather than these kind of statistical studies where you cannot control everything (apart from mouse models which most people reject for being a mouse model)

From TFA:

  “There are many studies trying to decipher the link between diet and human health, and it’s very difficult to understand the underlying mechanisms because of the wide variety of foods people eat. But if we focus on just the nutrients and metabolites derived from food, we begin to see how they influence physiology and pathology,” said Jing Chen, PhD, the Janet Davison Rowley Distinguished Service Professor of Medicine at UChicago and one of the senior authors of the new study.

> It is a multivariate situation [...] It could well be that it is not diary or meat but the amount of glucose/fructose one eats which really affects this.

Your missing puzzle piece is the fact that we do multivariate adjustment models to adjust for cofounders.

You might as well ask "How do we know whether it's the cigarettes or the fact that people who don't smoke also tend to exercise and eat vegetables? I guess we can never know!"

It is an epistemic error to say "we did something about X, therefore X is not a problem". There are always characteristics of a population that aren't modeled. This is why randomization is considered so important.

Some but not all. In the case of meat, it so happens that a homogenous population of non-smokers in the US, the Seventh-Day Adventists, have a very high proportion of vegetarians…

There might be an impact, but it’s not clear what the impact is. I’m no biologist, but I’d wager your volume of immune cells changes quite a bit over your lifetime. I’d be more interested in seeing the long-term health outcomes of vegetarians vs. non-vegetarians.

This comment is from a completely different paper and is looking at various blood count levels of 174 women. The submitted paper seems more interesting and is investigating TVA in particular as a potential supplement to complement other cancer treatments.

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