[rfvdbvcvb]

bioavailability of nutrients is a very neglected topic when people discuss nutrition.

Most Dr. I've spoken to aren't even aware that iron from animal sources is far more available than from plants (the consequence being that my wife was able to avoid the iron containing pre-natal vitamin, which causes her nausea, after blood work confirmed her iron levels were great)

[throwaway5752]

A few points

1. heme vs non-heme absorption is different 1. vegetarians and vegans do not have a high incidence of iron-deficiency induced anemia 3. plant base sources of food often have higher iron density that animal sources (tofu vs lean ground beef - it surprises people that tofu has substantially more iron) 4. too much iron can be harmful and the body lacks means of excreting excess: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4839665/

[rfvdbvcvb]

3. " have higher iron density " Actually, it doesn't surprise me in the least. Very many foods contain much more Fe than meat. But density is, largely, irrelevant. Stainless steel is 98% Fe but, if you swallow a small bar of it, you'd poop it right out without absorbing mg of Fe.

What matters is the "effective density" or, for a given gm of food, how many mg of Fe does your body take from it?

4. " too much iron can be harmful"

Indeed. And very many fascinating studies are coming out associating Fe with very many modern ailments (the modern post-industrial age fellow eating meat in excess).

Women do excrete quite a bit of it though and they, and growing kids, need iron.

2. I'm not doubting that vegans can be healthy, but its not universally true. There are people who cannot absorb non animal sourced iron. these people don't stay vegans for very long (they either die, or quit). Either way, those who cannot absorb iron don't stay in in the vegan pool [0].

I'm guessing your link refers to this point. The study is culturally dependent (a study on healthy Chinese men eating real Chinese food).

Also, non-healthy people didn't get recruited to the study (therefore selecting the sample for people who can absorb vegetable iron)

[0] This point is important. Let's say you have a group of people which includes people with weak-ish livers. These people feel sick when their livers are stressed.

Now you do a study on the effects of moderate alcohol consumption vs. total abstinence. The people who feel ill when their livers are stressed are, all else being equal, more likely to be teetotalers.

Well your sample of moderate drinkers now, on the whole, are being drawn from a healthier population. This skews your result.

[throwaway5752]

My understanding is absorption of heme iron is only twice non-heme sources. I think that is why, on the balance, vegans have adequate iron levels. Hemochromatosis seems separate from this subject, but perhaps you can help me here - I don't know if hemochromatis leads to differential heme/non-heme absorption or if it's linear. Point taken on menses, however.

I think I will go back to a prior comment and just say this submission is bad and didn't teach anybody any useful new information. Vegans can be healthy, and kids raised on a vegan diet can be healthy. Non vegans can be healthy.

Bad parents are going to be bad parents and that is the real problem here. It would be nice to treat the root causes of that (poor access to medical care, poor education, poorly curated information online, poor social support networks) that worry about 2ary manifestations of that (people given infants almond milk because they are ignorant of nutrition, people not vaccinating their children).