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Essential Nutrient: Iron [Discussion]

Our body needs iron to carry oxygen, help enzymes work, and to regulate and maintain itself. Iron exists in two forms in the diet: heme iron, from animal foods such as meat and fish, and non-heme iron, found in plants and widely used in iron supplements.

How well do we absorb iron?

Heme iron is absorbed at about 25-30%, while non-heme iron is absorbed at about 3-5%.

Does anything interfere with our ability to absorb iron?

Heme iron seems to be mostly unaffected by dietary inhibitors. Non-heme iron is inhibited by phytates, polyphenols, calcium, and some forms of protein, but can also be enhanced by ascorbic acid and meat.

Meat Factor

Meat also contains a "meat factor" that enhances non-heme iron absorption from other foods.

Improving absorption of non-heme iron using Vitamin C

Ascorbic acid forms a chelate with insoluble non-heme iron in the low pH of the stomach, which persists and remains soluble in the alkaline environment of the duodenum. This greatly improves absorption.

References:

View original on discuss.online
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xep
discuss.online

I learned about the requirement for ferric iron reduction to ferrous iron by duodenal cytochrome B from the video on DHAA by Coach Stephen that Jet posted.

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jet
hackertalks.com

Meat also contains a “meat factor” that enhances non-heme iron absorption from other foods.

Is this necessarily a net-positive absorption? i.e. could the absorption of other foods be higher by they interfere with the meat absorption itself?

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xepreply
discuss.online

Layrisse and co-workers (6, 7, 8, 9) first reported the meat effect on nonheme iron absorption. They observed that veal muscle, veal liver, and fish increased by 150% the nonheme iron absorption in human subjects consuming meals of black beans and maize. Cook and Monsen (10) confirmed these findings in human absorption studies using semisynthetic liquid meals containing glucose, corn oil, minerals, and a protein component. They demonstrated a 2-fold higher nonheme iron absorption from meals containing beef, pork, chicken, and fish as compared with the same meal containing egg albumin. Bjorn-Rasmussen and Hallberg (11) similarly reported that the addition of chicken, beef, or fish to a maize meal increased nonheme iron absorption 2–3-fold compared with no influence with the same quantity of protein added as egg albumin.

It's quite a significant improvement, but from the references the biggest factor appears to be ascorbic acid:

Enhancers of iron absorption are dominated by the effect of ascorbic acid (vitamin C), which can overcome the effects of all dietary inhibitors when it is included in a diet with high non-heme iron availability (usually a meal heavy in vegetables).

Perhaps if you eat a lot of plants and not much meat it might be a decent idea to eat something containing some ascorbic acid with your meal.

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Essential Nutrient: Iron [Discussion] | Spyke