Calcium effect on iron absorption

[Giraffe]

https://raypeatforum.com/forums/posts/96928/ [The lead skeptic on Peatarian posted a number of studies showing that almost nothing impacts absorption of heme-iron, that which is found in red meat.

Calcium and Iron Interactions
Inhibition of haem-iron absorption in man by calcium
http://journals.cambridge.org/action/di ... 4593000546

The present studies were designed to examine whether Ca interfered with the enhancing effect of meat on haem-Fe absorption. We found that the inhibition was the same whether biosynthetically radio-Fe-labelled haemoglobin was given in meals with or without meat. The haem-Fe absorption ratio with: without added Ca was 0.59 (SE 0.07) when Ca was added to a hamburger meal, and 0.052 (se 0.03) when added to a wheat roll. These values were not significantly different (t 0.95; P = 0.35). The inhibition of haem-Fe absorption by Ca is, thus, a direct effect on the absorption of haem-Fe and not an indirect counteracting effect of the well-known enhancing effect of meat on haem-Fe absorption. Control studies were conducted to ensure that haem-Fe had not been degraded to non-haem-Fe during preparation of the foods. Since Ca inhibits the absorption of haem- and non-haem-Fe to the same extent, the present results strongly suggest that Ca interferes with the transport of Fe through the mucosal cell, and at a late stage, is common for haem and non-haem-Fe transport. The observations that Ca strongly interferes with the absorption of both haem- and non-haem-Fe have important nutritional implications.

Calcium: effect of different amounts on nonheme- and heme-iron absorption in humans.
http://ajcn.nutrition.org/content/53/1/112.short
http://ajcn.nutrition.org/content/53/1/ ... l.pdf+html

Calcium also had a direct dose-related inhibiting effect on iron absorption, noted by adding calcium to the rolls after they had been baked instead of to the dough. Iron absorption was reduced by 50-60% at doses of 300-600 mg Ca. Giving 165 mg Ca as milk, cheese, or calcium chloride reduced absorption by 50-60%. The same amount of calcium also significantly reduced heme-iron absorption, suggesting that the effect of calcium is related to the mucosal transfer of iron.

 

[mujuro]

I'm glad you posted this. Took me a while to find the article. Here it is http://peatarianreviews.blogspot.com.au/2015/02/neither-coffee-milk-or-vitamin-c.html

It would appear that the main contention is regarding coffee and milk, but he does go on to cite two or three articles detailing the failure of high calcium carbonate doses to alter "iron status in healthy adults". As usual, conflicting data between parties. I am trying now to find holes in these studies he has referenced which would explain the disparities.

 

[Giraffe]

I compared two studies:

Hallberg et al (see my post above) = Calcium diminishes iron absorption at low doses.

Doses between 40 and 600 mg Ca were studied. The inhibition was clearly dose related up to 300 rng Ca.

Gaitán et al (the study that was discussed at Peatarian - see link in Mujuro's post)
http://jn.nutrition.org/content/early/2 ... 1.full.pdf

Calcium diminished iron absorption only at high doses, starting at ~ 800 mg calcium.

Differences in Design

The Hallberg study looked at the effect when calcium was added to a meal, while in the Gaitán study the minerals where ingested on empty stomach. The underlying question was: Can both minerals be supplemented together?

Gaitán researched the effect of calcium chloride; Hallberg researched the effect of calcium as milk, cheese and calcium chloride.

Calcium chloride was used because maximum effect was expected, compared to other calcium salts.

 

[Giraffe]

Also see Haidut's recent thread Biomarker for liver iron overload.