Tea lowers iron status in women with low levels

A reader pointed out a paper that will be published in the May issue of Food Research International on tea and iron absorption.

The study tested black tea and green tea (1 liter per day with meals), independently for four weeks each, on both vegetarian and omnivore women. It found:

  • Black tea lowered serum ferritin levels in omnivore women, but not vegetarian women.
  • Both teas lowered serum ferritin levels in both omnivore and vegetarian women who began the study with serum ferritin levels below 20 µg/l.
  • Male vegetarian and omnivore ferritin levels were not affected, but none started with serum ferritin levels below 20 µg/l.

This study supports my suggestion from earlier this month:

“If your iron status is always fine when tested, then I don’t see a need to change your tea drinking habits; but if you have a tendency towards iron deficiency, it’s probably a good idea to avoid drinking tea with meals.”

Reference

Schlesier K, Kühn B, Kiehntopf M, Winnefeld K, Roskos M, Bitsch R, Böhm V. Comparative evaluation of green and black tea consumption on the iron status of omnivorous and vegetarian people. Food Research International. 2012 May;46(2):522-27. | link

2 Responses to “Tea lowers iron status in women with low levels”

  1. LynnCS Says:

    Very very interesting. I have had an iron problem in the recent past and now test ok after treatment, and was a tea drinker. Now am trying to stay away from all the normal coffee and tea products and go for the more “herbal” items. I think I may have found one of the problems. Thanks!

  2. theveganscientist Says:

    It’s mainly the polyphenols (tannins) that chelate to various +2 cations including zinc, Iron, Copper, Calcium, etc… You find this sort of phenomena in many foods. Structurally, phytates, polyphenols, tannins, oxalates, etc… all contain adjacent “-OH groups, which, with the metal ions, form a nice little 6 member ring, the preferred geometry of metallo-organic complexes.

    This leads to some interesting effects like altering the crystal structure of kidney stones making them smaller and rounder, even the eugenol in clove oil binds to Zn+2 to make a sort of paste used as a temporary tooth filling.

    I’ve even read a couple of papers implying phytates may delay bone mineralization decreasing the grain size leading to thinner, but more pliable bones.

    I’m still looking for preferred binding affinities of these ions as it might be able to explain varying results of iron status vs diet.

    For example if Ca+2 >Fe+2 or Mn+2 >> Fe+2 then putting calcium fortified soy milk in your tea/coffee may spare some iron in the former and explain why vegetarians may be spared (somewhat) the effects in the latter.

    I think before indoor plumbing these compounds may have regulated mineral status as we probably at a lot more dirt on our food.

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