Herbal Teas Inhibit Iron Absorption

Breaking news from 1999:

Many herbal teas inhibit iron absorption. I hate to hear bad news about people’s good habits, and I particularly don’t like it when it’s from 1999 and I’m just finding out about it now! As I’ve mentioned before, I have been working on an iron article for the Vegetarian Nutrition Practice Group and one of the reviewers pointed me to the study below showing that herbal teas inhibit iron absorption. In the past, I had thought herbal tea did not inhibit iron absorption. Sadly, I was wrong.

The herbal teas tested were camomile, vervain, lime flower, pennyroyal, and peppermint. Cocoa also inhibited iron absorption, as did coffee and black tea. The iron absorption was tested against iron-enriched white bread with only water, and these beverages reduced iron absorption by 50% or more (usually more), with black tea being the worst offender cutting iron absorption by about 80%+.

The good news is that this study pinpoints a benefit of iron-enriched white bread! Who would have thought that white bread could be healthier than herbal tea? Guess it all depends on your perspective.

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.

I have updated the Iron section of VeganHealth.org to reflect this study.

Reference

Hurrell RF, Reddy M, Cook JD. Inhibition of non-haem iron absorption in man by polyphenolic-containing beverages. Br J Nutr. 1999 Apr;81(4):289-95. | link

17 Responses to “Herbal Teas Inhibit Iron Absorption”

  1. Marie H Says:

    Well, I drink tea all day long…pot after pot after pot. I use two tea bags per pot, so probably consume six tea bags worth of tannins and caffeine per day. (my kiddos drink it too.) I am normally either anemic or on the borderline. I have had iron transfusions in the past (by far the fastest way to increase your blood iron levels). Amazingly, currently I am, for the first time in my adult life, NOT near anemia.
    That being said, I have suspected tea to be a culprit. My question is how much time between drinking tea and eating a meal is needed? Half hour? two hours?
    Just found your blog today via the VeganRD (whose blog I just found yesterday.) Sadly, I am not working on my paper due Monday because I’m reading vegan blogs…
    Anyway…thank you in advance.

  2. Jack Norris RD Says:

    Marie,

    I’m not sure how much time you have to wait between drinking tea and eating foods with iron for the tea not to significantly effect the iron absorption. It will probably be on a continuum where 30 minutes is better than nothing and two hours is a lot better than 30 minutes. I would look at it in a relative way – if you’ve normally been drinking herbal tea with every meal, stop doing that and wait perhaps an hour after meals. That should make a difference for you.

  3. rick Says:

    Hi Jack,

    Nice video on Vegan Break,”Vegan Nutrition 101.” I wonder if you misspoke on the iron section there though. “Studies of vegan men show that our iron status is fine, but some vegan women will have a hard time absorbing iron.” My understanding is: (a) vegan males’ and females’ iron absorption is basically the same. (b) animal-based iron (heme) is more easily absorbed than plant-based iron (non-heme). (c) Female vegans are more prone to iron deficiency than male vegans due to regular iron loss via menstruation. (d) Female vegans are more prone to iron deficiency than female non-vegetarians because female non-vegetarians eat heme iron.

    Is there yet another strike against female vegans regarding iron? Do they also have a more difficult time absorbing non-heme iron than male vegans?

    Also, since I think heme iron is not found in a non-vegan vegetarian diet, that the iron concerns are the same with vegetarians as with vegans.

    Would you please let me know if I am on track here?

    Thanks for the great blog!
    Rick

  4. Jack Norris RD Says:

    Rick,

    You are correct that it is a combination of the loss of iron while menstruating and, presumably, low iron absorption, that can be a problem for some vegetarian women, and not that vegetarian women absorb iron less than vegetarian men. I didn’t phrase that very well in the video. I have not seen any studies comparing the iron absorption between vegetarian men and women.

    But now that you brought this up, I suppose it has not be fully determined that the reason some vegetarian women have iron deficiency is because their absorption is low – perhaps their losses are simply greater?

    Yes, iron concerns for lacto-ovo vegetarians appear to be about the same as for vegans.

  5. LynnCS Says:

    Every time I can avoid buying a new expensive product, I appreciate it. I was just getting ready to get some fancy new tea to substitute for the old regular teas and coffees I gave up 6 months ago. Have been wanting something ever since. Going to stick with green smoothies and juices. Every time I think I can ‘get away’ with something, it doesn’t work. I have been terribly anemic in the past. Maybe all that tea and coffee had something to do with it. Thanks for saving my pocket book and saving me from the obsession. Getting over it here.

  6. rick Says:

    Veg*ns probably absorb iron as well as non-veg*ns; that is slightly different than saying plant-based (non-heme) iron is less well absorbed than animal-based (heme) iron. It just so happens that veg*ns don’t eat heme iron.

    Also, I’d be surprised if veg*n females lose more iron than non-veg*n females, because I cannot think of a mechanism that would account for that, but that isn’t saying much. I suppose it is possible that (a) veg*ns start menstruating earlier in life than non-veg*ns, (b) have longer or heavier periods than non-veg*ns, or (c) stop menstruating later in life than non-veg*ns, but I am not aware of any of that to be true. I would anticipate that iron loss is directly proportional to amount of blood loss, and probably not proportional to other factors. This is all little more than conjecture on my part though.

    That said, perhaps it might be reasonable as one method of many to combat anemia in females, to consider using hormones (e.g., birth control pills) that reduce monthly menstruation to quarterly.

    Since non-heme iron is less well absorbed than heme iron, I would anticipate that, even though veg*n males have adequate iron levels, that their iron levels would nevertheless be lower than non-veg*n males. That might be a good thing, because I think that iron levels that are too high might be associated with certain health problems such as heart disease.

  7. Jack Norris RD Says:

    Rick,

    Cross-sectional studies on vegetarian women have shown them to have higher rates of iron deficiency than the population at large, but they did not have higher rates than the omnivore women they were being compared to in those studies. So, in terms of cross-sectional studies, it is not clear that vegetarian women have higher rates of iron deficiency. Prospective studies have not been performed.

    So, our assumption in this discussion, that veg women have higher iron deficiency rates, may not even be true. But if it is, there is an easy explanation as to why veg women would have higher rates – the lack of heme iron in their diets. I was just pointing out that it hasn’t actually been tested to prove beyond a shadow of a doubt that it is all due to a lack of heme iron.

    Given that I have, anecdotally, heard of a number of women becoming anemic after becoming vegetarian, I think it’s a safe bet that veg women have slightly higher rates of iron deficiency anemia than omnivores, and that this can almost entirely be explained by the inability of some to adequately absorb plant iron.

    Part of the problem in absorbing plant iron could be a lack of lysine in the diet. Lysine supplement have been shown to increase iron status in women with a stubborn iron deficiency and since lysine can be low in some vegan diets (that do not contain 2-3 servings of legumes/quinoa per day), it’s possible that this could be a cause. Or, perhaps veg women are more likely to drink herbal tea with meals than non-veg women? It’s possibly a combination of numerous factors across a population.

    Is that enough conjecture for you in one response? I hope so.

  8. Colin Says:

    Why such emphasis on herbal teas if coffee and tea have the same effect? If I hadn’t read closely I would have missed that coffee could be a problem as well.

  9. Jack Norris RD Says:

    Colin,

    Because I’ve been saying that about coffee and non-herbal teas for 10+ years now. But, I shouldn’t have assumed most readers were aware of this.

  10. Wendy Says:

    Dear Mr. Norris:

    I found this article (it is not related to tea inhibitory effect but it points out the novel mechanism for plant ferritin absorption):
    E. C. Theil, H. Chen, C. Miranda, H. Janser, B. Elsenhans, M. T. Nunez, F. Pizarro, K. Schumann. Absorption of Iron from Ferritin Is Independent of Heme Iron and Ferrous Salts in Women and Rat Intestinal Segments. Journal of Nutrition, 2012; DOI: 10.3945/jn.111.145854

  11. Steve W Says:

    Note that the tea in the study was brewed for 10 minutes, and that black tea is bad, water is good and herb teas are somewhere in between.

    See also http://www.citeulike.org/article/9507143 -this suggests it’s not a veggie problem, and that omni’s don’t have better iron levels. The article itself concludes that “only women with low basal ferritin contents (< 25 ug/L) showed reduced levels of ferritin in serum after 2 weeks of drinking 1L of tea per day together with meals". Also, it suggests that green tea doesn't inhibit absorption. Also, (veggie & omni) men's iron levels were unaffected.

  12. Jack Norris RD Says:

    Steve,

    Thanks for pointing out that study! I got a copy of it and reported on it here:

    http://jacknorrisrd.com/?p=2736

  13. Dianne Says:

    I have low iron. I’m not a tea drinker, but sometimes drink green tea after lunch. Even for green tea, what is a suitable time to wait befog I drink it, so that the iron absorption does not get compromised?

  14. Jack Norris RD Says:

    Dianne,

    I’ve never seen research on the subject – I don’t think there is any – so I’d suggest at least an hour in your case.

  15. kamla Beepat Says:

    HI. .. my son thalassemia beta major ..I try to avoid giving him so much iron cause with regular blood transfusion one of the risk is iron overload which is not safe. I’m just abit concerned and would to know if it’s safe to give my son camomile tea to drink to help him sleep

  16. Jack Norris RD Says:

    Kamia,

    You should ask his doctor, this isn’t the place to get recommendations for someone with a serious medical issue.

  17. Adrienne Wright RN Says:

    Rule of thumb (hospital) is: 1 hour before meals/eating. 2 hours after meals/eating for anything that needs to be taken away from food.

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