Tuesday, May 20, 2014

Tea and iron

I remember that the last time that I was anemic, about ten years ago, I went to a dietician to see what I could do to improve the amount of iron that I absorb from food. The main thing that I remember from our discussion was that I was doing my best to absorb as little iron as possible from my diet.

The primary cause was/is tea. There's something in tea which prevents iron absorption. From that day, I started drinking herbal "tea" which is basically hot water with flavour: no caffeine, no tannins, no EGCG, no nothing. Obviously, drinking this is not going to cause any problems.

About a year ago I started drinking green tea: two teabags a day (I find that one teabag is sufficient for two cups), one in the morning and one in the afternoon. I drink two cups of black tea with milk in the afternoon/early evening. Yesterday, I started taking iron tablets: one at lunch, along with fresh fruit juice; the vitamin C in the juice aids iron absorption.

I was wondering whether green tea would have an affect on the amount of iron absorbed. I found this passageTannins are naturally occurring molecules in tea ... Many of them are found in other “healthy” foods, such as berries, pomegranates, and wine. Dietary iron comes in two forms: heme and non-heme. Heme iron is from meat sources and non-heme iron is from plant sources, such as cereal grains, legumes, and leafy greens. Heme iron is generally unaffected by tannins and is typically absorbed at a rate of 10-30%, depending on the body’s level of need for it at the time. Non-heme iron, on the other hand, IS affected by the tannins in tea and is only absorbed at a rate of only 2-10%. So, if you eat meat and are not diagnosed as anemic, then you will have no problems drinking as much tea as you like before, after, and during meals. However, if you are vegetarian/vegan and/or are diagnosed anemic, then you may want to place some restrictions on your tea drinking. Here’s why:

Tannins chelate non-heme iron. This means that they form an insoluble bond with some of the iron molecules, making it undigestible. The degree of chelation is dose-dependant: the more tea you drink during a meal, the less iron is absorbed. (FYI, calcium also chelates iron, particularly when taken in a large dose as a supplement, and foods such as spinach and soy are thought to chelate iron at a similar rate to tea.) The typical decrease in iron absorption from a meal with a cup (as in measuring cup) of tea in clinical studies is approximately 30-60%. If you’re already low on iron it can make a big difference. This reduction in absorption can be minimized in several ways.

The most commonly suggested means of managing non-heme iron and tea are to drink less tea and to not drink tea with meals. Three to four cups of tea a day is perfectly fine for a healthy vegetarian/vegan or for someone with mild anemia, provided you don’t drink it all during your one iron-rich meal of the day. Drinking tea no less than an hour before and after your meals greatly reduces the inhibition of iron absorption.

Calcium can also act as a friend rather than a foe in iron absorption. By adding a splash of milk to your tea, you can cause the tannins to bind with calcium BEFORE either one can bind with your iron.

From this, I can see two recommendations for my lifestyle: 
  1. Not to drink milk in the hour preceeding lunch
  2. Not to drink green tea for two hours after lunch
(I don't drink milk after lunch for Jewish dietary reasons). Neither of the above will be a problem although I shall have to start carrying herbal teas with me instead of green tea. 

[SO: 3582; 2, 13, 33]

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