Leanne Pratt - Does drinking Tea inhibit Iron Absorption?

The effect of tea on iron absorption is something I get asked about a lot, and because the answer is slightly complex, there is a lot of misinformation out there about it.  So let’s find out what the real story is about iron and tea.

Tea contains Tannins
The reason tea gets a bad rap in regards to iron absorption is because it contains a substance called Tannins.  These are naturally occurring molecules in tea and act as astringents to the skin as the tighten tissues.  You can feel the effects of tannins in tea when you drink a strong black tea and get a dry feeling in your mouth.

Tannins are also great applied externally to skin and is the reason why tea bags are used under the eyes to reduce puffiness.

You also find tannins in other substances, commonly bound with tannic acid (which is used to tan hides to make leather).  But although the tannins in tea are in the same class of chemicals as tannic acid, tea does NOT contain ANY tannic acid.   This is an important distinction.

The tannins in tea are different and contain catechins (like EGCG) and other bioflavonoids (molecules that are noted for their antioxidant properties). This class of tannins are responsible for the dark colour and astringent taste in some teas. The same type of tannins are found in other foods such as berries, pomegranates, and wine.

So how do tannins affect iron absorption?
There is a point to all this talk about Tannins.  Because of their astringency and ability to bind to certain nutrients Tannins can affect iron absorption – in some cases! 

It all comes down to the type of iron you are consuming.  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 (from meat) is generally unaffected by tannins.
• Non-heme iron, on the other hand, IS affected by the tannins in tea.

So, if you eat meat and are not diagnosed as anaemic, 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 anaemic, 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.

How to drink tea and still absorb iron (if you are a vegetarian)
• 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 anaemia, 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.

• Vitamin C can help. Some studies have shown a threefold increase in non-heme iron absorption due to an increase in vitamin C intake during a meal. Or a little lemon in your tea goes a long way.

• Adding milk to your tea can also help.  The protein and calcium in the milk can cause the tannins to bind with calcium BEFORE either one can bind with your iron.

• If you prefer green or white teas you will reduce the amount of tannins per cup. Separate studies have stated that green tea reduces iron uptake by about 30% and black tea reduces iron uptake by about 60%, though no major comparative studies in iron absorption have been performed to date.

• A tasty solution is to avoid oversteeping your tea, as oversteeping releases excess tannin (hence the bitter taste of overbrewed tea).

Finally, tea’s reduction of iron absorption may be of use to people with hemochromatosis, a disease that causes the body to stockpile iron.  One study showed using high tannin tea reduced the storage of iron in the system (by about 30%) and, thus, reducing the necessity/frequency of drawing blood as a means of treatment.