Can Drinking Tea Hinder Iron Absorption From Food?

Some studies have suggested that drinking coffee, tea, and other caffeinated beverages inhibits iron absorption, but can an herbal tea, such as chamomile, peppermint, or ginger tea, also reduce iron absorption?

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Effects of Tannins and Oxalates

Tannins and oxalates are some of the naturally occurring tea compounds that are said to inhibit the absorption of iron. They bind with iron, specifically non-heme iron found in plant foods such as beans, peas, leafy green vegetables, and nuts. (The other type of iron, heme iron, is found in animal foods such as meat, chicken, and fish.)

Tannins in Black Tea

Tannins found in black tea give it its dark reddish-brown color and characteristic full-bodied, astringent flavor. Tannins have different purposes, from protecting a plant from pests to promoting the growth of the plant.

Although the amount of tannins in black tea varies depending on the variety, growing condition, and processing method, black tea is considered one of the major sources of tannins in the human diet. (Other significant sources include red wine, oak-aged white wine, chocolate, and coffee.)

Other types of tea, including green tea, white tea, and oolong tea, are also made from the same plant as black tea, known as Camellia sinensis. They generally contain different types of tannins.

Factors like steeping time and the degree of fermentation affect the tannin content in tea. Fermented teas such as pu-erh and oolong tea typically contain more tannins than white tea.

Tannins in Herbal Teas

Herbal teas (which are technically tisanes or infusions) can contain tannins. Although more is known about the effect of black tea on iron absorption, some claim that herbal tea, particularly higher-tannin tea, may inhibit iron.

Herbs and spices said to contain tannins include:

Rooibos and honeybush teas are sometimes said to be low in tannins, however, there is little evidence that the tannin content in fermented rooibos or honeybush is less than other teas.

Research

At this point, very few studies have examined the effects of herbal tea on non-heme iron absorption.

One review found that although certain tannins may inhibit iron absorption during one meal, there is little research to say whether tannins affect iron over the long term. More studies are needed to determine these effects.

In an older study published in the British Journal of Nutrition, researchers tested different teas and cocoa and found that they inhibited iron absorption. The study found iron absorption Inhibition rates varied by the type:

  • Black tea: 79 to 94%
  • Peppermint tea: 84%
  • Pennyroyal tea: 73%
  • Cocoa: 71%
  • Vervain tea: 59%
  • Lime flower tea: 52%
  • Chamomile tea: 47%

Adding milk had little or no influence on iron absorption.

In a 2007 study published in the European Journal of Clinical Nutrition, researchers determined the iron levels in 954 healthy adults and also estimated their tea intake. They found that iron levels were not related to black, green, and herbal tea consumption, nor to type or strength of tea, infusion time, or time of tea drinking.

However, a study published in the American Journal of Clinical Nutrition in 2017 found that tea consumed with a meal decreased non-heme iron absorption, but that tea consumption one hour after a meal didn't decrease iron absorption to the same extent.

There is very little conclusive research to say how tannins in herbal teas affect iron absorption.

What Should You Do?

If you have followed a vegetarian or vegan diet, have been told to reduce the tannins in your diet, or if you have iron-deficiency anemia, consult your healthcare provider about food and beverages that would be suitable for you.

Avoid over-steeping tea to reduce the number of tannins and oxalates in tea. Vitamin C improves the absorption of non-heme iron.

Keep in mind that too much iron in the body can cause problems. If you regularly drink tea and are concerned about whether you're absorbing the iron, talk with your healthcare provider before upping your intake of iron (particularly from supplements).

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