Tea and Iron Deficiency: Is there cause for concern?

Tea is known for its health benefits. However, it has a label that has stuck to it for decades: it makes you anaemic, lacking in iron! Does tea make you feel flat rather than help you? What exactly do we know about tea and iron?

Why do we need it so badly for our bodies?

Before 1932, we didn't know the importance of iron for the body! And yet it circulates in your bloodstream all day long. Iron is one of the major components of our hemoglobin, the protein in red blood cells. Iron will bind oxygen molecules, which then allows the red blood cells to carry it to our organs. Moreover, iron is an indispensable element for the activity of certain molecules in the body, particularly those molecules that allow the repair and synthesis of our DNA (Puig et al. 2017 et Abbaspour et al. 2014)

Iron is contained in many high-protein foods such as animal meat, egg white and certain legumes (lentils, spinach, etc.). There are two forms of iron: heme iron (i.e. iron contained in the heart of a ring of organic molecules) and non-heme iron (in free form). The haeminic form is more easily absorbed by our body than the non-haeminic form, so it is recommended that we diversify our sources of iron. (Harvard Nutrition Source)

Our iron is stored in our bodies in the liver, spleen, muscles, bone marrow and bones through ferritin. Transferrin is a protein in the blood that will help transport iron to the intestines, where it is absorbed and redistributed to other organs. This entire absorption mechanism is regulated by a hormone called hepcidin. It prevents too much iron from being absorbed, which could be toxic to the body (Nicolas et Vaulont, 2005)

The balance of iron is based on our diet and the proteins that ensure its storage and absorption by the intestines. If there is not enough iron in the body, it is anemia.

Anaemia, a more common condition than we think...

It is estimated that anaemia affects more than 30% of the population. To assess anemia, a blood test is taken to detect the amount of haemoglobin in the blood, which correlates with the amount of iron in the blood. It is estimated that between 11 g/dL of blood and 18 g/dL of blood is required (variations exist between age and sex). Anemia can be caused by many conditions, but the most common cause is iron deficiency in the diet and menstrual periods. One of the most obvious signs of anaemia is severe fatigue, potentially related to a lack of oxygen transport by red blood cells. Depending on the severity of the anemia, there may be vascular problems, for example. This is not a disease to be taken lightly (Turner et al. 2020)

It's nice of you to give me a course in pathophysiology, but tea in all this?

Of all the studies on tea and iron absorption, the 1975 study by Disler et al. is one of the best known. Briefly, the authors subjected volunteers to an iron-rich diet. These people then drank either water (negative control) or tea. The authors found that the level of iron absorbed was almost divided by four when the people drank tea, without suffering from anaemia.

This property of tea to absorb iron is linked to molecules with a thousand and one virtues:  polyphenols. The polyphenols contained in tea, like catechins, are capable of forming complexes with iron. This prevents the iron from being taken up by the intestines during absorption. This leads to a decrease in the level of iron in the body.

So tea is good ... and bad at the same time?

The answer is not as mixed as one might think. A lot has been read in recent years that tea can lead to anemia. But under what conditions? In a 1995 clinical case (Gabrielli et De Sandre 1995), a young woman had chronic anaemia that worsened from week to week. After investigation of her lifestyle and diet, it appears that the young woman was drinking more than 1.5 litres of tea per day and no longer drank any other source of fluid. While the authors did not look at the amounts of leaves used or the drinking periods, it can be assumed that she was drinking during meals, the period when iron is most exposed and therefore more easily absorbed by tea.

But what about the case where tea is consumed without excess (i.e. no more than 3 cups of tea per day)?

Studies of iron absorption from tea have been conducted mainly in animals and humans. In 2017, Delimont et al.. compiled a number of studies on this topic.

In animals, the results are very contrasted, regardless of whether it is black tea polyphenol extracts or green tea for example. On the other hand, when we look at studies in humans, we can distinguish several interesting facts. Depending on the study carried out (a single meal, follow-up over several weeks, etc.), the results can be different. Indeed, the results seem more contrasted when the studies concern a single meal. In patient follow-ups over several weeks, the majority of studies did not conclude that tea interferes with iron absorption. If we look at the studies that found decreases in iron in the body, they are of the order of 5%. In one of these studies, patients were already anemic, which could indicate a fragility of patients already anemic for tea.

Moreover, depending on the source of polyphenols used (extracts, condensed tannins, etc.) the effects may be different since several studies have even observed an increase in iron absorption. In all the studies compiled, there was no anemia triggered by tea.

This recent compilation of epidemiological studies in humans is consistent with an earlier compilation (2004) conducted in the United Kingdom. In the 35 studies reviewed, Nelson et al. demonstrated that daily tea consumption did not lead to the development of chronic anemia.

How to drink tea to avoid any risk of iron deficiency?

Health professionals recommend that tea consumption should be spaced between meals. A study released in 2017 only confirms these recommendations. Indeed, Fuzi et al. showed that drinking tea one hour after a meal reduced iron absorption by 50%. This can be explained by the fact that iron is quickly absorbed in the intestines. It can therefore be assumed that tea absorbs only part of the iron from the diet.

So don't worry, tea will not make you anaemic! Tea can reduce iron absorption (especially if drunk with meals) but can be dangerous if people already have anaemia or if they have a breeding ground for anaemia. To limit this negative effect of tea, tea consumption and meals should be spaced at least one hour apart.

However, in pathology research, this ability of tea to bind iron appears relevant. For example, in cancer, cancer cells accumulate a number of errors in their genome. Eventually, they can die from them. To do this, they activate numerous mechanisms to repair their DNA to prevent damage and continue to function. However, we saw at the very beginning that iron is important for DNA repair molecules. By depriving cancer cells of iron, they may no longer be able to activate these repair systems and have a better chance of dying. This type of strategy is still very early, but each new atypical strategy is one step closer to a cure.