Drinking strong tea causes severe anemia, what is the truth?

Recently, there was a news report that a 65-year-old man usually pays great attention to maintenance, eats light food, has a regular work and rest schedule, and loves to drink tea and take walks. However, he suddenly fainted recently and was sent to the hospital for examination, which showed that he had severe iron deficiency anemia. After questioning, it was found that the old man loved to drink strong tea. The teacup he carried with him was often half tea and half water, and the amount of tea he drank a day was about 50 grams.

In fact, "insufficient iron intake" is common among the population, but when there are no obvious symptoms, people don't pay attention to it. It is still rare for the elderly man in the news to have iron deficiency.

So can we still drink tea? What should we pay attention to in our daily diet to avoid iron deficiency?

Drinking tea will not cause iron deficiency for most people. Tea is a very healthy beverage. Tea polyphenols, theanine, tea saponins, etc. are all good for health. The benefits of moderate intake of caffeine far outweigh the "possible harm" for health. Of course, in theory, if you drink tea "for a long time and in large quantities", the oxalic acid, polyphenols, caffeine and other ingredients in it may affect the absorption of iron. For example, tea polyphenols can form substances that are difficult to dissolve with iron.

So, whether it is tea or coffee, the health advice is to drink it in moderation.

So, how much is the right amount?

Generally, the caffeine intake is used as an indicator, and it is recommended to "not exceed 400 mg of caffeine per day". The caffeine content of tea is generally in the range of 20-40 mg/g. The dissolution rate of caffeine in boiling water is very high, so when estimating, it can be assumed that all of it is soaked in the tea.

According to this standard, if the old man in the news can really drink 50 grams (one liang) of tea every day, then the caffeine intake is roughly 1,000 to 2,000 mg, which can be said to be "large". In addition, this is his daily habit, which is a typical "long-term large intake", which may indeed affect the absorption of iron.

However, ordinary people do not need to worry about iron deficiency caused by drinking tea. Ordinary tea bags contain 2 to 4 grams of tea. Even if you drink 5 bags a day, and soak each tea bag in two or three cups of water (this amount of water intake exceeds the daily recommended water intake), the total amount of tea is roughly in the range of 10 to 20 grams, which is still not a "large amount". Most people drink less than 10 grams of tea a day, so there is no need to worry about the "large amount" problem.

Avoid iron deficiency and do not pursue a light diet. Iron is an essential trace element for the human body. Iron deficiency can cause anemia, lethargy, fatigue and a series of other symptoms. The human body cannot produce iron and loses some every day, so it needs to be supplemented from the diet.

How much iron the human body needs to take in every day is determined by two factors: "how much iron is lost every day" and "how efficient iron is absorbed from the diet". There is no precise data on how much iron the human body loses every day, but it is generally estimated to be 0.9 to 1.0 mg/day, which is roughly equivalent to 14 micrograms/kg body weight/day.

It should be noted that "0.9-1.0 mg/day" refers to the "iron intake required", not the "iron that should be contained in food". Only part of the iron in food can be absorbed by us, so "the absorption rate of the human body" and "the iron content of food" are equally important considerations.

Iron in food can be divided into two categories: heme iron and non-heme iron. Heme iron is mainly found in meat and animal offal, while non-heme iron is mainly found in plant foods.

The human body has a high absorption rate of heme iron, which can reach 15% to 35%. However, the absorption rate of non-heme iron varies greatly after it is ingested, which is affected by factors such as individual constitution, and the ingredients in the diet that promote and inhibit iron absorption.

Among them, the factors that promote iron absorption are vitamin C (and ascorbic acid derivatives) and meat. In one study, beef, chicken and fish increased the absorption rate of non-heme iron in corn by 2 to 3 times. The main factors that inhibit iron absorption are phytic acid and polyphenol compounds. In addition, calcium and certain proteins (such as milk, eggs and soy) also have a certain degree of inhibitory effect.

In short, the absorption rate of iron varies greatly in different diets. The World Health Organization and the Food and Agriculture Organization of the United Nations believe that people whose diets are rich in meat and vitamin C can absorb 15% of iron, while people whose diets are mainly grains and potatoes and whose meat and vitamin C intake is limited can absorb only 5% of iron.

Many elderly people regard "light diet" and "more vegetables and less meat" as a way to maintain health, thinking that this is to maintain the body. In fact, this diet may affect the absorption of iron and is inconsistent with the true concept of health. As far as iron supplementation is concerned, there must be enough iron in the food and the diet structure must be reasonable to improve the absorption rate of iron and avoid iron deficiency.