People with poor digestive function cannot eat black fungus? How many of these rumors about black fungus do you believe?

During the Spring Festival, sumptuous family dinners are indispensable, and wood ear mushrooms, as a versatile and delicious ingredient, often appear in New Year’s Eve dinners and festive dishes.

However, various rumors about black fungus frequently appear during festivals, such as "people with poor digestive function cannot eat black fungus" and "black fungus can clear and moisten the lungs". These statements seem to make sense, but what is the truth?

Today, we will uncover the truth behind these rumors about fungus, so that everyone can eat scientifically and safely while enjoying holiday delicacies!

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1. People with poor digestive function

Can’t eat fungus?

The saying that "people with poor digestive function cannot eat black fungus" is actually a misunderstanding. Black fungus is a healthy food rich in dietary fiber. Eating it in moderation will not only not increase the burden of digestion, but may help improve digestion. The dietary fiber content of dried black fungus does seem to be very high, at 29.9 grams per 100 grams, but we do not eat dried black fungus directly. We must soak it before we eat it. The dietary fiber content of soaked black fungus per 100 grams will drop significantly , to only 2.6 grams per 100 grams, which is similar to that of celery leaves, chestnut pumpkin, sweet potato leaves, etc., and is not particularly high among vegetables.

As long as it is handled correctly and consumed in moderation, even people with poor digestive function can cook and eat water-soaked black fungus as ordinary vegetables . The key is to chew it carefully and grind the food into smaller particles so that it can better contact with the digestive juice, which can reduce the burden on the stomach and intestines, so you can eat black fungus with confidence.

2. Can eating fungus clear and moisten the lungs?

When the air is seriously polluted or there is haze, you will often see some articles recommending eating black fungus to clear the lungs. The reason is: black fungus can clear and moisten the lungs and improve respiratory health.

"Eating black fungus can clear and moisten the lungs" is a widely circulated saying, especially among people who pay attention to health preservation. However, from a scientific point of view, this saying is not true. Although black fungus is a nutritious and healthy food, it has no direct relationship with "clearing and moisturizing the lungs".

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In nutrition, there is no so-called "lung-clearing food" . First of all, the lungs are the organs responsible for gas exchange, and food is ingested through the digestive system and cannot directly affect the lungs. Therefore, "lung-clearing" is more of a figurative description rather than an actual physiological process. The main components of fungus are dietary fiber and plant polysaccharides, which are helpful in promoting intestinal peristalsis and improving metabolism, but they do not directly affect lung function through the blood or other pathways.

Secondly, "moistening the lungs" usually refers to relieving throat and airway discomfort caused by dryness or inflammation, such as coughing or dry throat. Foods containing more water and pectin (such as pears, loquats, etc.) do have a certain relieving effect, but fungus does not have such properties. Although fungus is rich in colloids, the effects of these substances are mainly concentrated in the intestines, not the respiratory system.

In addition, some people believe that fungus has an "adsorption effect" and can absorb pollutants such as PM2.5 that enter the human body and excrete them out of the body, but this statement is not scientific. The adsorption effect of fungus is mainly reflected in its rich dietary fiber and plant polysaccharides, which can help clean up intestinal waste and promote digestive system metabolism. However, this "adsorption" is limited to the digestive system and has nothing to do with the lungs. After PM2.5 and other pollutants enter the human body, they mainly enter the lungs through the respiratory system and cannot be "absorbed" and excreted through food.

Therefore, don’t expect that eating black fungus can clear your lungs. When it is foggy or in a dusty environment, the key is to wear a mask and take good protection.

3. Can eating black fungus supplement iron?

"Eating black fungus can supplement iron" is a common saying. Many people believe that black fungus is rich in iron and is a natural iron supplement. However, from a nutritional point of view, this statement is not entirely accurate. The iron content of dried black fungus seems to be very high, 97.4 mg/100 g, but we usually soak the dried black fungus before eating it. The weight of the black fungus increases several times after soaking, and its unit iron content will be greatly diluted, so the amount of iron obtained by eating black fungus is not much. Under normal circumstances, 5 grams of dried black fungus is enough to make a meal for one person, and the iron content is about 4.8 mg.

In addition, the iron in black fungus is non-heme iron, and its absorption rate is relatively poor, only 2% to 20%, usually less than 5%. Expecting to eat black fungus to replenish iron and blood is actually not very effective.

Although wood ear is a healthy food, rich in dietary fiber and plant polysaccharides, which are beneficial to intestinal health, its effect as a source of iron supplement is limited. In contrast, animal liver, animal blood, lean meat, and razor clams are not only high in iron content, but also contain heme iron, which has a better iron supplement effect.

4. Is dried black fungus more nutritious?

Many people believe that dried black fungus has higher nutritional value and is more beneficial to health than soaked black fungus. This statement is not entirely correct.

Most of the dried black fungus on the market are obtained by processing fresh black fungus through sun drying, hot air drying, microwave drying, etc. The drying process has little effect on most of the nutrients in the black fungus , including polysaccharides, proteins, minerals, etc. Although many nutrients are concentrated, a lot of water-soluble vitamins are lost.

Therefore, in terms of nutrition, the nutritional difference between dried fungus and fresh fungus after being soaked in water is not much , so there is no need to worry about it.

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However, if safety is considered, dried black fungus is more recommended. Fresh black fungus contains porphyrin-like photosensitive substances, which have almost no effect on healthy people and can be eaten with confidence, but it is not very friendly to people with abnormal porphyrin metabolism. They may cause allergies and induce solar dermatitis, with symptoms such as skin itching, redness and swelling.

There is no need to worry about this problem with dried black fungus, because the drying process can decompose most of the porphyrins, and the soaking, rinsing, and cooking processes before eating can remove some of the porphyrins.

Tips: Pay attention to the temperature and time when soaking black fungus. Generally, soak it in cold water for 3 to 4 hours. If time is tight, soak it in warm water for about 20 minutes.

As a nutritious food, black fungus does help promote intestinal health and provide dietary fiber, but it is not a universal "health magic weapon", so don't over-mythologize it. Even if your digestive function is weak, you can still eat black fungus, just chew it slowly, but don't count on it to replenish iron, blood, and clear the lungs. Don't worry about whether dried black fungus or fresh black fungus is more nutritious. The nutritional value of dried black fungus after soaking is similar to that of fresh black fungus.

Only by eating scientifically and matching food properly can we truly make food play its due role and protect our health. While enjoying delicious food, remember to stay rational and choose the ingredients that suit you so that you can take better care of your body.

References

[1] Yang Yuexin. Chinese Food Composition Table 6th Edition Volume 1[M]. Peking University Medical Press, 2018

[2] Yang Yuexin. Chinese Food Composition Table 6th Edition Volume 2[M]. Peking University Medical Press, 2019

[3]. Chai Jing, Peng Cao. Causes of haze formation and its impact on human health[J]. World Latest Medical Information Abstracts, 2017.

Planning and production

Author: Xue Qingxin, registered nutritionist

Reviewer: Zhang Na, Associate Researcher, Doctoral Supervisor, Peking University School of Public Health