Eating soil is worse than eating duck blood? Are “lung-clearing” foods really useful?

Audit expert: Wang Guoyi

Postdoctoral fellow in Nutrition and Food Safety, China Agricultural University

Did you have a "dusty" day at work yesterday?

As the north ushers in large-scale sandstorm weather, friends living in Beijing are deeply affected. As of 21:00 on April 10, the air quality in the entire city has turned red and black, and has fallen into a severe pollution level.

Source: Screenshot of Beijing Daily Weibo/Beijing Environmental Monitoring Official Website

In dusty weather, even in an office with closed doors and windows, there is a smell of dirt everywhere. It is inevitable that people worry whether these fine dusts that penetrate everywhere will be inhaled into the lungs and cause harm ?

As a result, many people turned their attention to "lung-clearing foods" such as duck blood, and the sales of duck blood vermicelli soup also increased accordingly.

Source: Weibo screenshot

Well, I'm sure everyone is wondering, does duck blood really have the effect of "clearing the lungs" as folk legends say? Do "lung-clearing foods" really clear the lungs? Let's take a look today.

How does dust in the air affect your health?

As we all know, sandstorm weather is a weather condition in which there is a large amount of dust in the air.

Dust refers to solid particles with a diameter of less than 75 microns suspended in the air . Dust is everywhere and is one of the main reasons for maintaining the earth's temperature. However, the combustion of fuel and the emission of automobile exhaust release a large amount of particulate matter, which absorbs other substances and undergoes various reactions to generate secondary pollutants, which not only causes air pollution but also endangers human health.

Sandstorm source: Wikipedia

How does air dust affect health? Generally speaking, particles with a diameter larger than 10 microns can be intercepted by the villi in the nasal cavity and expelled from the body through sneezing and coughing; however, dust with a smaller particle size is easy to settle in the lungs.

The smog often mentioned in the news is mainly formed by dust particles with a diameter of 2.5 microns , which is the familiar PM2.5. PM2.5 carries a large amount of toxic and harmful substances, has a long transmission distance, and can be suspended in the air for a long time. Although the macrophages in the human immune system can phagocytize and remove PM2.5 to a certain extent, it is not thorough. The remaining particles will enter the bronchioles of the lungs and cause deposition, causing respiratory diseases and even lung cancer.

Source丨Editor

Many people have no idea about the size of PM2.5. For example, human hair looks very small to the naked eye, but its diameter is between 50 and 70 microns. By comparison, you can imagine how tiny dust particles are.

However, there are also smaller particles that can penetrate deep into the alveoli and then enter the blood, causing blood poisoning and vascular hardening, followed by cardiovascular disease.

The issue of air pollution has received a lot of attention, and at the same time the term "clear lungs" has also come into people's attention.

Are “lung-clearing” foods really effective?

In daily life, we have all heard of foods that can clear and moisten the lungs , such as duck blood, pig blood, snow pear, white fungus, etc. Can eating these foods really remove the inhaled dust? The answer is no .

First of all, as mentioned earlier, dust enters the lungs through the respiratory tract, while the "lung-clearing" food we eat enters the body through the digestive tract, and after digestion and absorption, it enters the blood through the villi of the small intestine. It can be said that it is "across the sea" from the particulate matter in the lungs, and is in two different channels, without any clearing effect at all.

Source of duck blood vermicelli丨Baidu Encyclopedia

Some people may say that after eating "lung-clearing" food, the stool will turn black, which is "detoxification". In fact, it is not. The color of stool is indeed related to food, but in addition to food reasons, it may also be related to physical diseases. Generally, the cause of black stool may be digestive tract ulcers or tumors, or short-term supplementation of a large amount of iron.

Duck blood is rich in iron , and black stools will indeed appear after consumption, but it has nothing to do with "clearing the lungs".

Stewed Tremella and Lotus Seeds Source: Wikipedia/Mk2010

In fact, in modern medicine, there is also a technology for cleaning the lungs, which is lung lavage , but it is usually used to treat patients with pneumoconiosis and aspiration pneumonia, and is not suitable for treating diseases caused by air pollution.

As for the "lung clearing" often mentioned in traditional medicine, this lung clearing is not the same as that lung clearing. It refers to clearing the lungs and relieving heat, alleviating respiratory symptoms such as coughing and sputum. It is just habitually called "lung clearing" food by people, and it cannot deal with lung problems caused by air pollution.

In general, there is no scientific basis for clearing the lungs with food, and there is currently no method to remove dust that enters the human body.

How to protect lung health?

Although "clearing the lungs" is not achievable, some measures can be taken in daily life to reduce lung damage and keep the lungs healthy.

The following are some effective protection methods in sandstorm weather:

>>>> Take good personal protection and avoid going out during dusty weather

Since sandstorms contain a large amount of inhalable particulate matter PM2.5, which can cause the occurrence and aggravation of cardiovascular diseases, generally speaking, when encountering sandstorms, you should reduce the number of times you go out, and it is best to stay indoors, close the doors and windows, and use an air purifier.

>>>>Wear a mask when going out

Most people cannot avoid going out, so they need to wear masks. Ordinary medical masks have little protection against particles smaller than 10 microns. You can choose N95 or KN95 masks, which can effectively filter PM2.5 and other pollutants. If you have breathing problems, you can also choose a model with a breathing valve.

Source: pixabay

>>>>Wash your hair as soon as possible after returning home from an outing

Dust storms not only contain PM2.5 and PM10, but also carry sand, pollen, catkins, etc. When the sandstorm weather is severe, some people may feel that they become dusty after going out, and this is not a personal illusion.

As we all know, hair has a large number of hairs, a small diameter, a large total area, and secretes oil, which can absorb a lot of sand and dust. Therefore, it is best to wash your hair and blow dry it as soon as possible after returning home. Friends with long hair can also comb their hair to reduce the contact area between sand and hair.

>>>>Rinse the nasal cavity

Although we cannot clear our lungs, we can clean our noses. The nose can filter out a large part of the dust particles, but sneezing and coughing are not pleasant, so you can clean your nasal cavity properly.

Nasal cleaning source: Wikipedia/Aikhan

Friends in need can buy a nasal rinser online, inject professional nasal rinse salt solution or saline solution, and rinse the nasal cavity according to the instructions. In addition to taking anti-allergic drugs, patients with allergic rhinitis can also wash their noses, which is helpful to relieve rhinitis symptoms.

In general, "lung protection" is very important. Avoiding inhalation is the most effective way to prevent dust from damaging the body. From a macro-environmental perspective, protecting the environment and reducing environmental pollution are the fundamentals of "lung protection". As a member of our home planet, we also need to make joint efforts.