According to popular science knowledge, we know that this is because green tomatoes contain solanine. If we eat them raw, we will feel numb in our mouths, and if we eat too much, it will easily cause gastrointestinal discomfort. However, tomatoes that are maturing gradually contain less solanine, so we can only eat them raw. Fresh day lily contains a kind of colchicine. Although it is nontoxic, it is absorbed by the gastrointestinal tract and oxidized into "colchicine" in the body, which is harmful to health and needs to be washed, soaked and blanched, so it is healthier to eat. There are also lentils such as green beans, which need to be cooked thoroughly before eating, because the saponin in the skin and the hemagglutinin in the beans will have a strong stimulation on the gastrointestinal tract. Saponin is saponin, which is a toxic protein in itself, but after cooking and processing, the toxic protein is decomposed at high temperature and is safe to eat.

It can be seen that in our daily vegetables, the common vegetables, such as day lily, tomatoes and beans, which have been artificially planted for many years, contain "harmful substances" themselves, and if they are not properly cooked and eaten, they will also cause physical discomfort and even food poisoning. Then, obviously, some of the unruly edible wild vegetables must also contain harmful substances that are harmful to human health.

For example, these two kinds of wild vegetables, Pteridium aquilinum and Toona sinensis buds, which are very familiar to everyone, both contain harmful substances that are harmful to people's health. Old people in the village say that they are "poisonous" when eaten raw. Picking (buying) in spring will bring negative effects on health and even serious consequences, and the original intention of tasting wild vegetables will be lost. If we know some "characteristics" of these two edible wild vegetables, it is just like knowing that puffer fish is poisonous. We don't eat it casually. As long as we can handle, cook and eat it properly, we can taste it from time to time in spring, and our life will be healthier and more perfect. Besides, these two traditional wild vegetables have a wide audience and have been eaten by the people for many years. As long as you don't know how to eat indiscriminately, you can enjoy the taste of spring.

Pteridium aquilinum: This traditional wild vegetable has the reputation of "king of wild vegetables". It has been popular among the people for many years, and many people like to eat the food cooked by Pteridium aquilinum. Usually, people wash the picked fresh bracken, remove the old terrier of bracken and the fist, rinse it with clear water several times repeatedly, wash off the floating soil and the fluff on the surface, and blanch it in boiling water for 2 minutes until the bracken changes color, becomes soft and feels soft. Then immediately scoop it up and take a "cold bath" for the cooked bracken, then soak it in cold water for a certain period of time, and then you can make the processed bracken into Shan Ye delicious food according to your personal preference, or store it in the refrigerator, so that you can try it from time to time.

With the continuous improvement of people's material living standards and the emphasis on food safety, relevant experts have found that Pteridium aquilinum contains a natural toxin called protopterin, which may be highly carcinogenic to mammals, and it has been classified as a class 2B carcinogen by the World Cancer Organization. This kind of 2B carcinogen has limited evidence of carcinogenicity to human beings and insufficient evidence of carcinogenicity to experimental animals. Or the evidence of carcinogenicity to humans is insufficient, and the evidence of carcinogenicity to experimental animals is sufficient. In fact, as early as in our history, Sun Simiao, the "sage of medicine", said that eating bracken "takes a long time to get worse", which shows that eating bracken often will have a negative impact on people's health.

So, a friend said, why do people in our village eat bracken and Toona sinensis buds every year and find nothing wrong? Otherwise, bracken can't be the "king of wild vegetables". The reason is simple. According to the life experience handed down from generation to generation, the bracken picked by farmers has excellent growth environment, no pollution and good quality. Moreover, after soaking and blanching in boiling water, the original fern glycoside will be dissolved in water, which will evaporate when it is heated, or it will be cooked at high temperature to reduce the harmful substances in bracken; And for this seasonal wild vegetable, it's just a taste from time to time every year. From this, we can easily see that there are three "no's" for villagers to eat bracken-not raw, not much, not often, which greatly reduces the invisible harm of carcinogens to human body. So we should eat bracken skillfully, not because we can't eat it.

Toona sinensis: Toona sinensis buds are traditional seasonal wild vegetables, and they exist in many rural areas. In order to facilitate picking and beautify the environment, people in many places also like to plant Toona sinensis trees in front of and behind their houses until spring comes. There is a Toona sinensis tree planted in my old yard. Due to the geographical and climatic factors in the north, it has not sprouted yet. However, it doesn't matter. Because of the delicious Toona sinensis buds and many fans, Toona sinensis has become a cash crop in some places. It is densely planted in sheds and other ways to provide consumers with Toona sinensis buds early to generate income, so many supermarkets now sell Toona sinensis buds.

People who often come into contact with Toona sinensis know that its leaves contain nitrate and nitrite through some popular science knowledge, and the older the Toona sinensis buds, the higher the harmful substances. When I was a child, I was not sensible. When I looked at the fresh and tender Toona sinensis buds, I sometimes picked one at random and ate it raw. Adults will tell us that we can't eat it raw and that it is "poisonous", which will endanger people's health. According to the popular science knowledge about Toona sinensis, the average per kilogram of Toona sinensis bud contains more than 3 nitrite, and the content of nitrite per kilogram of old Toona sinensis leaves can be as high as 53.9. People will be poisoned if they eat too much nitrite, so it is not aimless for some people in the village to say that Toona sinensis is "poisonous". This has also been reported in the media, so I won't repeat it here.

In order to reduce the negative impact of Toona sinensis bud on health, and the fragrance of lips and teeth is endless, people know that the tender Toona sinensis bud has less harmful substances, while nitrite is easily soluble in water according to the summary of life experience and modern science knowledge about Toona sinensis bud. Therefore, first of all, we try to pick or buy fresh and tender Toona sinensis buds with low harmful substances content, and then soak and clean them several times, which can effectively reduce the content of harmful substances. Then, after boiling water, the nitrite content in it is greatly reduced. After treatment, the toxin in the processed or cooked Toona sinensis buds is very small, and it is as low as normal level, so it will not have too much negative impact on our health.

Conclusion: Pteridium aquilinum and Toona sinensis buds do contain some substances harmful to human body, so they are truly "poisonous" wild vegetables. As long as you don't eat it raw, don't eat it too much, don't eat it for a long time, and taste it occasionally, it can be said that it is beneficial and harmless to your health.

Friendly reminder: Some domestic dishes that have been planted for many years still contain "poison", not to mention some wild vegetables. For example, Hong Feng Cai, which contains a lot of pyrrolizidine alkaloids, has hepatotoxicity and is very harmful to the body after long-term consumption; There are also young leaves of Solanum nigrum, which contain solanin. Improper or excessive consumption can also cause human poisoning. So you see, wild vegetables are still wild vegetables after all. Although some wild vegetables are still used as food and medicine, some people with physical fitness are not suitable for eating. People who don't understand should pay attention. First of all, we should know the related wild vegetables. For example, Toona sinensis buds are highly similar to Ailanthus altissima buds. If we don't know, we can't pick them at random, so as to avoid picking them wrong, and the problem of eating them by mistake is quite serious. Let's talk about picking, processing, cooking and eating wild vegetables. As long as we master the correct methods and taste them occasionally, it can promote people's health and taste the flavor of the season. This is also the beautiful original intention of those who eat wild vegetables. # Three Rural Issues Challenge #