Want to eat vegetables healthily and safely, but there are so many misunderstandings?

Recently, my mother has frequently told me about various food safety issues related to vegetables while cooking. She is worried about the safety of off-season vegetables and wants to grow vegetables on her balcony. She is also worried that the soil on the balcony is not fertile enough, which will lead to a decrease in the nutrient content of the vegetables she grows. She wants me to buy vegetables online. She is also worried that the vegetables she buys online may have been stored for too long and are not fresh. She saw some new and exotic vegetables recommended by the old sisters in the community and thought that eating vegetables could cure diseases and maintain health... In short, for friends like my mother who care about the nutrition and safety of vegetables but don't understand the principles behind them, eating vegetables is really a lot of problems. Why not come together with everyone today to solve these puzzles about eating vegetables and strive to eat safe and cost-effective fresh vegetables.

Image source: Tuchong Creative

1. When growing vegetables on the balcony, be careful with the details

Out of concern for occasional food shortages and food safety issues, friends who have the conditions have started to think about their own balconies, and even celebrities have begun to grow some easy-to-grow vegetables on their balconies. However, growing vegetables on the balcony is not that simple, and there are many details that need to be paid attention to. First of all, you need to select the vegetables you grow. "Urban farmers" may not be familiar with vegetable seeds. If they accidentally buy wild vegetable seeds that are not suitable for family consumption and grow a plate of poisonous vegetables, it would be quite dangerous. A few years ago, there was a news report that a couple was obsessed with growing vegetables on the balcony, but they did not choose the right seeds and grew "balcony wild vegetables" that poisoned the whole family. Secondly, the soil, containers and fertilizers used for growing vegetables should be carefully selected. It is difficult to find soil for growing vegetables in the city, and some people go to small parks or road green belts to dig soil and take it home. However, many parks are transformed from ruins or garbage dumps, and green belts absorb car exhaust for many years. These soils may have been contaminated by heavy metals and organic waste. When vegetables grow, they will transfer various pollutants from the soil and concentrate them in the stems and leaves through enrichment. Therefore, whether the soil used for growing vegetables is safe directly affects the safety of vegetables. Vegetable growing containers should avoid unqualified foam boxes, plastic tubes, and waste barrels containing paint. Fertilizers should not be directly applied with untreated household organic fertilizers (such as feces) to prevent bacterial and parasitic infections. It seems that it is not so easy to enjoy a pastoral life in the city. You need to master more knowledge of botany and planting to grow vegetables with peace of mind.

2. Off-season vegetables are safe to eat

Most of the winter vegetables rely on off-season vegetables, but some people always worry that off-season vegetables have pesticides, fertilizers, hormone residues, or do not taste like vegetables and have no nutrition.

In fact, the concept of "off-season vegetables" is more applicable to the north, because in the vast southern region, especially in the warm subtropical cities, "seasonal vegetables" can be eaten all year round. There are three sources of "off-season vegetables" on the northern market: one is "southern vegetables" that travel all the way from the south to the north. Except for the loss of some sugars, vitamins and flavor substances during transportation and storage, which affects the taste, the content of other nutrients is almost the same as when they were in their hometown. If "southern vegetables" are not over-applied with pesticides, fertilizers or plant hormones during the growth and development period, such hidden dangers will not appear out of thin air after being transported to the north. The second type of off-season vegetables comes from local fruit and vegetable cold storage. Some vegetables that are particularly suitable for long-term storage (such as roots, melons and tomatoes, and garlic sprouts) are purchased and stored in large quantities in summer and autumn, and sold in winter. Strictly speaking, they are not "off-season vegetables", but "vegetables sold off-season". Due to the low storage temperature, the loss of nutrients in these vegetables is still within an acceptable range. So what about the nitrite problem that people are more worried about? Nitrates in vegetables will turn into nitrites under the action of bacteria, but bacteria need a certain temperature to survive and react. The low temperature environment in the cold storage is not suitable for bacteria to survive, so there is no need to worry about the safety of the second type of "off-season vegetables". The third type, namely the local "greenhouse vegetables", is the real "off-season vegetables". As long as the appropriate temperature and humidity in the greenhouse are guaranteed, the vegetables can grow happily, regardless of whether it is cold outside the greenhouse. However, the "artificial environment" cannot completely simulate the sunshine and temperature in summer and autumn. Although it has little effect on the nutritional content, it directly affects the taste and flavor of the vegetables. As for the problem of pesticide residues in off-season vegetables that everyone is worried about, the current national random inspections have found that most of the pesticide residues in greenhouse vegetables do not exceed the prescribed limits, and the residues of some low-toxic pesticides and organophosphorus pesticides can also be degraded within a few hours by light.

It can be said that off-season vegetables have more merits than demerits. Apart from being inferior to seasonal vegetables in taste and aroma, the nutritional difference is not that significant, and there is no need to overreact to the issue of pesticide residues.

3. Novel vegetables, not cost-effective, just experience

In the past two years, many new and strange vegetables have appeared on the market, such as "sprout" vegetables - wheat sprouts, buckwheat sprouts, radish sprouts, Chinese toon sprouts, alfalfa sprouts, etc., with a variety of varieties. Because of the cultivation method, sprouts are almost not involved in food safety issues such as pesticides and fertilizers, but they should not be deified for this reason. Some people believe that insisting on drinking wheat sprout juice can fight tumors and lower blood lipids/blood pressure/blood sugar, which is biased. Although sprouts contain nutrients such as dietary fiber and vitamins, there is currently no reliable research basis to support the claim that sprouts are health-promoting. If you abandon regular treatment for this reason, it will really be more trouble than gain. Other new and expensive vegetables, such as Brussels sprouts and finger carrots, are small and charming in appearance and expensive, but their nutritional value is not much better than ordinary cabbage and carrots, so there is no need to blindly pursue them.

4. Online shopping for vegetables has both advantages and disadvantages, so wait and see

In recent years, online shopping for vegetables has become a new choice for young people to buy vegetables because of its convenience and speed. However, there are also troubles in online shopping for vegetables. Sometimes the express delivery is late and delays cooking, sometimes the quality of the vegetables is too poor and unsatisfactory, and sometimes there are only organic vegetables on the website, but the price is shocking. In addition, the safety of online shopping vegetables is not fully guaranteed. The quality of vegetables on different platforms varies, and the food safety issues caused by this are annoying; it is also difficult to judge whether some expensive vegetables are really picked on the same day or organic vegetables. Such things make many people wait and see about online shopping for vegetables. If you are busy at work, it is recommended to choose a large shopping platform when shopping for vegetables online. Usually, such platforms have a stable supply of goods, and have a good quality control system from picking to delivery, so the quality of the dishes is more guaranteed. At the same time, some fresh food purchasing websites will invite nutritionists to settle in and give users some suggestions on dish matching, which is beneficial to health.

It is necessary to worry about the food you eat, but it is unnecessary to worry too much. As long as you understand the risk points of food safety, you don't need to worry too much. Choosing fresh vegetables and combining them in various ways can achieve a good balance between nutrition and safety.

The article is produced by Science Popularization China-Starry Sky Project (Creation and Cultivation). Please indicate the source when reprinting.

Author: Wang Lu, Chinese registered dietitian, Master of Public Health, Peking University

Reviewer: Xue Qingxin, the first batch of nutrition instructors of the National Health Commission, China registered nutritionist