Cut before washing—large loss of nutrients
With the exception of small varieties like bok choy choy sum, most vegetables need to be cut before cooking. Many people have the habit of cutting vegetables first and then washing them, not realizing that many nutrients and beneficial substances in vegetables are water-soluble. When cut, vegetables lose a large amount of nutrients into the water during the washing process. The correct method is to wash first, then cut.
Squeezing vegetable juice—improper disposal
When making the filling for wontons or dumplings, vegetables need to be finely chopped, which produces a large amount of juice. Some people squeeze out the juice to make the filling easier to shape or handle, discarding 70% of the vitamins and minerals in the vegetables. The correct way is to chop vegetables along with ingredients like dried tofu, mushrooms, and meat, mixing them to allow the vegetable juice to seep into the other ingredients. Additionally, some people eat bean sprouts but only eat the sprouts, not the beans. In fact, the beans contain three times more vitamin C than the sprouts.
Storage for too long—destroys vitamins
Some people buy a large quantity of vegetables at once and eat them over several days. The result is not only a poor texture but also a gradual loss and destruction of vitamin C. Vegetables contain nitrates, which can be reduced to nitrites in the air. Nitrites can convert normal hemoglobin to methemoglobin, which loses its ability to carry oxygen, causing symptoms such as cyanosis in the nails and lips, and even shortness of breath all over the body. Vegetables have a high water content and are prone to growing mold, which can produce various mycotoxins. These toxins not only adhere to the surface but can also penetrate deep into the vegetable, and they cannot be destroyed even by heating. Therefore, vegetables should be eaten as fresh as possible.
Improper refrigeration—cucumbers cannot be stored below 10°C
Low temperatures can delay the spoilage of vegetables, but lower is not always better. Basically, no vegetables can be frozen. Most are best stored at 3°C to 10°C, while cucumbers cannot be stored below 10°C. If refrigerated at around 4°C, the cucumber's color will darken, its body will soften, and a transparent, gel-like liquid will be visible after cutting, causing the cucumber to lose its fresh aroma completely.
Eating raw vegetables—know the varieties
Vegetables that can be eaten raw are those that are naturally non-toxic and not contaminated. However, the vast majority of vegetables on the market today have been sprayed with pesticides, and often more than one type. Although people are accustomed to soaking vegetables before washing, this only removes about 40% of the pesticides, and cooking further breaks them down. Eating these vegetables raw can harm your health, especially the outer older leaves, which should not be eaten. Some vegetables are naturally toxic and must be cooked to destroy these toxins, such as sword beans and hyacinth beans.
Cooking for too long—vitamin C is oxidized by heat
Vitamin C in vegetables is easily oxidized and decomposed by heat. The loss is smaller when stir-frying over high heat or heating with a lid for a short time. If cooked for 10 minutes, vitamin C can be reduced by 60% or more.
Eating leftover meals—decreasing nutrients
Some people, for convenience, cook a large bowl at a time and eat it for the next meal or even the day after. They don't realize that this causes a large loss of vitamin C and B vitamins. According to measurements, stir-fried green vegetables lose 20% of their vitamin C after 15 minutes, 30% after 30 minutes, and 50% after 1 hour. Leftover meals are also prone to spoilage and can easily cause food poisoning. Therefore, it is best to cook and eat immediately for both hygiene and nutrition.
Using too much oil—animal and vegetable oil are the same
Many people are afraid of eating meat, animal fat, and consuming too much fat, but they add a lot of vegetable oil when cooking, otherwise they find the taste bland. In fact, animal and vegetable oils are the same; every gram of oil produces 37.656 KJ of energy. Therefore, whether it's animal or vegetable oil, consuming too much can lead to obesity or "rich man's diseases" such as high blood lipids, diabetes, and cardiovascular diseases due to excessive caloric intake. So, oil should be used in moderation. The recommended daily intake is 25g of oil per person, not exceeding 30g.
Not eating the vegetable broth—discarding vitamin C
When cooking, about 30% to 70% of the vitamin C dissolves into the broth. Therefore, you should not only eat the vegetables but also drink the broth.
Not removing oxalic acid from spinach—affects calcium absorption
Everyone knows that spinach is high in oxalic acid and tofu is high in calcium. If spinach and tofu are cooked together, it forms calcium oxalate, which the human body cannot absorb, affecting calcium uptake. Spinach is a superior vegetable, not only rich in nutrients but also with a bright color. So, many people simply stir-fry spinach or cook it with other foods. In fact, the oxalic acid in spinach is客观存在的 (objectively present). No matter how you cook it, if you don't remove the oxalic acid beforehand, you will still consume it when eating the spinach. In the digestive tract, oxalic acid can also bind with calcium from other foods, preventing its absorption. Oxalic acid may also be absorbed into the bloodstream after digestion, where it binds with calcium in the blood, wasting calcium that has already been absorbed by the body. Therefore, there is no need to avoid cooking spinach with tofu. The correct way is to first blanch the spinach (including other vegetables high in oxalic acid like bamboo shoots) in boiling water for 1-2 minutes to dissolve the oxalic acid, then remove the blanched spinach and cook it with anything, including tofu, without affecting calcium absorption.
Long-term vegetarianism—incomplete nutrition
Nowadays, some people are scared of the high incidence of high blood pressure, high blood lipids, high blood sugar, and cardiovascular diseases caused by high-fat, high-protein, and high-calorie diets, so they only eat vegetarian food. If it is necessary to eat vegetarian food for a short period for medical reasons, that is acceptable. However, long-term vegetarianism, especially for teenagers, is more harmful than beneficial. This is because most plant proteins are "incomplete proteins" in nutritional science, lacking many essential amino acids that the human body needs. In contrast, chicken, duck, fish, meat, eggs, and dairy products contain more complete proteins and fat-soluble vitamins like A and D.