When it comes to heating vegetables, some people always say that they will lose vitamins. Especially for those who advocate eating raw, avoiding the loss of vitamins due to heating is the most common reason. More "health preservation master" said surprisingly: vitamins will decompose when they exceed 40 ℃, so it is useful to eat them raw. Today, with the development of history, mankind is the only creature that can cook and eat food. Do we need to go back to the era of raw food? How many vitamins will vegetables lose when cooked?
Loss of heating
First of all, vitamins are not a substance, but a large class of substances. The characteristics of each vitamin are different, and the stability in the face of various conditions is also different. Vitamin C is easily soluble in water. Some B vitamins, such as folic acid, vitamin B6 and vitamin B12, are also soluble in water. It is easier to lose them when boiled in water. Steaming is a better way to retain these water-soluble vitamins than boiling. These unstable vitamins, vitamin E and vitamin K will also be lost under light conditions. In addition, their environment, such as acidity and alkalinity, will also affect their stability. Some metals, such as iron and cobalt, can cause vitamin E and vitamin B12 to lose activity. Strictly speaking, the "inactivation" of vitamins is not the two states of "life" and "death", but the loss of how much.
The heating temperature and time of various foods are different, and the heating has different effects on different vitamins. Therefore, "how many vitamins will be lost when food is cooked" is not an easy question to answer. The USDA database contains various vitamins in common foods. Some people counted the data of various foods in the "raw" and "cooked" states, excluded the influence of the change of water content, and obtained the loss proportion of various vitamins after heating. Although these figures are not necessarily very accurate, they are enough for us to get a meaningful impression: vitamin A and vitamin E are not affected by temperature. After cooking, they lose about 10%, vitamin C loses 16%, while vitamin B1 is the most unstable, with a loss of 26%, and other vitamins are basically within this range. Generally speaking, when the food is cooked, the loss of vitamins is about 10% ~ 25%.
Benefits of heating
But heating does not simply lead to vitamin loss. Heating is of positive significance to the absorption of vitamins. Some foods contain so-called "anti vitamin substances", which can combine with vitamins and affect the absorption of the human body. Heating will destroy these substances, thus increasing the absorption rate of vitamins. β Carotene is an example. It exists in a variety of vegetables, such as carrots, spinach, sweet potatoes, broccoli and so on. This is the main way for vegetarians to get vitamin A. But when eating raw vegetables β The absorption rate of carotene is very low, and heating can greatly increase its absorption rate. Interestingly, if heated at ultra-high temperature for a long time, it will change from bioactive trans structure to inactive CIS structure, so after these vegetables are canned β The loss of carotene will be relatively large. However, the usual cooking cannot reach that temperature, so there is no need to worry about daily cooking.
The loss of vitamins by heating is 10% ~ 25%, which is not much or less. However, considering the possible problems of eating raw vegetables, such as pathogenic bacteria and some toxins that need to be destroyed by heating, it is difficult to simply say whether vegetables should be eaten raw or cooked. In fact, for vitamins, instead of paying too much attention to "loss", it is better to focus on the source. Different foods are rich in different vitamins. If you eat more diversified foods, the total amount of various vitamins may be more, and it doesn't matter if you lose anything. After all, what our body needs is that all kinds of vitamins meet a certain demand, not one or two. The more, the better.