Many people often take pork liver for "eyesight", and many kindergartens stipulate that they should eat pork liver once or twice a week. Some women and children''s health care institutions also require pregnant women to eat pork liver regularly. One of the main reasons for these practices is that pig liver is rich in vitamin A. But is pig liver really the best source of vitamin A?

　　Vitamin A plays an important role in the human body as its name "A"-the first. Vitamin A, also known as retinol, is an important substance to maintain the health of the skin and organs and mucous membranes of the body; it is the key to determine the eyesight of the eyes under dark light; it is an important influencing factor of human immunity; it is to promote the skeletal system And the core substance of reproductive system development; also has anti-cancer effect.

　　Vitamin A required by the human body can be directly ingested from animal foods (such as fish, meat, eggs, milk, etc.), but also from plant foods (vegetables, fruits, whole grains, etc.) Β-carotene in the conversion. In general, the absorption rate of β-carotene in food in the intestine is about 1/3, of which about 1/2 (this ratio is also related to the overall level of vitamin A in the body) can be converted into vitamin A (retinol ), so the efficiency of converting β-carotene to vitamin A is generally considered to be 6:1.

　　This ratio is easy to cause misunderstanding: taking beta-carotene is not as effective as taking vitamin A directly. This is not the case. There is sufficient evidence that after ingesting β-carotene, the efficiency of its conversion to vitamin A is sufficient to meet the body''s need for vitamin A, which can basically replace vitamin A intake (of course, from the perspective of a balanced diet, We still advocate the combination of animal foods and plant foods).

　　 Moreover, the most important thing is that the β-carotene that has not been converted to vitamin A also has other important physiological functions. It has antioxidant effects and is an effective capture of reactive oxygen species (free radicals). Antioxidants are important to prevent lipid peroxidation, prevent cardiovascular diseases, tumors, and delay aging. In other words, β-carotene can not only be converted into vitamin A, play the role of vitamin A, but also have antioxidant effects that vitamin A does not have. Therefore, those foods rich in β-carotene, such as broccoli, carrots, squash, leeks, spinach, tomatoes, shepherd''s purse, sweet potatoes and other vegetables and fruits such as citrus and apples are the best sources of vitamin A. What''s more, these vegetables and fruits also contain many other healthy ingredients.

　　Comparatively speaking, animal liver and other internal organs, egg yolk, lean meat and other foods rich in vitamin A are not the best sources of vitamin A. Because they generally contain more cholesterol or saturated fat, and other safety hazards. Therefore, it is not wise to eat more pig liver to increase the vitamin A (playing the "eyesight" role of pig liver). Many kindergarten recipes require that pig liver be eaten once or twice a week. People should eat more fresh, dark vegetables and fruits to obtain sufficient and healthy β-carotene.