Vitamin A is also called retinol and anti-dry eye factor, the English name is Vitamin A, and the aldehyde derivative of vitamin A is called retinal. Vitamin A is a fat-soluble vitamin, and vitamin A is a component of rhodopsin, which is a weak light in visual cells and is associated with night blindness.
The source of vitamin A is divided into animal food sources and plant food sources. Vitamin A in animal food sources is divided into vitamin A1 and vitamin A2. Vitamin A1 is mainly found in the liver of marine fish and mammals, and its activity is high. Vitamin A2 is mainly found in the liver of freshwater fish, and its activity is relatively low, so animals Vitamin A mentioned in the source of sexual foods generally refers to vitamin A1, such as cod liver oil. Vitamin A in plant food sources mainly refers to β-carotene and other carotene. β-carotene and other carotene can be converted into retinal under the catalysis of enzymes in the human body, and retinal in the yellow Under the action of aldehyde reductase, it can be reduced to retinol, which is vitamin A, and the conversion of β-carotene into vitamin A is the highest in carotene, so carotenoids in plant food sources generally refer to β-carotene.
In the Tang Dynasty, Sun Sizhen recorded that animal liver can treat night blindness in "The Golden Essentials", which means that vitamin A can treat night blindness. Can vitamin A really alleviate the symptoms of night blindness?
The photoreceptor of the human eye is a cone-shaped cell and a rod-shaped cell in the retina. In the cone-shaped cells and rod-shaped cells, the photoreceptor pigments are purple-purple and rhodopsin, and the purple-blue is the sensible light. Quality is the feeling of low light, these two substances are composed of retinal and opsin, so vitamin A has the effect of protecting vision.
As mentioned above, vitamin A is associated with night blindness. This is because the rhodopsin, which is composed of rhodopsin, is converted into retinal, retinoic and opsin, and purple. The quality will disappear. At this time, if you enter a dark place, the rhodopsin that can feel the weak light disappears, so that people can't see things in the dark place, and if the human body contains enough vitamin A, It can quickly form a rhodopsin with opsin, so it can be seen in a dark place after a short period of recovery, but if the vitamin A in the human body is not sufficient, the time to reconstitute rhodopsin will be prolonged. It will be invisible for a long time in a dark place, and a serious lack of vitamin A may cause night blindness.
So enough vitamin A can prevent night blindness, so which foods contain more vitamin A? The following small series will introduce the content of vitamin A in natural foods.
Content of vitamin A and carotene in 100 grams of food:
Sheep liver: 20,972 micrograms (vitamin A)
Chicken liver: 10414 micrograms (vitamin A)
Mango: 1342 micrograms (vitamin A) 8050 micrograms (carotene)
Broccoli: 1202 micrograms (vitamin A) 7210 micrograms (carotene)
Pig liver: 4972 micrograms (vitamin A)
Carrot: 668 micrograms (vitamin A) 4010 micrograms (carotene)
Spinach: 487 micrograms (vitamin A) 2920 micrograms (carotene)
Amaranth: 352 micrograms (vitamin A) 2110 micrograms (carotene)
Lettuce: 298 micrograms (vitamin A) 1790 micrograms (carotene)
Cabbage: 280 micrograms (vitamin A) 1680 micrograms (carotene)
Orange: 277 micrograms (vitamin A) 1660 micrograms (carotene)
Cream: 1042 micrograms (vitamin A)
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