Vitamin A is responsible for our epidermis, it forms our visual purple, regulates body growth and skeleton formation. It also contributes to cholesterol excretion and makes our body more resistant to infections. It is considered that a person needs around 1.5 grams of this vitamin per day. (Hereinafter the numbers stated are based on official averages).
Its shortage leads to night vision disorders – night blindness. In worse cases skin becomes pale and dry, hair can start to fall and horizontal marks appear on the nails. There can also be permanent blackheads and acne. People get tired faster, children stop growing.
Nevertheless, no matter whether your diet is vegetarian or not, you are not going to lack retinol. Meat-eaters receive a lot of it from all the animal products, butter, eggs and cheese. However, in the case of protein excess, usage of retinol increases rapidly. One also needs more vitamin A during hard physical or intellectual work, diseases and pregnancy. The need for all vitamins increases during all intense activities in general.
All vegetables contain provitamin A – carotene that turns into retinol when combined with fats and bile. That does not mean, of course, that you should only eat carrot together with sour cream or butter. 100 grams of carrot contain more than 2-day norm of carotene. There is also a lot of it in sorrel, spinach, parsley, pumpkin, tomatoes and etc. Consequently, vegetarians do not have any problems with retinol, especially considering the fact that the liver creates a storage of this vitamin that is enough for 2-3 years (that is, if the liver is healthy).
Hypovitaminosis (insufficiency) and avitaminosis (severe deficiency) are likely to happen to people that consume mostly canned food or vegetarians who do not eat enough fresh vegetables and fruits (if they do not practice exercises for biosynthesis improvement).
There have been cases of intoxication with vitamin A. Usually it affects children that take too many synthetic medicines. Among the first signs of acute hypervitaminosis are strong headaches, vertigo and nausea. Severe intoxication can also occur if you eat at once 200 grams of liver of polar bears, polar birds, walruses, seals or whales. These products contain a lot of vitamin A. There was also a story about a person who died after eating just carrot for more than a month. On the other hand, there were almost no more cases of carotene intoxication or retinol excess while eating normally.
Vitamin A is quite resistant to heating and does not require any special preservation measures. In the process of cooking just about 10% of it is lost. However, retinol is destroyed by the effect of atmospheric oxygen, especially when exposed to sunlight (e.g. rancid butter, dried fruits, long defrosting).
Text: from the book of A Eddar "The treatise of nutrition".