Vitamins are organic molecules that we need in the diet for the chemical reactions that maintain life. Vitamins can be soluble or fat soluble in water. Here I will discuss a fat soluble vitamin a. Other fat-soluble vitamins are D, E and k. Water-soluble vitamins are c and the Bs.
Fat soluble vitamin a are stored in the body as a substance called retinol, which is also the type we receive in the diet of products of animal origin. Retinol can be transformed into other forms of retinal, Retinoic acid and vitamin A. Retinoic acid is a form of vitamin a flowing through cell membranes and in the nucleus of the cells to modify the expression of genes, turning genes or disable.
Retina is a molecule contained in the retina of the eye, is helping to change the energy of the light into electrical signals that get sent in the brain and eventually find themselves in the visual cortex, the area of the brain involved in the perception of the view. Vitamin a is therefore an essential component of the vision, and in fact the first symptom of vitamin a to appear is night-blindness.
There are multiple sources of fat soluble vitamin A, which is absorbed best is Retinol and occurs almost exclusively in food of animal origin. Liver is the best source and cod liver oil also contains a massive amount. Eggs, meat, fish and fat as butter contain some too certain dairy products.
The plant forms are known as carotenes, and in particular alpha and beta carotene. They are composed of similar to vitamin A molecules, which are broken down into vitamin a in the digestive tract. They are not nearly as bioavailable in the form of retinol and the body shape only as much vitamin a of them properly, vitamin a toxicity is therefore not possible to overconsumption of carotenes.
A variety of vegetables and fruits contain the carotenes, and therefore, it is possible to cross the vitamin a plant foods only, although I recommend you eat foods for animals too because all other essential micronutrients they contain. Carrots, sweet potatoes and broccoli are all excellent sources of carotenes.
I would recommend having some fat with vegetables, to increase the rate of absorption of the vitamin, but any fat soluble vitamin must be consumed with grease to be properly absorbed. One or two tablespoons of something like olive oil could be the case.
The RDA for vitamin a is 900 micrograms for men and 700 micrograms for women. Vitamin a deficiency is major causes of blindness and death in third world countries, but in Western societies, serious deficiency is rare. I wouldn't recommend supplementing vitamin A, at least, or contained in the average multi or a tablespoon of cod liver oil, because that too large part can be harmful and cause birth defects.
