Vitamin A is fat-soluble and stored in the liver. Part of the vitamin is obtained by consuming animal fat, and part is produced in the intestine from beta-carotene. In organism, it comes in a variety of forms called retinoids because they are important for the health of the eye (retina).
How does it work?
This vitamin prevents night blindness (nyctalopia), maintains the skin and cells of the mucous membranes of the respiratory and digestive system and helps to build bones and teeth. It is necessary for reproduction, normal growth and development. Vitamin A is extremely important for the immune system, including cells in the mucous membranes of the respiratory and digestive system, and are essential for the defense agains many diseases.
MAIN USEFUL EFFECTS: vitamin A is best known for its ability to maintain (especially night) vision and help adjust to viewing in darkness. It can alleviate the symptoms of ”dry eye”, the condition that occurs in many developing countries, and is associated with the severe shortage of this vitamin.
Since it strengthens the immune system, this essential nutrient significantly enhances the resistance to infectious diseases including laryngitis, cold, flu and bronchitis. It can also help with herpes labial and herpes zoster, skin warts (caused by viruses), eye infections and fungal infections, and possibly allergies. This vitamin can help in the fight against breast and lung cancer, and can also prolong the life of patients with leukemia. Animal studies say that vitamin A slows the growth of melanoma, deadly form of skin cancer. It also helps cancer patients by enhancing the function of chemotherapy if the level of this vitamin in the body is enough.
ADDITIONAL USEFUL EFFECTS: during the 40s of the last century, vitamin A was first used in the treatment of skin diseases, including acne and psoriasis, but the doses were very large and toxic. Safer forms were later introduced, especially retinoic acid, which is sold as a prescription drug. There are also anti-acne and wrinkle creams that contain some forms of vitamin A. For the treatment of skin diseases such as acne, dry skin, eczema, rosacea and psoriasis, small doses of this vitamin can be used (up to 7500 μg per day), but only under medical supervision.
At the optimal level in the body, vitamin A stimulates wound healing and accelerates recovery from ligament and ankle sprain. The effect is also manifested in the digestive system, where it helps in the treatment of inflammatory bowel disease and ulceration. In addition, a sufficient amount of vitamin A helps in recovery after a stroke. Women with too long and abundant menstruation sometimes suffer from the lack of this vitamin.
How much vitamin A is needed?
The recommended daily amount of vitamin A is 600 μg for women and 700 μg for men.
IF YOU TAKE TOO LITTLE: the lack of vitamin A in the United Kingdom is rare, and the symptoms are night (or even complete) blindness and greatly reduced resistance to infections. In older people, sometimes a milder deficiency occurs, due to insufficient amounts of this vitamin in the diet. During contagious diseases such as pneumonia, vitamin A supplements decrease.
IF YOU TAKE TOO MUCH: although doses up to 1500 μg are safe, take vitamin A supplements only if prescribed by your doctor! This applies especially to pregnant women and women who are trying to get pregnant because there is a risk of fetal injury. Taking bigger doses increases the risk of excessive vitamin accumulation. One dose of 150 mg can cause weakness and vomiting, and only 7500 μg per day during the six weeks can cause serious liver disease. Signs of toxicity are dry and cracked skin, brittle nails, hair loss, bleeding gums, loss of body weight, nervousness, fatigue and nausea.
How to take it?
DOSAGE: it is advised not to take more than 800 μg of this vitamin per day to avoid excessive accumulation. An alternative is to take mixed carotenoids.
USE GUIDELINES: take these dietary supplements with food; a small amount of fat improves absorption. Vitamin E and zinc help the body to absorb vitamin A, and it increases the absorption of iron.
Plenty of Vitamin A is in fish, egg yolk, butter, intestines (90 grams of liver has 2500 μg of vitamin A) and enriched milk (check on the packaging whether it is an enriched product). Big amounts of beta-carotene are found in yellow, orange, red and dark green fruits and vegetables; beta-carotene can be ”transformed” into the vitamin A in the body.
IMPORTANT: vitamin A can accumulate in the body, so you should not take too much. The safer form is beta-carotene.