Vitamin A Benefits, Sources, Dosage, and Functions

Vitamin A (and carotene) keep mucous membranes healthy; thus, it protects against infections, even in infants. Extremely important in fighting infections. It prevents night blindness, eye diseases, and weak eyesight. It is important for skin, hair, gastrointestinal juices, and digestion. It prevents premature aging and senility and increases lifespan. It helps blood capillaries work better and protects against cardiovascular disease.

This vitamin is important in treating skin disorders, dry eyes, cancer, light sensitivity of eyes, and vaginal candidiasis. It also affects growth and development, is necessary for reproduction, and helps the immune system. It protects against death among children with measles in developing countries. Carotenes provide far more antioxidant effects than vitamin A.

Vitamin A Sources

Vitamin A (retinol) is a pure yellow, fat-soluble crystal. (Its other name, retinol, comes from the fact that it is found in the eye’s retina.) Vitamin A is found in meat, milk, and eggs. The safer and very nutritious carotenes (also called carotenoids) are pro-vitamin A. They are found in abundance in fruits and vegetables and are converted by the liver into vitamin A. Taking carotene in larger amounts is always safe because the liver only converts the amount needed by the body into vitamin A.

Richest sources – Dark green leafy vegetables.

Other sources – Green and orange fruits and vegetables, especially carrots, lighter green vegetables, yams, tomatoes, mangos, Hubbard squash, cantaloupe, and apricots. Lesser amounts are in legumes, grain, and seeds.

Beta-carotenes – These are the most active form of carotenes and are most abundant in green plants, carrots, sweet potatoes, squash, apricots, and green peppers. (Although red, cayenne does not contain pro-vitamin A carotene.) The best supplement form of carotenes is nonhydrogenated palm oil (absorbed 4-10 times better than any other type). In addition, palm oil has minimal fat content.

Carotenes are the most widespread group of naturally occurring pigments and are intensely colored (red and yellow) fat-soluble compounds. Along with chlorophyll, they are used by plants in photosynthesis to make carbohydrates (sugars, starches, and cellulose). Of the more than 600 carotenes, only 30-50 have vitamin A activity. Beta-carotene has the most pro-vitamin A activity, but several other carotenes have greater antioxidant effects. One of the richest sources of carotenes is fresh carrot juice.

Deficiency Symptoms

Prolonged deficiency can produce frequent colds, retarded growth, lack of appetite and vigor, eye infections, poor vision, night blindness, frequent infections, bad teeth and gums, scaly and dry skin, and a weakened sense of smell and hearing.

Absorption Factors

The conversion of carotenes into vitamin A depends on protein status, thyroid hormones, zinc, and vitamins C, D, E, and choline. Both vitamin A and carotene absorption require essential fatty acids and zinc. When an adequate intake of carotenes is achieved after a meal, no further absorption occurs. Vitamin C, D, E, and choline in the diet, and bile action by the liver is needed to absorb vitamin A and carotenes. Some fatty acids in the meal (vegetable oil, etc.) increase vitamin A and carotene absorption. Liver disease reduces its utilization by the body.

Toxicity Symptoms

Dry and fissured skin, brittle nails, alopecia, gingivitis, chapped lips, anorexia, irritability, fatigue, and nausea. Intracranial pressure with vomiting, headache, joint pain, stupor, papilledema, and prolonged toxicity results in bone fragility and thickening of long bones. There are never any toxicity symptoms from eating carotenes.

Dosage and Cautions

RDA 5000 IU/ ODA 5000 IU/ TDA 20000-30000 IU. It is best to take it only in the form of beta-carotene, the vegetable-source precursor of vitamin A. The therapeutic dose of vitamin A (not carotene) would be 25000 units daily for only a few days! It is dangerous to take too much of this vitamin (which is oil soluble and stores well). In contrast, carotene is safe. The liver will only convert as much of the vitamin as is needed. During an acute viral infection, a single oral vitamin A dose of 50000 IU for 1-2 days (at the most!) is safe, even in infants. Overdosage of vitamin A is dangerous.

Other dosage cautions: Do not regularly take more than 5000 IU daily! Do not take large amounts of it for a long period! Regular use of 50000 IU can cause weakness, hair loss, headaches, enlarged liver and spleen, anemia, stiffness, and joint pain. Beware of fish liver oils! They are extremely rich in vitamins A and D and can damage the heart muscle! Women who might be pregnant must not use vitamin A supplements; instead, use beta-carotene.

Accidental ingestion of a single large dose (100000-300000 IU) reduced acute toxicity in children; however, if no more is taken, complete recovery will result. Toxicity occurs in adults taking more than 50000 IU daily for several years. Women of childbearing age must be careful when taking vitamin A. Daily doses of 10000 IU (found in some supplements) during the first three months of pregnancy are possibly linked to congenital disabilities.

HEALTH DISCLAIMER: The information on this website is for educational uses only and is not a substitute for professional medical advice. Always consult an authorized healthcare provider for any health concerns before using any herbal or natural remedy. We do not establish, treat, cure, or prevent any disease. Reliance on any material from this website is solely at your own risk. We are not responsible for any adverse effects resulting from the use of information or products mentioned on this website.

REFERENCES

Vance Ferrell, Harold M. Cherne, M.D. 2010. The Natural Remedies Encyclopedia. Altamont : Harvestime Books, 2010. pp. 105, 106. Vol. Seventh.

Last update on 2025-04-20 / Affiliate links / Images from Amazon Product Advertising API