Vitamin A is a group of unsaturated nutritional organic compounds that includes several pro vitamin A carotenoids (most notably beta carotene). In foods of animal origin, there is a major form of vitamin A. The retinol form functions as a storage form of the vitamin.
It is recorded in history that Hippocrates cured night blindness by prescribing ox liver to the patients, which is now known to contain high quantities of vitamin A. In 1912, Frederick Gowland Hopkins demonstrated that unknown accessory factors found in milk, other than carbohydrates, proteins, and fats were necessary for growth in rats.
By 1913 one of these substances was independently discovered by Mc Collum and Davis as a fat soluble “accessory factor” that was needed for proper growth of rats, fed a synthetic diet. The “accessory factors” were termed as “fat soluble”in 1918 and later “vitamin A” in 1920. In 1919, steenbock proposed a relationship between yellow plant pigments and vitamin A.
It (retinol, retinoic acid) is a nutrient important to vision, growth, cell division, reproduction and immunity. Vitamin A also has antioxidant properties. Antioxidants are substances that might protect your cells against the effects of free radicals — molecules produced when your body breaks down food or is exposed to tobacco smoke and radiation. Free radicals might play a role in heart disease, cancer and other diseases.
Vitamin A is found in many foods, such as spinach, dairy products and liver. Other sources are foods rich in beta-carotene, such as green leafy vegetables, carrots and cantaloupe. Your body converts beta-carotene into vitamin A
As an oral supplement, vitamin A mainly benefits people who have a poor or limited diet or who have a condition that increases the need for vitamin A, such as pancreatic disease, eye disease or measles. If you take vitamin A for its antioxidant properties, keep in mind that the supplement might not offer the same benefits as naturally occurring antioxidants in food.
The recommended daily amount of vitamin A is 900 micrograms (mcg) for adult men and 700 mcg for adult women. Excessively high intake leads to accumulation in liver and tissues beyond the capacity of normal binding proteins, so the free, unbound vitamin A circulates in the system and causes liver and bone damage, hair loss, vomiting and headaches. The common toxicity signs and symptoms include increased cerebrospinal fluid pressure, hepatomegaly, joint pains, excessive skin dryness, scaling, desquamation and alopecia in addition , excess of the retinoid compounds have been found to cause fetal deformations. Thus, women who have a chance of becoming pregnant should avoid treatment with medications. Retinoids tend to be very long acting; side effects and birth defects have been reported to occur months after discontinuing retinoid therapy. If you are or might become pregnant, talk to your doctor before taking vitamin A. Excess use of vitamin A during pregnancy has been linked to birth defects.
About 70-90% of retinol is normally absorbed. However, in people with very low fat intake (less than 10% of energy from fat), absorption of both retinol and carotene is impaired and thus are associated with vitamin A deficiency.
Research on oral vitamin A for specific conditions shows:
● Acne.Large doses of oral vitaminA supplements don't appear to affect acne.
● Age-related macular degeneration. A large clinical trial showed that people at high risk of advanced age-related macular degeneration reduced their risk of developing the condition by 25 percent by taking a specific combination of vitamins that included beta-carotene. It's not entirely clear what role beta-carotene played.
● Cancer.The association between use of vitaminA supplements and reduced risk of lung, prostate and other types of cancer is unclear.
● Measles.VitaminA supplements are recommended for children with measles who are at an increased risk of vitamin A deficiency. Research suggests that supplementation might reduce death due to measles.
● VitaminA deficiency .People who have low
levels of vitaminA appear to benefit most from vitamin A supplements. This kind of deficiency isn't common in the United States. Vitamin A deficiency causes anemia and dry eyes.
Beyond use as an oral supplement, vitamin A is used in topical creams to reduce fine wrinkles, splotches and roughness and treat acne.
Thanks Giving
This article is written and submitted to The E Today by Shrushti Mehta.
We thank her for her research and analysis and hope to see the awareness about health and nutrition being spread ahead to larger mass of our citizens.