More about Vitamin A
Vitamin A is a fat-soluble substance that plays a vital role in the maintenance of optimal vision and in the treatment of skin conditions. It may also improve immune function and combat tumor growth in certain cancers, but unlike many other vitamins, there is such a thing as too much Vitamin A.
Beta-carotene is a precursor to Vitamin A — it is converted to Vitamin A by the body. See beta-carotene for more details.
Vitamin A has a strong influence on the health of the eyes and is used to relieve numerous conditions. Most notably, it has been shown to combat and even reverse night blindness. Vitamin A also helps keep the covering of our eyes, called the cornea, healthy, while a deficiency may allow our eyes to become easily inflamed and irritated.
Vitamin A has been shown to be essential to our bodies' ability to fight infections, and a deficiency may be particularly damaging when we're fighting viral infections. While not alone in being a necessary nutrient for immune-system function, Vitamin A is unique in that it is not just required for a healthy immune system but has been shown to stimulate immune response even when we are not deficient.
Oral Vitamin A supplementation in very high doses was once used to treat severe cases of acne. New developments and the potential for toxicity at effective levels have made this practice virtually obsolete.
Today, the most popular form of Vitamin A for skin treatments is Retin-A — a very strong topical form of Vitamin A. Retin-A is also used as an anti-wrinkle cream as it appears to help keep skin healthy by removing old cells and stimulating the growth of new skin cells. While the removal of the old cells may cause the skin to redden and peel, this appears to be a temporary side effect for few people.
Keep in mind that while Retin-A is a form of Vitamin A, you cannot expect high doses of oral Vitamin A to cause wrinkles to disappear. This topical form is very strong and used in a totally different fashion than the supplement.
Vitamin A's antioxidant capabilities may be optimal at levels that border on the high range of safety; thus, beta-carotene may be the better choice for maximal antioxidant benefits.
Deficiency symptoms and causes
While one study showed Vitamin A deficiencies in elite athletes as high as 25%, deficiency is not a large concern for those who eat a healthy diet with regular intakes of foods rich in Vitamin A, such as liver (with the exception of polar bear livers*), high-fat fish, and whole milk products. These are all great sources of Vitamin A... and of fat — which is not conducive if you are trying to lose or maintain bodyfat levels.
Another avenue to reach the required levels of Vitamin A is to make dark, leafy green vegetables and some fruits a regular part of your diet, as they are rich sources of beta-carotene, which can supplement the effects of Vitamin A.
It is possible to get the recommended levels of Vitamin A in your diet, but whichever route you choose, you've got your work cut out for you. Most Americans' (athletes centrally included) diets are short on fruits and vegetables and incorporate an abundance of processed food, thus providing less than the RDA of Vitamin A.
The requirements for Vitamin A can be further stressed by the use of many medications, including cortisone; regular intake of alcohol; deficiencies of Vitamin E; and stress from exercise or life in general.
Even mild deficiencies can lead to visual impairment, including night blindness and tired eyes; dry skin; and lowered resistance to infections. More severe deficiencies could lead to atrophy of the thymus and spleen, bone softness, fatigue, and insomnia.
On the other side of deficiency is toxicity. Fat-soluble vitamins, such as A, are stored (as you might guess from the name) in our bodyfat. This means that unlike Vitamin B, a water-soluble vitamin which is passed through the body rather rapidly, Vitamin A can be stored to some extent. This is great because you don't have to take it every day. However, it also means that if you take high dosages (exceeding 15,000 IU daily) for a long period of time, you may accumulate too much of it.
*In addition, massive single doses will cause a toxic reaction — as was the case when some arctic explorers enjoyed a meal of polar bear liver, possibly the richest source of Vitamin A available in nature. It is estimated that they consumed over 2,000,000 IU in a short time, over 400 times the RDA, and paid the price for it, suffering from symptoms such as headache, drowsiness, and vomiting. Take away: keep your polar bear liver intake in check — moderation is key here.
In your quest to maintain optimal Vitamin A levels and avoid toxicity, many experts have suggested using a combination of Vitamin A and the pro-vitamin A, beta-carotene. Beta-carotene is a precursor to Vitamin A, which means it can convert to Vitamin A but does so without the risks of toxicity. Approximately 12,000 IU's of beta-carotene converts to 5,000 IU's of Vitamin A.
While Vitamin A is used most commonly by people who have difficulty seeing at night, especially when driving, it may also be beneficial for folks who are fighting infections, leading stressful lives, or exercising intensely.