About 15 percent of Americans, mostly infants and children, get less than the RDA value for vitamin A. Fortunately, the average person has about a two-year supply of vitamin A in their liver, so you have to eat a vitamin A-deficient diet for many months before symptoms will develop.
Mild vitamin A deficiency may be easily overlooked. Dry, rough skin is common. Sometimes the skin can crack and may even become infected. The infection develops because cracks and rough areas in the skin leave openings for microorganisms to enterr and because vitamin A is needed for a strong immune response.
The most recognizable sign of vitamin A deficiency is night blindness (difficulty seeing at night or in low light). This is followed by further damage to the cornea in the form of a condition called xerophthalmia. If left untreated, severe vitamin A deficiency can lead to permanent blindness. Vitamin A deficiency is leading worldwide cause of blindness in childhood and is an enormous problem in many developing countries.
People who are deficient in vitamin A have an increased susceptibility to respiratory infections because of changes in the cells that line the respiratory tract. Because of their depressed immune response, deficient children develop more severe forms of common childhood diseases. And as mentioned earlier, measles can be lethal in a vitamin A-deficient child.
Other possible effects of vitamin A deficiency include slow growth, thickening of bone, kidney stones that originate with changes in some of the cells that line the kidney tubules, diarrhea, and reduced production of steroid hormones in the body. Steroids are produced by the adrenal gland and are a part of your natural response to stress and your immune function. Failure to make these important hormones will leave your immune system in a less-than-ideal slate. Damage to hearing, taste, and smell, nerve damage, and reduced sweat gland function may also occur.
It is possible to measure vitamin A in your blood, but the results of this test are difficult to interpret because of the large amounts that are stored in the liver. Repeatedly low blood value are a direct indication of a severe vitamin deficiency that demands immediate attention.
Adults may develop symptoms of vitamin A toxicity after taking more man 50,000 IU a day for long periods of time or after taking a single dose of 300,000 IU or more. Infants given 7,500 to 15,000 RE (25,000-50,000 IU) of vitamin A for thirty days have developed toxicity symptoms. In children, vitamin A toxic has usually been caused by an overzealous parent giving excessive quantities of supplemental vitamin A. Infants and children who are given 6,000 RE (20,000 IU) of vitamin A a day and who are not deficient are likely to develop overdose symptoms after several months.
Vitamin A overdose is characterized by vomiting, fatigue, swelling due to fluid accumulation, hydrocephalus (water on brain), and headache (caused by excess fluid in the skull, resulting in increased pressure on the brain). Vitamin A overdose has, in some cases, been misdiagnosed as a brain tumor. Other symptoms of overdose are liver and lymph gland enlargement, difficulty sleeping, joint pains, constipation, and rough skin. The effects of an overdose of vitamin A will usually reverse themselves after you stop taking the vitamin.
Since the body will convert as much carotenoid to retinol as it needs, it is possible to have excess unconverted carotene in the blood. A very high concentration of unconverted carotenoids in the blood is known as hypercarolenosis and can cause a yellow discoloration of the skin. This condition has been confused with jaundice, but the two are not related. Hypercarotenosis is unsightly but usually not dangerous.
Toxicity and Pregnant Women
Pregnant women taking excess vitamin A risk bearing a child with birth defects because of the action of the vitamin on the developing fetus. Some of the possible defects are urinary tract malformations, hydrocephalus, and bone deformities. If you are pregnant, do not exceed your doctor’s recommendation for any vitamin or drug, including vitamin A. Current recommendations are to take no more than 10,000 IU per day during pregnancy, and prenatal vitamins contain no more than this amount. But vitamin supplements containing up to 50,000 IU per capsule are readily available, so be careful when selecting a product.
Vitamin A can interact with corticosteroid-type drugs, oral contraceptives, calcium, zinc, and mineral oil. It can also interfere with certain blood tests.
Vitamin A supplements may be given to counteract any of the standard symptoms of vitamin A deficiency reviewed earlier in the profile. However, such symptoms will not be alleviated by viamin A unless they are, in fact, caused by vitamin deficiency.
Plant carotenoids are excellent free-radical scavengers and quenchers of singlet oxygen. As such, they play a role in protecting our cells against oxidative damage and presumably help protect us from a number of chronic diseases linked to free-radical damage.
As discussed earlier, measles can be life-threatening if the child deficient in vitamin A. It has been recommended that the vitamin A status of all seriously ill patients with measles be checked and a high-dose supplement given if needed. A program of pro¬viding vitamin A supplements to children in some developing countries has lowered the infant death rate due to infections.
Animals deficient in vitamin A get cancer more often and their tumors spread more quickly than animals without this deficiency. There is evidence that the same thing holds true for people: Those who are deficient in vitamin A may be at an increased risk of developing cancer, and individuals who do get the disease may find that their cancer spreads more quickly. Low vitamin A intake from vegetables is directly related to an increase in cancer of the lung, bladder, and larynx. However, it is not know; whether the protective effect of vitamin A can be attributed to beta carotene, other plant carotenoids, retinol, or some other component of green and yellow vegetables. Our best advice is to eat plenty of vegetables, as high vegetable intake is consistently associated with lower risk of cancer.
Retinoic acid is me form of vitamin A required for norm cell differentiation and thus cancer prevention. Unfortunately, it is metabolized too quickly and is too toxic in high doses to be practical for therapeutic use in cancer treatment. Other synthetic derivatives of retinoic acid (called, as a group, retinoids) show some promise and are under investigation.
Treatment of Acne
One of the symptoms of vitamin A deficiency is acne like condition. This observation led to the use of vitamin A capsules as an acne treatment in the 195s and 1960s and consequently to the discovery that high doses of vitamin A are toxic. After several decades of using vitamin A capsules to treat acne, the consensus is that the treatment is only marginally effective and carries a significant risk of toxicity.
In the 1970s retinoic acid applied to the skin became popular as an acne treatment, and it is still used today. Topical retinoic acid appears to reduce the plugging of sebaceous (oil-producing) glands. Plugged sebaceous glands can become infected and turn into pimples. Retinoic acid also mildly irritates the skin and causes peeling, which also helps to free plugged sebaceous glands.
Retinoic acid cream or lotion is not the ideal treatment. It can take months for the treatment to begin working, and it is irritating to the skin. In the search for more potent and less toxic retinoic acid derivatives, researchers have discovered several that can be taken by mouth without the usual adverse effects. isotretinoin, or 13-cis-retinoic acid, has been of some benefit to people who suffer from the most severe form of acne and who have not responded to other forms of treatment. These retinoic acid derivatives are strong teratogens (they cause birth defects), and patients on the drug must take steps to make sure they do not get pregnant.
Treatment of Psoriasis
Several retinoic acid derivatives are used with some success to eat psoriasis. These drugs are available only by prescription and carry a significant risk for causing birth defects if taken during pregnancy.
We cannot recommend that you take this vitamin to treat alcoholism, allergies, angina pectoris, arteriosclerosis, arthritis, asthma, ad breath, broken bones, bronchitis, canker sores, cataracts, colitis, the common cold, constipation, cystitis, diabetes, diarrhea, double vision, ear infections, emphysema, epilepsy, eye-strain, fever, flu, gout, hair problems, hay fever, headache, heart attack, heart failure, hemorrhoids, hemophilia, hepatitis, infertility, jaundice, kidney stones, learning disabilities, liver cirrhosis, meningitis, mononucleosis, muscular dystrophy, nail problems, osteomalacia, prostate trouble, psychosis, sinusitis, stroke, swollen glands, thyroid disease, tuberculosis, vaginitis, varicose veins, or worms.
Despite its toxicity, vitamin A can be obtained in any strength without a prescription. Attempts by the FDA to attempt to limit the doses that can be purchased without a prescription have been met with fierce opposition by nutritionally oriented consumer groups.
We do not recommend taking more than 10,000 IU a day unless you are under the guidance of a licensed health care professional who is expert in therapy with vitamin A. This is especially true if you are or might become pregnant. Do not lake vitamin A doses over 10,000 IU per day if you are pregnant or if there is any chance you may become pregnant.
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