Vitamin A is a fat-soluble vitamin. Retinol is one of the most active, or usable, forms of vitamin A, and is found in animal foods such as liver, whole eggs, whole milk and in some fortified food products. Retinol is often called preformed vitamin A. It can be converted to retinal and retinoic acid, other active forms of the vitamin A family.
Some plant foods contain darkly colored pigments called provitamin A carotenoids that can be converted to vitamin A. In the U.S., approximately 30% of vitamin A consumed is provided by provitamin A carotenoids. Beta-carotene is a provitamin A carotenoid that is more efficiently converted to retinol than other carotenoids.
For example, alpha-carotene and b-cryptoxanthin are also converted to vitamin A, but only half as efficiently as beta-carotene. Lycopene, lutein, and zeaxanthin are other carotenoids commonly found in food. They are not sources of vitamin A but have other health promoting properties.
Vitamin A is essential for innumerable biological functions – growth, night and color vision, healthy skin, immune response, reproductive and adrenal function, bone and cartilage development, epithelial maintenance, cell membrane stability, and mucous secretions.vitamin A[/glossary] to be a “toxic vitamin” or one of little value because its potential dangers have been exaggerated. Toxicity is related to dosage and form — everything is harmful at some level. Water-soluble vitamin A does not bioaccumulate in the liver as the typical fat-soluble form does. Very high doses (above 100,000 IU per day) of the water-soluble form are routinely used by many alternative doctors for a variety of conditions with a much greater degree of safety.
There is no question that, when taken in excess, fat-soluble vitamins can accumulate in tissues and cause symptoms of toxicity. A 1995 study reported that women who take more than 10,000 IU of preformed vitamin A daily during the first three months of pregnancy run an increased risk of having a child with birth defects. The study neglects to point out, however, that a vitamin A deficiency also puts an unborn child at risk and that vitamin E may prevent vitamin A from oxidizing and becoming toxic.
Although women of child-bearing age must be extremely cautious (consult a doctor before taking over 10,000 IU of either form), in other circumstances vitamin A can have profound therapeutic effects. It fights infection and supports the immune system right along with zinc lozenges, vitamin C and echinacea. The World Health Organization recommends large doses of vitamin A to treat measles — a leading killer in developing countries. The late nutrition pioneer, Carlton Fredericks, Ph.D., recommended single doses of vitamin A as high as 200,000 IU for three to five days to stop the onset of a cold. Since vitamin A is important for the body’s first line of defense, the mucous membrane, it may well be the anti-infective vitamin of choice. Therapeutic doses also help treat glaucoma and conjunctivitis (an inflammation of the mucous membrane that lines the eyelids). In this instance, topical, sterile vitamin A is used.
Healthy adults produce vitamin A from vegetable carotenes, but many people, particularly infants, diabetics and individuals with poor thyroid function, do so less efficiently. Vitamin supplements can be an important source of vitamin A for such people, yet many vegetarian and prenatal products contain only beta carotene, which appears to convert to vitamin A at a fixed rate. Preformed vitamin A delivers the desired dosage more reliably; it is found naturally in foods such as yellow and dark-green vegetables, fruits, dairy foods, eggs and cod liver oil.
Toxicity symptoms include chapped lips, dry skin, headache, fatigue, emotion swings and muscle or joint pain.
References
Dunne, L. Nutrition Almanac, 12-13, McGraw-Hill, NY, 1990
Rothman, K. “Teratogenicity of high vitamin A intake,” New England Journal of Medicine 333: pp.1369-73, Nov. 23, 1995
Vitamin A can help with the following
Parkinson's Disease / Risk
Vitamin A works with other antioxidants to provide a protective effect.
Allergy / Intolerance to Foods (Hidden)
Please see the link between Food Allergy and Digestive Enzymes.
Allergic Rhinitis / Hay Fever
The following vitamins can help your symptoms: vitamin A (10,000 to 15,000 IU per day); vitamin B6 (50 to 100mg per day); vitamin B5 (50 to 75mg per day); vitamin C (1,000mg three to four times per day); vitamin E (400 IU per day).
Gluten Sensitivity / Celiac Disease
In one study, six people with diet-treated celiac disease had abnormal dark-adaptation tests (indicative of “night blindness”), even though some were taking a multivitamin that contained vitamin A. Some of these people showed an improvement in dark adaptation after receiving larger amounts of vitamin A (10,000–25,000 IU per day), either orally or by injection. [Lancet 1973;2: pp.1161-4]
Anemia (Iron deficiency)
Vitamin A and iron supplementation had the following effect on anemic pregnant women: 35% became non-anemic with only Vitamin A. 68% became non-anemic with just iron supplementation. 97% became non-anemic after supplementation with both Vitamin A and iron. [Lancet, 342 (8883), November 27, 1993, pp.1325-1328]
IBS (Irritable Bowel Syndrome)
See the link between IBS and Vitamin B12.
Lyme Disease
Vitamin A deficiency appears to be both a consequence of Lyme disease (Borrelia burgdorferi infection) and a factor in the resulting arthritis susceptibility. Although not known definitively, taking vitamin A may improve joint symptoms. Vitamin A-deficient mice were found to be more susceptible to arthritis following infection by the spirochete that produces Lyme disease in humans. [J Infect Dis 1996 Oct;174(4): pp.747-51]
Cystic Fibrosis
One of the fat soluble vitamins, along with D and E, which may not be absorbed properly in CF. There are water soluble preparations of these available.
Osteoporosis / Risk
In a study of 72,337 women aged 34-77 years, there were 603 incidences of hip fracture. Women taking a vitamin A supplement had a 40% increased risk of hip fracture. This risk was increased among those who consumed at least 3,000 mcg/day of retinol equivalents of vitamin A from the diet. [JAMA January 2, 2002;287(l): pp.47-54]
Animal, human, and laboratory research suggest an association between greater vitamin A intake and weaker bones. Researchers have also noticed that worldwide, the highest incidence of osteoporosis occurs in northern Europe, a population with a high intake of vitamin A. However, decreased biosynthesis of vitamin D associated with lower levels of sun exposure in this population may also contribute to this finding.
To further test the association between excess dietary intake of vitamin A and increased risk for hip fracture, researchers in Sweden compared bone mineral density and retinol intake in approximately 250 women with a first hip fracture to 875 age-matched controls. They found that a dietary retinol intake greater than 1,500 mcg/day (more than twice the recommended daily intake for women) was associated with reduced bone mineral density and increased risk of hip fracture as compared to women who consumed less than 500 mcg per day. [Ann Intern Med. 1998;129: pp.770-778]
If osteoporosis is present, and vitamin A treatment is indicated for other reasons, it would be wise to limit the duration of high dose vitamin A use.
There is no evidence of an association between beta-carotene intake and increased risk of osteoporosis. Current evidence points to a positive osteoporosis risk in postmenopausal women who are consuming increased amounts of food or supplemental vitamin A in its retinol form only.
Diabetes Type II
Recent research shows that Type II diabetics who consumed foods high in vitamin A were the most efficient insulin users. [Facchini, F., et al. “Relation between dietary vitamin intake and resistance to insulin-mediated glucose disposal in healthy volunteers,” Am J of Clin Nutr 63: pp.946-49, June 1996]
Pancreatectomy
Fat-soluble vitamins such as A, D, E and K are absorbed more efficiently in the presence of fat. A low fat diet results in poorer absorption of the fat soluble vitamins.
Bile (from the liver and gallbladder) breaks down large fat molecules to tiny droplets which provide lipase (from the pancreas) with an enormously increased surface to work on. This action takes place in the small intestine and the lipase involved here is a part of the pancreatic secretion.
Night Blindness
When you enter a dark room, the vitamin A changes shape and helps your eyes realize that you’ve entered a dark room.
Despite this heavy demand for vitamin A, it still is pretty hard to develop a deficiency of this nutrient in the United States, where the foods in which it is contained are plentiful. Common staples such as milk and margarine are fortified with vitamin A, and orange and yellow foods such as sweet potatoes and carrots are rich sources of beta-carotene. (Beta-carotene is a precursor of vitamin A and converts to vitamin A in the body.) We need to depend on outside sources for vitamin A because the body can’t make its own.
A healthy liver is usually able to store up to a year’s supply of vitamin A. You would have to be chronically deprived of vitamin A food sources for quite a while for it to affect your sight, as is the case with millions of children in developing nations.
“Night blindness resulting from vitamin A deficiency is very, very, very, very rare in individuals who live in America,” says Dr. Reichel. And even if it does develop, it can frequently be reversed within an hour by injections of vitamin A.
Most people with night blindness have eyes that mobilize vitamin A so slowly that it takes a while to adjust to the dark, says Dr. Reichel. People notice it most often when they’re going into theaters or driving at night.
Adolescent Acne
Vitamin A (150,000-300,000iu/day) may help decrease sebum production also. This very high level of vitamin A can have toxic side effects over a long period of time, so must be used in a special form and under naturopathic supervision.
Warts
Vitamin A ( a water-soluble kind only) taken orally at 100,000IU /day for a month, then 50,000IU/day for 1 month, then 25,000IUK/day may cause warts to disappear. Vitamin A helps normalize cell resistance and assists the immune system. Do not take over 10,000IU/day if there is any chance of pregnancy.
Eczema
Vitamin A can be useful in any skin healing process. Levels of 10-15,000 IUs are usually sufficient.
Adult Acne
Vitamin A has been shown to be effective in treating acne when used at very high doses (300,000 to 400,000IU per day) for many months, but caution must be advised because vitamin A toxicity can result. The toxicity potential means that this therapy must be monitored closely, conducted with a water-soluble form of vitamin A and probably be used in lower doses (100,000 to 200,000IU) along with other therapies, not as a single treatment.
Breast Cancer
Vitamin A and vitamin D3 inhibit breast cancer cell division and can induce cancer cells to differentiate into mature, noncancerous cells. Vitamin D3 works synergistically with tamoxifen (and melatonin) to inhibit breast cancer cell proliferation. Breast cancer patients should take 4000 to 6000 IU of vitamin D3 every day on an empty stomach. Water-soluble vitamin A can be taken in doses of 100,000 to 300,000 IU every day. Monthly blood tests are needed to make sure toxicity does not occur in response to these relatively high daily doses of vitamin A and vitamin D3. After 4 to 6 months, the doses of vitamin D3 and vitamin A can be reduced. If pregnancy is a possibility, these doses of vitamin A should not be used.
Menorrhagia (Heavy Periods)
In one study, serum retinol levels (a measure of vitamin A levels) were found to be significantly lower in women with menorrhagia than in healthy controls. One should not exceed 10,000 IU per day if at risk of becoming pregnant.
Cervical Dysplasia
Vitamin A can be used at 75,000 IU per day for 2 months or until Pap smear results improve, then 25,000 IU per day as a maintenance dose. The preferred form is water-soluble vitamin A. However, doses of vitamin A over 10,000 IU/day should not be considered if pregnancy is a possibility. Vitamin A injections into the cervix have been used successfully when other methods have failed.
Susceptibility To Miscarriages
Vitamin A, vitamin E, and beta-carotene levels tend to be lower in women who have miscarried; these nutrients are generally found in prenatal vitamins.
Premenstrual Syndrome / PMDD
Vitamin A has been shown to be beneficial in reducing PMS symptoms when given in doses of 100,000 to 300,000iu per day in the second half of the menstrual cycle. These levels should only be achieved by a water-soluble form of vitamin A and supervised by a Natural Doctor. Beta-carotenes may be better indicated since they are less toxic and endogenous regulation of conversion to retinol helps maintain more appropriate levels. The enzymatic conversion of beta-carotene to vitamin A is increased twofold during mid-ovulation. It is believed that there is a storage capacity for beta-carotene, which is converted to retinol as needed by the corpus luteum.
Motherhood Issues
The risk of vitamin A deficiency is higher for young children whose mothers are vitamin A deficient. Maternal vitamin A deficiency results in reduced fetal stores and lower levels of vitamin A in breastmilk.
Infants and young children who are vitamin A deficient are at an increased risk of appetite loss, eye problems, lower resistance to infections, more frequent and severe episodes of diarrhea and measles, iron deficiency anemia, and growth failure. Infections and inflammation accelerate the use and loss of vitamin A.
The increased risk of illness leads to an increased risk of death. Studies show that in communities where vitamin A deficiency is prevalent, improving vitamin A status reduces child deaths by an average of 23%. Vitamin A is particularly protective against deaths due to diarrhea and measles and may reduce the severity of malaria symptoms.
In the first six months of life, breastmilk protects the infant against infectious diseases that can deplete vitamin A stores and interfere with vitamin A absorption. Vitamin A intake of a breastfed child depends on the vitamin A status of the mother, the stage of lactation, and the quantity of breastmilk consumed. From birth to about six months of life, frequent breastfeeding can provide the infant with all the vitamin A needed for optimal health, growth, and development. Breastmilk is generally higher in nutritional value than alternative foods and liquids fed to children in developing countries. Consumption of other foods decreases the amount of breastmilk consumed and may disrupt the infant’s absorption of vitamins and minerals from the breastmilk. Therefore, exclusive breastfeeding until six months of age helps ensure sufficient vitamin A intake.
Possible Pregnancy-Related Issues
The U.S. RDA is 4,000 IU or 800mg. NOTE: Be very careful to avoid high doses of over 10,000 IU per day during pregnancy or if there is a likelihood of becoming pregnant soon.
Key
| May do some good |
| Likely to help |
| Highly recommended |
| May have adverse consequences |
| Reasonably likely to cause problems |
| Avoid absolutely |
Glossary
Vitamin A
A fat-soluble vitamin essential to one's health. Plays an important part in the growth and repair of body tissue, protects epithelial tissue, helps maintain the skin and is necessary for night vision. It is also necessary for normal growth and formation of bones and teeth. For Vitamin A only, 1mg translates to 833 IU.
Retina
A 10-layered, frail nervous tissue membrane of the eye, parallel with the optic nerve. It receives images of outer objects and carries sight signals through the optic nerve to the brain.
Provitamin
A substance found in certain foods, that the body may convert into a vitamin. Also called previtamin.
Beta-Carotene
The most abundant of the carotenoids, beta-carotene has strong provitamin A activity and is a stronger antioxidant than vitamin A. It is widely accepted today as a cancer preventative. It is found in leafy green and yellow vegetables, often missing in children's diets. Beta-Carotene is believed to be a superior source of Vitamin A because it is readily converted into a more active form of the substance: your body converts it to Vitamin A as needed.
Carotenoid
A group of red, orange and yellow pigments found in plant foods and in the tissues of organisms that consume plants. Carotenoids have antioxidant activity and some, but not all, can act as precursors of vitamin A. Studies have shown that several carotenoids other than beta-carotene are potent antioxidants that provide profound health benefits. Because of this, the scientific community has now recognized the importance of natural mixed carotenoids including beta-carotene.
Cartilage
Specialized fibrous connective tissue that forms the skeleton of an embryo and much of the skeleton in an infant. As the child grows, the cartilage becomes bone. In adults, cartilage is present in and around joints and makes up the primary skeletal structure in some parts of the body, such as the ears and the tip of the nose.
IU
International Units. One IU is 1/40th (0.025) of a microgram (mcg).
Vitamin E
An essential fat-soluble vitamin. As an antioxidant, helps protect cell membranes, lipoproteins, fats and vitamin A from destructive oxidation. It helps protect red blood cells and is important for the proper function of nerves and muscles. For Vitamin E only, 1mg translates to 1 IU.
Immune System
A complex that protects the body from disease organisms and other foreign bodies. The system includes the humoral immune response and the cell-mediated response. The immune system also protects the body from invasion by making local barriers and inflammation.
Zinc
An essential trace mineral. The functions of zinc are enzymatic. There are over 70 metalloenzymes known to require zinc for their functions. The main biochemicals in which zinc has been found to be necessary include: enzymes and enzymatic function, protein synthesis and carbohydrate metabolism. Zinc is a constituent of insulin and male reproductive fluid. Zinc is necessary for the proper metabolism of alcohol, to get rid of the lactic acid that builds up in working muscles and to transfer it to the lungs. Zinc is involved in the health of the immune system, assists vitamin A utilization and is involved in the formation of bone and teeth.
Vitamin C
Also known as ascorbic acid, Vitamin C is a water-soluble antioxidant vitamin essential to the body's health. When bound to other nutrients, for example calcium, it would be referred to as "calcium ascorbate". As an antioxidant, it inhibits the formation of nitrosamines (a suspected carcinogen). Vitamin C is important for maintenance of bones, teeth, collagen and blood vessels (capillaries), enhances iron absorption and red blood cell formation, helps in the utilization of carbohydrates and synthesis of fats and proteins, aids in fighting bacterial infections, and interacts with other nutrients. It is present in citrus fruits, tomatoes, berries, potatoes and fresh, green leafy vegetables.
pH
A measure of an environment's acidity or alkalinity. The more acidic the solution, the lower the pH. For example, a pH of 1 is very acidic; a pH of 7 is neutral; a pH of 14 is very alkaline.
Mucous Membranes
The membranes, such as the mouse, nose, anus, and vagina, that line the cavities and canals of the body which communicate with the air.
Glaucoma
A disease of the eye characterized by vision loss due to an increase in the pressure of fluid within the eye. This rise in pressure results from a build-up of aqueous fluid and leads to progressive damage to the optic nerve that transmits visual signals to the brain. Over time, glaucoma can lead to a gradual loss in peripheral vision. There are usually no signs that you're developing glaucoma until vision loss occurs.
Topical
Most commonly 'topical application': Administration to the skin.
Diabetes Mellitus
A disease with increased blood glucose levels due to lack or ineffectiveness of insulin. Diabetes is found in two forms; insulin-dependent diabetes (juvenile-onset) and non-insulin-dependent (adult-onset). Symptoms include increased thirst; increased urination; weight loss in spite of increased appetite; fatigue; nausea; vomiting; frequent infections including bladder, vaginal, and skin; blurred vision; impotence in men; bad breath; cessation of menses; diminished skin fullness. Other symptoms include bleeding gums; ear noise/buzzing; diarrhea; depression; confusion.
Thyroid
Thyroid Gland: An organ with many veins. It is at the front of the neck. It is essential to normal body growth in infancy and childhood. It releases thyroid hormones - iodine-containing compounds that increase the rate of metabolism, affect body temperature, regulate protein, fat, and carbohydrate catabolism in all cells. They keep up growth hormone release, skeletal maturation, and heart rate, force, and output. They promote central nervous system growth, stimulate the making of many enzymes, and are necessary for muscle tone and vigor.
Chapped
Roughened, reddened, or cracked skin, especially as a result of cold or exposure.
Teratogenicity
Property of an agent that causes physical defects in the developing embryo.