Vitamin A
3-Dehydroretinol, 3-Déhydrorétinol, Acétate de Rétinol, Antixerophthalmic Vitamin, Axerophtholum, Dehydroretinol, Déhydrorétinol, Fat-Soluble Vitamin, Oleovitamin A, Palmitate de Rétinol, Retinoids, Rétinoïdes, Retinol, Rétinol, Retinol Acetate, Retinol Palmitate, Retinyl Acetate, Rétinyl Acétate, Retinyl Palmitate, Rétinyl Palmitate, Vitamin A Acetate, Vitamin A Palmitate, Vitamin A1, Vitamin A2, Vitamina A, Vitamine A, Vitamine A1, Vitamine A2, Vitamine Liposoluble, Vitaminum A.
Vitamin A is a vitamin. It can be found in many fruits, vegetables, eggs, whole milk, butter, fortified margarine, meat, and oily saltwater fish. It can also be made in a laboratory. Carotenoids are a group of yellow or orange chemicals found in plants. Some of these can be converted to vitamin A in the body.
Vitamin A is used for treating vitamin A deficiency. It is also used to reduce complications of diseases such as malaria, HIV, measles, and diarrhea, and to improve growth, in children with vitamin A deficiency.
Women use vitamin A for heavy menstrual periods, premenstrual syndrome (PMS), vaginal infections, yeast infections, "lumpy breasts" (fibrocystic breast disease), and to prevent breast cancer. Some women with HIV use vitamin A to decrease the risk of transmitting HIV to the baby during pregnancy, childbirth, or breast-feeding. It may also be used to prevent various complications during and following childbirth and to improve infant development.
Men use vitamin A to raise their sperm count.
Some people use vitamin A for improving vision and treating eye disorders including age-related macular degeneration (AMD), glaucoma, retinitis pigmentosa, and cataracts. It may also be used to promote healing after eye surgery.
Vitamin A is also used for skin conditions including acne, eczema, psoriasis, cold sores, wounds, burns, sunburn, keratosis follicularis (Darier's disease), ichthyosis (noninflammatory skin scaling), lichen planus pigmentosus, and pityriasis rubra pilaris.
It is also used for gastrointestinal ulcers, Crohn's disease, parasites in the intestines, gum disease, diabetes, Hurler syndrome (mucopolysaccharidosis), sinus infections, hayfever, respiratory infections, osteoarthritis, tuberculosis, and urinary tract infections (UTIs). It is also used to reduce symptoms of a liver disease associated with drinking too much alcohol (alcoholic hepatitis) and of Parkinson's disease.
Vitamin A is also used for shigellosis, diseases of the nervous system, nose infections, loss of sense of smell, asthma, allergy prevention, persistent headaches, kidney stones, overactive thyroid, iron-poor blood (anemia), deafness, ringing in the ears, and precancerous mouth sores (leukoplakia).
Other uses include preventing and treating cancer, including non-Hodgkin's lymphoma, and to reduce side effects during cancer treatment. It is also used for protecting the heart and cardiovascular system, slowing the aging process, and boosting the immune system.
Vitamin A is applied to the skin to improve wound healing, reduce wrinkles, and to protect the skin against UV radiation.
How does it work?
Vitamin A is required for the proper development and functioning of our eyes, skin, immune system, and many other parts of our bodies.
Effective for...
- Vitamin A deficiency. Taking vitamin A by mouth is effective for preventing and treating symptoms of vitamin A deficiency. Vitamin A deficiency can occur in people with protein deficiency, diabetes, over-active thyroid, fever, liver disease, cystic fibrosis, or an inherited disorder called abetalipoproteinemia.
Possibly Effective for...
- Breast cancer. Premenopausal women with a family history of breast cancer who consume high levels of vitamin A in their diet seem to have lower risk of breast cancer. It is not known if taking vitamin A supplements has the same benefit.
- Cataracts. People who consume high amounts of vitamin A in their diet seem to have a lower risk of developing cataracts.
- Measles. Taking vitamin A by mouth seems to reduce the risk of measles complications or death in children with measles and vitamin A deficiency.
- Precancerous lesions in the mouth (oral leukoplakia). Research suggests that taking vitamin A can help treat precancerous lesions in the mouth.
- Pregnancy-related death. Taking vitamin A before and during pregnancy seems to reduce the risk of death by 40% in malnourished women.
- Pregnancy-related nightblindness. Taking vitamin A during pregnancy seems to reduce nightblindness by 37% in malnourished women. Vitamin A might work better for this condition when taken with zinc.
- Diarrhea after giving birth. Taking vitamin A before, during, and after pregnancy reduces diarrhea after giving birth in malnourished women.
- Eye disease affecting the retina (retinitis pigmentosa). Taking vitamin A can slow the progression of an eye disease that causes damage to the retina.
Possibly Ineffective for...
- Atopic disease. Giving a single dose of vitamin A to infants does not seem to prevent atopy.
- Breathing problems that affect newborns (bronchopulmonary dysplasia). Research shows that injecting vitamin does not reduce the risk of breathing problems in most low birth weight infants.
- Gastrointestinal side effects of chemotherapy. Taking vitamin A by mouth does not seem to prevent diarrhea or mouth pain caused by chemotherapy in children.
- Fetal and early infant death. Taking vitamin A supplements before, during, or after pregnancy does not seem to prevent infant death during the first year of life. Also giving vitamin A supplements to infants does not seem to prevent death.
- Intestinal parasites. Giving a single dose of vitamin A to children taking medicine to treat intestinal parasites does not seem to prevent reinfection compare to only taking the medicine.
- Skin cancer (melanoma). Research shows that taking a high dose of vitamin A by mouth does not increase relapse-free survival in people with melanoma.
- Miscarriage. Women who take vitamin A by mouth, alone or in combination with other vitamins before or during early pregnancy, do not have a lower risk of miscarriage or stillbirth.
- Osteoarthritis. Taking vitamin A does not seem to reduce pain in people with spinal osteoarthritis who have adequate levels of vitamin A. Also, taking a specific product containing selenium, vitamin A, vitamin C, and vitamin E does not appear to improve osteoarthritis symptoms.
- Tuberculosis. Low levels of vitamin A are common in people with tuberculosis. However, taking vitamin A does not appear to improve symptoms or decrease the risk of death in people with this condition.
Likely Ineffective for...
- Head and neck cancer. Taking vitamin A by mouth does not reduce the risk of developing new tumors or improve survival in people with head and neck cancer.
- HIV transmission. Taking vitamin A by mouth does not lower the risk of passing HIV to the fetus during pregnancy, to newborns during delivery, or to infants during breastfeeding. In fact, early research suggests that HIV-positive women who take vitamin A supplements during pregnancy might have an increased risk of passing HIV to their babies through breast milk.
- Lower airway infections. Taking vitamin A by mouth does not prevent or reduce symptoms of lower airway infections in children. In fact, vitamin A is linked with a slight increase in the risk of respiratory tract infections in children.
- Pneumonia. Taking vitamin A by mouth does not help treat or prevent pneumonia in children living in developing countries.
Insufficient Evidence to Rate Effectiveness for...
- Alcohol-related liver disease. Early research shows that taking vitamin A together with coenzyme Q10 and other vitamins and minerals does not improve survival in people with liver disease caused by alcohol use.
- Anemia. Taking vitamin A may help increase levels of proteins that store iron. This may reduce the risk of anemia in children and pregnant women. However, in developing nations in which anemia is common, taking vitamin A (retinol) with iron and folate does not seem to improve anemia in pregnant women compared to taking only iron and folate.
- Cervical cancer. Research suggests that increased vitamin A levels in the blood or higher vitamin A intakes are associated with a lower risk of cervical cancer. However, this only appears to be the case when both forms of vitamin A, retinol and carotenes, are considered. Intake of retinol alone is not linked with a reduced risk of cervical cancer.
- Child development. Taking vitamin A does not appear to improve growth in children with normal nutrition. However, taking vitamin A might improve growth in children with vitamin A deficiency.
- Cancer that starts in the bone marrow (chronic myelogenous leukemia (CML)). Early research shows that taking vitamin A along with an anticancer drug does not improve survival in people with this condition compared to taking the anticancer drug alone. In fact, taking vitamin A along with this drug might increase the risk of toxicity.
- Rectal damage caused by radiation therapy. Early research suggests that taking vitamin A (retinol palmitate) can reduce rectal symptoms caused by pelvic radiotherapy.
- Colon and rectal polyps (colorectal adenoma). Taking a combination supplement containing selenium, zinc, vitamin A, vitamin C, and vitamin E might reduce the recurrence of precancerous polyps in the large intestine.
- Colorectal cancer. Taking vitamin A alone or along with beta-carotene does not seem to prevent colorectal cancer.
- Surgery to improve blood flow to the heart (coronary artery bypass). Early research suggests that taking vitamin A might reduce the time needed in intensive care during this type of surgery. It also might reduce the time in the hospital after surgery.
- Esophageal cancer. Higher intake of vitamin A and beta-carotene is linked to a reduced risk of esophageal cancer. But taking vitamin A in combination with beta-carotene does not seem to prevent esophageal cancer.
- Stomach cancer. Taking vitamin A alone or with beta-carotene does not seem to prevent stomach cancer.
- HIV. Taking vitamin A during pregnancy does not seem to reduce the risk of death for the mother or child. Also, vitamin A supplementation during pregnancy does not seem to prevent HIV progression in women with HIV and low levels of vitamin A. However, giving vitamin A to HIV-positive infants and children might reduce the risk of HIV-related death.
- Diarrhea related to HIV. Taking vitamin A might decrease the risk of death from diarrhea in children with vitamin A deficiency, with or without HIV. But conflicting results exist.
- Infant development. Giving vitamin A as a shot might improve brain development by one year in some infants. But it seems to work only in very small infants who are also given nitric oxide gas.
- Lung cancer. Most research suggests that taking vitamin A does not increase survival in people with lung cancer. Also, taking vitamin A with beta-carotene might increase the risk of lung cancer in smokers and people exposed to asbestos. But it's not clear if this effect is due to beta-carotene. It's possible that this increased risk is linked with beta-carotene use, not vitamin A.
- Malaria. Taking vitamin A by mouth seems to decrease malaria symptoms in children less than 3 years-old living in areas where malaria is common. But taking vitamin A does not seem to improve symptoms or prevent death caused by of a severe form of malaria that affects brain function.
- Non-Hodgkin lymphoma. People who consume higher amounts of vitamin A in the diet seem to have a slightly lower risk of non-Hodgkin's lymphoma.
- Ovarian cancer. Early research suggests that taking vitamin A does not reduce the risk of developing ovarian cancer.
- Overall mortality. Taking vitamin A does not seem to reduce the risk of death in healthy adults. Some research suggests that giving vitamin A to children aged 6 months to 5 years might decrease the risk of death, especially in those at risk for vitamin deficiency. But conflicting results exist.
- Pancreatic cancer. Taking vitamin A along with beta-carotene does not seem to prevent pancreatic cancer.
- Parkinson's disease. Early research suggests that blood levels or dietary intake of vitamin A are not associated with risk of Parkinson's disease.
- Recovery from laser eye surgery (photoreactive keratectomy). Taking vitamin A by mouth along with vitamin E seems to improve healing after laser eye surgery.
- Prostate cancer. Vitamin A intake from the diet does not seem to be linked with a reduced risk of prostate cancer.
- Age-related macular degeneration (AMD).
- Glaucoma.
- Improving immune function.
- Preventing and speeding recovery from infections.
- Promoting good vision.
- Relieving hay fever symptoms.
- Wound healing.
- Other conditions.
Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, and Insufficient Evidence to Rate (detailed description of each of the ratings).
Vitamin A is LIKELY SAFE for most people when taken by mouth or given as a shot into the muscle in amounts less than 10,000 IU daily.
Vitamin A is POSSBILY UNSAFE when taken by mouth in high doses. Some scientific research suggests that higher doses might increase the risk of osteoporosis and hip fracture, particularly in older people. Adults who eat low-fat dairy products, which are fortified with vitamin A, and a lot of fruits and vegetables usually do not need vitamin A supplements or multivitamins that contain vitamin A.
Long-term use of large amounts of vitamin A might cause serious side effects including fatigue, irritability, mental changes, anorexia, stomach discomfort, nausea, vomiting, mild fever, excessive sweating, and many other side effects. In women who have passed menopause, taking too much vitamin A can increase the risk of osteoporosis and hip fracture.
There is growing concern that taking high doses of antioxidant supplements such as vitamin A might do more harm than good. Some research shows that taking high doses of vitamin A supplements might increase the chance of death from all causes and possibly other serious side effects.
Vitamin A is LIKELY SAFE for children when taken in the recommended amounts. The maximum amounts of vitamin A that are safe for children are based on age:
- Less than 2000 IU/day in children up to 3 years old.
- Less than 3000 IU/day in children ages 4 to 8 years old.
- Less than 5700 IU/day in children ages 9 to 13 years old.
- Less than 9300 IU/day in children ages 14 to 18 years old.
Excessive use of alcohol: Drinking alcohol may increase vitamin A's potentially harmful effects on the liver.
Anemia: People who are anemic and have low levels of vitamin A might need to take iron along with a vitamin A supplement to treat this condition.
Disorders in which the body does not absorb fat properly: People with conditions that affect fat absorption, such as celiac disease, short gut syndrome, jaundice, cystic fibrosis, pancreatic disease, and cirrhosis of the liver, are not able to absorb vitamin A properly. To improve vitamin A absorption, these people should use vitamin A preparations that are water-soluble.
A type of high cholesterol called "Type V hyperlipoproteinemia": This condition might increase the chance of vitamin A poisoning. Do not take vitamin A if you have this condition.
Intestinal infections: Intestinal infections such as hookworm can reduce how much vitamin A the body absorbs.
Liver disease: Too much vitamin A might make liver disease worse. Do not take vitamin A if you have liver disease.
Malnutrition: In people with severe protein malnutrition, taking vitamin A might result in having too much vitamin A in the body.
Zinc deficiency: Zinc deficiency might cause symptoms of vitamin A deficiency to occur. Taking a combination of vitamin A and zinc supplements might be necessary to improve this condition.
Medications for skin conditions (Retinoids)Interaction Rating: Major Do not take this combination.
Some medications for skin conditions have vitamin A effects. Taking vitamin A pills and these medications for skin conditions could cause too much vitamin A effects and side effects.
Antibiotics (Tetracycline antibiotics)Interaction Rating: Moderate Be cautious with this combination.Talk with your health provider.
Vitamin A can interact with some antibiotics. Taking very large amounts of vitamin A along with some antibiotics can increase the chance of a serious side effect called intracranial hypertension. However, taking normal doses of vitamin A along with tetracyclines does not seem to cause this problem. Do not take large amounts of vitamin A if you are taking antibiotics.
Some of these antibiotics include demeclocycline (Declomycin), minocycline (Minocin), and tetracycline (Achromycin).
Medications that can harm the liver (Hepatotoxic drugs)Interaction Rating: Moderate Be cautious with this combination.Talk with your health provider.
Taking large amounts of vitamin A might harm the liver. Taking large amounts of vitamin A along with medications that might also harm the liver can increase the risk of liver damage. Do not take large amounts of vitamin A if you are taking a medication that can harm the liver.
Some medications that can harm the liver include acetaminophen (Tylenol and others), amiodarone (Cordarone), carbamazepine (Tegretol), isoniazid (INH), methotrexate (Rheumatrex), methyldopa (Aldomet), fluconazole (Diflucan), itraconazole (Sporanox), erythromycin (Erythrocin, Ilosone, others), phenytoin (Dilantin), lovastatin (Mevacor), pravastatin (Pravachol), simvastatin (Zocor), and many others.
Warfarin (Coumadin)Interaction Rating: Moderate Be cautious with this combination.Talk with your health provider.
Warfarin (Coumadin) is used to slow blood clotting. Large amounts of vitamin A can also slow blood clotting. Taking vitamin A along with warfarin (Coumadin) can increase the chances of bruising and bleeding. Be sure to have your blood checked regularly. The dose of your warfarin (Coumadin) might need to be changed.
The following doses have been studied in scientific research:
ADULTS
BY MOUTH:
- General: Recommended Dietary Allowance (RDA) levels for adults have been established: men 14 years and older, 900 mcg/day (3000 IU); women 14 years and older, 700 mcg/day (2300 IU); pregnancy 14 to 18 years, 750 mcg/day (2500 IU); 19 years and older, 770 mcg/day (2600 IU); lactation 14 to 18 years, 1200 mcg/day (4000 IU); 19 years and older, 1300 mcg/day (4300 IU). Tolerable Upper Intake Levels (UL) for vitamin A have also been established. The UL is the highest level of intake that is likely to pose no risk of harmful effects. The ULs for vitamin A are for preformed vitamin A (retinol) and do not include provitamin A carotenoids: adolescents 14 to 18 years (including pregnancy and lactation), 2800 mcg/day (9000 IU); adults age 19 and older (including pregnancy and lactation), 3000 mcg/day (10,000 IU).
- For precancerous lesions in the mouth (oral leukoplakia): Weekly dose of 200,000-300,000 IU of vitamin A has been used for 6-12 months.
- For reducing death during pregnancy: Weekly doses of 23,000 IU of vitamin E have been used before and during pregnancy.
- For reducing night blindness during pregnancy: Weekly doses of 23,000 IU of vitamin E have been used before, during, and after pregnancy. It seems to work best if taken in combination with 35 mg of zinc daily in women who also have low levels of zinc.
- For diarrhea after pregnancy: Weekly doses of 23,000 IU of vitamin E have been used before, during, and after pregnancy.
- For eye disease affecting the retina (retinitis pigmentosa): Daily doses of 15,000 IU of vitamin A, sometimes along with 400 IU of vitamin E daily, has been used.
Vitamin A dosage is most commonly expressed in IU, but dosage in micrograms is sometimes used.
Eating 5 servings of fruits and vegetables per day provides about 50% to 65% of the adult RDA for vitamin A.
BY MOUTH:
- General: Adequate Intake (AI) levels of vitamin A for infants have been established: birth to 6 months, 400 mcg/day (1300 IU); 7 to 12 months, 500 mcg/day (1700 IU).
- For measles: Vitamin A 100,000 to 200,000 IU orally for at least two doses has been used in children less than 2 years-old.
Recommended Dietary Allowance (RDA) levels for children and adults have been established: children 1 to 3 years, 300 mcg/day (1000 IU); 4 to 8 years, 400 mcg/day (1300 IU); 9 to 13 years, 600 mcg/day (2000 IU). Tolerable Upper Intake Levels (UL) for vitamin A have also been established. The UL is the highest level of intake that is likely to pose no risk of harmful effects. The ULs for vitamin A are for preformed vitamin A (retinol) and do not include provitamin A carotenoids: infants and children from birth to 3 years, 600 mcg/day (2000 IU); children 4 to 8 years, 900 mcg/day (3000 IU); 9 to 13 years, 1700 mcg/day (6000 IU); and 14 to 18 years (including pregnancy and lactation), 2800 mcg/day (9000 IU).