Overview of Vitamin 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.
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 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.
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, and cataracts.
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, gum disease, diabetes, Hurler syndrome (mucopolysaccharidosis), sinus infections, hayfever, and urinary tract infections (UTIs).
Vitamin A is also used for shigellosis, diseases of the nervous system, nose infections, loss of sense of smell, asthma, 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, 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 Vitamin A work?
Vitamin A is required for the proper development and functioning of our eyes, skin, immune system, and many other parts of our bodies.
Uses & Effectiveness of Vitamin A?
Vitamin A is 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.
Vitamin A is 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 reduced risk of developing breast cancer. It is not known if taking vitamin A supplements has the same benefit.
Cataracts. Research suggests that high intake of vitamin A in the diet is linked to a lower risk of developing cataracts.
Diarrhea related to HIV. Taking vitamin A along with conventional medicines seems to decrease the risk of death from diarrhea in HIV-positive children with vitamin A deficiency.
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.
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.
Recovery from laser eye surgery (photoreactive keratectomy). Taking vitamin A by mouth along with vitamin E seems to improve healing after laser eye surgery.
Complications after pregnancy. Taking vitamin A seems to reduce the risk of diarrhea and fever after pregnancy in malnourished women.
Complications during pregnancy. Taking vitamin A by mouth seems to reduce the risk of death and night blindness during pregnancy in malnourished women.
Eye disease affecting the retina (retinitis pigmentosa). Research suggests that taking vitamin A can slow the progression of an eye disease that causes damage to the retina.
Vitamin A is Possibly Ineffective for
Breathing problems that affect newborns (bronchopulmonary dysplasia). Research shows that injecting vitamin does not reduce the risk of breathing problems in low birth weight infants.
Gastrointestinal side effects of chemotherapy. Taking vitamin A by mouth does not prevent or reduce gastrointestinal side effects of chemotherapy in children.
Fetal and early infant death. Taking vitamin A supplements before, during, or after pregnancy does not seem to reduce the risk of fetal or early infant death when taken by malnourished women. However, giving vitamin A to some infants seems to lower the risk of infant death in areas where malnutrition or vitamin A deficiency is common.
A type of skin cancer called melanoma. Research shows that taking vitamin A by mouth does not increase disease-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 a specific product containing selenium, vitamin A, vitamin C, and vitamin E (Selenium ACE) does not appear to improve osteoarthritis. Also, taking additional vitamin A does not reduce pain in people with spinal osteoarthritis who have adequate levels of vitamin A.
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 tuberculosis.
Vitamin A is 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 respiratory tract infections. Taking vitamin A by mouth does not prevent or reduce symptoms of lower respiratory tract infections in children. In fact, vitamin A is linked to 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.
Vitamin A is Insufficient Evidence 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 alcohol-related liver disease.
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 a specific vitamin A product (Aquasol, Armour Pharmaceuticals) together with busulfan therapy does not improve survival in people with chronic myelogenous leukemia. Taking vitamin A with busulfan therapy might also 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.
Colorectal cancer. Taking vitamin A alone or in combination with beta-carotene does not seem to prevent colorectal cancer.
Esophageal cancer. Some population research suggests that higher intake of beta-carotene and vitamin A is linked to a reduced risk of esophageal cancer. However, other higher quality evidence suggests that taking vitamin A in combination with beta-carotene does not prevent esophageal 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 seems to reduce the risk of HIV-related death.
Lung cancer. Early research suggests that taking vitamin A by mouth might improve survival and reduce the development of new tumors in people with lung cancer. However, other research shows that vitamin A has no effect on lung cancer survival. Also, vitamin A seems to increase the risk of lung cancer in smokers and people exposed to asbestos.
Ovarian cancer. Population research suggests that taking vitamin A does not reduce the risk of developing ovarian cancer.
Overall mortality. Giving vitamin A to children aged 6 months to 5 years seems to decrease the risk of death, especially in those at risk for vitamin deficiency. However, taking vitamin A does not seem to reduce the risk of death in healthy adults.
Pancreatic cancer. Taking vitamin A in combination with beta-carotene does not seem to prevent pancreatic cancer.
Prostate cancer. Vitamin A intake from the diet does not seem to be linked with a reduced risk of prostate cancer.
Stomach cancer. Taking vitamin A alone or with beta-carotene does not seem to prevent stomach cancer.
Promoting good vision.
Age-related macular degeneration (AMD).
Preventing and speeding recovery from infections.
Improving immune function.
Relieving hay fever symptoms.
More evidence is needed to rate vitamin A for these uses.
Side Effects & Safety Issues of Vitamin A
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 units 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 units/day in children up to 3 years old.
• Less than 3000 units/day in children ages 4 to 8 years old.
• Less than 5700 units/day in children ages 9 to 13 years old.
• Less than 9300 units/day in children ages 14 to 18 years old.
Vitamin A is POSSIBLY UNSAFE for children when taken by mouth in high doses. When amounts greater than those recommended are taken, side effects can include irritability, sleepiness, vomiting, diarrhea, loss of consciousness, headache, vision problems, peeling skin, increased risk of pneumonia and diarrhea, and other problems.
Special Precautions & Warnings for Vitamin A
Pregnancy and breast-feeding: Vitamin A is LIKELY SAFE for pregnant or breast-feeding women when taken in recommended amounts of less than 10,000 units per day. Larger amounts are POSSIBLY UNSAFE. Vitamin A can cause birth defects. It is especially important for pregnant women to monitor their intake of vitamin A from all sources during the first three months of pregnancy. Forms of vitamin A are found in several foods including animal products, primarily liver, some fortified breakfast cereals, and dietary supplements.
Excessive use of alcohol: Drinking alcohol may increase vitamin A’s potentially harmful effects on the liver.
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.
Vitamin A Interactions?
Do not take this combination
Medications for skin conditions (Retinoids) interacts with VITAMIN A
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.
Be cautious with this combination
Antibiotics (Tetracycline antibiotics) interacts with VITAMIN A
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. But taking normal doses of vitamin A along with tetracyclines doesn't 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) interacts with VITAMIN A
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) interacts with VITAMIN A
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.
Dosing of Vitamin A
Adequate Intake (AI) levels of vitamin A for infants have been established: birth to 6 months, 400 mcg/day (1300 units); 7 to 12 months, 500 mcg/day (1700 units).
Recommended Dietary Allowance (RDA) levels for children and adults have been established: children 1 to 3 years, 300 mcg/day (1000 units); 4 to 8 years, 400 mcg/day (1300 units); 9 to 13 years, 600 mcg/day (2000 units); men 14 years and older, 900 mcg/day (3000 units); women 14 years and older, 700 mcg/day (2300 units); pregnancy 14 to 18 years, 750 mcg/day (2500 units); 19 years and older, 770 mcg/day (2600 units); lactation 14 to 18 years, 1200 mcg/day (4000 units); 19 years and older, 1300 mcg/day (4300 units). 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 units); children 4 to 8 years, 900 mcg/day (3000 units); 9 to 13 years, 1700 mcg/day (6000 units); 14 to 18 years (including pregnancy and lactation), 2800 mcg/day (9000 units); adults age 19 and older (including pregnancy and lactation), 3000 mcg/day (10,000 units).
Vitamin A dosage is most commonly expressed in units, 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.
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