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THE VITAMIN A FAMILY
Vitamin A is a family of fat-soluble vitamins. Retinol is one of the most active, or usable, forms of vitamin A, and is found in animal foods such as liver and eggs. 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 your body can convert to vitamin A. Approximately 26% and 34% of vitamin A consumed by men and women is provided by these provitamin A carotenoids. Beta-carotene is a provitamin A carotenoid that is more efficiently converted to retinol than other carotenoids. For example, alpha-carotene is also converted to vitamin A, but only half as efficiently as beta-carotene. Lycopene, lutein, and zeaxanthin are other carotenoids commonly found in food. Your body cannot convert them to vitamin A, but they help maintain good health in other ways.
Vitamin A plays an important role in vision, bone growth, reproduction, cell division and cell differentiation, which is the process by which a cell decides what it is going to become. It also maintains the surface linings of your eyes and your respiratory, urinary, and intestinal tracts. When those linings break down, bacteria can enter your body and cause infection (9). Vitamin A also helps your body regulate its immune system. The immune system helps prevent or fight off infections by making white blood cells that destroy harmful bacteria and viruses. Vitamin A may help lymphocytes, a type of white blood cell that fights infections, function more effectively. Vitamin A also may help prevent bacteria and viruses from entering your body by maintaining the integrity of skin and mucous membranes.
Some carotenoids, in addition to serving as a source of vitamin A, have been shown to function as antioxidants in laboratory tests. However, this role has not been consistently demonstrated in humans. Antioxidants protect cells from free radicals, which are potentially damaging by-products of your body's metabolism that may contribute to the development of some chronic diseases.
VITAMIN A
This famed vision-enhancing nutrient was isolated in 1930, the first fat-soluble vitamin to be discovered. The body acquires some of its vitamin A through animal fats. The rest it synthesizes in the intestines from the beta-carotene and other carotenoids abundant in many fruits and vegetables.
Vitamin A is stored in the liver. Small amounts are also found in most human tissues in chemical forms called retinoids, a name related to the vitamin's critical effect on vision (and particularly on the retina of the eye).
Although vitamin A is probably best known for promoting and maintaining healthy eyesight, it has other important functions as well. Vitamin A prevents night blindness and other eye problems, as well as some skin disorders, such as acne. One of its major contributions is to improve the body's resistance to infection. It enhances immunity, may heal gastrointestinal ulcers, protects against pollution and cancer formation, and is needed for the maintenance and repair of epithelial tissue, of which the skin and mucous membranes are composed. Other surface linings that are improved and maintained include the intestinal tract, urinary tract, and respiratory tract, protecting them from harmful bacteria and viruses so that they cannot get into your body. Vitamin A boosts immunity by enhancing the infection-fighting actions of the white blood cells called lymphocytes, thus protecting the body against colds, influenza, and infections of the kidneys, bladder, lungs, and mucous membranes. Vitamin A acts as an antioxidant, helping to protect the cells against cancer and other diseases. It is important in the formation and growth of bones and teeth, the division of cells in your body, aids in fat storage, and is vital to human reproduction. This important vitamin also slows the aging process. Protein cannot be utilized by the body without vitamin A. See Antioxidants for more information.
A deficiency of vitamin A may be apparent if dry hair or skin, dryness of the conjunctiva and cornea, poor growth, and/or night blindness is present. Other possible results of vitamin A deficiency include abscesses in the ears; insomnia; fatigue; reproductive difficulties; sinusitis, pneumonia, and frequent colds and other respiratory infections; skin disorders, including acne; and weight loss.
THE CAROTENOIDS
The carotenoids are a class of compounds related to vitamin A. In some cases, they can act as precursors of vitamin A; some act as antioxidants or have other important functions. The best known of the carotenoids is beta-carotene, but there are others, including alpha- and gamma-carotene, lutein, and lycopene. When food or supplements containing beta-carotene are consumed, the beta-carotene is converted into vitamin A in the liver. According to recent reports, beta-carotene appears to aid in cancer prevention by scavenging, or neutralizing, free radicals.
Taking large amounts of vitamin A over long periods can be toxic to the body, mainly the liver. Toxic levels of vitamin A are associated with abdominal pain, amenorrhea, enlargement of the liver and/or spleen, gastrointestinal disturbances, hair loss, itching, joint pain, nausea and vomiting, water on the brain, and small cracks and scales on the lips and at the corners of the mouth. No overdose can occur with beta-carotene, although if you take too much, your skin may turn slightly yellow-orange in color. Beta-carotene does not have the same effect as vitamin A in the body and is not harmful in larger amounts unless you cannot convert beta-carotene into vitamin A. People with hypothyroidism often have this problem. It is important to take only natural beta-carotene or a natural carotenoid complex. Betatene is the trade name for a type of carotenoid complex extracted from sea algae. It is used as an ingredient in various products by different manufacturers.
SOURCES OF VITAMIN A
FOOD SOURCES
Vitamin A can be found in animal livers, fish liver oils, and green and yellow fruits and vegetables. Foods that contain significant amounts include apricots, asparagus, beet greens, dulse, fish liver and fish liver oil, garlic, kale, mustard greens, papayas, peaches, pumpkin, red peppers, spirulina, spinach, sweet potatoes, Swiss chard, turnip greens, watercress, and yellow squash.
Whole eggs, whole milk, and liver are among the few foods that naturally contain vitamin A. Most fat free milk and dried nonfat milk solids sold in the US are fortified with vitamin A to replace the vitamin A lost when the fat is removed. Fortified foods such as fortified breakfast cereals also provide vitamin A. The tables of selected food sources of vitamin A list a variety of animal sources of vitamin A and plant sources of provitamin A carotenoids.
It is important for you to regularly eat foods that provide vitamin A or beta-carotene even though your body can store vitamin A in the liver. Stored vitamin A will help meet your needs when intake of provitamin A carotenoids or preformed vitamin A is low. HERBAL SOURCES
Vitamin A is also present in the following herbs: Alfalfa, Borage Leaves, Burdock Root, Cayenne (Capsicum), Chickweed, Eyebright, Fennel Seed, Hops, Horsetail, Kelp, Lemongrass, Mullein, Nettle, Oat Straw, Paprika, Parsley, Peppermint, Plantain, Raspberry Leaf, Red Clover, Rose Hips, Sage, Uva Ursi, Violet Leaves, Watercress, and Yellow Dock.
SELECTED FOOD SOURCES OF VITAMIN A
As the 2000 Dietary Guidelines for Americans state, "Different foods contain different nutrients. No single food can supply all the nutrients in the amounts you need". The following tables list a variety of dietary sources of vitamin A and provitamin A carotenoids. As the tables indicate, liver, eggs and whole milk are good animal sources of vitamin A. Many orange fruits and green vegetables are good sources of provitamin A carotenoids. Including these foods in your daily diet will help you meet your daily need for vitamin A. In addition, food manufacturers fortify a wide range of products with vitamin A. Breakfast cereals, pastries, breads, crackers, cereal grain bars and other foods may be fortified with 10 to 15 percent of the DV for vitamin A. If you want more information about building a healthful diet, refer to the Dietary Guidelines for Americans and the Food Guide Pyramid.
If you want more information about building a healthful diet, refer to the Dietary Guidelines for Americans and the Food Guide Pyramid.
TABLE OF SELECTED ANIMAL SOURCES OF VITAMIN A
Animal sources of vitamin A are well absorbed and used efficiently by the body.
FOOD IU/International Units %DV* Liver, beef, cooked, 3 oz. 30,325 610 Liver, chicken, cooked, 3 oz. 13,920 280 Egg substitute, fortified, 1/4 cup 1355 25 Fat free milk, fortified w/ vitamin A, 1 cup 500 10 Cheese pizza, 1/8 of a 12 inch diameter 380 8 Milk, whole, 3.25% fat, 1 cup 305 6 Cheddar cheese, 1 oz. 300 6 Whole egg, 1 medium 280 6 Swiss cheese, 1 oz. 240 4 Yogurt, fruit flavored, low fat, 1 cup 120 2 % DV = Daily Value. DVs are reference numbers based on the Recommended Dietary Allowance (RDA). They were developed to help consumers determine if a food contains a lot or a little of a specific nutrient. The DV for vitamin A is 5,000 IU (1,500 micrograms retinol). The percent DV (%DV) listed on the nutrition facts panel of food labels tells adults what percentage of the DV is provided in one serving. Percent DVs are based on a 2,000 calorie diet. Your Daily Values may be higher or lower depending on your calorie needs. Foods that provide lower percentages of the DV also contribute to a healthful diet.
TABLE OF SELECTED PLANT SOURCES OF VITAMIN A (FROM BETA CAROTENE)
Plant sources such as beta carotene are not as well absorbed as animal sources of vitamin A.
FOOD IU/International Units %DV* Carrot, 1 raw (7.5 inches) 20,250 410 Carrots, boiled, 1/2 cup slices 19,150 380 Carrot juice, canned, 1/2 cup 12,915 260 Mango, raw, without refuse, 1 fruit 8,050 160 Sweet potatoes, 1/2 cup Junior mashed 7,430 150 Spinach, boiled, 1/2 cup 7,370 150 Cantaloupe, raw, 1 cup cubes 5,160 100 Kale, boiled, 1/2 cup 4,810 100 Vegetable soup, prepared with equal volume water, 1 cup 3,005 60 Pepper, sweet, red, raw, 1/2 cup sliced 2,620 50 Apricots, without skin, canned in water, 1/2 cup halves 2,055 40 Spinach, raw, 1 cup 2,015 40 Broccoli, frozen, chopped, boiled, 1/2 cup 1,740 35 Apricot nectar, canned, 1/2 cup 1,650 30 Oatmeal, instant, fortified, low sodium, dry, 1 packet 1,050 20 Tomato juice, canned, 6 oz. 1,010 20 Ready-to-eat cereal, fortified, 1 oz. (15% fortification) 750 15 Peaches, canned, water pack, 1/2 cup halves or slices 650 15 Peach, raw, 1 medium 525 10 Papaya, raw, 1 small 430 10 Orange, raw, 1 large 375 8 Asparagus, boiled, 4 spears 325 6 Tomato, red, ripe, raw, 1/2 inch thick slice 170 2 *DV = Daily Value. DVs are reference numbers based on the Recommended Dietary Allowance (RDA). They were developed to help consumers determine if a food contains a lot or a little of a specific nutrient. The DV for vitamin A is 5,000 IU (1,000 RE). The percent DV (%DV) listed on the nutrition facts panel of food labels tells adults what percentage of the DV is provided by one serving. Percent DVs are based on a 2,000-calorie diet. Your Daily Values may be higher or lower depending on your calorie needs. Foods that provide lower percentages of the DV will contribute to a healthful diet.
COMMENTS
Antibiotics, laxatives, and some cholesterol-lowering drugs interfere with vitamin A absorption.
CAUTIONS
If you have liver disease, do not take a daily dose of over 10,000 IU of vitamin A in pill form, or any amount of cod liver oil. If you are pregnant, do not take more than 10,000 IU of vitamin A daily. Children should not take more than 18,000 IU of vitamin A on a daily basis for over one month.
If you hypothyroidism, avoid beta-carotene, because your body probably cannot convert beta-carotene into vitamin A.
SPECIFIC CONDITIONS VITAMIN A MAY HELP
Promote Healthy Vision: This nutrient is involved in the proper functioning of the retina of the eye and is essential for the integrity of the mucous membranes surrounding the eyes. It is invaluable in preventing night blindness, and assisting the eye in adapting from bright light to darkness. Vitamin A eyedrops (available over-the-counter) are also effective in treating a disorder known as dry eye, caused by a failure of the tear glands to produce sufficient fluid.
Ward Off Infections: By supporting the healthy maintenance of mucous membranes, vitamin A may be useful for fighting colds and other common infections. In the case of chronic bronchitis, the nutrient encourages healing of damaged lung tissue and may even help to prevent recurrences. In a Brazilian study of men with chronic lung disease, it was found that participants who were given 5,000 IU of vitamin A daily for 30 days could breathe more easily than those who took a placebo.
Fight Cancer: This immune-system booster may be of value in combating breast and lung cancers and in increasing the survival rate of leukemia patients. It may also protect against the development of a melanoma (a form of skin cancer that is often malignant). In addition, some research indicates that cancer patients with high vitamin A levels respond particularly well to chemotherapy treatment.
Treat Skin Disorders: Vitamin A is helpful in treating skin disorders, such as acne, eczema, psoriasis, and rosacea. Research has shown that vitamin A is vital for healthy skin. In the 1940s, high doses were prescribed for conditions such as psoriasis and acne. This practice ended abruptly with the realization that such high doses are toxic.
Today, health care providers commonly prescribe safer medications made from derivatives of vitamin A, such as retinoic acid (Retin A, a popular prescription cream for acne and wrinkles) and isotretinoin (Accutane, an oral drug prescribed for severe acne). Short of prescription medications, however, careful use of moderate oral doses - see the Dosage Recommendations Chart - may be key to promoting skin health.
Control Cold Sores: Vitamin A has well-known antiviral properties, and it may be worth trying orally to boost immunity. Liquid forms can even be applied directly to cold sores, also known as fever blisters, which develop as a result of a herpes simplex viral infection.
Correct Hair & Scalp Problems: One of the signs of a vitamin A deficiency (albeit a severe one) is flakiness of the scalp. Correcting the deficiency may eliminate this often itchy and embarrassing condition. But keep in mind that more isn't always better when it comes to vitamins: Too much vitamin A (more than 100,000 IU a day) taken over a long time can actually cause hair loss (among other problems).
Encourage Wound Healing: When applied to the skin, vitamin A cream or ointment can accelerate the healing of minor cuts, burns, and scrapes.
Protect Against Certain Gastrointestinal Problems: Because it is helpful in protecting the lining of the digestive tract, vitamin A may ease symptoms of inflammatory bowel disease and ulcers. A large study of health care providers ages 40 to 75 showed that those who were least likely to suffer from ulcers of the duodenum (a part of the small intestine) were the ones who had the highest intake of vitamin A, mainly from a combination of diet, multivitamins, and supplements.
Note: Vitamin A has also been found to be useful for a number of other disorders. For information on these additional ailments, see the Dosage Recommendations Chart for Vitamin A.
SUPPLEMENT FORMS
Tablet. Suppository. Softgel. Ointment. Liquid. Cream. Capsule.
RECOMMENDED DIETARY INTAKE
The RDA for vitamin A is 5,000 IU daily for men, and 4,000 IU daily for women.
Dietary Reference Intakes are reference values used for planning and assessing diets for healthy people. The Recommended Dietary Allowance (RDA), one of the DRIs, recommends the average daily dietary intake level that is sufficient to meet the nutrient requirements of nearly all (97-98 percent) healthy individuals in each age and gender group. RDAs for vitamin A are listed as Retinol Activity Equivalents (RAE) to account for the different activities of retinol and provitamin A carotenoids. RDAs are also listed in International Units (IU) because food and some supplement labels list vitamin A content in International Units (1 RAE in micrograms = 3.3 IU). The 2001 RDAs for adults and children (21) in mcg RAE and IUs are:
RECOMMENDED DIETARY ALLOWANCES FOR VITAMIN A FOR CHILDREN & ADULTS IN MICROGRAMS (mcg) RETINOL ACTIVITY EQUIVALENTS (RAE) & INTERNATIONAL UNITS (IUs)
AGE CHILDREN MEN WOMEN PREGNANCY LACTATION Ages 1-3 300 mcg
or
1000 IU*Ages 4-8 400 mcg
or
1333 IUAges 9-13 600 mcg
or
2000 IUAges 14-18 900 mcg
or
3000 IU700 mcg
or
2333 IU750 mcg
or
2500 IU1200 mcg
or
4000 IUAges 19+ 900 mcg
or
3000 IU700 mcg
or
2333 IU770 mcg
or
2565 IU1300 mcg
or
4335 IU*Food labels list vitamin A in International Units (IU).
There is insufficient information to establish a RDA for vitamin A for infants. An adequate intake (AI) has been established that is based on the amount of vitamin A consumed by healthy infants who are fed breast milk. The AI for vitamin A for infants ages 0 to 6 months is 400 micrograms per day (1,330 IU). The AI for vitamin A for infants ages 7 to 12 months is 500 micrograms per day (1,665 IU).
Results of two national surveys, the third National Health and Nutrition Examination Survey (NHANES III 1988-91) and the Continuing Survey of Food Intakes by Individuals (CSFII 1994) suggested that the dietary intake of some Americans does not meet recommended levels for vitamin A. These surveys highlight the importance of encouraging all Americans to include dietary sources of vitamin A in their daily diets.
There is no separate RDA for beta-carotene or other provitamin A carotenoids. The Institute of Medicine report suggests that consuming 3 to 6 mg of beta-carotene daily will maintain plasma beta-carotene blood levels in the range associated with a lower risk of chronic diseases. A diet that provides five or more servings of fruits and vegetables per day and includes some dark green and leafy vegetables and deep yellow or orange fruits will provide recommended amounts of beta-carotene.
VITAMIN A DEFICIENCY
If You Get Too Little: Vitamin A deficiency rarely occurs in the United States, but it is still a major public health problem in the developing world. Although few people in the United States suffer from a deficiency of vitamin A, those with vitamin-poor diets are at risk (indeed, some elderly individuals fall into this category). From 3 to 10 million children develop xeropthalmia, damage to the cornea of the eye, and 250,000 to 500,000 go blind each year from a deficiency of vitamin A. Most of these children live in developing countries.
Signs of Vitamin A Deficiency: Low levels can significantly reduce resistance to infection, cause a flaky scalp, and contribute to heavy or prolonged menstrual periods. And very low levels of this nutrient can cause night blindness or even complete blindness.
Night blindness is one of the first signs of vitamin A deficiency. In ancient Egypt it was known that night blindness could be cured by eating liver, which was later found to be a rich source of vitamin A.
Vitamin A deficiency contributes to:
- Blindness by making the eye very dry and promoting damage to the retina of the eye.
- Dry skin, dry hair, broken fingernails.
- Decreased resistance to infections.
In countries where immunization programs are not widespread and vitamin A deficiency is common, millions of children die each year from complications of infectious diseases such as measles. When there is not enough vitamin A, cells lining the lung lose their ability to remove disease-causing microorganisms. This may contribute to the pneumonia associated with vitamin A deficiency.
There is increased interest in subclinical forms of vitamin A deficiency, described as low storage levels of vitamin A that do not cause overt deficiency symptoms. This mild degree of vitamin A deficiency may increase children's risk of developing respiratory and diarrheal infections, decrease growth rate, slow bone development, and decrease likelihood of survival from serious illness. Children living in the United States who are considered to be at increased risk for subclinical vitamin A deficiency include:
- Toddlers and preschool age children.
- Children living at or below the poverty level.
- Children with inadequate health care or immunizations.
- Children living in areas with known nutritional deficiencies.
- Recent immigrants or refugees from developing countries with high incidence of vitamin A deficiency or measles.
- Children with diseases of the pancreas, liver, intestines, or with inadequate fat digestion/absorption.
Vitamin A deficiency can also occur when vitamin A is lost through diarrhea, depletion of liver stores of vitamin A, and through an overall inadequate intake, as is often seen with protein-calorie malnutrition.
Low plasma retinol concentration, which is considered a good indicator of inadequate vitamin A nutritional status, can also result from an inadequate intake of protein, calories, and zinc. These nutrients are needed to make Retinol Binding Protein (RBP), which is essential for mobilizing vitamin A from your liver and transporting vitamin A to your general circulation.
Iron deficiency can also limit the metabolism of vitamin A, and iron supplements provided to iron deficient individuals may improve vitamin A nutriture as much as iron status.
Excess alcohol intake depletes vitamin A from your body and is associated with reduced vitamin A intake. It is very important for anyone who consumes excessive amounts of alcohol to include good sources of vitamin A in his or her diet. Vitamin A supplementation may not be recommended for individuals who abuse alcohol because alcohol may increase liver toxicity associated with excess intakes of vitamin A. A medical practitioner would need to evaluate this situation and determine the need for vitamin A supplementation.
VITAMIN A DEFICIENCY PREVENTION
As a result of the adverse health effects of vitamin A deficiency in children, the World Health Organization (WHO) and the United Nations International Children's Emergency Fund (UNICEF) issued joint statements about vitamin A and children's health. Both agencies recommend vitamin A administration for all children diagnosed with measles in communities where vitamin A deficiency is a serious problem and where death from measles is greater than 1 percent. In 1994, the American Academy of Pediatrics recommended vitamin A supplementation for two subgroups of children likely to be at high risk for subclinical vitamin A deficiency. These subgroups were children 6-24 months of age who had been hospitalized with measles and hospitalized children older than 6 months.
Fat malabsorption can promote diarrhea and prevent normal absorption of vitamin A. This is most often seen with cystic fibrosis, sprue, pancreatic disorders, and after stomach surgery. Healthy adults usually have a one-year reserve of vitamin A stored in their livers and should not be at risk of deficiency during periods of temporary or short term fat malabsorption. Long-term problems absorbing fat, however, can result in deficiency, and in these instances physicians may advise vitamin A supplementation. Children may only have enough stores of vitamin A to last several weeks. Physicians treating children with fat malabsorption may recommend vitamin A supplementation.
Vegetarians who do not consume eggs and dairy foods need greater amounts of provitamin A carotenoids to meet their need for vitamin A. It is important for vegetarians to include a minimum of five servings of fruits and vegetables daily and to regularly choose dark green leafy vegetables and orange and yellow fruits to consume recommended amounts of vitamin A.
VITAMIN A, BETA CAROTENE & CANCER
Surveys suggest an association between diets rich in beta-carotene and vitamin A and a lower risk of many types of cancer. There is evidence that a higher intake of green and yellow vegetables or food sources of beta-carotene and/or vitamin A may decrease the risk of lung cancer. However, a number of studies that tested the role of beta-carotene supplements in cancer prevention did not find it to be protective. In a study of 29,000 men, incidence of lung cancer was greater in the group of smokers who took a daily supplement of beta-carotene. The Carotene and Retinol Efficacy Trial, a lung cancer chemoprevention trial that provided randomized subjects with supplements of beta-carotene and vitamin A, was stopped after researchers discovered that subjects receiving beta-carotene had a 46 percent higher risk of dying from lung cancer. The IOM states that "beta-carotene supplements are not advisable for the general population," although they also state that this advice "does not pertain to the possible use of supplemental beta-carotene as a provitamin A source for the prevention of vitamin A deficiency in populations with inadequate vitamin A nutriture". EXCESSIVE VITAMIN A & VITAMIN A TOXICITY
If You Get Too Much: Excessive vitamin A can cause serious health problems. It is virtually impossible to get too much of this nutrient from foods; the body makes only what it needs from carotenoid-rich fruits and vegetables. But care is needed when taking supplements containing "preformed" vitamin A, meaning it has been synthesized for you already during the manufacturing process.
Symptoms of Vitamin A Toxicity: Symptoms include dry and cracking skin, brittle nails, excessive hair loss, bleeding gums, weight loss, irritability, nausea, and fatigue. An extremely high single dose - 500,000 IU, for example - can cause vomiting and weakness.
Hypervitaminosis A refers to high storage levels of vitamin A in the body that can lead to toxic symptoms. There are three major adverse effects of hypervitaminosis A:
- Birth defects.
- Liver abnormalities.
- Reduced bone mineral density that may result in osteoporosis.
When toxic symptoms arise suddenly, which can happen after consuming very large amounts of preformed vitamin A over a short period of time, signs of toxicity include nausea and vomiting, headache, dizziness, blurred vision, and muscular uncoordination.
Although hypervitaminosis A can occur when very large amounts of liver are regularly consumed, most cases of vitamin A toxicity result from an excess intake of vitamin A in supplements. The Institute of Medicine has established tolerable upper levels (UL) of intake for vitamin A from supplements to help prevent the risk of toxicity. The risk of adverse health effects increases at intakes greater than the UL.
TABLE OF UPPER LIMITS (UL) IN MICROGRAMS (mcg) & INTERNATIONAL UNITS (IU) FOR RETINAL ACTIVITY EQUIVALENTS
AGE CHILDREN MEN WOMEN PREGNANCY LACTATION Ages 0-12
Months600 mcg
or
2000 IU*Ages 1-3 600 mcg
or
2000 IUAges 4-8 900 mcg
or
3000 IUAges 9-13 1700 mcg
or
5665 IUAges 14-18 2800 mcg
or
9335 IU2800 mcg
or
9335 IU2800 mcg
or
9335 IU2800 mcg
or
9335 IUAges 19+ 3000 mcg
or
10,000 IU3000 mcg
or
10,000 IU3000 mcg
or
10,000 IU3000 mcg
or
10,000 IU
Retinoids are compounds that are chemically similar to vitamin A. Over the past 15 years, synthetic retinoids have been prescribed for acne, psoriasis, and other skin disorders. Isotretinoin (RoaccutaneŽ or AccutaneŽ) is considered an effective anti-acne therapy. At very high doses, however, it can be toxic, which is why this medication is usually saved for the most severe forms of acne. The most serious consequence of this medication is birth defects. It is extremely important for sexually active females who may become pregnant and who take these medications to use an effective method of birth control. Women of childbearing age who take these medications are advised to undergo monthly pregnancy tests to make sure they are not pregnant.
EXCESSIVE CAROTENOIDS & HEALTH RISKS
Nutrient toxicity traditionally refers to adverse health effects from a high intake of a particular vitamin or mineral. For example, large amounts of active, or preformed, vitamin A (naturally found in animal foods such as liver but also available in dietary supplements) can cause birth defects.
Provitamin A carotenoids such as beta-carotene are generally considered safe because they are not traditionally associated with specific adverse health effects. The conversion of provitamin A carotenoids to vitamin A decreases when body stores are full, which naturally limits further increases in storage levels. A high intake of provitamin A carotenoids can turn the skin yellow, but this is not considered dangerous to health.
Recent clinical trials that associated beta-carotene supplements with a greater incidence of lung cancer and death in current smokers raised concern about the safety of beta-carotene supplements. However, conflicting studies make it difficult to interpret the health risk. For example, the Physicians' Health Study compared the effects of taking 50 mg beta-carotene every other day to a placebo (sugar pill) in over 22,000 male physicians and found no adverse health effects. Also, a trial that tested the ability of four different nutrient combinations to inhibit the development of esophageal and gastric cancers in 30,000 men and women in China suggested that after 5 years those participants who took a combination of beta-carotene, selenium and vitamin E had a 13 percent reduction in cancer deaths. One point to consider is that there may be a relationship between alcohol and beta-carotene because "only those men who consumed more than 11 g per day of alcohol (approximately one drink per day) showed an adverse response to B-carotene supplementation" in the lung cancer trial.
The Institute of Medicine did not set a Tolerable Upper Intake Level (UL) for carotene or carotenoids. Instead, they concluded that beta-carotene supplements are not advisable for the general population. As stated earlier, however, they may be appropriate as a provitamin A source or for the prevention of vitamin A deficiency in specific populations.
GENERAL THERAPEUTIC DOSAGE INFORMATION
SPECIAL TIPS
Some sources measure vitamin A in retinol equivalents (RE) rather than international units (IU); one RE is equivalent to 3.3 IU.
Most multi-vitamins offer vitamin A as beta-carotene, an antioxidant that the body can convert to vitamin A. However, the amount of vitamin A produced during this conversion is small and inadequate for those conditions in which vitamin A itself was shown to be therapeutic.
For improved resistance to colds, flu, and other viral infections: Take 50,000 IU twice a day for five days; then reduce to 25,000 IU a day, if necessary, for no more than 10 days.
Be sure to check out the Dosage Recommendations Chart for Vitamin A, which lists therapeutic dosages for specific ailments at a glance.
GUIDELINES FOR USE
Make sure to take vitamin A supplements with food; some fat in the diet will enhance absorption.
Both vitamin E and zinc aid the body in using vitamin A. In turn, vitamin A facilitates the absorption of iron from foods. A good daily multiple-vitamin & mineral supplement will provide the necessary amounts.
GENERAL INTERACTIONS
Do not take vitamin A with isotretinoin or other acne drugs. Together, they may cause high blood levels of vitamin A, which can lead to unwanted side effects.
VITAMIN A - SPECIFIC DRUG INTERACTIONS
Isotretinoin: When taken together, levels of vitamin A in the body may build up, increasing the chance of side effects.
Resorcinol: When taken together, levels of vitamin A in the body may build up, increasing the chance of side effects.
Sulfur Topical: When taken together, levels of vitamin A in the body may build up, increasing the chance of side effects.
Tazarotene: When taken together, levels of vitamin A in the body may build up, increasing the chance of side effects.
DOSAGE CAUTIONS
Do not exceed recommended doses of vitamin A. Large doses of preformed vitamin A can build up to toxic levels.
If you are pregnant or trying to get pregnant, do not take more than 5,000-10,000 IU of vitamin A daily. Higher amounts may result in birth defects. Practice birth control if consuming doses greater than 5,000-10,000 IU, and for a month after stopping.
AILMENTS DOSAGE Acne Bronchitis
Chronic: 10,000 IU a day. Take no more than 5,000-10,000 IU per day if you are pregnant.Burns Cold Sores Common Cold Crohn's Disease Cuts, Scrapes, & Wounds Ear Aches Eczema
Chronic: 5,000-10,000 IU day; may be partially covered by your daily multi-vitamin and antioxidant complex.Flu Hair Problems Kidney Stones
Maintenance: 10,000 IU a day; may be partially covered by your daily multivitamin and antioxidant complex.Psoriasis Rosacea Shingles Sore Throat Strains & Sprains Hyperthyroid Disease Ulcers Warts
REFERENCES
National Institutes of Health (NIH), Bethesda, MD, in conjunction with the Office of Dietary Supplements (ODS) in the Office of the Director of NIH.
VITAMIN A & CAROTENE SUPPLEMENTS
Beta Carotene (Dry Natural), 100% Natural Dunaliella Salina, Nature's Way, 25,000 IU, 100 Caps
Beta Carotene from Nature's Way is a potent and popular antioxidant found in plants and vegetables. Antioxidants help combat free radicals and molecules which damage cells and DNA.
Beta Carotene (Natural Dunaliella Salina), Nature's Way, 100% Natural, 25,000 IU, 100 Softgels
Nature's Way beta carotene is 100% all natural from Dunaliella Salina.
Dry Vitamin A & D, Nature's Way, 15,000 / 400 IU, 100 Caps
Vitamin A & D are both involved in the cycles of mineral and hormone balance which help to maintain normal bone formation and density. In addition, Vitamin A is an important nutrient in maintaining cell membrane integrity, and normal vision and reproduction.
Multi-Carotene Antioxidant, Nature's Way, 60 Softgels
Protectamins Multi-Carotene Antioxidant Carotene Supplement contains several antioxidants from the Carotene family, and the highest level of Alpha Carotene available, naturally extracted from red palm fruit.
Sure Sight Liquid Formula, Eye Supplement, Dairy Free & Kosher, Dynamic Health, 8 fl. oz.
This Sure Sight Liquid Eye Supplement helps maintain vision and eye health. Dynamic Health Sure Sight liquid dietary supplement is a unique formulation of the highest quality ingredients that have been clinically tested to help maintain vision and eye health.
Vitamin A, 10,000 IU, 100% Natural, Nature's Way, 100 Softgels
Nature's Way vitamin A is 100% natural from fish liver oil. It contains no artificial ingredients or preservatives.
Vitamin A, Fish Liver Oil, NOW Foods, 25,000 IU, 250 Softgels
NOW Foods Vitamin A from Fish Liver Oil provides high quality Vitamin A which is essential for the maintenance of healthy epithelial tissue which is found in the skin, eyes, respiratory system, GI and urinary tracts.
Herbal Remedies: Vitamin A / Carotenoids / Retinol Information
Herbal Remedies: Vitamin A / Carotenoids / Retinol Supplements & Products
MoonDragon's Health & Wellness: Nutrition Basics - Vitamins Index
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HELPFUL PRODUCTS & FURTHER EDUCATION
Prescription for Nutritional Healing: The A-To-Z Guide To Supplements
-- by Phyllis A. Balch, James F. Balch - 2nd Edition
Prescription for Nutritional Healing: The A-To-Z Guide To Supplements
-- by Phyllis A. Balch, James F. Balch - 4th Edition
Prescription for Herbal Healing: The A-To-Z Reference To Common Disorders
-- by Phyllis A. Balch
The Complete Guide to Natural Healing
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Mountain Rose Bulk Herbs
Mountain Rose Aromatherapy Oils
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