Vitamin A

Beta-carotene is a pro-vitamin A, fat-soluble compound found in plants. The body converts beta-carotene to Vitamin A. Retinol is the precursor to active forms of Vitamin A. These forms include retinal, which is used in vision and reproduction, and retinoic acid, needed in growth and genetic differentiation. Synthetic forms of retinoic acid, such as Accutane, are used for severe acne. Vitamin A is found in liver, kidney, butter, whole milk, and fortified milk products. Vitamin A has a high absorption rate. The liver contains 90% of the body's Vitamin A.

A variety of studies have found mixed outcomes on the power of Vitamin A supplements in preventing child mortality. It is estimated that 200 million children across the world under the age of 5 are deficient in this vitamin. Extreme deficiencies result in blindness, serious damage to the immune system, and death.

Vitamin A is used as an immune enhancer in viral diseases. Supplements of this vitamin led to a 50% decrease in mortality from measles in developing countries according to a 1993 report.1 In the United States children with measles were found in 1992 to be deficient in Vitamin A and responded well to supplementation.2 Vitamin A also helps in the production of glycoproteins (such as mucus), which control cell differentiation and gene expression. Deficiency may affect cell tissues and mucus linings of the respiratory, urinary, and secretory glands. Vitamin A is used to treat excess keratin (hyperkeratosis), which is responsible for bumpy skin, acne, psoriasis and other skin conditions. For these conditions it is usually given in high doses which can be toxic. A safe dose for acne treatment is less than 25,000 I.U. per day. High doses during pregnancy are dangerous, and can result in birth defects.

Carotenes are the pigments which provide color in plants and flowers. These naturally occurring, fat-soluble compounds assist in the photosynthesis process, protecting plants and organisms from free radicals which are created in the conversion of sunlight to chemical energy. Some carotenes can be converted into Vitamin A in the body. While beta-carotene has the greatest pro-vitamin A activity, there are other carotenes that are much more powerful antioxidants. These include alpha-carotene and lycopene, which have well-noted anti-cancer effects.

Carotenes with pro-vitamin A activity are found in green leafy vegetables as well as yellow and orange vegetables. The greater the intensity of color, the greater the carotene concentration. Carotenes are also found in legumes, grains, fish, poultry, milk, and egg yolks. They are also added to some foods for coloring. Carotenes require bile, fat, protein, antioxidants, and pancreatic enzymes for absorption.

Carotenes have a lower absorption rate than Vitamin A. This absorption rate decreases with an increase in dietary carotene intake. Carotene supplements are better absorbed than carotenes from the diet. The conversion of carotenes to Vitamin A depends on adequate levels of protein, thyroid hormone, zinc, and Vitamin E. When retinol levels are sufficient, fewer carotenes are converted.

A study from 1984 found carotene content in body tissues to be the primary factor in determining the maximum lifespan in mammals.3 Animal studies from 1992 also indicate that alcohol and beta carotene supplements can lead to liver damage.4 Other studies point to beta caroteneÕs susceptibility to oxidative damage. Concern has been raised over the association of high doses of supplemental beta-carotene to increased cancer risks in smokers and heavy drinkers.5 The most famous of these studies was conducted in Finland on more than 29,000 male smokers and drinkers.6 Subjects were assigned to take daily supplements of beta-carotene, Vitamin E, both vitamins, or a placebo over a period of 5-8 years. The death rate and incidence of lung cancer was highest in the beta-carotene group. The group taking beta carotene and Vitamin E had no increased cancer risk. This indicates the need for beta carotene to be supplemented with other antioxidants for protection. The group taking no supplements had the lowest risk for lung cancer and were consuming the most beta-carotene from dietary sources.

Most scientists point to the flaws in the Finnish study, arguing the findings are less than conclusive. Because cancer is a disease that is thought to develop over the course of a lifetime, the short duration of the study may not have been enough to explain its outcome. Though the study suggests a link between beta-carotene and cancer, it offers no biological explanation. The outcome cannot be generalized to populations dissimilar to the one used in the study.

Another study conducted in the U.S. by the National Cancer Institute was cut short due to the fatal effects of beta carotene.7 This study was conducted in male and female smokers who were also asbestos workers. In smokers, beta carotene supplements seemed to increase lung cancer and their fatality rate. However, nonsmokers cut their cancer risks. Yet another study conducted on U.S. physicians found no effect either way for beta carotene, even in smokers. Countering all of these studies on the negative outcomes of beta carotene are several which report the benefits of dietary carotene.

From all of this research, it appears that people in high risk groups for cancer and heart disease should be cautious when taking synthetic beta carotene. Supplements should be taken by those who do not smoke and should be taken with other antioxidants such as Vitamins C and E, and selenium.

Vitamin A and beta carotene deficiency is common in HIV and may be responsible for the decline in T helper cells. Deficiency is associated with an increased mortality rate to HIV. Beta carotene may be the preferred form for AIDS patients, as retinoic acid may increase the replication of HIV. Its role in reproductive functions has been documented in animal studies. Cows fed on a diet deficient in beta carotene experienced delayed ovulation and an increase in follicular and luteal cysts.8 Supplemental beta carotene decreased the number of ovarian cysts in cows, according to a 1983 report.9

1 Fawzi WW, et al., Vitamin A supplementation and child mortality. JAMA 269, 898-903, 1993.

2 Arrieta AC, et al., Vitamin A levels in children with measles in Long Beach, California. J Pediatr 121, 75-78, 1992.

3 Cutler RG, Carotenoids and retinol: Their possible importance in determining longevity of primate species. Proc Natl Acad Sci 81, 7627-7631, 1984.

4 Leo MA, et al., Interaction of ethanol with beta-carotene: Delayed blood clearance and enhanced hepatoxicity. Hepatology 15, 883-891, 1992.

5 Albanes D, Heinonen O, Huttunen J, et al: The effect of Vitamin E and beta-carotene on e incidence of lung cancer and other cancers in male smokers. N Eng J Med 1994;330:1029-1035. Also see Mayne, Handelman, and Beecher, Beta-carotene and lung cancer promotion in heavy smokers- a plausible relationship. J Nat. Cancer Inst. Nov. 6, 1996. 88(21), 1513-1515.

6 The Alpha-tocopherol, Beta-carotene Cancer Prevention Study Group, The effect of vitamin E and beta-carotene on incidence of lung cancer and other cancers in male smokers. N Engl J Med 330, 1029-1035, 1994.

7 Omenn GS, et al., The beta-carotene and retinol efficacy trial (CARET) for chemoprevention of lung cancer in high risk populations: Smokers and asbestos-exposed workers. Cancer Res 54 (Suppl.), 2038S-2043S, 1994.

8 Editor, Metabolism of beta-carotene by the bovine corpus luteum. Nutr Rev, 41, 357, 358, 1983.

9 Editor, Metabolism of beta-carotene by the bovine corpus luteum. Nutr Rev, 41, 357, 358, 1983.

• Apricots, fresh
• Asparagus
• Broccoli
• Cantaloupe
• Carrots, sliced
• Endive, raw
• Kale
• Leaf lettuce
• Liver
• Mustard greens
• Pumpkin
• Spinach
• Squash, winter
• Sweet potatoes
• Watermelon

Available as:

Capsules or tablets. Take with or immediately after food to ensure maximum absorption.

Oral solution: Dilute in at least 1/2 glass water or other liquid. Take with meals or 1 to 1-1/2 hours after meals unless otherwise directed by your doctor.

A constituent of many multivitamin/mineral preparations.1

1 From Griffith HW, Vitamins, Minerals, and Supplements.

VITAMIN A: PROVEN BENEFITS

• Aids in treatment of many eye disorders, including prevention of night blindness and formation of visual purple in the eye.
• Promotes bone growth, teeth development, reproduction.
• Helps form and maintain healthy skin, hair, mucous membranes.
• Builds body's resistance to respiratory infections.
• Helps treat acne, impetigo, boils, carbuncles, open ulcers when applied externally.
• What this vitamin does:
• Essential for normal function of retina. Combines with purple pigment of retina (opsin) to form rhodopsin, which is necessary for sight in partial darkness.
• May act as co-factor in enzyme systems.
• Necessary for growth of bone, testicular function, ovarian function, embryonic development, regulation of growth, differentiation of tissues.1

1 From Griffith HW, Vitamins, Minerals, and Supplements.

VITAMIN A: UNPROVED SPECULATED BENEFITS

• Helps control glaucoma.
• Buffers against cancer.
• Guards against effects of pollution and smog.
• Cushions against stress.
• Speeds healing.
• Helps in removal of age spots.
• Fights infections.
• Fights skin diseases.
• Shortens duration of some illnesses.1

1 From Griffith HW, Vitamins, Minerals, and Supplements.

VITAMIN A: SPECIAL CONSIDERATIONS

• Anyone with inadequate caloric or nutritional dietary intake or increased nutritional requirements.
• Pregnant or breast-feeding women.
• Those who abuse alcohol or other drugs.
• People with a chronic wasting illness, excess stress for long periods or who have recently undergone surgery.
• Those with a portion of the gastrointestinal tract surgically removed.
• People with recent severe burns or injuries.1
• Miscellaneous information:
• Many months of a Vitamin-A-deficient diet are required before symptoms develop. Average person has a 2-year supply of Vitamin A stored in the liver.
• Steroids are produced by the adrenal gland and are part of the natural response to stress and immune function. Failure to make these important hormones leaves immune system in a less-than-ideal state.1

1 From Griffith HW, Vitamins, Minerals, and Supplements.

VITAMIN A: DEFICIENCY SYMPTOMS

• Night blindness
• Lack of tear secretion
• Changes in eyes with eventual blindness if deficiency is severe and untreated
• Susceptibility to respiratory infection
• Dry, rough skin
• Changes in mucous membranes
• Weight loss
• Poor bone growth
• Weak tooth enamel
• Diarrhea
• Slow growth1

1 From Griffith HW, Vitamins, Minerals, and Supplements.

VITAMIN A: UNPROVED SPECULATED SYMPTOMS

Bone thickening

Kidney stones

Diarrhea

Reduced production of steroid hormones1

1 From Griffith HW, Vitamins, Minerals, and Supplements.

VITAMIN A: LAB TESTS TO DETECT DEFICIENCY

• Many months of deficiency required before lab studies reflect deficiency.
• Plasma Vitamin A and plasma carotene
• Dark-adaptation test
• Electronystagmogram
• Electroretinogram
• Serum level; dark adaptation test1

1 From Griffith HW, Vitamins, Minerals, and Supplements.

VITAMIN A: OPTIMAL LEVELS

• 10,000-25,000 IU for adults.
• 8,000 IU for women who are pregnant or soon to become pregnant.

VITAMIN A: MINIMUM DOSAGE

Recommended Dietary Allowance (RDA):

Estimate of adequate daily intake by the Food and Nutrition Board of the National Research Council, 1989. RDA for Vitamin A is expressed in retinol equivalents (RE).

One RE = 1 mcg retinol or 6 mcg beta-carotene. IU = International units.

Age Retinol Equivalents International Units

0-6 months 375RE 2,100IU

6-12 months 375RE 2,100IU

1-3 years 400RE 2,000IU

4-6 years 500RE 2,500IU

7-10 years 700RE 3,300IU

MALES

11+ years 1,000RE 5,000IU

FEMALES

11+ years 800RE 4,000IU

Pregnant 800RE 4,000IU

Lactating 1st 6 mos 500RE +2,500IU

2nd 6 mos 500RE +2,500IU

Don't take if you:

• Are allergic to any preparation containing Vitamin A.
• Consult your doctor if you have:
• Cystic fibrosis
• Diabetes
• Intestinal disease with diarrhea
• Kidney disease
• Liver disease
• Overactive thyroid function
• Disease of the pancreas

Over age 55:

• More likely to be malnourished and need supplement.
• Dosage must be taken carefully to avoid possible toxicity.

Pregnancy:

• Daily doses exceeding 8,000 IU can produce growth retardation and urinary-tract malformations of fetus.
• Don't take megadoses.

Breast Feeding:

• Breast-feeding:
• Don't take megadoses.

Effect on lab tests:

• With chronic Vitamin-A toxicity, lab tests show INCREASED blood glucose, blood-urea nitrogen, serum calcium, serum cholesterol, serum triglycerides.
• Poor results on dark-adaptation test
• Poor results on electronystagmogram
• Poor results on electroretinogram

Storage:

• Store in cool, dry place away from direct light, but don't freeze.
• Store safely out of reach of children.
• Don't store in bathroom medicine cabinet. Heat and moisture may change action of vitamin.

Others:

• Children are more sensitive to Vitamin A and are more likely to develop toxicity with dosages exceeding the RDA.
• Toxicity is slowly reversible on withdrawal of Vitamin A but may persist for several weeks.1

1 From Griffith HW, Vitamins, Minerals, and Supplements.

VITAMIN A: OVERDOSE/TOXICITY

Signs and symptoms:

Bleeding from gums or sore mouth, bulging soft spot on head in babies, sometimes hydrocephaly ("water on brain"), confusion or unusual excitement, diarrhea, dizziness, double vision, headache, irritability, dry skin, hair loss, peeling skin on lips, palms and in other areas, seizures, vomiting, enlarged spleen and liver. NOTE: Toxicity symptoms usually appear about 6 hours after ingestion of overdoses of Vitamin A. Symptoms may also develop gradually if overdose is milder and over a long period of time.

What to do:

For symptoms of overdosage: Discontinue vitamin, and consult doctor. Also see ADVERSE REACTIONS OR SIDE EFFECTS.

For accidental overdosage (such as child taking entire bottle): Call emergency services, the telephone operator, or the nearest Poison Control Center.1

1 From Griffith HW, Vitamins, Minerals, and Supplements.

VITAMIN A: ADVERSE REACTIONS OR SIDE EFFECTS

Reaction or effect What to do

• Abdominal pain Discontinue. Call doctor immediately.
• Appetite loss Discontinue. Call doctor when convenient.
• Bone or joint pain Discontinue. Call doctor immediately.
• Discomfort, tiredness or weakness Discontinue. Call doctor when convenient.
• Drying or cracking of skin or lips Discontinue. Call doctor immediately.
• Fever Discontinue. Call doctor immediately.
• Hair loss Discontinue. Call doctor immediately.
• Headache Discontinue. Call doctor when convenient.
• In children, premature closure of epiphyses Discontinue. Call doctor immediately.
• (the end parts of bones where growth occurs from birth through adolescence)
• Increase in frequency of urination Discontinue. Call doctor when convenient.
• Increased sensitivity of skin to sunlight Discontinue. Call doctor when convenient.
• Irritability Discontinue. Call doctor immediately.
• Vomiting Seek emergency treatment.
• Yellow-orange patches on soles of feet, Seek emergency treatment.1
• palms of hands or skin around nose and lips

1 From Griffith HW, Vitamins, Minerals, and Supplements.

VITAMIN A: INTERACTION WITH OTHER SUBSTANCES

• Antacids decrease absorption of Vitamin A and fat-soluble vitamins D, E, K.
• Anti-coagulants increase likelihood of spontaneous or hidden bleeding.
• Cholestyramine, colestipol decreases absorption of Vitamin A.
• Mineral oil, neomycin, sucralfate, and isioretinoin increase likelihood of Vitamin A toxicity.
• Oral contraceptives increase Vitamin A concentrations.
• Vitamin E: Normal amount facilitates absorption, storage in liver and utilization of Vitamin A. Excessive dosage may deplete Vitamin A stores in liver.
• Tobacco decreases absorption. Smokers may need supplementary Vitamin A.
• Chronic alcoholism interferes with the body's ability to transport and use Vitamin A.1

1 From Griffith HW, Vitamins, Minerals, and Supplements.

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