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Optimal Vitamin A Nutrition from Preformed Vitamin A and Beta Carotene

Provitamin A and Preformed Vitamin A from Natural Sources

Vitamin A is a fat-soluble nutrient that occurs in nature in two forms: preformed vitamin A and provitamin A, or carotene.

• Carotene is derived from plants and is converted by the body to vitamin A.
• Preformed vitamin A is concentrated in certain tissues of animal products in which the animal has metabolized the carotene contained in its food into vitamin A.

That vitamin A is essential for human health is well established. Research indicates that no more than 50,000 I.U. of vitamin A per day can be utilized by the body except in therapeutic cases, where up to 100,000 I.U. are recommended. It has been suggested that the best level is somewhere between 25,000 I.U. and 50,000 I.U.^(1-3) While preformed vitamin A can be toxic at extremely high doses given over a prolonged period, beta carotene has extremely low toxicity.⁽²⁾ Although excessive intake of beta carotene does not appear to be toxic, carotenemia, a yellowish discoloration of the skin, may occur. The condition has no adverse effects and disappears when carotene intake is reduced.^(2,3)

Most of the beta carotene consumed in the human diet is converted in the intestine and liver to Vitamin A, but some is absorbed intact from the intestines by the lymphatics and circulates in the blood. While research indicates that both preformed vitamin A and beta carotene have a protective effect against infection and some types of cancer, it is suggested that they operate through different mechanisms — vitamin A through its role in the maintenance of epithelial tissue and beta carotene through its antioxidant effect as a powerful scavenger of singlet oxygen.⁽⁴⁾

While many health professionals now recommend using beta carotene only,⁽²⁾ because of its low toxicity, preformed vitamin A also has some advantages.

Preformed vitamin A is absorbed by the body 3 to 5 hours after ingestion, whereas the conversion and absorption of carotene takes 6 to seven hours. Beta carotene is converted to vitamin A by fat-splitting enzymes and bile salts. The conversion process is stimulated by the hormone thyroxin. Patients with hypothyroidism, as well as some diabetics, are unable to convert beta carotene to vitamin A.⁽¹⁾

Intake of polyunsaturated fatty acids with carotene results in rapid destruction of carotene unless other antioxidants are also present.⁽¹⁾

To provide optimal vitamin A nutrition, A-25 Plex provides both beta carotene and preformed vitamin A from natural sources.

Vitamin A is essential for, among other things, vision (especially night vision), regulation of cell development, reproduction and immunity. Studies in third-world populations have demonstrated the enormous power of this vitamin in boosting resistance to infection and reducing the related mortality.⁽²⁾

The power of vitamin A to boost immunity is due in part to its essential role in the maintenance of epithelial tissue. It is necessary for the proper function of the cornea, all mucous membranes, the lining of the gastrointestinal tract, the lungs, the vagina, the urinary tract, the bladder and the skin. By maintaining healthy epithelium, vitamin A can also interrupt the process by which some cancers are initiated.^(1,3)

In the absence of vitamin A, these specialized tissue cells secrete a hard protein (keratin) rather than the mucus needed for protection and lubrication. Although keratin is a normal protein of hair and nails, it dries and hardens epithelial tissues. When this occurs, cell function is impaired or halted. The tissue wastes away and becomes susceptible to bacterial infection.⁽³⁾

One of the first symptoms of vitamin A deficiency is night blindness.⁽¹⁾ In the body, vitamin A combines with the protein opsin to form rhodopsin (visual purple). Rhodopsin occurs in the rod cells of the retina and is responsible for visual dark adaptation. When light strikes the retina this molecule is split, a small amount of retinal is destroyed and a constant supply of circulating retinal is needed for synthesis of visual purple. Other light-sensitive pigments also require vitamin A, including iodopsin, cyanopsin and porphyropsin (color pigments in the cone cells of the retina).⁽³⁾

Vitamin A is essential in the chemical process whereby cholesterol is converted into female estrogens and male androgens. Insufficient supply of these hormones results in degeneration of the sex organs.⁽¹⁾

Vitamin A is important in growth, in formation  and modeling of endochondral tissues of long bones and in the normal spacing of teeth. It is also necessary for the synthesis of certain proteins and compounds that can inhibit the formation of tumors.⁽³⁾

A chronic lack of vitamin A in the diet results in:

• Keratinosis and hyperkeratosis ^(1-3)
• Night blindness and other eye problems^(1,3)
• Bitot’s spots (dry patches on the conjunctiva)⁽³⁾
• Reduced resistance to infection^(1-3)
• Impaired growth⁽³⁾
• Weight loss and anorexia⁽³⁾
• Diminished saliva and histological changes in taste buds.⁽³⁾
• Reduced steroid synthesis⁽³⁾
• Improper tooth and bone formation and crooked teeth.^(1,3)
• Slower production of RNA⁽¹⁾

Deficiency can occur due to inadequate dietary supply or increased need and rapid loss of the vitamin in response to conditions such as pneumonia, hyperthyroidism, chronic nephritis, scarlet fever and some respiratory infections. Smoking, environmental pollution and heavy use of the eyes for watching television and working under glaring lights increases the need for vitamin A.⁽¹⁾

In addition, certain conditions which interfere with the body’s absorption or use of vitamin A can cause a deficiency:

• Diseases where absorption is impaired such as celiac disease and tropical sprue.⁽³⁾ Hypothyroidism where conversion of carotene to vitamin A is impaired.⁽¹⁾
• Diabetics also have a diminished capability to convert carotene to retinol, and, if placed on a restricted diet without insulin, the diabetic can develop a low-grade deficiency.^(1,3)
• A diet low in fat, resulting in little bile reaching the intestine, can cause carotene and vitamin A to be lost in the feces.⁽¹⁾
• Approximately 90% of the body’s vitamin A is stored in the liver. An adequate supply of zinc is needed to mobilize the vitamin out of storage.⁽¹⁾
• Excessive consumption of alcohol, excessive iron and use of mineral oil, cortisone and other drugs interfere with absorption.⁽¹⁾

Even cold weather can hinder the transport and metabolism of both vitamin A and carotene.⁽¹⁾

WARNING:  This publication and the product contained herein have not been approved or evaluated by the Food and Drug Administration. This publication, and the product contained herein are not intended to diagnose, treat, cure or prevent any disease. The product relates to nutritional support only.

1. Kirschmann, J and Dunne, L, Nutrition Almanac, Second Edition, McGraw-Hill, 1984.

2. Handler, S, The Doctors’ Vitamin and Mineral Encyclopedia, Simon & Schuster, 1990.

3. Garrison, R and Somer, E, The Nutrition Desk Reference, Keats Publishing, New Canaan, CT, 1985.

4. Bland, J, et al, 1984-1985 Yearbook of Nutritional Medicine, Keats Publishing Co., 1985.

Product No. 978 Fill Size: 100 Softgel Capsule
Each softgel capsule contains:
Vitamin A (Beta Carotene) 15,000 I.U. 300%
Vitamin A (Natural) 10,000 I.U. 200%
Alfalfa 5 mg. *
Cranberry 5 mg. *
Carrot Oil 6 mg. *
Lecithin 5 mg. *
Other ingredients: gelatin.

*Daily Value not established

Suggested Usage: One or more capsules daily.
Price:  $13.00