Vitamin A and Beta-Carotene

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General Description:

There are two types of vitamin A:

  • Retinol, or vitamin A, which is preformed vitamin A, is found in animal foods.
  • Beta-carotene, or pro vitamin A, which is a precursor to vitamin A and is found almost exclusively in plant foods.
  • Retinol, named after the retina of the eye, is fat-soluble, as is beta-carotene

Actions:

  • the liver will convert beta-carotene into vitamin A only as it is needed (prevents possible toxicity)
  • if you eat an abundance of plant foods, you will ensure that you are receiving a sufficient supply of carotenoids which, like carotene, can be converted to vitamin A in the body
  • body deposits some of the extra carotene in some body tissues, such as the skin, and uses some of the excess as an antioxidant to fight free radicals that cause aging and cancer
  • takes 6 mcg.(1 mcg. = 3.3 IU) beta-carotene to yield 1 mcg. RE of vitamin A
  • the average carrot contains 18,000 IU of active beta-carotene
  • essential for growth in young animals, healthy skin and mucous membranes, cell growth, reproduction, normal immunity, and healthy bones
  • promotes healthy eyes – helping you to see in dim light and preventing the disease xeropthalmia that can lead to blindness.
  • retinol makes the visual purple of your eyes that is essential for night vision
  • promotes healthy organs – essential to health of tissues lining lungs, digestive system, and the genitourinary tract.
  • beta-carotene cause macrophages to release TNF
  • vitamin A builds resistance to all kinds of infections as it is a ”membrane conditioner”
  • essential during pregnancy and lactation
  • helps maintain testicular tissue in a healthy state
  • aids in the secretion of gastric juices and in the digestion of proteins
  • prevents premature aging and senility
  • protects against the damaging effects of polluted air
  • increases the permeability of capillaries contributing to better tissue oxygenation

Deficiency:

  • deficiency is not very common in America
  • average diet contains 5,400 IU of vitamin A
  • ”night blindness” is often the first sign
  • prolonged deficiency may result in lumps of hard skin forming on various body parts, eye inflammations, poor vision, and severe eye damage can occur (cornea dries out and ulcerates)
  • increased susceptibility to infections, especially in the respiratory tract; and frequent colds
  • retarded growth in children; lack of appetite and vigor; defective teeth and gums
  • rough, scaly, and dry skin, and such skin disorders as acne, pimples, boils, premature wrinkles, and psoriasis
  • dry, dull hair, dandruff, and excessive hair loss
  • nails which peel and/or are ridged
  • poor senses of taste and smell
  • prolonged diarrhea can inhibit vitamin A absorption.
  • other malabsorption syndromes, such as Celiac disease and Crohn’s disease can also put you at risk of vitamin A deficiency, as can obstruction of the bile, liver, and/or gallbladder ducts
  • laxatives can inhibit the absorption of vitamin A
  • the drug Clofibrate, to treat high blood triglycerides, can decrease the body’s ability to absorb carotene
  • the body’s ability to convert beta-carotene to vitamin A is impaired in three conditions: diabetes, hypothyroidism, and severe liver malfunctioning

Interactions and Toxicity:

  • toxicity of vitamin A does not normally occur for most people in normal health until they take a dose above 1000mcg RE/kg of body weight
  • 25,000 IU/day for adults is usually considered safe except in the case of pregnancy (should not exceed 6,000 IU)
  • one should not take a vitamin A supplement if currently taking Accutane
  • the drug cholestyramine (Questran), which lowers blood cholesterol levels, may also interfere with vitamin A absorption (as well as other fat-soluble vitamins)
  • the pill can increase the amount of vitamin A in the blood as well as the rate at which beta-carotene is converted to vitamin A
  • OTC mineral oil (laxative) can also prevent A absorption
  • high doses of vitamin A can cause miscarriages and birth defects
  • carotenemia or hypercarotenemia are terms referring to high blood carotene levels which accompany the yellow skin syndrome
  • one can distinguish between carotenemia and jaundice by looking at the whites of the eyes – white in the case of carotenemia and yellow in the case of jaundice
  • a very high intake of carrots during pregnancy has been reported to cause a yellowing of the skin in both the mother and newborn
  • a study in rats showed that large doses of carotene adversely affected bone development and the ability to maintain pregnancy

Sources:

  • beta-carotene: carrots, dark green leafy vegetables, melons, squash, yams, tomatoes, eggs

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