COLLOIDAL MINERALS Beta-Carotene
What is the use and function of Beta-Carotene ?
There are over 600 carotenoids in nature. Carotenoids generally contain a conjugated
polyene structure which is efficient at absorbing light, and are the major yellow
and red pigments in many fruits and vegetables. Beta-carotene (C40 H56) and
alpha-carotene are responsible for the orange color of carrots, and lycopene
for the red color of tomatoes; astaxanthin imparts a red or pink color to lobsters
and salmon. The term "carotene" refers to carotenoids which contain only carbon
and hydrogen (e.g. beta-carotene, alpha-carotene, lycopene), while the term
"xanthophylls" refers to compounds which contain hydroxyl groups (lutein, zeaxanthin,
beta-cryptoxanthin) or keto groups (canthaxanthin) or both (astaxanthin).
In animals some carotenoids (particularly beta-carotene) serve as dietary precursors
to vitamin A, and many of them may function as fat-soluble antioxidants. Because
they are present in much lower concentrations than is alpha-tocopherol, some
questions have been raised about their physiological importance as antioxidants.
However, increased consumption of foods rich in carotenoids is associated with
decreased risk of some degenerative diseases, and there is some evidence also
for their role in improving immune function. In plants they serve as antioxidants
to protect the highly reactive photosystems and also act as accessory photopigments.
One study has found that carotenoid deficiency is associated with skin changes
(including acne and dermatitis). These changes were detrimental but not life-threatening.
This effect should be confirmed by additional studies before making dietary
In the last few years increasing numbers of reports have suggested that the
use of Beta-Carotene may act to prevent the development of various malignancies.
Beta-Carotene and other similar compounds have differentiating properties that
appear to affect cell growth and maturation. Beta Carotene is not toxic to the
liver even in high doses in contrast to Vitamin A. Large doses of Beta Carotene
will increase the body's demands for Vitamin E; therefore, those of you on 50,000
to 100,000 units of beta carotene per day. You will need to also increase your
vitamin E to 1,000 to 2,000 units per day. The definitive role of beta carotene/vitamin
E is yet to be understood, but there is sufficient reason to use beta-carotene
in a dose of 50,000 units per day. There is no need to supplement this with
carrot juice or vitamin A. Beta carotene, like vitamin A and E is stored in
the liver. Current clinical trials in prevention of cervix cancer and cancer
of the lung and breast are using beta-carotene. This may also be helpful in
the prevention of colon cancer and melanoma.
No formal diet recommendation for carotenoids has yet been established but some
experts suggest intakes of 5 to 6 mg daily (about twice the average daily American
intake). Individual dietary carotenoid consumption is quite variable.
Carotenoids are biosynthesized only in plants and some bacteria, thus foods
of plant origin are the primary dietary source for humans. Intestinal absorption
can be poor, and depends on the presence of dietary fat. Mild cooking (steaming)
increases bioavailability of carotenoids while overcooking can destroy some
forms. The extent of conversion of provitamin A carotenoids to vitamin A seems
to be variable but is less than 50%.
The carotenoids are remarkably devoid of toxicity, and serve as good nontoxic
sources of vitamin A. Massive overconsumption of carotenoids can result in yellowing
of the skin, especially of the hand and ears (xanthosis cutis), but has no adverse
health effects. The color disappears within a week or so after reducing intake
of carotene-rich foods.
Canthaxanthin and beta-carotene have been used pharmacologically to treat erythropoietic
porphyria, a disease characterized by extreme sensitivity of the skin to sunlight.
Most recent interest has focused on antioxidant, anticancer, and immune-enhancing
properties of carotenoids. Research is also continuing on food carotenoids as
sources of dietary provitamin A.
For further information:
Britton, G. (1995) Structure and properties of carotenoids in relation to
function. FASEB J. 9: 1551-1558
Krinsky, N.I. (1993) Actions of carotenoids in biological systems. Ann. Rev.
Nutr. 13: 561-587.
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Minerals:Vitamin E an important anti-oxidant
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