|
Eat
Your Naturally Colorful Foods!
October 20,2008
The rich hues of fresh fruits and vegetables are not only aesthetically pleasing; they're good for you, too. Most yellow, orange and red pigments synthesized by plants are called carotenoids, and are essential to a healthy diet. These fat-soluble antioxidants are made by plants to protect themselves from free radical damage and help the body in countless ways (1). By maintaining a healthy, varied diet, it is possible to receive what you need; in today's busy world, thinking about adding a supplement isn't a bad idea, especially since carotenoids have been shown to work best when consumed in combinations.
Common
Carotenoids
Of the more than 600 identified carotenoids, the ones most commonly
found in the North American diet are beta-carotene, alpha-carotene,
gamma-carotene, lycopene, lutein, beta-cryptoxanthin, zeaxanthin and
astaxanthin (2). It is important to note that different carotenoids
form different pigments, which can perform a variety of functions. For
example, alpha-carotene, beta-carotene and beta-cryptoxanthin are found
in orange fruits and vegetables, such as carrots, apricots, mangoes,
peaches, squash and sweet potatoes. Dark green vegetables, like spinach,
kale and collard greens, are good sources of beta-carotene and lutein.
Lycopene and astaxanthin compose the red tints: the former mostly in
fruits and vegetables such as tomatoes, guava and grapefruit, and the
latter generally in crustaceans and fish such as salmon (3). If a food
is naturally colorful, it most likely contains carotenoids.
Vitamin
A Connection
About 50 carotenoids are categorized as provitamin A carotenoids (2).
These carotenoids can be converted by the body to retinol, one of the
most useable forms of vitamin A, and include alpha-carotene, beta-carotene
and beta-cryptoxanthin. Vitamin A is essential for normal growth and
development, immune system function and vision. Often, mothers tell
their children that eating carrots (which are good sources of vitamin
A and beta-carotene) will help their eyesight, which is true, as the
vitamin A helps convert light into readable signals for the brain (1).
In addition, beta-carotene has been found to have its own unique antioxidant
actions. While the carotenoids lutein, zeaxanthin and lycopene have
no reported vitamin A activity, they remain important for other reasons;
if your diet contains insufficient amounts, you should consider taking
supplements containing these carotenoids.
Why
We Need Them
Carotenoids are important for a wide range of functions, including bone
health, eye health, cancer prevention, prostate health, infections and
more. Extensive research is being performed on the use of carotenoids
to reduce the risk of cardiovascular disease and some cancers. For example,
increased levels of beta-carotene and vitamin A have been correlated
with a lower risk of cancer, with data reporting a threefold decrease
in lung cancer and an 80% decrease in cervical cancer (4). Other cancer
risks that seem to be reduced with the consumption of adequate vitamin
A and carotenoids include prostate, breast and skin cancer. In fact,
vitamin A possibly helps women in the treatment of breast cancer. The
two ruling hypotheses behind this are that the vitamin A helped protect
the women from the toxicity of the powerful drugs combating the cancer
or that it interacted with the drugs in a way that increased their effectiveness.
An important function of all carotenoids is their ability to facilitate intercellular communication by stimulating synthesis of connexin proteins (5). This communication is particularly important as researchers believe poor communication between cells may partly cause cell overgrowth, which is a condition that can eventually lead to cancer (2).
In addition, two carotenoids, lutein and zeaxanthin, may benefit eye health, particularly for slowing the development of age-related macular degenerations and cataracts. The macula is at the center of the retina, and its breakdown is the leading cause of blindness among Americans over the age of 65 (1). Together, these carotenoids form the yellowish macular pigment that efficiently absorbs blue light. This protects critical, delicate eye structures from harmful ultraviolet light and light-induced oxidative damage.
In and of themselves, carotenoids contain powerful antioxidant properties. They protect from oxidative stress damage (which increases the body's risk of disease) by quenching the single oxygen molecule and dissipating the energy as heat and scavenging radicals to prevent or terminate chain reactions (3). Although beta-carotene is one of the most well-known carotenoids, astaxanthin has demonstrated superior antioxidant capabilities.
When
There's Too Much
Experts say that it is not possible to consume too much of any of the
carotenoids through diet or supplementation. The only negative effect
consuming large quantities of carotenoids may produce is carotenemia,
which is a slight orange coloring of the skin—and is completely harmless.
In reality, it is a sign that the body has converted as much beta-carotene
to active A as it can. In fact, it may be beneficial in the fight against
sunburns and skin cancer, as this pigmentation provides additional,
internal protection against sunburn (4). WF
References
1. J. Challem and L. Brown, Basic Health Publications User 's Guide
to Vitamins and Minerals (Basic Health Publications, North Bergen, NJ
2002).
2. George Mateljan Foundation, World's Healthiest Foods, www.whfoods.com,
accessed September 2, 2008.
3.AstaFactor, www.astaxanthin.org, accessed September 2, 2008.
4. S. Lieberman and N. Bruning, The Real Vitamin and Mineral Book (Avery
Publishing Group, Garden City Park, New York, 1997).
5. National Institutes of Health, Office of Dietary Supplements, "Dietary
Supplement Fact Sheet: Vitamin A and Carotenoids," http://ods.od.nih.gov/fact-sheets/vitamina.asp,
accessed September 2,2008.
|
|||||||
