Sunday, March 01, 2009

Vitamin A supplements and cancer risk

A little is essential, a lot, apparently, is too much of a good thing.

Enamored with the potential of anti-oxidants in fruits and vegetables in cancer prevention, scientists theorized that concentrating these worthy phytonutrients in supplement form might be even better yet. Several studies through the years designed to test this theory on vitamin A derivatives such as carotene (that substance which imparts the orange color to carrots, sweet potatoes, melons, etc.) have been abruptly halted when smokers enrolled in the trials who took the real deal beta-carotene preparations developed lung cancer at a significantly higher rate than those on placebos.

University of North Carolina researchers took another tact and arrived at the same conclusion. They examined data from 77,000 Americans over 10 years--correlating use of dietary supplements with subsequent cancer diagnoses. Note that these subjects were not assigned to a certain vitamin or placebo but rather self-reported their use of over-the-counter vitamin pills.

Not only did beta-carotene again prove problematic in a cancer-causing sort of way for the smokers in the study group, but retinol and lutein demonstrated a potent total dose-related association with lung cancer risk. The longer a person took these supplements, the greater their risk compared with those smokers who did not use them--53% for retinol and 102% for lutein!

Lutein, of course, is recommended to help prevent macular degeneration, an age-related eye condition that can result in significant vision loss. The researchers did not comment on the conflicting reasons to take or pass up lutein, but perhaps persons who smoke should pass up the lutein.


Michael Edson, MS, L.Ac. said...

Vitamin A supplementation is particularly important for people with retinal issues. For example, research supports taking 15,000 IU per day of Vitamin A for those with Retinitis Pigmentosa.

Vitamin A is a necessary structural component of rhodopsin or visual purple, the light sensitive pigment within rod and cone cells of the retina. If inadequate quantities of vitamin A are present, vision is impaired.

The 11-cis retinal form of vitamin A is essential for the neural transmission of light into vision.

A deficiency of vitamin A causes a deficit in the pigment needed by rod cells (responsible for our night vision). As a result, if fewer rod cells are able to sufficiently respond in darker conditions, night blindness can result.

Betacarotene is the water-soluble version of vitamin A (which is fat soluble), and can be converted to Vitamin A by the body as needed.

Food sources for betacarotene include yellow and orange vegetables, including yams, carrots and sweet potatoes, asparagus, spinach, butternut squash, kale, bok choy, mangoes, cataloupe and apricots.

Top sources of vitamin A include: beef liver, egg yolk, cheddar cheese and fortified milk.

For more information on nutrition and vision, go to Natural Eye Care

Mauigirl said...

Kind of scary. My mom, who still smokes, takes lutein for AMD. Of course, she's 90, so maybe it doesn't matter at this point.

Reality Man said...

"Tack," not "tact."

Anonymous said...

Reality man makes a good point, albeit with little tact, in his public correction of language usage. Taking a different tack, is the retinol of which they speak the same as in Retin-A, which is the only thing that keeps my face from looking like a 16 year old's? In your opinion, could you absorb enough of this to be worried about? Signed, Former Smoker.