Researchers from Ohio State University say there could be health hazards associated with consuming too much beta-carotene. Beta-carotene is a naturally occurring pigment that gives color to foods such as carrots, sweet potatoes and certain greens. It is an antioxidant and converts to vitamin A in the body.
Now, scientists at Ohio State University have found that certain molecules that derive from beta-carotene have an opposite effect in the body: they actually block some actions of vitamin A, which is critical to human vision, bone and skin health, metabolism and immune function.
Because these molecules derive from beta-carotene, researchers predict that a large amount of this antioxidant is accompanied by a larger amount of these anti-vitamin-A molecules, as well.
Previous research established that when beta-carotene is metabolized, it is broken in half by an enzyme, which produces two vitamin A molecules. In this new study, the researchers showed that some of these molecules are produced when beta-carotene is broken in a different place by processes that are not yet fully understood and act to antagonize vitamin A.
The new findings might explain the outcome of a decades-old clinical trial that has left scientists puzzled for years. In that trial, people at high risk for lung cancer - smokers and asbestos workers - were given massive doses of beta-carotene over a long period of time in an attempt to lower that risk. The trial ended early because more supplemented participants developed cancer than did those who received no beta-carotene.
"Those trials are still sending shockwaves 20 years later to the scientific community," said Earl Harrison, an investigator at Ohio State's Comprehensive Cancer Center. "What we found provides a plausible explanation of why larger amounts of beta-carotene might have led to unexpected effects in these trials."
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Source: Ohio State University