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Clearing the Air: Can Carrots Really Cause Lung Cancer?

If you were to randomly ask people on the street if carrots are good for you, you will most likely get a resounding yes. The general public today may not have heard about the beta-carotene and lung cancer controversy that shocked nutritional experts back in 1994.

The Alpha-Tocopherol, Beta Carotene Cancer Prevention (ATBC) Study

More than two decades ago, the U.S. National Cancer Institute decided to work with the Finnish National Public Institute in figuring out if beta-carotene and alpha-tocopherol (Vitamin E)  supplementation will help reduce lung cancer risk among 29,133 male smokers — 50 to 69 years of age, most of whom are from southwestern Finland. With antioxidants becoming a buzzword in the 90s, the researchers presumed that a supplementation of Vitamin E, beta-carotene, or both will significantly reduce incidence of lung cancer amongst the subjects.  It turned out that the researchers' initial presumption was wrong!

The result of the ATCC research was published in the highly regarded New England Journal of Medicine on April 14, 1994. Methodically, the subjects were divided into four groups — one group received 20 mg of synthetic beta carotene daily; the second group received 50 mg of synthetic vitamin E daily; the third group received both of these supplements. The fourth group was the placebo folks and didn't receive any supplementation. After following the subjects for a period of 5 to 8 years, the beta-carotene group unexpectedly increased their risk of lung cancer by 18 percent. The study's abstract concluded:

We found no reduction in the incidence of lung cancer among male smokers after five to eight years of dietary supplementation with alpha-tocopherol or beta carotene. In fact, this trial raises the possibility that these supplements may actually have harmful as well as beneficial effects.

The disquieting results of the ATBC trial led to another research two years later – the CARET study.

The Beta-Carotene and Retinol Efficacy Trial (CARET)
In 1996, a team of researchers in the United States, headed by Dr. Gilbert S. Omenn of the Fred Hutchinson Cancer Research Center sought out to test if a combination of 30 mg of beta-carotene and 25 000 IU of Vitamin A taken daily against placebo will help reduce risk of lung cancer among 18,314 men and women who were smokers, former smokers, or workers exposed to asbestos.

The findings, published in the New England Journal of Medicine and the Journal of National Cancer Institute, was equally stunning as the ATBC study. The researchers had to halt the supplementation 21 months earlier of its expected completion date because they discovered 28% more incidence of lung cancer and 17% more deaths in the active intervention group, or from those that took carotene and vitamin A supplements daily. The conclusion in the Journal of National Cancer Institute's abstract stated:

The results are highly consistent with those found for ?-carotene in the Alpha-Tocopherol Beta-Carotene Cancer Prevention Study in 29,133 male smokers in Finland. Individuals at high risk of developing lung cancer, i.e., current smokers and asbestos-exposed workers, should be discouraged from taking supplemental ?-carotene (and the combination of ?-carotene with vitamin A). Safety and efficacy should be demonstrated before recommending use of vitamin supplements in any population.

Can Beta Carotene in Carrots Really Cause Lung Cancer?
The beta carotene content of carrots is consistently touted for its powerful antioxidant properties. Generally, the body converts beta carotene into Vitamin A which in turn is essential for optimum skin health as well as boosting immunity. So what went wrong?

First, it is interesting to note that the beta-carotene component used in the aforementioned well-constructed studies were supplements and synthetically-derived. The beta-carotene and other carotenoid components in carrots and other whole food sources work differently than its synthetic counterparts. Furthermore, the experiments conveyed that isolating a certain vitamin or nutrient does not have the same beneficial effect when a nutrient is derived from whole foods and is allowed to work synergically with other nutrients.

Second, both studies were done in subjects that already had lung cancer, heavy smokers, former heavy smokers, or workers who were exposed to asbestos.

Smoking and Asbestos Exposure
Overall, the occurrence of lung cancer has nothing to do with eating too many carrots. Chronic cigarette smoking and asbestos exposure are far more influential in causing lung cancer. Avoiding asbestos exposure is not as easy as quitting smoking or avoiding secondhand smoke exposure though. Therefore, workers exposed to asbestos should be knowledgeable enough in handling potentially hazardous and toxic substances. The HAZWOPER (Hazardous Waste Operations and Emergency Response) training is one method of helping workers exposed to asbestos reduced their risk. After a 40-hour HAZWOPER certification by OSHA-authorized trainers, employees will be able to take preventative measures of exposure and be more familiar in dealing with co-workers who may be exposed to asbestos in large amounts.

If you're a heavy smoker or have been exposed to asbestos for long periods at work, it is best to avoid taking beta carotene supplements. Yet no one's stopping you from feasting on carrots, pumpkins, and sweet potatoes!