Over a six-year period, random groups received either (1) 50 mg of vitamin E (approximately 66 IU); (2) 20 mg of beta carotene (approximately 33,333 IU); (3) 50 mg of vitamin E and 20 mg of beta carotene; or (4) a placebo. The results were as follows:
- The beta carotene group had 18 percent more lung cancer with a 15 percent higher death rate than other groups.
- The group that took beta carotene and vitamin E together had neither a reduced nor increased incidence of lung cancer.
- Within the placebo group, those with the highest blood levels of beta carotene and vitamin E had the lowest risk for developing lung cancer. This subgroup did not take beta carotene and vitamin E supplements, but consumed a diet rich in fresh fruits and vegetables.
In my September 23, 1994 article in "DC," "Is Beta Carotene Safe?", I raised questions with this study and recommended against reducing beta carotene supplements for smokers and nonsmokers alike, because there have been so many studies on the benefits of antioxidants, including studies showing beta carotene can reduce the incidence of stroke and heart disease in nonsmokers and nondrinkers. I felt that when one looked at many studies that showed the positive benefits of beta carotene, it was premature to recommend that smokers reduce beta carotene based on one study.
Earlier this year, the Beta Carotene and Retinol Efficiency Trial (CARET) made headlines when the planned six-year study was halted after four years. The CARET study included 18,314 people who were either heavy smokers (average 50-pack years -- one pack a day for 50 years or two packs a day for 25 years), or were exposed to high amounts of asbestos, a known cause of lung cancer. Participants were given either 30 mg (50,000 IU) of beta carotene and 25,000 IU of vitamin A or a placebo. The beta carotene group had 28 percent more lung cancer and a 17 percent higher death rate. Standing alone, the Finnish study to me was a fluke, but now that another large trial on a similar population, taking similar amounts of a single nutrient, had similar results, I have recommended to my patients who smoke and cannot/will not quit:
1. Do not take more than 10,000 IU of beta carotene supplements.
2. Consume 8 to 10 servings of fresh fruit and green orange-red vegetables per day.
3. Take a strong multivitamin, multimineral supplement with 100 percent of the RDA of all minerals and rich in the entire family of antioxidants.
4. Take at least 800 IUs of vitamin E a day.
5. Take at least 1500 mg of vitamin C a day.
There are at least 600 different types of carotenoids. The easiest one to measure in the blood is beta. In the Finnish study, the group with higher levels of beta carotene in their blood (who did not take supplemental beta carotene) had a lower risk for developing lung cancer. For 20 years studies have shown that people who have high levels of beta carotene have a lower risk to develop many types of cancer, along with heart disease and stroke. Many of these studies were not tightly controlled and the groups with high beta carotene levels had them from the foods they ate and not from supplements. We assumed that, because in study after study high blood levels of beta carotene correlated with positive health effects, beta carotene was the reason. However, people who consume diets rich in fruits and vegetables ingest hundreds of phytochemicals in the carotenoid and flavonoid families, many of which are undiscovered. Furthermore, as we continue to isolate and research individual compounds we are finding a plethora of substances that can have powerful effects on human physiology, both alone and in combination with other synergistic and/or antagonistic phytochemicals.
For some unknown reason(s) high amounts of supplemental, synthetic beta carotene appears to be harmful to 20 percent of long-term, heavy smokers. Maybe beta carotene protects cancer cells; maybe high levels of beta carotene prevent the uptake of other phytochemicals; maybe heavy smokers' livers cannot properly metabolize beta carotene. We just don't know yet.
Until it is proven otherwise, heavy smokers or former heavy smokers should not take large amounts of beta carotene alone.
The good news is, if you don't smoke, beta carotene will not increase your chances of getting lung cancer and may still help reduce your chances of getting other types of cancer.
If we have learned anything from this study, it should be that (1) we should be careful when we extrapolate data from studies; (2) no one supplement can substitute for whole foods; and (3) people who are at risk for a given disease or are already sick and want to take supplements should do so under the guidance of a health care professional knowledgeable in nutrition. Finally, we should not use this study to extrapolate that taking a vegetable pill with a few phytochemicals in it can substitute for a diet rich in fresh whole fruits and vegetables and low in processed foods.
G. Douglas Andersen, DC, DACBSP, CCN
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