The news media and video have been trumpeting anti-vitamin research findings from a study in the New England Journal, dated April 14, 2004. The lead article:1 reported a large-scale research on the effect of vitamin E and beta-carotene on cancer. The conclusions were very direct: "we found no overall reduction in the incidence of lung cancer or in mortality due to this disease among male smokers who received dietary supplementation...The results of this study raise the possibility that these substances may have harmful as well as beneficial effects."
The media took this research as a retraction of the wellspring of positive news about nutrition and health of the past few years. They are mistaken, for in fact this study actually proves only that a one-a-day vitamin-antioxidant supplement does not cure lung cancer. That is not very surprising. What is surprising is that our National Cancer Institute, which supported this study in Finland, would ever dream that the inadequate antioxidant supplements used in this study, lacking in vitamin C, zinc, selenium and cysteine and dozens of other essential nutrients, would work at all.
The strategy of the study was to divide the 30,000 men into four groups of 7500, who where then given identical-looking pills containing either a placebo, carotene, vitamin E, or both vitamin E and carotene. The study was touted as the most carefully designed study of supplemental antioxidants against cancer to date. Don't get me wrong. I am glad the study was done, for it helps to bracket in the limits of what to expect from antioxidants. But the media interpretation comes across somewhat like the sports pages: cancer wins, vitamins lose. Go back to conventional medicine and take your chemotherapy, surgery and radiation, as if that is all there is to it.
It is hard to maintain one's faith in nutrients in the face of such negative reports. But actually this research only applies to specific conditions: i.e. long-term smokers in Finland, all men, average age 57 years. The question answered is whether beta-carotene along with a small supplement of vitamin E for 6 years can correct the cancerous lung damage caused by an average 36 years of smoking a pack a day in this population. The answer is No.
The study does not answer other important questions: would higher doses of vitamin E have more impact? Two recent American studies showed no benefits of vitamin E against heart attacks unless taken at a dose over 100 mg per day. In this cancer study, the vitamin E was supplied at a dose of only 50 mg per day and raised blood levels by only a third. Studies with successful outcomes have used larger doses that doubled vitamin E blood levels.
Carotene is known to be cancer-preventive but not curative. There are over a dozen research studies that document the cancer-preventive role of carotene and at the level of cell biology there is good evidence that carotene is the premier and essential antioxidant in tissues subject to low oxygen tension, i.e. in organs with poor circulation and metabolic deficits.
Carotene is not a cancer-causing agent; however it does interact with vitamin E, and recent research indicates that carotene supplements actually deplete vitamin E. This could interfere with the protective effect of vitamin E—unless the vitamin E was provided at a large dose. This was very likely why, in this study, an almost 20 percent increase in lung cancer was observed in the sub-group on carotene alone. There was also an increase in heart attacks and an 8 percent increase in all deaths in the men who were given carotene. In the sub-group given 50 iu of vitamin E there was a reduction in prostate cancer but not over-all mortality.
In long-term smokers, it is likely that undiagnosed early cancer was already in existence before the start of the study, too late for carotene to show a benefit. Would the inclusion of other nutrients have made a difference? Vitamin C, vitamin A, zinc, selenium and the amino acids cysteine and methionine all interact to give cancer protection. And the many studies that do document antioxidant protection against cancer and heart disease are mostly based on calculated amounts of antioxidant vitamins in foods. Thus, most of the data that we have points to the power of antioxidants, not as single agents but in harmony with other nutrient factors.
The authors of the carotene-vitamin E study refer to a recent five year study in China2 in which supplementation with smaller amounts of vitamin E (30 mg) and beta-carotene (15 mg) were associated with significant reduction in cancer mortality. But the Chinese also gave selenium (50 mcg). How could 50 millionths of a gram of this trace mineral make such a difference? Because this is the amount of selenium required to activate the antioxidant enzyme, glutathione peroxidase, which is the most important protection against cancer-causing chemicals at the cell membrane, even more powerful than vitamin E, or carotene.
When the baseline diets of the subjects were analyzed and divided into four groups, from lowest to highest intakes of vitamin E and carotene respectively, those with the lowest intake of vitamin E were 50 percent more likely to develop cancer and those with lowest intake of carotene were 25 percent more likely to do so. That means that those men whose diets naturally contained vitamin E were at an advantage compared to those who were deficient; and to a smaller extent the same for carotene.
What are the food sources of vitamin E? Seeds, nuts, beans, whole grains and vegetable oils are especially rich, and also green leafy vegetables. Carotene is particularly rich in yellow, green and red colored vegetables, particularly carrots, sweet potatoes and tomatoes. It is intriguing to consider that the vitamin E sources are likely to be high in selenium and other minerals as well; while the carotene sources are not.
What to conclude from all this? First, don't believe headlines; do read the fine print—and think. Common sense tells us that a diet full of a variety of vegetables, fruits, seeds and nuts is more likely to confer health benefits than a diet of processed food and cardboard. No controversy on that point. But, because we are a nation that subsists to a large extent on processed and devitalized food, it is a good idea to supplement our food with nutrient concentrates in tablet or capsule form. And when in doubt about the adequacy of our personal nutrition, measurement of vitamin and mineral levels is available to know for sure if your own vitamins are ready to work for you.
1. Heinonen OP and Albanes D: The effect of vitamin E and beta-carotene on the incidence of lung cancer and other cancers in male smokers. NEJM 1994; 330:1029-35.
2. Blot WJ, Li JY, Taylor PR et al. Nutrition intervention trials in Linxian China: suplementation with specific vitamin/mineral combinations, cancer incidence and disease specific mortality. J Natl Cancer Inst 1993; 85:1483-92
©2007 Richard A. Kunin, M.D.