Eventually, a randomized clinical trial was conducted, as part of the so-called Women's Health Initiative. Findings published in 2002 not only found no protection to the heart but actually reported some harm.
Epidemiology's detractors say they have no trouble finding other cases than hormones where frequently cited and sometimes influential epidemiology studies have later turned out to be wrong or exaggerated.
In 1993, Harvard University scientists published two cohort studies reporting that vitamin E protected people from coronary heart disease. One, the Nurses Health Study, followed over 87,000 middle-aged female nurses without heart disease for up to eight years. It found that the 20% of nurses with the highest vitamin E intake had a 34% lower risk of major coronary disease than those with the lowest fifth of intake.
The other study followed almost 40,000 male health professionals without heart disease for four years -- and found a 36% lower risk of coronary disease in those men taking more than 60 IU of vitamin E per day compared with those consuming less than 7.5 IU.
In the three years after these studies appeared, each was cited by other research papers more than 400 times, according to John Ioannidis, an epidemiologist at the University of Ioannina School of Medicine in Ioannina, Greece. Vitamin E therapy for heart patients became widespread -- a 1997 survey published in the American Journal of Cardiology reported that 44% of U.S. cardiologists reported routine use of antioxidants, primarily vitamin E.
The therapy was finally put to the test in a Canadian randomized clinical trial of about 2,500 women and 7,000 men aged 55 years or older who were at high risk for cardiovascular events.
The findings -- reported in 2000 -- showed that an average daily dose of 400 IU vitamin E from natural sources for about 4 1/2 years had no effect on cardiovascular disease.
Yet, Schwartz says, seven years after that finding, her patients continue to take vitamin E in the belief that it will protect their hearts. "I am still taking people off of vitamin E," she says of her patients, some of whom have heart disease.
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Study of studies
In a provocative 2005 paper, Ioannidis examined the six most frequently cited epidemiological studies published from three major clinical journals between 1990 and 2003. He found that four of the six findings were later overturned by clinical trials.
