BOSTON, Mass. - For 20 years, Helena Bauk has been reporting her health and habits -- one of 120,000 participants in the 30-year-long Nurse's Health Study.
There's new information Tuesday: Doctors had hoped aspirin could cut colon cancer risk. But the nurse's study found it takes ten years at such high doses that there is a risk of stomach bleeding.
"The doses of aspirin that are needed to prevent colorectal cancer appear to be quite different than the doses of aspirin need to prevent cardiovascular disease," says Dr. Andrew Chan of Massachusetts General Hospital.
How does the nurse's study get such detailed, critical information? Every two years, Helena Bauk and the others take a few hours to answer an extensive questionnaire.
But for the 35 scientists designing and analyzing the questionaires is a full time job.
How do they decide? There are probably thousands of potential questions.
"Well, we have respectful and collegial battles over every square inch of the questionnaire to try to make the best use of this opportunity," says Dr. Meir Stampfer, Harvard School of Public Health.
It's the opportunity to study not just medications, but the effects of lifestyle, including exercise, weight -- and perhaps most famously -- diet on the risk for disease.
"In almost every aspect of diet you can find very large contrasts within this population," says Dr. Walter Willett, Harvard School of Public Health.
The studies have dispelled many myths: Not all fat is bad. Some things like eggs and coffee, once feared, do not pose a danger. But other diet components like processed grains and so-called trans fats can be very dangerous.
Do you get tired of being called the 'Food Police?'"
"I sometimes get called the 'Food Police,'" says Dr. Willett, "but I'm really not out there with a Billy stick and that kind of thing."
But he is armed with a solid information from decades of study of the nurses.