Where do they get all this stuff, anyway? Month after month, the stories hit the press like Elvis sightings: Hot dogs cause leukemia. Margarine causes heart attacks. Apples are evil and fat is fatal, unless the fruit is organic and the fat is olive oil, which is good for you - except when you eat too much of it.
No wonder the public has a collective case of whiplash from the nutrition warnings that are doled out like water torture: Is this going to be the last droplet? How long before the next one hits?Now that food and nutrition have become a near obsession with many Americans, diet studies and advice will keep coming. The only umbrella available to consumers is to read closely and question authority.
Stop looking for the one miracle food that will take weight off or burn fat and cholesterol. Each food scare shouldn't mean an immediate purge of the refrigerator's contents.
"Don't be swayed too much by the headlines," said Peter Greenwald, director of Cancer Prevention and Control at the National Cancer Institute. "In diet, you don't usually have sudden results. Single factors may be minor or even trivial."
"People think that nutrition changes all the time," said Marion Nestle of the Department of Nutrition at New York University. "But the simple issues that are not that interesting - get most of your calories from grains and fruits and don't eat a lot of meat and dairy products - that part does not change at all, ever."
One pitfall of nutrition studies comes when the information is gathered outside the controlled environment of a laboratory and based on interviews of the patient's behavior over a period of years.
"There's a lot of human error in self-reporting on dietary intake," Nestle said.
Just because a report gets into print doesn't mean that its findings are absolute.
"I think a problem that's inherent in the (medical journal) field is that people want simple stories," said Regina Ziegler, a nutritional epidemiologist at the NCI. "If there is complexity or caveats in the discussion, you may deter your chances of getting accepted for publication. And we all want our papers accepted."
Ziegler's advice is to beware of sensational findings that are the result of a single study.
"There are a couple of basic rules," Nestle said. "The first thing is you need to have common sense. Ask `Do the results of this study make sense?' In the case of the margarine study: `How serious a problem is this?' People don't eat a diet of just margarine."
The sometimes conflicting nutrition advice is confusing, says Chris Rosenbloom, an associate professor in Nutrition and Dietetics at Georgia State University. But that shouldn't cause people to give up healthful eating habits entirely."