Q: There are so many different opinions about what you should and shouldn't eat. How does one determine what information is reliable?
A: It's definitely a challenge. While watching TV or surfing the internet you are constantly exposed to ads, blogs, and articles about diet and health. Perhaps relatives and friends who are trying to be helpful send you web links about what you should or shouldn't be eating to lose weight, prevent cancer, or dodge heart disease.
Sometimes these sites quote an "expert" claiming why one particular diet is the best yet. You need to be especially wary of articles that aim to sell you a special supplement. Unlike pharmaceuticals, which undergo extensive testing to prove they're effective and safe before they can be sold, dietary supplements can be sold without proof of effectiveness or safety.
Throughout the year, myriad nutrition studies get headlines in the news. This includes study results published in highly respected journals that seem contradictory.
That's why the findings of any single nutrition study should not change in your eating habits. But several high-quality studies that come to similar conclusions just might.
According to the Culinary Institute of America and the Harvard T.H. Chan School of Public Health, a reliable nutrition study has these key attributes:
— It looks at people — not animals, which often respond to diets differently than humans do.
— It involves a large number of participants (the range depends on the type of study), which is necessary to reach statistically reliable conclusions.
— It measures health outcomes, such as heart disease or diabetes, or quality of life.
— It follows people over many years. That applies to prospective or cohort studies, which periodically record people's diets and watch to see if they develop a disease, as well as randomized trials, which assign people to different diets and follow them over time. Randomized trials are often the most desirable, but they're harder to do because people don't always stick to the diet.
— Its findings are confirmed by similar studies, including short-term ones (lasting weeks or months) that measure biochemical or physiological markers (such as blood pressure or cholesterol levels) that are relevant to the disease in question.
(Howard LeWine, M.D., is an internist at Brigham and Women's Hospital in Boston and assistant professor at Harvard Medical School. For additional consumer health information, please visit www.health.harvard.edu.)
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