As a nutrition professor, I am constantly asked why nutrition advice seems to change so much and why experts so often disagree. Whose information, people ask, can we trust? I’m tempted to say, “Mine, of course,” but I understand the problem. Yes, nutrition advice seems endlessly mired in scientiﬁc argument, the self-interest of food companies and compromises by government regulators. Nevertheless, basic dietary principles are not in dispute: eat less; move more; eat fruits, vegetables and whole grains; and avoid too much junk food.
“Eat less” means consume fewer calories, which translates into eating smaller portions and steering clear of frequent between-meal snacks. “Move more” refers to the need to balance calorie intake with physical activity. Eating fruits, vegetables and whole grains provides nutrients unavailable from other foods. Avoiding junk food means to shun “foods of minimal nutritional value” — highly processed sweets and snacks laden with salt, sugars and artiﬁcial additives. Soft drinks are the prototypical junk food; they contain sweeteners but few or no nutrients.
If you follow these precepts, other aspects of the diet matter much less. Ironically, this advice has not changed in years. The noted cardiologist Ancel Keys (who died in 2004 at the age of 100) and his wife, Margaret, suggested similar principles for preventing coronary heart disease nearly 50 years ago.
But I can see why dietary advice seems like a moving target. Nutrition research is so difﬁcult to conduct that it seldom produces unambiguous results. Ambiguity requires interpretation. And interpretation is inﬂuenced by the individual’s point of view, which can become thoroughly entangled with the science.
Marion Nestle is Paulette Goddard Professor in the department of nutrition, food studies and public health and professor of sociology at New York University. She received a Ph.D. in molecular biology and an M.P.H. in public health nutrition from the University of California, Berkeley. Nestle’s research focuses on scientiﬁc and social factors that inﬂuence food choices and recommendations. She is author of Food Politics (2002, revised 2007), Safe Food (2003) and What to Eat (2006). She also writes a popular nutrition blog, Food Politics.
Reprinted with permission. Copyright © 2007 by Scientific American, a division of Nature America, Inc. All rights reserved. For more information about the issue, go to: http://www.scientificamerican.com/article.cfm?id=eating-made-simple