Introduction to special issue

Optimizing the diet

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Science  16 Nov 2018:
Vol. 362, Issue 6416, pp. 762-763
DOI: 10.1126/science.aav9415

Maximum performance or maximized health benefits require a nutritious mix of foods in the diet.

PHOTO: SCOTT SUCHMAN; STYLING: NICHOLE BRYANT

In every stage race, competitive cyclists perform an experiment of sorts to discover who can most efficiently turn dietary energy sources into maximal power output on the bike. More broadly, we're all interested in diet because abundant evidence shows that diet has major effects on human health and resistance to rampant diseases associated with aging, such as obesity, cardiovascular disease, and diabetes. Advice on what constitutes a healthy diet is more prevalent and more inconsistent than ever. For this special issue, we checked in with the experts. On the question of how much fat we should eat, recommendations have swung from one extreme to the other. We consulted with a group of scientists representing different sides in the debate over the proportion of fat in a healthy diet and, importantly, which particular fats are most healthful. We share our meals with trillions of bacteria in the digestive system, so a promising and emerging area of investigation explores how diet influences our give-and-take interaction with gut symbionts. It's not just what you eat but when you eat it, and periods of fasting have some remarkable benefits. A pervasive theme is that much of the disagreement and confusion reflects a lack of solid scientific studies on humans. Clearly, many more well-designed studies are needed to determine the best diet for people, and how that varies with activity, at different life stages and for different individuals. And individual needs can be extreme—a cyclist at the top of the sport recorded massive carbohydrate loading before an intense stage, eating the equivalent of 85 slices of bread!

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