The debate about sustainable diets has focused on meat production, which requires lots of land and water to grow grain to feed livestock. It also contributes to methane emissions. But the Cabinet secretaries with final authority say the 2015 dietary guidelines won't include sustainability goals. David McNew/Getty Images hide caption

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Despite losing his sense of taste and smell to Alzheimer's disease, Greg O'Brien says grilling supper on the back deck with his son on a summer evening is still fun. Sam Broun/Courtesy of Greg O'Brien hide caption

itoggle caption Sam Broun/Courtesy of Greg O'Brien

On the left, olive oil, which is low in saturated fat and high in monounsaturated fat, which may lower bad cholesterol levels. On the right, coconut oil, which is 90 percent saturated fat and may raise bad cholesterol levels. iStockphoto hide caption

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Bottom round roast is one cut of beef that fits the government's definition of "lean." Still, the definition is confusing to consumers, nutrition scientists argue. Paul Polis/Corbis hide caption

itoggle caption Paul Polis/Corbis

A government-appointed panel concluded in a recent report that Americans should eat less red meat and processed meat. A more plant-focused diet is better for health and the environment, it found. Andrew Burton/Getty Images hide caption

itoggle caption Andrew Burton/Getty Images

A daily cup of joe (or two) may help protect against Type 2 diabetes and cardiovascular disease. And an egg a day will not raise the risk of heart disease in healthy people, according to a panel of nutrition experts. Premshee Pillai/Flickr hide caption

itoggle caption Premshee Pillai/Flickr

The University of California's Nutrition Policy Institute has proposed that MyPlate include an icon for water. UC Division of Agriculture and Natural Resources hide caption

itoggle caption UC Division of Agriculture and Natural Resources