Watch what you eat -- or they will
It’s hard to imagine anyone in this country hadn’t got an inkling, by now, that eating fruits and vegetables is good for us.
Not that we necessarily do it. Two recent reports examined whether Americans are eating as many fruits and vegetables as the government recommends. Both concluded no, and that Americans are eating the same -- inadequate -- amount of produce as they have for decades.
But how do the government and scientists even know what we’re eating? Are there cameras hidden in the broccoli?
The data come from various places. One of the new reports, published in the American Journal of Preventive Medicine, analyzed data from a long-running survey known as NHANES, run by the Centers for Disease Control and Prevention. Every few years, thousands of volunteers are interviewed about what foods, and how much, they ate in the last 24 hours. Quantities are estimated using fake fruit or pictures of portion sizes. (Most Americans have blown-up ideas of what a “portion” is: four Girl Scout Thin Mint cookies is a “portion,” not half a box.) Participants also track their diet for a few days, then mail in that information.
The other study, published in the CDC’s Morbidity and Mortality Weekly Report, used data from another CDC study, called BRFSS for short. Each year, 350,000 volunteers are called and asked health questions, including ones on fruits and vegetables.
Scientists can also figure out what people are eating by asking people to keep food diaries, or by taking blood samples and looking for tell-tale nutrients. The U.S. Department of Agriculture takes a different tack -- calculating diet based on produce grown and sold minus what is exported, goes bad or is lost, says USDA economist Jean Buzby. Such data were used in a 2005 study that reported, unlike the two recent studies, that Americans ate 20% more fruits and vegetables in 2005 than in 1970. Yet even these data don’t come close to finding we eat enough produce: A 2006 report coauthored by Buzby estimated that if Americans ate as much produce as they’re supposed to, farmers would need to harvest at least twice the current acreage.
But can we at least tell how healthy the diet of Americans is? Older NHANES surveys lumped French fries in with all potatoes, even though the nutritional value of fries differs a lot from, say, boiled potatoes. The newer NHANES surveys did so too -- to stay consistent. “There’s been a lot of criticism about including fried potatoes,” says Tiffany Gary of Johns Hopkins School of Public Health, lead author of the recent NHANES study.
Another twist: The NHANES and USDA keep track of various kinds of fruits and vegetables, but the BRFSS doesn’t. This can lead to head-scratching differences. The recent NHANES report says that more people are getting enough veggies -- but not fruit. The BRFSS paper says the opposite: More Americans eat their fruit.
Some experts say that counting fruits and vegetables separately is important because the two have different nutrients. Not everyone agrees. “Whether something is called a fruit or a vegetable means nothing,” says Dr. David Heber, director of UCLA’s Center for Human Nutrition. The tomato, he says, is botanically a fruit but classed as a vegetable by decree of the U.S. Supreme Court, in 1893. This made tomatoes legally vegetables so they could, unlike fruits, be taxed. Nutritionists everywhere wonder if it will take such drastic measures to get us to eat our fruits and vegetables.
