Shifting America’s Diet
Factions continue to duke it out over what the nation’s dietary guidelines should be, but the scientists have had their say: less meat, less sugar, and please, eat your veggies
It’s an afternoon in late March, and Gershoff Professor Alice H. Lichtenstein, D.Sc., is in her office, listening to a live feed of what Americans have to say about the Scientific Report of the 2015 Dietary Guidelines Advisory Committee. The exercise requires a thick skin, as does reading the thousands of public comments that have been posted to the guidelines website. There is a plea to “recognize and promote the role that beans can play in the health of Americans” and a demand that “schools need to stop overcooking vegetables.” But one of the most repeated criticisms goes like this: “…my family does not need the federal government at our dinner table promoting the agenda of elitists and activists. …”
That would be aimed at Lichtenstein and the 13 other nationally recognized nutrition and health experts on the committee who spent 18 months going over the research for the report, which they submitted to the government in February. Now it’s time for the Department of Health and Human Services and the Department of Agriculture to decide what, if anything, they will include from the committee’s report in the actual Dietary Guidelines for Americans, which they will announce by the end of the year. It is a cycle that repeats every five years.
The commentary will go on for hours. As per federal rules, the committee has disbanded, and Lichtenstein, who served as co-chair, is officially out of the discussion, except as an observer. “I registered [for the live streaming] like any other person in order to have access to it,” she says. She’s not bitter; it’s just the process that keeps the science separate from the politics. The same goes for fellow committee member Professor Miriam Nelson, N85, N87, Ph.D., associate dean of the Tisch College of Citizenship and Public Service, and Associate Professor Timothy Griffin, Ph.D., who served as a consultant. (The Friedman School was the only institution to have three representatives work on the report.)
Follow the Science
After reviewing hundreds of studies, the committee outlined a way of eating that you’ve probably heard recommended many times before. A healthy dietary pattern, the report concludes, is higher in vegetables, fruits, whole grains, low and nonfat dairy, seafood, legumes and nuts; moderate in alcohol; lower in red and processed meats; and low in sugar-sweetened foods and drinks and refined grains.
Industry had made it clear that it has a beef with that “lower in red and processed meats” part, and a separate conclusion that a diet “lower in animal-based foods” is better for the health of the food system. This was by far the most controversial part of the report, with meat industry advocates rushing to defend the nutritional benefits of their products, while supporters of plant-based diets cheered the conclusions. The push-and-pull isn’t surprising, Lichtenstein says, but it takes away from what she sees is a selling point of the report’s recommendations: flexibility. You can go vegetarian; you can go Mediterranean; you can have meat and potatoes—just as long as the other half the plate includes green and orange vegetables.
“We have to get away from the idea that a healthy dietary pattern is punitive, that it tastes bad…” —Alice H. Lichtenstein
Selling the guidelines to consumers is important. Although the guidelines will affect what foods are included in the National School Lunch Program, the Women, Infants and Children (WIC) program and the Child and Adult Care Food Program, individual Americans, by and large, have not done a good job of following the guidelines.
Lichtenstein doesn’t want us to cringe anymore about what we eat: “We have to get away from the idea that a healthy dietary pattern is punitive, that it tastes bad, that it takes a long time to prepare, that you have to do it only because it is good for you.” Because the diet is brushed in broad strokes, it can be adapted to different cultural patterns and personal preferences, she says. “You can do it if you don’t eat meat, if you don’t mix meat and milk, if you eat several small meals, if you like three meals a day or even if you don’t like Brussels sprouts.”
The committee used many studies that compared dietary patterns—whole diets, from soup to nuts—rather than single nutrients like carbs, fats and proteins. The conclusions of these studies, it turns out, were very consistent. Whether the outcome they looked at was obesity, cardiovascular disease, high blood pressure, diabetes or certain cancers, the same way of eating pointed to lower risk.
People Don’t Eat Nutrients
The 2010 advisory committee explored this pattern-centered approach, and the 2015 committee delved deeper into the science. Why is it important? Because people don’t eat nutrients; they eat foods, and they don’t eat foods in isolation. “We know that in diets, when one thing goes down, another thing goes up,” Lichtenstein says. “We frequently end up with unintended consequences when we don’t take this into consideration and only talk about individual dietary components.”
She continues: “When we told people to reduce fat, assuming that would include saturated fat, we did not anticipate there would be this extraordinary proliferation of fat-free brownies, ice cream, cookies and crackers to fill the void, which are essentially all refined carbohydrate.”
What does a diet “higher” in fruits and vegetables and “lower” in red and processed meat mean? Higher and lower compared to what? In many of the studies the committee looked at, the health of people who ate the most of something was compared with that of the people who ate the least. The actual amounts varied among the studies, making pinpointing an optimal number difficult.
But three sample food patterns described in the report, and designed to provide all the nutrition we need while keeping calories in check, give some more detail. At the 2,000-calorie level, both the “healthy U.S.-style” pattern and the “healthy Mediterranean-style” pattern allow for 26 ounces of meat, poultry and eggs per week—less than the average American typically eats now. They differ in the seafood category, with the U.S.-style calling for 8 ounces per week, while the Mediterranean ups it to 15 ounces per week. All three diets call for two and a half cups of vegetables per day, although the “healthy vegetarian” pattern has twice as many beans and peas, at three cups per week.
Nelson, who was also on the 2010 advisory committee, says the meat recommendation is an incremental change from the previous report, which emphasized shifting to a more plant-based diet. “We weren’t as explicit in 2010 about eating less red and processed meat,” she says. “Less is relative to what we’re eating now. It’s not becoming vegetarians.”
It’s been a long road for the committee members, who were nominated for their expertise in 2012, appointed in 2013 and have held seven public meetings and weekly conference calls over the better part of two years.
In an op-ed, David Katz, director of Yale University’s Prevention Research Center, described the process this way: “Conflicts of interest had to be disclosed, and expunged. The work had to take place in the transparency of a veritable fish bowl, with multiple opportunities for public commentary along the way, including now. The 572-page report includes hundreds and hundreds of scientific citations, including papers espousing both sides of any given argument—because the job of the committee was to examine all sides and reach evidence-based consensus, not pave the way to a polarized position they already held before they started.”
The dietary guidelines as a whole have undergone only minor modifications since 1980.
Griffin was impressed with how little took place behind closed doors. “There was nothing opaque about it,” he says.
For now, the committee can only wait and see what parts of their work end up in the actual guidelines. Many people have pointed out that the meat industry’s reaction to the report is reminiscent of what happened the first time the government tried to give dietary advice. The 1977 Dietary Goals for the United States initially called for Americans to eat less meat. After protests from industry, that recommendation was nixed from the draft.
Arguing over the details is all well and good, but getting Americans onboard with a healthier diet and making it easier for people to make those healthy choices in restaurants, convenience stores and grocery aisles is time better spent, Lichtenstein says. After all, she adds, the guidelines as a whole have undergone only minor modifications since 1980, “yet we still haven’t moved the population to a huge extent toward them.”
Capping dietary cholesterol at 300 milligrams a day to prevent heart disease has long been a refrain of the dietary guidelines. But this year, the advisory committee suggested nixing it, coming to the same conclusion as the American Heart Association/American College of Cardiology, which did not include it in their 2013 guidelines. It reflects what has been a gradual change in the science, and in what people are eating. Currently, men get about 350 milligrams per day, and women about 250—a far cry from the 800 to 900 mg that people were consuming in the 1950s.
“The bottom line on cholesterol is that within the context of current intakes, increasing it up or down a little bit is unlikely to have a significant effect on plasma cholesterol levels,” says Lichtenstein, who is director of the HNRCA’s Cardiovascular Nutrition Laboratory. The exception is if you are genetically primed to hyper-respond to dietary cholesterol. There is no simple test, so people need to work with their health-care provider to determine their sensitivity.
This doesn’t mean that blood cholesterol isn’t important, or that diet doesn’t influence it. The main culprit behind high levels of LDL or “bad” cholesterol is saturated fat, and the committee said the science still points to limiting that to 10 percent of calories, specifically by replacing saturated fats, like butter, with polyunsaturated fats, like vegetable oils. The report notes that for every 1 percent of saturated fat people replace with polyunsaturated fat, the incidence of coronary heart disease goes down by 2 to 3 percent.
However, the report goes on, “reducing total fat (replacing total fat with overall carbohydrates) does not lower [cardiovascular disease] risk.” Indeed, the report doesn’t put a specific limit on how much fat people should eat. “The emphasis should be on total calories, not fat,” Lichtenstein says. That’s in keeping with the proposed changes to the Nutrition Facts label, which would no longer list a food’s calories from fat, because, as the FDA notes, “research shows the type of fat is more important than the amount.”
Coffee is not only safe, it may have health benefits.
“Coffee, whether it is decaf or regular, seems to be very health promoting,” says Nelson, who chaired the subcommittee that looked at food safety.
Drinking three to five normal cups of coffee a day, with up to 400 milligrams caffeine, was linked to a reduced risk of cardiovascular disease, Type 2 diabetes, Parkinson’s disease and some cancers.
That doesn’t mean that you have to start drinking coffee if you don’t already. “You can still be healthy without drinking coffee,” Nelson says. “But if you enjoy it, it fits into a healthy lifestyle.” The caveat: “You do have to think about calories if you are adding a lot of cream and sugar.”
The report’s statement on coffee started out as a question the committee had about the dangers of caffeine-heavy energy drinks, which are popular with teens and young adults.
While they found several studies that looked at coffee, there wasn’t enough evidence about high-caffeine drinks to draw a conclusion, despite case reports of hospital admissions and cardiac issues related to extremely high caffeine intake.
Pregnant women should stop at two cups per day.
In addition to endorsing a dietary pattern that is generally “low in sugar-sweetened foods and drinks and refined grains,” the report put a cap on added sugars. For the first time, the committee recommended limiting them to no more than 10 percent of calories. That may not seem like a huge reduction from the 13 percent that Americans currently average, but “if you’re an adolescent getting 17 percent from added sugar, it’s a big difference,” Nelson says.
One of the most talked-about parts of the advisory committee report was that for the first time it included sustainability of the food system as part of its scientific review. The committee’s conclusion was that “a diet higher in plant-based foods… and lower in animal-based foods, is more health promoting and is associated with less environmental impact than is the current U.S. diet.”
But even before they drew their conclusion, the pushback began. “Pseudoscience,” warned one agricultural engineer. “Not within the committee’s expertise,” said the North American Meat Institute. Congress, as part of a spending bill, even directed the secretary of agriculture to rein in the committee to keep it from “incorporating agricultural-production practices and environmental factors into their criteria.”
Still, the committee pressed on. “Our work is congressionally mandated,” says Professor Miriam Nelson, Ph.D., who chaired the subcommittee on food sustainability and safety. “We were aware of the chatter that was happening, but we were insulated because we are independent.”
The committee decided the question was within its purview because sustainability affects food security. Ensuring Americans have access to affordable, healthy foods has been a central theme of the guidelines since they were first issued in 1980. “If you care about food security, you really need to care about sustainable diets,” Nelson says. The argument is that if the American diet as a whole is too taxing on our land, water and other resources, we will be unable to produce enough food to feed everyone in the long run.
“And we’re not talking about 50 or 100 years from now,” says Associate Professor Timothy Griffin, Ph.D., director of the Agriculture, Food and Environment Program (AFE) at the Friedman School. “This is about the short term and the long term.”
If the American diet as a whole is too taxing on our land, water and other resources, we will be unable to produce enough food to feed everyone in the long run.
Because the committee members needed more depth in sustainability and agriculture, Griffin was asked to serve as a consultant, one of three the committee brought on to provide additional expertise.
Despite charges in the press that they were “radical nutritionists” forwarding a liberal agenda, the committee members didn’t undertake the question of sustainability knowing where the research would lead them.
“We didn’t plan this to begin with; we let the science dictate this,” Nelson says. “There were actually 15 high-quality studies that we could review. And the best is when studies have a slightly different approach but they all come up with a similar finding. And every one of them did.”
Even Griffin was struck by the harmony. “I didn’t expect this to be as true as it was, but the level of agreement across those studies was very strong.”
The studies the sustainability subcommittee used were by necessity different from randomized control trials and cohort studies, but no less valuable. “We were looking at really good, high-quality science,” Nelson emphasizes.
It was also narrow in scope, says Griffin. “We weren’t looking at climate change. We weren’t looking at greenhouse gases,” he says. “We were using methodologies that were directly related to healthy and sustainable diets.”
“We’re not saying you have to become a vegetarian.” —Miriam Nelson
Several of the studies they reviewed involved food-pattern modeling. Such modeling takes what is known about how much land is needed to grow particular foods and then connects it to how a population eats—or could eat, with the right incentives.
Among that research was the work of Christian Peters, Ph.D., an assistant professor in the AFE program with a special interest in the impact of dietary preferences on land use. For a study published in 2007, he looked at 42 different diets to determine which offered the most effective use of farmland in New York state. (A follow-up study, looking at the national level, has been submitted for publication.) The diet that fed the most people was a low-fat vegetarian diet. But when he looked at diets with higher amounts of fat—such as a vegetarian diet with plenty of oils and a diet with small amounts of meat or eggs—the omnivore diet was more efficient. Why? Because oil-producing crops like corn and soybeans require high-quality acreage, while cows, sheep and goats can be raised on lower-grade hay and pasture lands, which might not otherwise be put to use.
The key here is “small amounts” of meat—about two cooked ounces per day in his study, a fraction of the current American average.
“From where we are now, with almost six ounces of cooked meat per day, moving in the direction of less meat is almost certainly going to reduce impact,” Peters says.
“We’re not saying you have to become a vegetarian,” says Nelson, pointing out she has five cows on her family farm. “I believe that if people want to eat meat, they should eat meat.”
In fact, the sustainability subcommittee’s conclusions were in line with what the committee as a whole found is good for public health.
“It’s not this landslide change in advice,” Peters says. Still, he wasn’t surprised to see the meat industry up in arms. “It’s a very inconvenient message to be told that your industry needs to shrink in terms of output,” he says. He wonders whether meat producers would be able to adapt to changing demand by adding value. “Organics is purporting to go in that direction. Could you make meat greener, sell less of it, but still sell it for the same amount of money as you were making before?”
Griffin is adamant that the dietary guidelines are first and foremost about nutrition and public health, as they should be. But he thinks that the facts about sustainability could act as an additional motivator for people to adopt healthier eating habits. It’s a win-win.
Many clearly agree. By the time the public-comment period on the report closed in May, more than three-quarters of the nearly 30,000 comments were in support of the sustainability language, Nelson points out.
And if the sustainability wording finds no place in the final guidelines, was it still a valuable exercise? “Sure,” Griffin says. “More conversation about this is better than less. That is a good outcome.”
Julie Flaherty, the editor of this magazine, can be reached at firstname.lastname@example.org.