Regardless of who issues them, guidelines for health promotion and disease prevention universally recommend diets that are largely plant-based, meaning those that include plenty of fruits, vegetables, grains, beans, and nuts. The U.S. dietary guidelines also recommend foods in the “protein” category. Grains, beans, and nuts are good sources of protein, but the guidelines use “protein” to mean low-fat dairy, lean meats, and fish. Recommended eating patterns include all these foods, relatively unprocessed, but with minimal addition of salt and sugars. Such patterns provide nutrients and energy in proportions that meet physiological needs but also minimize the risk of obesity, type 2 diabetes, and other chronic diseases. One more definition: “Patterns” refer to diets as a whole, not to single foods. No one food makes a diet healthful. The healthiest diets include a wide variety of foods in each of the recommended categories in amounts that balance calories.
In their largely unprocessed forms, foods from the earth, trees, or animals are healthful by definition. So why, you might ask, would the producers of foods such as cranberries, pears, avocados, or walnuts fund research aimed at proving that these particular foods—rather than fruits, vegetables, or nuts in general—have special health benefits? Marketing, of course. Every food producer wants to expand sales. Health claims sell. The FDA requires research to support health claims and greatly prefers studies that involve human subjects rather than animals.
All of this explains why Royal Hawaiian Macadamia Nut petitioned the FDA in 2015 to allow it to say in advertisements that daily consumption of macadamias—along with eating a healthy diet—may reduce the risk of heart disease. The 81-page petition cited several studies done in humans, one of them funded by the Hershey Company, which sells chocolate-covered macadamias. The FDA ruled that it would permit a qualified health claim for macadamia nuts with this precise wording: “Supportive but not conclusive research shows that eating 1.5 ounces per day of macadamia nuts, as part of a diet low in saturated fat and cholesterol and not resulting in increased intake of saturated fat or calories may reduce the risk of coronary heart disease.” Can a statement this cumbersome help sell macadamia nuts? Definitely, with a little help from the press: “Go nuts, folks! FDA declares macadamia nuts heart healthy.”
Legitimate scientific questions can be asked about specific foods—their nutrient content or digestibility, for example—but most such issues were addressed ages ago. Foods are not drugs. To ask whether one single food has special health benefits defies common sense. We do not eat just one food. We eat many different foods in combinations that differ from day to day; varying our food intake takes care of nutrient needs. But when marketing imperatives are at work, sellers want research to claim that their products are “superfoods,” a nutritionally meaningless term. “Superfoods” is an advertising concept.
But what is wrong with promoting the benefits of healthful foods? Wouldn’t we be better off eating more of them? Yes, we would, but many industry-funded studies are misleading, which is why the FDA requires so many qualifications in the claims it allows. This kind of research is designed to produce results implying that people who eat this one food will be healthier and can forget about everything else in their diets. Research aimed at marketing raises questions about biases in design and interpretation, may create reputational risks for investigators, and reflects poorly on the integrity of nutrition science. It also raises questions about the role of government agencies in promoting single-food research and about their failure to do a better job of regulating marketers’ claims about health benefits based on that research. To illustrate why such concerns matter, consider some of the marketing issues related to a well-known healthy food: blueberries.
The trade association Wild Blueberries of North America wants you to understand that frozen, fresh Wild Blueberries (always capitalized) are better for you than unfrozen, fresh supermarket highbush berries: “Jam-packed with a variety of natural phytochemicals such as anthocyanin, Wild Blueberries have twice the antioxidant capacity per serving of regular blueberries. A growing body of research is establishing Wild Blueberries as a potential ally to protect against diseases such as cancer, heart disease, diabetes and Alzheimer’s.” This is an impressive range of health benefits for a tiny fruit consumed in small amounts, but selling them as an antioxidant powerhouse has done wonders for the Maine wild-blueberry industry.
For years, I have had a potted highbush-blueberry plant on my 12th-floor Manhattan terrace, satisfyingly productive in years when I can manage to fend off the hordes of voracious finches. Unlike the easy-to-get-at highbush varieties, the wild ones grow close to the ground on sandy soils left behind by receding glaciers and are more difficult to harvest. In Maine, these blueberries are an important agricultural commodity. Since 1945, Maine blueberry growers have supported research—then and now focused on production practices—at the state’s university. As techniques improved, blueberry growers produced more berries. These needed to be sold.
The Maine Wild Blueberry Commission consulted with marketing specialists. In 1992, a consultant advised focusing on taste as a means of differentiating wild blueberries from cultivated blueberries. But the consultant then read an article in a USDA magazine extolling the virtues of plant antioxidant pigments in “boosting the immune system, reducing inflammation and allergies, [and] detoxifying contaminants and pollutants.” The article said that USDA investigators had invented an assay for antioxidants demonstrating that blueberries have the highest levels of any fruit tested (kale was highest among vegetables). The consultant advised the commission to focus on antioxidants. From 1997 to 2000, half of the Maine Wild Blueberry Commission’s marketing resources went into repositioning blueberries as a health icon. The strategy worked. Maine’s wild-blueberry industry flourished—at least for a while. Recent overproduction and competition from Canadian fruit have dropped prices below profitability.
I love blueberries, wild and cultivated, but they are a fruit like any other. Their antioxidants may counteract the damaging actions of oxidizing agents (free radicals) in the body, but studies of how well antioxidants protect against disease yield results that are annoyingly inconsistent. When tested, antioxidant supplements have not been shown to reduce disease risk and sometimes have been shown to cause harm. The USDA no longer publishes data on food antioxidant levels “due to mounting evidence that the values indicating antioxidant capacity have no relevance to the effects of specific bioactive compounds, including polyphenols on human health.” The U.S. National Center for Complementary and Integrative Health at the NIH judges antioxidants as having no special benefits. People who eat more fruits and vegetables have less risk of chronic disease, but nobody really knows whether this is because of antioxidants, other food components, or other lifestyle choices.
Blueberries, like every other fruit and vegetable, have a unique combination of antioxidants. So what? It is best not to expect miracles—like this especially wishful-thinking headline: “Blueberries associated with reduced risk of erectile dysfunction.” Two of the authors of this study reported receiving funding from the U.S. Blueberry Highbush Council “for a separate project unrelated to this publication.”
A more critical question is what to make of all this. If I may overgeneralize, the quality of single-food marketing studies does not always hold up to scrutiny. For example, a nutritional biochemist criticized a 2015 raisin study connected to funding from the California Marketing Raisin Board for its misuse of statistics and for comparing raisins to processed snack foods: “With the design used you can’t really say that raisins were ‘good’ for the participants, just not as bad as the junk snacks.”
Even when done well, studies so clearly aimed at marketing skew the research agenda. If food companies were not funding marketing studies, investigators might be working on more important biological problems. All these foods are highly nutritious and well worth eating for their taste and texture—as well as for their health benefits. Is one fruit, vegetable, or nut better for you than another? The answer, as I keep saying, depends on everything else you eat or do. People who habitually eat largely plant-based diets are healthier. Variety in food intake and calorie balance are fundamental principles of healthful diets.
Again, to be fair, not all studies funded by plant trade associations come out the way they are supposed to. The California Strawberry Commission, for example, sponsored a study to see whether eating 40 grams of dried strawberry powder a day—equivalent to a pound of strawberries—would counteract the effects on blood lipids of eating a high-fat diet. It did not. I do not want to even think about strawberry powder. But does this result mean we should not be eating strawberries? Of course not. All fruits, vegetables, and nuts have vitamins, minerals, fiber, antioxidants, and other components that collectively promote health. If we are fortunate enough to have choices, we can eat the ones we like.
This post is adapted from Nestle’s new book, Unsavory Truth: How Food Companies Skew the Science of What We Eat.