Earlier this month, word leaked that a nutrition panel advising the federal government would recommend scrapping decades-old warnings about the harmful effects of cholesterol. Washington’s very first dietary guidelines, issued by a U.S. Senate committee in 1977, had urged Americans to reduce consumption of meat and dairy products with the aim of cutting cholesterol levels by 25 percent. Subsequent federal guidelines, reissued every five years starting in 1980, continued to make a similar recommendation, even though the scientific evidence linking cholesterol to heart disease was—and is— inconclusive, at best.
But any hope that the backtracking on cholesterol by the Dietary Guidelines Advisory Committee signaled a new willingness by Washington’s scientific advisors to reevaluate the larger nutrition instruction it peddles to the public turns out to have been premature. As the Washington Post noted, the committee also faced choices in several other controversial areas of nutrition. The science justifying restrictions on consumption of the saturated fats contained in red meat and dairy products is also disputed. Far from backing off some of its previous positions, the dietary committee’s recently released recommendations are consistent with its previous approach—and add a new twist. The nutritionists chosen by the Obama administration now want the government to urge Americans to increase intake of certain foods, such as vegetables, in pursuit of a more environmentally “sustainable” diet—advice that has little direct link to personal health and goes well beyond the traditional purview of the federal dietary guidelines.
Washington’s dietary guidelines have been controversial from the outset, largely because they advised Americans on how to adjust their diets to reduce cardiovascular disease—chiefly heart attacks and stroke. The American public became increasingly concerned with the issue of heart disease starting in the 1950s, when some of the press declared the country was in the grip of an emerging epidemic. Americans, living longer, were experiencing greater numbers of heart attacks and strokes. In searching for medical causes for a problem that didn’t necessarily have a single source (heart diseases can be the result of a combination of factors), some researchers focused on the role of cholesterol, an organic molecule, whose presence was found in plaque buildup in arteries. Experts theorized that consumption of products rich in cholesterol or saturated fat, which prompts the body to manufacture more of its own cholesterol, was behind the rise in heart disease. But others vehemently disagreed, pointing to studies that showed that people living in cultures with diets rich in saturated fats sometimes had low rates of heart disease.
The science wasn’t close to being settled by the time the Select Senate Committee on Food and Nutrition issued the first guidelines in early 1977. The committee was led by Senator George McGovern, who had been heavily influenced by the views of low-fat diet guru Nathan Pritikin. According to Gary Taubes in his book Good Calories, Bad Calories, McGovern even attended one of Pritikin’s month-long seminars. The committee’s work reflected the Pritikin perspective, which called for decreasing fat intake from 40 percent of calories to 30 percent, and increasing carbohydrate consumption to 60 percent of calories. In a refrain that was to become familiar, supporters argued that even though the science was inconclusive, there would be little risk in America’s changing its diet in such a fashion. The press largely welcomed the guidelines, trumpeting them as helpful advice in an age of dietary uncertainty. The surrounding political and cultural environment contributed to the acceptance of the guidelines, too. As Taubes notes, the 1970s were a time of rising interest in vegetarianism both as a diet and as an expression of an environmentally “sustainable” lifestyle, as reflected in the popularity of Frances Moore Lappé’s best-selling Diet for a Small Planet.
The scientific community’s support for the guidelines wasn’t unanimous. The National Academy of Sciences said in an official statement that there was “no reason for the average healthy American to restrict consumption of cholesterol, or reduce fat intake” as long as people kept their weight under control. Rockefeller University researcher Edward Ahrens characterized the committee’s questionable recommendations as the equivalent of treating the American population as “a homogenous group of [laboratory] rats.” Over time, new research did little to end the scientific controversy. The results of two massive and expensive studies sponsored by the National Institutes of Health and published in the early 1980s, which were meant to clear up the issue of fat, cholesterol, and diet, turned out to be inconclusive. In 1992, a review of 19 worldwide studies on cholesterol, published in the scientific journal Circulation, found no correlation between death rates and cholesterol in women, and showed that while men with very high cholesterol levels (above 240) were disproportionately likely to suffer heart attacks, men with low cholesterol (below 160) were more likely to die from all causes than those with normal levels. In 2006, three separate papers published in the Journal of the American Medical Association on the results of the Dietary Modification Trial, an eight-year study of 50,000 women, found that “a low-fat diet does not significantly reduce the risk of breast cancer or colorectal cancer, nor does it reduce cardiovascular disease.” A 2010 article published in The American Journal of Clinical Nutrition, which described research into the dietary habits of 350,000 individuals, found no link between consumption of saturated fat and heart disease. Speculating on the results, the researchers noted that saturated fats raise levels of HDL, or so-called “good” cholesterol, which may offset any increases in LDL, or “bad” cholesterol.
In recent years, some researchers have attacked the notion that advising people to adopt a diet lower in meat and dairy products and higher in carbohydrates would be harmless at worst. In a 2008 article in The American Journal of Preventive Medicine, three researchers from the Albert Einstein School of Medicine—including former president of the International Hypertension Society, Dr. Michael Alderman—noted that Americans have significantly cut their fat intake and increased consumption of carbohydrates over the last three decades. The result has been a sharp increase in obesity which “possibly laid the groundwork for a future increase in [cardiovascular disease].” He and his colleagues argued that some recommendations in the guidelines were based on “weak evidentiary support” in the form of studies that showed only a correlation between diet and certain diseases or conditions, not an exact causal relationship. While defenders of the current recommendations argue that the government’s advice urges switching to particular types of carbohydrates, namely whole grains that are rich in fiber, a 2010 article in Nutrition magazine argued that the definition of what constitutes a “whole grain” has been broad and confusing to the public. “A fundamental flaw in the [Dietary Guidelines Advisory Committee] report’s support of whole grain and fiber intake is that these terms are defined inconsistently, and their definitions appear to be shaped to promote processed carbohydrate foods as healthy,” the article said. A more recent article in the cardiology journal Open Heart by medical researcher James DiNicolantonio observed that replacing saturated fats with carbohydrates created increased risk of diabetes and obesity, as well as a lowering of HDL or “good” cholesterol.
Even as the scientific rationales for eating less meat and fewer dairy products have fallen away, the dietary guidelines committee has found a new reason to steer people away from these foods—but one that has little bearing on individual health. The nutrition experts now invoke the concept of “environmental sustainability” to advise Americans to adopt a more plant-based diet, which the committee claims will “ensure a healthy food supply will be available for future generations.” The committee made its recommendations despite a directive from Congress last year to the Obama administration to stick to nutritional advice and ignore “agricultural production practices and environmental factors” in the new dietary guidelines. Congress issued that directive after hearing that the nutrition panel was seeking information on the environmental impact of farm animal foods, an area that green groups have been pushing the federal guidelines to consider for years. As in some of its past recommendations, the new directive fails to consider what may be the unintended consequences of population-wide changes to diet that have not been rigorously examined or tested. In urging people further away from meat in their diet, the committee recommends, for instance, choosing seafood from “non-threatened” stocks. One reason for that qualifier is that, thanks in part to dietary recommendations, Americans have already cut their per capita consumption of red meat by 34 percent since 1970 and shifted some of their diet toward fish, adding to what the dietary guidelines themselves recognize as overfishing and shortages of some varieties of seafood. Meanwhile, the actual impact on the environment will be minimal. The Environmental Protection Agency estimates that American agriculture accounts for just 8 percent of the country’s greenhouse gas emissions.
In his 1968 bestseller The Population Bomb, Paul Ehrlich famously declared that “the battle to feed all of humanity is over. In the 1970s the world will undergo famines . . . nothing can prevent a substantial increase in the world death rate.” At the time, the world’s population was 3.5 billion, less than half what it is today. Though no such cataclysm took place, environmental groups began striving to turn meat-eating into an ethical issue—claiming the very survival of humanity was at stake. Having failed to make a convincing case against animal products on health grounds, these groups have finally won a victory in Washington. What impact that has on the health of Americans remains to be seen.