Last October, embarrassing emails leaked from New York Citys Department of Health and Mental Hygiene disclosed that officials had stretched the limits of credible science in approving a 2009 anti-obesity ad, which depicted a stream of soda pop transforming into human fat as it left the bottle. “The idea of a sugary drink becoming fat is absurd,” a scientific adviser warned the department in one of the emails. Nevertheless, Gothams health commissioner, Thomas Farley, saw the ad as an effective way to scare people into losing weight, whatever its scientific inaccuracies, and overruled the experts.
Americas public-health officials have long been eager to issue nutrition advice ungrounded in science, and nowhere has this practice been more troubling than in the federal governments dietary guidelines, first issued by a congressional committee in 1977 and updated every five years since 1980 by the U.S. Department of Agriculture.
Controversial from the outset for sweeping aside conflicting research, the guidelines have come under increasing attack for being ineffective or even harmful, possibly contributing to a national obesity problem. Unabashed, public-health advocates have pushed ahead with contested new recommendations, leading some of our foremost medical experts to ask whether government should get out of the business of telling Americans what to eat — or, at the very least, adhere to higher standards of evidence.
Until the second half of the 20th century, public medicine, which concerns itself with community-wide health prescriptions, largely focused on the germs that cause infectious dis-eases. Advances in microbiology led to the development of vaccines and antibiotics that controlled — and, in some cases, eliminated — a host of killers, including smallpox, diphtheria and polio. These advances dramatically increased life expectancy in industrialized coun-tries. In the United States, average life expectancy improved from 49 years at the beginning of the 20th century to nearly 77 by the centurys end.
As the threat of communicable diseases receded, public medicine began to turn its attention to treating and preventing health problems that werent germ-caused, such as chronic heart disease and strokes, the death rates for which seemed to be soaring after World War II. Some observers cautioned that the apparent increase might be the result of diagnostic advances, which had improved doctors ability to detect heart ailments. This possibility, however, failed to deter the press and advocacy groups like the American Heart Association from declaring the arrival of a frightening epidemic.
One theory blamed the problem on the American diet, and in particular on cholesterol — both the kind you ingest when you eat animal products and the kind your body produces when you eat saturated fats. It wasnt an unreasonable idea; cholesterol is, after all, one component of the plaque that clogs arteries and causes heart attacks and strokes.
But isolating the true causes of coronary disease proved elusive. Multiple factors — not just diet but other personal habits, such as smoking, and genetics as well — were potential contributors. And measuring the influence of diet was especially difficult because of big variations among individuals in everything from blood composition to their response to different foods. Numerous studies on diet proved so inconclusive that in 1969, the National Institutes of Health found no hard evidence that what people ate had a significant impact on heart disease.
Nevertheless, in the 1970s, Democratic Sen. George McGoverns Select Committee on Nutrition and Human Needs decided to fight the apparent epidemic by making recommendations on nutrition. “Our diets have changed radically within the past 50 years; Mc-Govern declared, ”with great and very often harmful effects on our health.“
As science writer Gary Taubes notes in Good Calories, Bad Calories, the McGovern committee, in coming up with its diet plan, had to choose among very different nutritional regimes that scientists and doctors were studying as potentially beneficial to those at risk for heart disease. Settling on the unproven theory that cholesterol was behind heart disease, the committee issued its guidelines in 1977, urging Americans to reduce the fat they consumed from 40 percent to 30 percent of their daily calories, principally by eating less meat and fewer dairy products. The committee also advised raising carbohydrate intake to 60 percent of ones calories and slashing ones intake of cholesterol by a quarter.
Some of the countrys leading researchers spoke out against the guidelines and against population-wide dietary recommendations in general. Edward Ahrens, an expert in the chemistry of fatty substances at Rockefeller University, characterized the guidelines as ”simplistic and a promoter of false hopes“ and complained that they treated the population as ”a homogenous group of [laboratory] rats while ignoring the wide variation“ in individual diet and blood chemistry.
The Food and Nutrition Board of the National Academy of Sciences released its own dietary suggestions, which saw ”no reason for the average healthy American to restrict consumption of cholesterol, or reduce fat intake; and just encouraged people to keep their weight within a normal range.
The McGovern dietary recommendations werent just ahead of the science; they were racing ahead of it. Two of the most important government-sponsored studies on the role of fat and cholesterol in heart disease didnt appear until the early 1980s, long after the committee had promulgated its advice. The results hardly cleared things up.
The first study, known as the Multiple Risk Factor In-tervention Trial, followed 12,866 people between 35 and 57 at risk for heart disease. Some of these subjects were placed on a low-fat, low-cholesterol diet; others were merely told to keep seeing the family doctor. The study found no statistically significant difference in mortality rates between the two groups.
The results of the second study, the Lipid Research Clinics Coronary Primary Prevention Trial, appeared in 1984 and continue to spark debate. Using the drug cholestyramine to reduce high cholesterol rates in a group of male test subjects, the study reported a lower death rate for those on the drug than for subjects who took a placebo. Did this mean that cholesterol was to blame for heart disease, after all?
Some observers, including Ahrens, cautioned that the average cholesterol level of the American public was far lower than that of the test group taking cholestyramine, meaning that there was nothing in the study to suggest that a nationwide effort to change citizens diets would make much difference in public health. But the press seemed to prefer a narrative that made diet a major cause of heart attacks.
The scientific controversy grew more intense. In 1992, an authoritative review of 19 cholesterol studies worldwide found that, while men with cholesterol levels above 240 were disproportionately likely to suffer heart attacks, men with cholesterol levels below 160 were disproportionately likely to die from all causes, including lung cancer, respiratory disease and digestive disease — an outcome that suggested a relationship be-tween low cholesterol levels and disease, something scientists had never considered.
The study also showed no difference in mortality rates for men with cholesterol levels between 160 and 240, even though the guidelines advised keeping levels below 200. Perhaps most surprisingly, the study also found that cholesterol levels made no difference at all in death rates among women.
More recent research has further undermined the cholesterol-as-bad-guy hypothesis. Scientific American summed up the disturbing state of the evidence in April 2010. The magazine cited a meta-analysis — that is, a combination of data from several large studies — of the dietary habits of 350,000 people worldwide, published in The American Journal of Clinical Nutrition, which found no association between the consumption of saturated fats and heart disease.
Another recent study noted by Scientific American, by Harvard nutrition and epidemiology professor Meir Stampfer and associates and published in The New England Journal of Medicine, tracked 322 moderately obese people, each following one of three diets: a low-fat, calorie-restricted diet of the sort that the American Heart Association recommends; a so-called Mediterranean diet, rich in vegetables and low in red meat; and a low-carbohydrate diet without any calorie restrictions. Not only did the low-carb dieters lose the most weight, the study found; they also had the healthiest ratio of HDL (so-called good) cholesterol to LDL (bad) cholesterol.
The latest nutritional thinking has indeed zeroed in on carbohydrates as a likely cause of heart disease. Easily digestible carbs, in particular — starches like potatoes, white rice and bread from processed flour, as well as refined sugar — make it hard to burn fat and also increase inflammations that can cause heart attacks, several studies have concluded.
Looking at such evidence, several top medical scientists have concluded that the governments carb-heavy guidelines may actually have harmed public health. In 2008, three researchers from the Albert Einstein School of Medicine observed in The American Journal of Preven-tive Medicine that since 1977, Americans have largely followed the governments advice, doubtless as conveyed by the doctors they consulted.
Men, for instance, cut their fat intake from 37 percent of their daily calories to 32 percent and increased their carbohydrate intake from 42 percent to 49 percent. Yet over the same three decades, the fraction of American men who were overweight or obese increased from 53 percent of the population to about 69 percent.
The doctors wondered whether this correlation was an unintended consequence of telling the entire population to change its eating patterns. “In general,” the doctors wrote, “weak evidentiary support has been accepted as adequate justification for [the U.S. dietary] guidelines. This low standard of evidence is based on several misconceptions, most importantly the belief that such guidelines could not cause harm.” But, they concluded, “it now seems that the U.S. dietary guidelines recom-mending fat restriction might have worsened rather than helped the obesity epidemic and, by so doing, possibly laid the groundwork for a future increase in CVD,” cardiovascular disease.
Its true that the particular kind of carbohydrates that the government has always rec-ommended are carbs rich in fiber, which arent as quickly digested as those starches implicated by the latest research. But its difficult to tell an entire population to change its dietary habits without sowing confusion about such fine points. Further, as an October 2010 article in Nutrition points out, the governments definition of what constitutes a fiber-rich grain is so broad as to include many foods that might actually promote heart disease because they are too easily digestible.
“At a minimum,” says one of the authors of the Nutrition piece, SUNY Downstate Medical Center biologist Richard Feinman, “if you have an area of controversy or ambiguity in the science, you shouldnt be issuing guidelines to the entire population.”
The guidelines themselves quietly acknowledge that they may have worsened public health. The 2000 version eliminated the recommendation to reduce intake of overall fat in favor of carbs, noting “the possibility that overconsumption of carbohydrates may contribute to obesity?”
But that was as far as the government would go. It retained the advice to limit consumption of saturated fat and to keep intake of cholesterol to 300 milligrams per day, for example, even though dietary cholesterol —that is, the cholesterol we ingest by eating animal products — has been discounted by many researchers as a source of plaque buildup.
Supporters of the guidelines have increasingly resorted to ad hoc, even political, justifications for them. In a 2008 American Journal of Preventive Medicine article, for example, two influential nutritionists, Marion Nestle of New York University and Steven Woolf of the Virginia Commonwealth University Medical Center, admit that “whether the evidence is good enough to recommend pop-ulation-based dietary changes comes down to a matter of subjective judgment.”
But developing dietary recommendations is still a crucial government responsi-bility, they argue, in part because the government is already heavily involved in food policies. “Dietary guidelines have implications at every level of government, from federal agencies such as the U.S. Department of Agriculture to the local school board,” they write, and without clear guidelines, big food industries and special interests could lobby political leaders and shape policy in unhealthy ways. But this argument makes sense only if you assume that the governments guidelines will be any healthier.
Nestle and Woolf also argue that governments success in persuading people to stop smoking justifies its efforts to change American eating habits. “If it was paternalistic for the government to advise people how to eat,” they ask rhetorically, “was it equally paternalistic ... to alert the public about the hazards of tobacco use and to recommend in 1964 that smokers give up cigarette smoking?” But the major scientific dissenters from government dietary policy dont accuse it of paternalism, though thats a legitimate argument; they find the governments evidence inadequate and its recom-mendations potentially harmful.
The governments response to the growing controversy has been to keep issuing the guide-lines — and call for more research. Asked last year whether the 2010 update would reflect the latest studies challenging previous recommendations, a USDA spokesperson merely suggested that the controversial areas be “put on the list of things to do with regard to more research.”
In other words, more research is needed to overturn or withdraw the current recom-mendations, even though they were based on inconclusive evidence from the start.
Original Source: http://www.dallasnews.com/opinion/sunday-commentary/20110513-steven-malanga-washington_s-diet-plan-can-make-you-fat-and-sick.ece