With the release of the eighth edition of the U.S. government’s Dietary Guidelines expected by year’s end, it seems reasonable to consider—with the “obesity plague” upon us and Americans arguably less healthy than ever before—whether the guidelines are to be trusted and even whether they have done more harm than good.
Many Americans have lost trust in the science behind the guidelines since they seem to change dramatically every five years. In February, for example, the Dietary Guidelines Advisory Committee declared that certain fats and eggs are no longer the enemy and that cholesterol is “not considered a nutrient of concern for overconsumption.” This, after decades of advising Americans to “watch their cholesterol.”
Such controversy is nothing new. U.S. Dietary Guidelines were first released by the Agriculture Department and the Department of Health and Human Services in 1980. One nutrition expert at the time, Edward “Pete” Ahrens, a groundbreaking researcher on fat and cholesterol metabolism, called the guidelines “a nutritional experiment with the American public as subjects . . . treating them like a homogeneous group of Sprague-Dawley rats.”
The original goals were to: 1) increase Americans’ carbohydrate consumption to 55%-60% of caloric intake; 2) reduce fat consumption to less than 30% from 40% of caloric intake; 3) reduce saturated fat to 10% of calories and increase poly- and monounsaturated fats each to 10% of calories; 4) reduce cholesterol intake to less than 300 milligrams a day; 5) reduce sugar intake by 40%; and 6) reduce salt consumption by 50%-80%.
These six goals, viewed in the context of what we know today, could hardly be more misdirected. That assessment starts with the guideline’s emphasis on increasing carbohydrates and reducing fat consumption, a strategy that research has documented is more likely to add excess weight than to improve health. Most recently, a study published in April in the American Journal of Clinical Nutrition found that “lowering the fat content of dairy or other foods may simply lead to increased carbohydrates consumption and explain . . . associations with weight gain.”
Promoting polyunsaturated fats as a safer alternative to saturated fats exposed the population to trans-fats, which are more harmful to heart health than the saturated fats they replaced. Focusing on cholesterol, experts now acknowledge, has limited health benefits—thus the advisory committee’s ending its long-standing recommendation of “no more than 300 mg/day.”
With nearly every edition of the Dietary Guidelines, the sodium recommendation has become more restrictive. The 1980 recommendation was “avoid too much,” which had evolved by 2010 into a population-wide limit of less than 2,300 mg/day and less than 1,500 mg/day for anyone over the age of 50 or at risk of heart disease. Decades of government surveys have found that the average sodium intake in the U.S. and world-wide is about 3,600 mg/day.
As for the increasingly restrictive government guidelines, a 2013 Institute of Medicine study concluded that the evidence supporting either benefit or harm of the sodium guidelines was “inconsistent and insufficient.” In other words, the study found no scientific justification for population-wide sodium reduction.
There is no debate that, since 1980, sugar intake in the U.S. has increased. What is rarely discussed is the likelihood that the original Dietary Guidelines were, in part, if not largely, responsible for that increase. Two unintended consequences of the emphasis on restricting dietary fat were an increased use of sugar in many food items, and the precipitous decline in milk intake and parallel increase in sugar-containing beverages such as soda pop and juice.
On Oct. 7, Health and Human Services Secretary Sylvia Mathews Burwell and Agriculture Secretary Tom Vilsack defended the guidelines before the House Agriculture Committee. As Chairman Michael Conaway (R., Texas) said in the hearing: “It is essential that the guidance that comes out of this process can be trusted by the American people.”
When asked in the hearing if the Dietary Guidelines had failed, Ms. Burwell suggested that Americans’ waistlines might well have been greater without them—an opinion not a fact. Mr. Vilsack’s reply to the same question was closer to the truth: “This is really about well-informed opinion,” he said. “I wish there were scientific facts. But the reality is stuff changes, right? Stuff changes.”
The view that governmental nutrition guidance is largely opinion-based was on display again in late October. The World Health Organization warned against eating processed and red meat, a finding based principally on observational studies as opposed to properly controlled clinical trials. Given that one third of the WHO committee did not agree with the report’s findings, it’s unclear if we really need to hold the bacon when we order eggs for breakfast.
A reasonable argument can be made that the only perspective of the original guidelines that proved correct was that they represented, as Ahrens stated, “a nutritional experiment” on the American public. By any reasonable standard of science, that experiment has failed.
Dr. McCarron is a research associate at the University of California-Davis department of nutrition and chairman-elect of the American Society for Nutrition’s Medical/Nutrition Council. He has consulted with food companies and, before 2010, with the Salt Institute, an industry group.