U.S. dietary guides criticized for potential harm
By Amy Norton
NEW YORK (Reuters Health) - Some researchers are questioning whether national guidelines advising Americans to eat a low-fat diet have had the unintended consequence of feeding the current obesity epidemic.
The federal government has issued official dietary guidelines every five years since the late 1970s. In 1990, a recommendation was added that people should get less than 30 percent of their daily calories from fat.
In the American Journal of Preventive Medicine, researchers at Albert Einstein College of Medicine in New York argue that the guidelines -- particularly those on fat -- may have done more harm than good.
Since the guides were issued, the collective U.S. waistline has continued to expand and many experts have expressed concern that Americans simply replaced their fat intake with sugar -- often in form of heavily marketed low-fat snack foods.
The dietary guidelines' fat-cutting advice had science behind it; saturated fat, like that found in meat and dairy, is known to raise cholesterol, and studies have shown that diets low in saturated fat can lower the risk of heart attack. Population studies from different countries have also found a correlation between high amounts of dietary fat and excess pounds.
However, there was insufficient evidence that the national recommendations to slash fat would be beneficial, according to the Einstein researchers. In the absence of that, they argue, the government should not give specific recommendations on what Americans should eat.
"We're trying to turn people's thinking around a little bit," lead author Dr. Paul R. Marantz told Reuters Health.
Part of the thinking behind the national dietary guidelines, according to Marantz, is that even if there is uncertainty about whether they will be beneficial, they are unlikely to do harm.
But the timing of the guidelines' low-fat emphasis and the nation's spike in obesity suggest that the guidelines might have contributed to the problem, the researchers say. Studies have found that while Americans have trimmed some fat from their diets in the past couple decades, their total calorie intake has, on average, gone up.
However, it's wrong to blame dietary guidelines for this, according to a commentary published with the article.
"A disturbing trend occurred during the years when the public was advised to limit dietary fat; food companies substituted sugars for fat in many processed foods, people increased their caloric intake, and the prevalence of obesity rose," write Dr. Steven H. Woolf, of Virginia Commonwealth University in Richmond, and Dr. Marion Nestle of New York University.
This, they add, only underscores the need for public health experts to "retool" their message, and advise people to watch calories, not just fat, and to get enough exercise.
Marantz contends that the government should have a higher standard of evidence before issuing specific guidelines on eating -- similar to what's expected of drug companies bringing a new product to the market.
He and his colleagues suggest that health officials might do better by giving Americans not guidelines, but nutrition information -- which includes acknowledging when the research evidence is spotty.
"Give us all the information you have," Marantz said, "but not a sound bite in the form of a guideline."
SOURCE: American Journal of Preventive Medicine, online January 22, 2008.