06.24.2015
by Parker Brown
Staff Writer, MedPage Today

Upcoming diet recommendations from a government panel should not place a limit on total dietary fat, two researchers argued in the Journal of the American Medical Association.

Earlier this year, the Dietary Guidelines Advisory Committee (DGAC) released a draft of new dietary guidelines that has since been both praised and criticized. The panel took a stand against added sugar, which many observers took as the right move. But some scientists have said that salt isn’t as detrimental to health as the draft revision claimed, and others contended that the recommendation to limit saturated fat was not in alignment with recent evidence.

Now, two researchers are calling attention to another aspect of the DGAC draft: that there is no advised limit on total dietary fat. The removal of that limit upended nearly 4 decades of dietary policy, wrote Dariush Mozaffarian, MD, DrPH, at Tufts University in Boston, and David Ludwig, MD, PhD, at the Boston Children’s Hospital, in a Viewpoint appearing Tuesday in JAMA.

“The limit on total fat [in current recommendations] presents an obstacle to sensible change, promoting harmful low-fat foods, undermining attempts to limit intakes of refined starch and added sugar, and discouraging the restaurant and food industry from providing products higher in healthful fats,” wrote the authors.

And in an email to MedPage Today, Mozaffarian added that recent evidence has shown that focusing only on total fat might be detrimental. “Many people don’t realize how far the science has advanced in recent years, with multiple major studies and pooled analyses demonstrating the lack of benefit, and the potential for harm, for focusing on total fat,” he wrote.

In 1980, the guidelines recommended that dietary fat be limited to less than 30% of one’s calories. In 2005, the number was changed to 20% to 35% of calories. Researchers reasoned then that limiting total fat would lower saturated fat and dietary cholesterol, which were thought to increase cardiovascular risk.

“But the campaign against saturated fat quickly generalized to include all dietary fat,” wrote the authors.

And a limit on total fat can also potentially decrease intake of unsaturated fats — found in nuts, vegetable oil, and fish — which have been shown to be healthy. In addition, consumption of unhealthy highly processed carbohydrates like added sugar, refined grains, and potato products is often inversely related to consumption of dietary fats, said the authors.

In recent years, evidence has been building that diets higher in healthful fats — even when they exceed the current limit of 35% — can reduce the risk of cardiovascular disease. At the same time, no evidence suggests that diets low in fat but high in carbohydrates prevent any major diseases.

In their draft guidelines, DGAC members wrote that 70% of the U.S. population consumes too many grains, and that consumption of low-fat or even non-fat products with high levels of refined grains and added sugars should be discouraged.

Mozaffarian and Ludwig said that the current restriction has implications for all aspects of diet. “From agriculture to food producers to school cafeterias to restaurants, the [current] Dietary Guidelines for Americans serve as a beacon for countless dietary choices in the public and private sector,” Mozaffarian said in a press release. “With obesity and chronic disease impacting public health so deeply, we can’t miss this critical opportunity to improve the food supply.”

The authors added that other policies should follow the evidence highlighted in the DGAC draft. The Nutrition Facts Panel, which is used by the FDA to provide information on nutrients to consumers, still uses a 30% limit on total dietary fat, they said, a number that has been “obsolete for nearly a decade.” The Institute of Medicine should also update their 15-year-old guidelines, Mozaffarian and Ludwig added.

DGAC members are independent scientists; they are chosen by the government to review the medical literature on nutrition. But they don’t issue the official dietary guidelines — that job falls to the federal Agriculture and Health and Human Services departments, which jointly revise the guidelines every 5 years and usually stick closely to the committee’s findings.

The departments are expected to finalize new guidelines by the end of this year.