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July 06, 2015
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The 2015 US Dietary Guidelines: 

Lifting the Ban on Total Dietary Fat

Dariush Mozaffarian, MD, DrPH1; David S. Ludwig, MD, PhD2
JAMA. 2015;313(24):2421-2422. doi:10.1001/jama.2015.5941. 
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Every 5 years, the US Department of Agriculture and Department of Health and Human Services jointly release the Dietary Guidelines for Americans. These guidelines have far-reaching influences across the food supply, including for schools, government cafeterias, the military, food assistance programs, agricultural production, restaurant recipes, and industry food formulations. An accurate revision of the Dietary Guidelines is crucial to the health of millions of people. Integral to this process is the Dietary Guidelines Advisory Committee (DGAC) report, just released,1 prepared by appointed scientists who systematically review the literature and provide evidence-based recommendations to the secretaries of Agriculture and Health and Human Services. In the coming months, the secretaries will review the DGAC recommendations; consider comments from the public, academics, advocacy groups, and industry; and finalize the Dietary Guidelines.

In the new DGAC report, one widely noticed revision was the elimination of dietary cholesterol as a “nutrient of concern.” This surprised the public, but is concordant with more recent scientific evidence reporting no appreciable relationship between dietary cholesterol and serum cholesterol1 or clinical cardiovascular events in general populations.2

A less noticed, but more important, change was the absence of an upper limit on total fat consumption. The DGAC report neither listed total fat as a nutrient of concern nor proposed restricting its consumption. Rather, it concluded, “Reducing total fat (replacing total fat with overall carbohydrates) does not lower CVD [cardiovascular disease] risk.… Dietary advice should put the emphasis on optimizing types of dietary fat and not reducing total fat.” Limiting total fat was also not recommended for obesity prevention; instead, the focus was placed on healthful food-based diet patterns that include more vegetables, fruits, whole grains, seafood, legumes, and dairy products and include less meats, sugar-sweetened foods and drinks, and refined grains.

With these quiet statements, the DGAC report reversed nearly 4 decades of nutrition policy that placed priority on reducing total fat consumption throughout the population. In 1980, the Dietary Guidelinesrecommended limiting dietary fat to less than 30% of calories. This recommendation was revised in 2005, to include a range from 20% to 35% of calories. The primary rationale for limiting total fat was to lower saturated fat and dietary cholesterol, which were thought to increase cardiovascular risk by raising low-density lipoprotein cholesterol blood concentrations. But the campaign against saturated fat quickly generalized to include all dietary fat. Because fat contains about twice the calories per gram as carbohydrate or protein, it was also reasoned that low-fat diets would help prevent obesity, a growing public health concern.

The complex lipid and lipoprotein effects of saturated fat are now recognized, including evidence for beneficial effects on high-density lipoprotein cholesterol and triglycerides and minimal effects on apolipoprotein B when compared with carbohydrate.3 These complexities explain why substitution of saturated fat with carbohydrate does not lower cardiovascular risk.1,2 Moreover, a global limit on total fat inevitably lowers intake of unsaturated fats, among which nuts, vegetable oils, and fish are particularly healthful.1,2 Most importantly, the policy focus on fat reduction did not account for the harms of highly processed carbohydrate (eg, refined grains, potato products, and added sugar)—consumption of which is inversely related to that of dietary fat.

As with other scientific fields from physics to clinical medicine, nutritional science has advanced substantially in recent decades. Randomized trials confirm that diets higher in healthful fats, replacing carbohydrate or protein and exceeding the current 35% fat limit, reduce the risk of cardiovascular disease.4,5 The 2015 DGAC report tacitly acknowledges the lack of convincing evidence to recommend low-fat–high-carbohydrate diets for the general public in the prevention or treatment of any major health outcome, including heart disease, stroke, cancer, diabetes, or obesity.1,2 This major advance allows nutrition policy to be refocused toward the major dietary drivers of chronic diseases.

For decades, carbohydrates were considered a foundation of a healthful diet, as evidenced by placement of grain products (including many highly processed items) at the base of the Food Guide Pyramid of 1992. However, by 2005, the Dietary Guidelines called for restriction of refined grains and added sugars due to growing evidence that refined carbohydrates increase metabolic dysfunction, obesity, and cardiovascular disease. Presently, US consumption of sugar-sweetened beverages is declining, likely related to both scientific research and associated publicity confirming their adverse health effects. Yet added sugar in other foods and, perhaps more importantly, refined grain products—including white bread, white rice, chips, crackers, cereals, and bakery desserts—continue to represent major sources of calories in the US food supply. 

The DGAC report highlights that more than 70% of the US population consumes too many refined grain products. Many of these foods enjoy a lingering health halo or at least a benign reputation, based on years of government guidelines and industry promotion. Recognizing this widespread misunderstanding, the 2015 DGAC report specifies that, “consumption of ‘low-fat’ or ‘nonfat’ products with high amounts of refined grains and added sugars should be discouraged.” The elimination of the upper limit on total fat would make it easier for industry, restaurants, and the public to increase healthful fats and proteins while reducing refined grains and added sugar.

In finalizing the 2015  0 Comment(s) Permalink

By Memorial Cardiology Associates
February 24, 2015
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