The Dietary Guidelines for Americans (DGAs) are intended to make Americans healthier through simple nutrition advice, but thirty-five years after the first guidelines were released, scientists are questioning the effectiveness and the science behind the guidelines. One nutrition expert, Dr. Dariush Mozaffarian, tells The New York Times that the federal government’s dietary recommendations for Americans are “basically best guesses.”

Dr. Mozaffarian, a Tufts University’s Friedman School of Nutrition Science and Policy Dean went on to say “I think now we know about 50 percent of what we need to know.”

With such inadequate and uncertain nutrition science behind the DGAs, it’s no wonder dietary advice is always changing. In the 1970s, we were told to stay away from fat and dietary cholesterol and that eggs would clog your arteries. Now, we are advised that eggs have nutritional value and butter is okay to consume after years of being told to avoid it.

“We are not going to reverse any of the chronic diseases in this country by changing the composition of the diet… People are always thinking it’s what they ate. They are not looking at how much they ate, or that they smoke or that they are sedentary,” said Dr. Barbara V. Howard, who was a principal investigator in the 2006 federal study of low-fat diets.

Nutrition science is complex. There is no one “perfect” diet that will fit everyone. The DGAs will impact Americans nationwide, so it is essential that they be based on sound science and provide recommendations that can be achievable in the real world for the majority of Americans.