Dietary Advances and Retreats

For the past 60 years the federal government has been advising consumers on how they can avoid heart attacks and strokes.  The federal government’s Dietary Guidelines Advisory Committee took advice from well-known food scientists even though the advising scientists often held conflicting conclusions.  The Advisory Committee’s advice to consumers changed slowly and has often been out of sync with the best food science conclusions.

The Advisory Committee and the Senate Select Committee on Nutrition and Human Needs (Select Committee) sometimes recommended and sometimes warned consumers against eating dietary animal fat, dietary trans fats, dietary sugars, and dietary cholesterol.  At first, cigarettes were ignored, but later the government advised that they were suspected of causing cancer.

As of 2015, the 2015-2020 Dietary Guidelines for Americans offers key recommendations that advise “a healthy eating pattern that accounts for all foods and beverages within an appropriate calorie level.”

That healthy eating pattern includes a variety of vegetables from all of the subgroups—dark green, red and orange, legumes (beans and peas), starchy, and other. The pattern includes fruits, grains, at least half of which are whole grains, fat-free or low-fat dairy, including milk, yogurt, cheese, and/or fortified soy beverages, and a variety of protein foods, including seafood, lean meats and poultry, eggs, nuts, seeds and soy products.

The healthy pattern limits saturated fats and trans fats, added sugars, and sodium, and it limits added sugars and saturated fats to less than 10% of daily calories.  The pattern should include less than 2,300 mg of sodium per day.  Early on, being overweight was not thought to be a health risk.  Now, being overweight and obese are considered to be factors leading to cardiovascular disease and stroke.  Vigorous exercise is included as part of the Guidelines.

The Cato Institute published an extremely helpful outline of federal dietary advice since the 1950s.  It chronicled the on-again, off-again recommendations from the Select Committee that are summarized below.

In 1977, dietary fat (consumed animal fat) was hypothesized as a cause of heart disease, and the Select Committee recommended eating carbohydrates instead.  However, in six randomized trials more than 2,400 subjects followed a regimen of reduced dietary fat and experienced a decline in circulating blood levels of cholesterol, but contrary to the Select Committee’s hypothesis, their mortality rates did not fall.

The Select Committee’s expectation that saturated fat was a likely cause of heart disease led to years in which many consumers migrated to trans fats and carbohydrates as substitutes.  Unfortunately, research later showed that trans fats lowered high-density lipoproteins (good cholesterol) and raised small low-density lipoproteins (bad cholesterol), which causes inflammation in arteries.  Vegetable fats (unsaturated) eventually became a Select Committee recommendation.

Carbohydrates had been a component advised in the Select Committee diet.  However, carbohydrates break down to sugars, and sugars increase bad cholesterol in the blood stream, which can lead to cardiovascular disease.

In 2015, 54% of physicians still believed eating cholesterol-rich food raises blood stream cholesterol and damages the heart, but the Select Committee classified high-cholesterol foods such as eggs, shrimp and lobster as nutrients that are safe to eat.  Dietary cholesterol is apparently not a cause of heart disease.

After recommendation mayhem over decades, dietary guidelines have settled down.  The current advice from the American Heart Association (AHA) is rather simple — dietary saturated fat increases cardiovascular disease.  Replacing fat with refined carbohydrates and sugars does not reduce the rate of heart disease.  Replacing saturated fat with unsaturated fat (not trans fat) reduces the rate of cardiovascular disease.  In short, the AHA recommends a “Mediterranean” diet which looks somewhat like the 2015-2020 Dietary Guidelines.

The Select Committee’s desultory dietary advice was less useful than Congress expected. The Dietary Guidelines are now founded on the best scientific advice.  Fewer of the early sources of error remain.  Lobbying by specific food producers, public policy capture by special interest groups, and errors in published scientific papers each had contributed to the Select Committee’s slow alignment with the best of food science.

The Select Committee was earnest in the advice it offered, and it generally avoided pontification, unlike today’s imperious food police.  That odious role is left to special interest groups, bossy acquaintances, and local politicians with little scientific training (often politically ambitious mayors).

Most consumers are now aware of which dietary choices are wise and which are not. We receive most of our advice from our doctors, trusted friends, and our family.  We are entitled to adjust our dietary choices to fit our needs from day to day, and we are prudent when it comes to nutritional choices made on behalf of our family and children.

Over the last two decades there has been an excess of unwelcomed, self-righteous food police reminding us to avoid being overweight, to avoid sugary sodas, and how many milligrams of salt we deserve.  The self-appointed food police go beyond offering advice when they enact statutes that increase food taxes and limit access to food that we might want.

Their meddling becomes destructive when it tries to veto components in school lunches we prepare for our children or when a bake sale is considered worthy of arrest.  Perhaps the most destructive intervention by food police is “fat shaming,” which is implied in many lectures against sugar intake.  Criticism of being overweight or obese actually worsens the problem.

In preparation for publishing the 2020-2025 Dietary Guidelines, we expect that the best of scientific food research will inform the Guidelines, and that the authors will be made available to clarify what they said.  Going forward, an update containing any new insights since the scientific foundations were published will be welcomed.

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