The field of medicine moves forward through evidence-based practices, using the best scientific data to develop recommendations for policy and treatment. In the related field of diet and nutrition, however, old beliefs die hard. Experts in the field often cling to outdated recommendations, even when the evidence does not support their long-held ideas.
For almost half a century, Americans have been told to minimize their consumption of butter, meat and salt. This dietary recommendation was supposed to protect people from heart attacks, strokes, hypertension, diabetes and obesity. In fact, these dietary guidelines were never based on solid scientific research, and they did nothing to reduce those diseases. Today, diabetes and obesity are more prevalent then when the guidelines were issued..
A meta-analysis published in the Annals of Internal Medicine looked at 72 studies with more than 600,000 participants showed there was no correlation between how much saturated fat people consumed and the risk of a fatal or nonfatal heart attack.
A study published in the Journal of Nutrition followed more than 2,000 heart disease patients over a period of five years. The study concluded:
There was no association between dietary intake of SFAs [saturated fatty acids] and incident coronary events or mortality in patients with established CAD [coronary artery disease].
In 2015, the United States Department of Agriculture issued its new dietary guidelines. In several areas, the guidelines are evidence-based, and reflect current science. But in the area of saturated fat, the guidelines remain unchanged. They recommend:
Sources of saturated fat should be replaced with unsaturated fat, particularly polyunsaturated fatty acids…
Red meat, butter, cheese, whole milk, corn oil and safflower oil are to be avoided. Clearly, this recommendation is not evidence-based. The time may come when new studies show the need for people to avoid saturated fats, but that science is not yet available.
Among the changes in the guidelines that do reflect the scientific evidence is the elimination of the prohibition on cholesterol. Early guidelines had told Americans to cut back on eggs, shrimp, lobster and chicken livers because they were high in cholesterol. Experts currently admit there is no science to support the idea these foods are dangerous.
The new guidelines remove the previous recommendation to avoid salt. Although the American Heart Association still insists that “all Americans reduce the amount of sodium in their diet to less than 1,500 mg a day,” the USDA insists that 2,300 milligrams is a more reasonable target. This revised recommendation reflects current science.
The Dietary Guidelines Advisory Committee has made one other recommendation that reflects the new scientific evidence. It encourages Americans to cut back on sugar. Research has demonstrated that sugar has contributed to the twin scourges of America today, diabetes and obesity.