Problems with the 2015 Dietary Guidelines for Americans: A Rebuttal

The article by DiNicolantonio, Harcombe & O’Keefe in the March/April 2016 Missouri Medicine makes four recommendations that conflict with the United States Department of Agriculture’s eighth edition of Dietary Guidelines For Americans 2015–2020.

The first recommendation regards consumption of grains, citing evidence that grain consumption increases small dense LDL particles and decreases HDL particles. The authors recommend that grains should be avoided and that “instead more natural, nutrient dense foods, such as meat, fish, eggs, vegetables, fruits, nuts and seeds” be consumed. The author’s second recommendation is to increase the amount of saturated fat intake found in meats, fish, eggs, dairy and other products, citing several populations that consume relatively high percentages of saturated fats and yet have a very low prevalence of cardiovascular disease. The third recommendation is not really a recommendation, but rather a refutation of the Dietary Guidelines to restrict salt intake to 2,300 mg daily; the authors cite evidence that reducing salt intake may increase risk of cardiovascular mortality secondary to stimulation of the renin-angiotensin pathway, and although the authors do not give specific alternative recommendations regarding salt intake, the implication is that salt intake should not be restricted. The fourth recommendation regards intake of unsaturated versus saturated fats, citing studies that indicate a Mediterranean diet is superior to a low-fat American Heart Association diet in terms of cardiovascular outcome and that replacing saturated fats with unsaturated fats increases the risk of cardiovascular death, insulin resistance, diabetes, obesity, and cancer. The authors thus recommend eating the saturated fats found in meats, fish, eggs and dairy products.

The Dietary Guidelines For Americans 2015–2020 is a 215-page document that is based upon the recommendations of a fifteen member Advisory Committee made up of distinguished scientists with expertise in nutrition. The recommendations are the result of original systematic reviews of the scientific literature by members of the Committee, a review of existing systematic reviews, meta-analyses, and reports by federal agencies or scientific organizations. The Committee cited evidence for their recommendations and classified the evidence as strong, moderate, or limited.¹

The purpose of this Point/Counterpoint is to emphasize the reservations I have regarding the authors’ recommendations. My intent is not to give a systematic review of the literature. I would refer the reader to a number of websites with extensive lists of references, including the National Institutes of Health, the Centers for Disease Control, the American Heart Association, and the American Diabetes Association.

1. Grains

The authors argue that grains are a relatively recent addition to the human diet (10,000 years ago) and that “common sense would advise caution being applied to recommendations to consume more of relatively recent adaptations to the food chain.” The authors also argue that grains are “nutritionally poor.” It should be noted that the life expectancy of homo sapiens 10,000 years ago was less than twenty years.

More importantly the authors ignore the primary recommendation of the Committee regarding grains. Most grain consumption in the United States is refined, and the primary thrust of the Committee is to substantially increase whole grain consumption to 50% of total grain consumption.¹

There is a huge body of evidence that demonstrates a decrease in cardiovascular disease, obesity, insulin resistance, Type 2 diabetes mellitus, hypertension, and a variety of cancers including colorectal cancer and pancreatic cancer associated with a relatively high consumption of whole grains. Diets high in whole grains result in decrease in total and LDL cholesterol, an increase in HDL cholesterol, and decreases in various markers for cardiovascular risk including C-reactive protein and homocysteine.^2,3,4,5

The author’s recommendation to avoid grains is not, in my opinion, thoughtful. The Committee’s recommendation to increase whole grain consumption is strongly supported by the evidence.

2. Saturated Fats

There are indeed studies, cited by the authors, that demonstrate no difference in cardiovascular risk in individuals who consume primarily saturated fats versus individuals who consume polyunsaturated fats. However, there are a plethora of studies that do demonstrate an increase in LDL cholesterol and cardiovascular mortality in individuals who consume diets high in saturated fats. The evidence is controversial. Most authoritative bodies, including the American Heart Association, the National Institutes of Health, the World Health Organization, the British Heart Foundation, and the American Dietetic Association, as well as many others, have position statements which cite an increase in cardiovascular mortality as a result of increased saturated dietary fat. The authors’ recommendation to in effect increase dietary saturated fat is, in my opinion, ill advised.^6,7,8

3. Salt

The authors cite a few studies, epidemiologic and meta-analyses, which indicate that salt restriction does not decrease cardiovascular mortality and might, in fact, increase cardiovascular mortality. There are many studies in the medical literature, prospective controlled studies, which show that salt reduction does indeed decrease cardiovascular mortality. High salt intake has clearly been shown to increase blood pressure, and increased blood pressure has been clearly shown to increase cardiovascular mortality. The authors imply that sodium restriction is unwarranted and may be harmful. I believe that implication is ill advised and at the least, caution for salt intake should be given to those individuals with hypertension or prehypertension and to individuals with known cardiovascular disease or who are at high risk for cardiovascular disease. ^9,10,11,12

4. Polyunsaturated Fats

There is a plethora of evidence that polyunsaturated fats decrease LDL cholesterol and decrease cardiovascular mortality compared to individuals who eat diets high in saturated fats. The authors cite a study comparing a Mediterranean diet supplemented with olive oil compared to a low fat diet, which shows that the Mediterranean diet decreases risk of cardiovascular outcomes. Olive oil is a monounsaturated oil which has been shown to decrease LDL cholesterol and cardiovascular risk, just as other polyunsaturated fats have been shown to decrease LDL cholesterol and cardiovascular risk. The authors summarize by stating that the Committee’s recommendation to consume polyunsaturated fats should be replaced with a recommendation to increase consumption of olive oil. This summary is followed by their official recommendation to increase “natural saturated and unsaturated fats found in meat, fish, eggs and dairy products.” Olive oil is not found in the meat, fish, eggs and dairy products that the authors recommend, and therefore the authors’ “alternative recommendation” does not seem to comport with their summary. The overwhelming evidence supports the idea that polyunsaturated and monounsaturated oils are healthier than saturated fats.^{8,13, 14,15}

Summary

In summary, the authors discuss the Dietary Guidelines’ recommendations for grains, salt, saturated fats, and unsaturated fats. The “alternative recommendation” at the end of each of these discussions is the same: eat meat, fish, eggs, dairy products and various seeds. I believe that Missouri physicians should be very cautious about accepting these recommendations. I would encourage each physician to read the Dietary Guidelines for Americans, eighth edition, and make his or her own determination regarding dietary recommendations, which may vary depending upon an individual’s underlying health problems and genetic predispositions.