Problems with the 2015 Dietary Guidelines for Americans: A Response to a Rebuttal

We appreciate the rebuttal to our brief review article in the March/April 2016 issue of Missouri Medicine by Dr. Daniels who points out some of his reservations regarding four of our alternative recommendations to the 2015 Dietary Guidelines for Americans. We respectfully counter his rebuttal with the following:

1. Grains

Dr. Daniels argues that the life expectancy of Homo sapiens 10,000 years ago was fewer than twenty years and that this may have something to do with the lack of grains in the diet. It is common knowledge that life expectancy, even as recently as the early 1900s was short due to infections and early-life (childhood) mortality and undoubtedly had nothing to do with a lack of grains in the diet. More revealing is when one has a closer look at numerous hunter-gatherer societies (who do not ingest grains in any significant amount). The age where most of the deaths are occurring in such hunter-gatherer societies is not very different than that of the United States. Indeed, despite a lack of modern medical treatments, most deaths are occurring in many hunter gatherer societies at a comparable age to that of the United States (85 y.o.), such as the Tsimane (78 y.o.), Hadza (76 y.o.), the Yanomamo (75 y.o.), and Aborigines (74 y.o.).¹ Importantly, these hunter-gatherer societies (again who lack any significant intake of grains if any at all) have a much lower rate of “diseases of westernization” including diabetes, hypertension, heart disease, dementia, and cancer.¹ Specifically regarding the last hunter-gatherer society, (Aborigines), O’Dea famously took urbanized diabetic Aborigines and placed them back on their traditional hunter-gatherer diet (lacking grains), which resulted in improvements in glucose tolerance as well as a fall in plasma triglycerides.²

Regarding the “huge body of evidence” suggesting that whole grains are metabolically healthy; of the four references provided by Dr. Daniels, only one includes randomized controlled trials. Regarding this line of evidence, it specifically found that compared to non-whole grain control diets, whole-grain diets lowered LDL-cholesterol and total cholesterol but had no effect on HDL or triglycerides. Our argument is not whether whole grains are healthier than refined grains (as suggested by Dr. Daniels) but rather if consumption of grains should be encouraged at all (whole or refined), as grains are a relatively new dietary insertion associated with a Western dietary pattern a pattern which associates with worse health outcomes. Thus, the evidence provided by Dr. Daniels does not counter our overall suggestion for replacing grains (refined or not) with whole (largely unprocessed) foods as are found in nature, such as leafy greens and other vegetables, fruits, nuts and seeds, fish, meat, and eggs.

2. Saturated Fat

Regarding the “evidence” cited by Dr. Daniels including health authorities such as the British Heart Foundation, World Health Organization, American Heart Association, etc. This would certainly not be considered grade A (level 1) evidence as compared to a meta-analysis of randomized studies. Moreover, Dr. Daniels seems to have taken our recommendation (i.e., increasing the intake of whole foods) and inappropriately extrapolated this “to in effect increase dietary saturated fat.” However, we are not promoting the increased intake of saturated fat, rather we are encouraging people to eat healthy whole foods, which may contain all three broad groups of fats (saturated, monounsaturated, and polyunsaturated). For example, beef contains nearly as much monounsaturated fat (oleic acid) as it does saturated fat and more unsaturated than saturated fat overall. Additionally, to support a reduction in the intake of saturated fat, based on a surrogate marker (LDL) is ironic, as this ignores the fact that the particular saturated fats that raise LDL also raise HDL^{3, 4} How is one to interpret an increase in the so-called “harmful” cholesterol level (LDL) when there is a concomitant increase in the “healthy” cholesterol (HDL) level? Additionally, when saturated fat replaces refined carbohydrates there appears to be a reduction in triglyceride levels and improvements in blood glucose. Thus, when one considers the overall lipid/ metabolic profile it appears that increasing saturated fat may actually improve health outcomes depending on what dietary substance is replaced.^{5, 6}

3. Salt

In regards to the author’s statement that, “There are many studies in the medical literature, prospective controlled studies, which show that salt reduction does indeed decrease cardiovascular mortality.” Ironically, the very meta-analysis of prospective studies cited by Dr. Daniels actually supports the notion that lowering sodium intake, as compared to normal sodium intake, increases all-cause mortality and cardiovascular disease events.⁷ The argument that, “High salt intake has clearly been shown to increase blood pressure, and increased blood pressure has been clearly shown to increase cardiovascular mortality,” ignores the fact that a higher salt intake also lowers heart rate, and that the product of the two (heart rate plus blood pressure) is generally improved with a higher salt intake compared to salt restriction.⁸ Since the overall damage to the heart (and the arterial tree) is a result of both blood pressure and heart rate, this does not seem to support salt restriction. Additionally, when one considers the fact that salt restriction increases triglycerides, LDL cholesterol, total cholesterol, aldosterone, renin, noradrenaline, and insulin levels, the small (and likely inconsequential) reduction in blood pressure is far outweighed by the harm.^9–11 Importantly, the “reduction in blood pressure” with salt restriction may actually reflect hypovolemia (a decrease in plasma/blood volume) and may in fact be a harmful effect in many.¹² Lastly, to generalize the effects of salt restriction as having an overall reduction in blood pressure ignores the fact that a similar percentage of people who get a reduction in blood pressure may actually have an increase in blood pressure of a similar magnitude with salt restriction.¹³ As with almost everything regarding health, moderation is the safest course. Excessive sodium restriction causes profound counter-regulatory hormonal disturbances such as activation of the sympathetic and renin angiotensin aldosterone systems. In summary, restricting the intake of sodium to less than 1,500 mg daily, and probably even less than 2,500 mg daily, will likely lead to worse health outcomes rather than improved ones compared to a moderate sodium diet of around 2,500 mg to 5,000 mg daily.

4. Polyunsaturated Fats

In regards to Dr. Daniels statement, “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.” It is rather bewildering that if this is indeed the case why Dr. Daniels does not cite a single reference supporting this statement. In fact, two meta-analyses of randomized controlled trials have found that when omega-6 PUFA replaces saturated fat plus trans-fat there is an increase in mortality and cardiovascular mortality (despite a reduction in cholesterol levels).^{14, 15} In regards to Dr. Daniels assertion that “olive oil is not found in meat,” in fact, oleic acid makes up a similar percentage of fatty acids as does saturated fat in meat, which again supports our overall message, that people eat foods not saturated fat.

Summary

In summary, the overall evidence in the literature does not support the following four recommendations supported by the 2015 Dietary Guidelines, including 1.) The consumption of grains, 2.) Restriction of saturated fat, 3.) Restriction of salt intake, and 4.) An increase in the intake of omega-6 PUFA (mainly via vegetable oils).

Our alternative recommendations to increase the intake of whole, largely unprocessed foods - such as vegetables, fruits, nuts and seeds, fish, meat, and eggs - as the most natural food available is in our opinion a much better overall recommendation for improving health and indeed is a much simpler message than the above four recommendations.