Wednesday, February 2, 2011

The Nutrition Debate #8: Epidemiologically Speaking: Patterns of Health and Illness

The dreaded Diseases of Civilization were first referenced in Installment #1 in this series. (See previously published installments archived at We began on that track about 10,000 years ago with the advent of agriculture, marking the transition from the Paleolithic era to the Neolithic. The nomadic hunter-gatherer discovered he could lead a more stationary existence on a diet largely comprised of cereal grains. This was a major shift in the human dietary. In the latter half of the last century this shift greatly accelerated. Today, many believe that this shift alone accounts for the emergent patterns of illnesses and medical disorders with which we are now beset.

In modern times, epidemiologists, who by definition look for patterns of health and illness in populations, have examined this change and associated factors in myriad retrospective studies. They have observed the health and illnesses of populations exposed to the “Western diet” and compared them to peoples who have lived in relative isolation without exposure to the dietary of the industrialized world.

Epidemiology, however, can only go so far. These studies typically show correlations in similar populations and differences in dissimilar populations. As we’ve noted earlier, however, correlation does not imply causation. “Epidemiological studies can only go to prove that an agent could have caused, but not that it did cause, an effect in any particular case” (emphasis added by me), according to the Wikipedia entry.

Nevertheless, in the early 1950’s noted physiologist Ancel Keys proffered his Lipid Hypothesis, based on selected data from a 22 country epidemiological study. In his original Six Country Analysis (1953), and later the Seven Countries Study, launched in 1956 and first published in 1970, Keys’s hypothesis implicated dietary fat, particularly saturated fat and cholesterol, in heart disease. Acceptance of his hypothesis grew quickly and allowed others, like the American Heart Association, to make educated, informed assertions. This in turn led to the AHA’s now well-known “risk factors,” the McGovern Report’s “Dietary Goals” and the now infamous (to me) “Dietary Guidelines for Americans” (see Installments #2 & #3). The latest of these guidelines were due to be finalized by HHS/USDA in December 2010 as I wrote this.

All of these “prescriptions” dispensed to the consumer “with an interest in eating” were still, however, nothing more than simple hypotheses and assertions. Hypotheses must be tested and retested by randomized controlled trials to produce and independently reproduce similar outcomes, and if they don’t, they must be rejected as false. There have been many large, lengthy and costly trials such as the Framingham Heart Study. These studies have continuously been revised, updated and reinterpreted and their outcomes disputed. Along the way, many medical researchers have come increasingly to view with skepticism the Lipid Hypothesis and its resultant restrictions on consuming fats, particularly saturated fat and dietary cholesterol. Many in the medical and nutrition professions now view those recommendations as deeply flawed and based on inadequate scientific proof.

Conversely, other aspects of the so-called Western diet, and in particular the specific dietary recommendations I have previously referred to as the Standard American Diet (SAD), which is 60% carbohydrate, have increasingly come to infer a causal relationship with various diseases and metabolic disorders. Chief among these is the Metabolic Syndrome.

The Metabolic Syndrome is relatively new on the scene and was first recognized in 1988 when it was mysteriously named Syndrome X. The Metabolic Syndrome, again according to Wikipedia, “is a combination of medical disorders that increase the risk of developing cardiovascular disease and diabetes. It affects one in five people, and prevalence increases with age. Some studies estimate the prevalence in the USA to be up to 25% of the population.” A recent story from Reuters, posted on 11/23/10, is headlined, “Half of Americans Facing Diabetes by 2020.” The lead-in then clarifies the headline as follows: “More than half of Americans will have diabetes or be prediabetic by 2020…” That is a daunting (and expensive) prospect.

In the next installment we’ll learn the clinical definition of Metabolic Syndrome and how is it diagnosed.

© Dan Brown 1/23/11

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