Retrospective #225: Diet and Type 2 Diabetes Risk

I keep hoping that someday I will read in the scientific or mainstream media that eating a low-carb diet will reduce the risk for Type 2 diabetes. I mean, it’s so obviously true that I am at a loss to explain why I don’t read it all the time. Then, a recent Diabetes in Control headline gave me renewed hope, until I saw the source and read the story.

The headline, ADA: Improving Quality of Diet Reduces Risk for Type 2 Diabetes, had me hopeful. The sub-title, “Consuming healthier foods improves risk independently of other lifestyle changes such as weight loss or physical activity,” gave me further encouragement. Then, my hopes crashed.

The story began, “Researchers at the Harvard School of Public Health have found that patients who ate more whole grains, fruits, vegetables, and less sweetened beverages and saturated fats improved their diet quality index scores by ten percent over four years. This reduced their risk for developing Type 2 diabetes by about 20% when compared to those who made no diet changes.” The “control” ate the Standard American Diet (SAD), which is filled with junk food.

The measurement tool that the Harvard “researchers” used was the “110-point Alternate Healthy Eating Index 2010” (AHEI). Harvard’s Walter Willett and colleagues developed the AHEI in 2010 to “improve on” the Healthy Eating Index (HEI) that was originally developed by the USDA in 1990 and updated every five years to conform to the changes in the USDA’s Dietary Guidelines for Americans. It measures diet quality as a function of conformance to the Guidelines.

A comparison of Harvard’s AHEI and the USDA’s HEI can be viewed on Yahoo. The Yahoos site’s main value, however, is that it provides links to both the 2010 AHEI and the HEI. In my view, obviously, the AHEI and HEI are both deeply flawed, not least for their views about fats, especially liquid fats (refined “vegetable” oils) made from polyunsaturated sources (corn, soy bean, sunflower, peanut, canola and others). In addition, both Harvard’s AHEI and the USDA’s HEI regard a “move to a plant-based diet” an “important step in the right direction,” according to the AHEI link. They would have you view “solid” (saturated) fats as harmful, and severely curtail your consumption of egg yolks, butter and red meat. Harvard is still hopelessly hamstrung by its Hammurabian bias. This latest “study” simply seeks to promote the “ancient” (50-year old) and totally erroneous bias against saturated fats.

The USDA’s Center for Nutrition Policy and Promotion [note the undisguised use of ‘promotion’ here] uses data collected via 24-hour recalls of dietary intake in national surveys to construct the HEI score. The methodology of Harvard’s 110-point AHEI uses “a scoring system similar to the USDA’s index…using information about daily diets collected from more than 100,000 female nurses and male health professionals taking part in two long-term studies.”

Harvard can’t be faulted for wanting to improve or replace the “one-size-fits-all” Dietary Guidelines for Americans. But just tweaking it, as Harvard does, is not the solution. Neither, however, do I fault some of Harvard’s tweaks. My main gripe is with their confounding of “more whole grains, fruits, vegetables,” with “less sweetened beverages and saturated fats.” And, in this last phrase, the conflating of “sweetened beverages and saturated fats.” Elsewhere, they (and the USDA) consistently conflate “saturated fats” and “trans fats.” These are egregious examples of using a rhetorical device to confuse and mislead the public. And it is downright damnable. Damnable, I say.

With respect to this particular “study” and public policy press release, how can Harvard say that the 10% improvement in diet quality index scores (over those who made no self-reported diet changes), and which lead to a 20% reduction in developing Type 2 diabetes, was attributable to reporting eating “more whole grains, fruits, vegetables,” or eating “eating less sweetened beverages and saturated fats.” Perhaps the 10% improvement in scores was attributable to the (self-reported) elimination of sweetened beverages without any change in saturated fat intake or whole grains, fruits and vegetables. Or eating more whole grains, fruits and vegetables and fewer sweetened beverages, but the same amount of saturated fat. Or any combination. But that’s epidemiology, a very weak “science,” at best.

But that’s about what I expected when I read that this “study” was a product of the Harvard School of Public Health. It is simply a promotional piece to advance their idea of a “healthy diet.” A perfect example of confirmation bias.