Wed, Sep-12-18, 03:46
Carbs, Good for You? Fat Chance!
From the Wall Street Journal
September 11, 2018
Carbs, Good for You? Fat Chance!
Dietary dogma’s defenders continue to mislead the public and put Americans’ health at risk.
By Nina Teicholz
The U.S. government’s nutrition advice since 1980 has mainly been to increase consumption of carbohydrates and avoid fats. Despite following this advice for nearly four decades, Americans are sicker and fatter than ever. Such a record of failure should have discredited the nutrition establishment. Yet defenders of the nutrition status quo continue to mislead the public and put Americans’ health at risk.
A widely reported study last month purported to show that carbohydrates are essential to longevity and that low-carb diets are “linked to early death,” as a USA Today headline put it. The study, published in the Lancet Public Health journal, is the nutrition elite’s response to the challenge coming from a fast-growing body of evidence demonstrating the health benefits of low-carb eating.
The authors relied on data from the Atherosclerosis Risk in Communities study, or ARIC, which since 1987 has observed 15,000 middle-aged people in four U.S. communities. Funded by the National Institutes of Health, ARIC may seem robust study, but it is based on a thin data set. Researchers’ food questionnaires typically feature between 100 and 200 dietary items, but participants in this study were queried on only 66. Popular foods such as pizza and energy bars were left out, with undercounting of calories the inevitable result. ARIC calculated that participants ate only 1,500 calories a day—starvation rations for most.
Further, the ARIC participants’ eating habits were tracked only twice, from 1987-89 and 1993-95. After 1995 the study’s participants were assumed to have continued eating the same diet for the next 15 years. During that time the Mediterranean diet craze hit and the junk-food industry exploded, yet ARIC captured none of these effects.
Diet questionnaires are inherently unreliable since people tend to under- and overestimate food quantities to make their diets look better. The Lancet authors’ treatment of the data also falls short. They make no mention of adjusting their results for alcohol consumption, for example, which is a critical factor in longevity.
It gets worse. The authors threw out any data on carb consumption from subjects who “developed heart disease, diabetes, and stroke” before the second diet visit, “to reduce potential confounding.” They don’t reveal how much evidence was dropped, but this seems like it would be the most relevant portion of any study about the relationship between carb consumption and disease.
Randomized controlled clinical trials are considered the scientific gold standard because they can demonstrate cause and effect, which ARIC’s associational data can’t. The authors of the Lancet study give short shrift to the more than 70 such trials that have looked at the health effects of a low-carb diet. While grudgingly acknowledging the “beneficial short-term weight loss and improvements in cardiometabolic risk” from high-fat/low-carb diets, the authors claim without evidence that such diets have been “hypothesised to stimulate inflammatory pathways, biological ageing, and oxidative stress.”
The Lancet authors, in recommending a “moderate” diet of 50% to 60% carbohydrates, essentially endorse the government’s nutrition guidelines. Because this diet has been promoted by the U.S. government for nearly 40 years, it has been tested rigorously in NIH-funded clinical trials involving more than 50,000 people. The results of those trials show clearly that a diet of “moderate” carbohydrate consumption neither fights disease nor reduces mortality.
Lancet Public Health (a separate journal from its more prestigious parent, the Lancet) charges contributors an “article processing fee” of $5,000. The journal publishes papers that need to be distributed “quickly” to “advance public health policies.” What exactly was the rush here? Given the lack of rigor, it seems the paper’s purpose was not to help people eat better and live longer but rather to quash public interest in low-carb, high-fat diets. Needlessly scaring people away from diets with established health benefits could endanger the public.
Ms. Teicholz is a science journalist, author of “The Big Fat Surprise,” and executive director of the Nutrition Coalition.