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Mandate is clear: Flawed dietary guidelines process must be reformed
The nation's senior scientific body recently released a new report raising serious questions about the "scientific rigor" of the Dietary Guidelines for Americans. This report confirms what many in government have suspected for years and is the reason why Congress mandated this report in the first place: our nation's top nutrition policy is not based on sound science.
In order to "develop a trustworthy DGA [guidelines]," states the report by the National Academies of Science, Engineering and Medicine (NASEM), "the process needs to be redesigned."
Among other things, the report finds that the guidelines process for reviewing the scientific evidence falls short of meeting the "best practices for conducting systematic reviews," and advises that "methodological approaches and scientific rigor for evaluating the scientific evidence" need to "be strengthened."
In other words, the Dietary Guidelines for Americans are far from the "gold standard" of science and dietary advice they need to be. In fact, they may be doing little to improve our health at all.
A crucial point, according to the report, is the need to upgrade the U.S. Department of Agriculture's Nutrition Evidence Library (NEL), which conducts the scientific literature reviews. The NEL needs more "up-to-date" methods, outside technical expertise and external peer review of its work. A review of the NEL process in 2015 published in The BMJ (British Medical Journal), for instance, found that several of the evidence reviews had not been conducted systematically, allowing for cherry picking or outside industry influence, and that some 33 percent of the scientific questions requiring systematic reviews did not receive a review.
Other recommendations by the National Academies report include improving transparency of the guidelines process and the need for the Guidelines to address not just healthy Americans but also those-now a majority-who are suffering from nutrition-related diseases.
For instance, rates of type 2 diabetes have quadrupled and obesity has nearly doubled since 1980, the very year that the guidelines were launched. For all of us in government, this is a matter of urgent concern.
It seems clear that the lack of sound science has led to a number of dietary tenets that are not just mistaken, but even harmful - as a number of recent studies suggest.
For instance, the guidelines' recommendation to eat "healthy whole grains" turns out not to be supported by any strong science, according to a recent study by the Cochrane Collaboration, a group specializing in scientific literature reviews. Looking at all the data from clinical trials, which is the most rigorous data available, the study concluded that there is "insufficient evidence" to show that whole grains reduced blood pressure or had any cardiovascular benefit.
Another recent study, called the Prospective Urban Rural Epidemiology (PURE), followed 135,335 people worldwide, and found that there was no effect on cardiovascular mortality with higher saturated fat consumption. This same finding has been echoed over the past decade in thirteen other review papers on saturated fats, on all the clinical trials and all the observational data to date.
Even more worrying, PURE found a link between the low levels of saturated fat currently recommended by the Dietary Guidelines and an increased risk of stroke.
The paper, which was published in The Lancet, concluded that "global dietary guidelines should be reconsidered in light of these findings." The study leader, Yusuf Salim, chair of cardiovascular medicine at McMaster's University and immediate past president of the World Heart Federation, added that "saturated fat in moderation actually appears good for you."
PURE additionally found that the lowest risk for cardiovascular or total mortality was for those consuming the most fat, up to the 45 percent of calories as measured in the study. Mortality was disturbingly higher among those consuming only 32-34 percent fat, as the Dietary Guidelines are currently modeled. This PURE data is also supported by a large amount of more rigorous trial evidence, including long-term data, showing that higher fat diets lead to more weight loss and better outcomes for blood glucose control, an important factor in type 2 diabetes.
How could the Dietary Guidelines have missed the mark on so much important evidence? The National Academies report provides not just an explanation, but also a roadmap into the future for how to put the guidelines on a firm scientific foundation.
It is imperative that the advice championed by our national nutrition policy be unimpeachable. With the process for the 2020 guidelines soon to be underway, now is the time for the Congress to take action to reform the Dietary Guidelines development process so that proposed guidelines work as intended - as a tool to restore and protect our nation's health.
Harris represents the 1st District of Maryland.