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USDA Ignoring the Science on Low-Carb Diets

Since 2014, the US Dept. of Agriculture has a record of "burying" the science

“I was wondering if we should have a separate section on low-carb diets rather than burying it,” wrote Harvard nutrition professor Frank Hu about the official expert report for the 2015 U.S. Dietary Guidelines for Americans. Over the past decade, thousands of scientistsdoctors and others have urged officials overseeing our nation’s nutrition policy to pay attention to studies on low-carbohydrate diets, yet even as the science has advanced rapidly, the federal agencies in charge of the guidelines seem ever-more intent on ignoring and yes, burying the science.

The literature on low-carb is now vast. A quick search for “low-carbohydrate” on pubmed.gov, a government database of scientific studies, today turns up 7,821 publications, including 858 clinical trials (the most rigorous kind of evidence).12 Compare this to the 401 trials on the “vegetarian diet,” which has been formally recommended by the U.S. guidelines since 2015.

Of course quantity is not quality, but the American Diabetes Association judged low-carb to have “most evidence for improving glycemia” [blood sugar control], the key issue for people with with diabetes. And the diet produces “more weight loss” than a higher-carb option, according to the American Heart Association.

Yet here is the recent history on how the U.S. Departments of Agriculture and Health and Human Services (USDA-HHS), the federal agencies that co-issue the guidelines every five years, have treated this large body of scientific literature:

  • For the 2015 guidelines, the USDA3 conducted a formal review of this literature and found 40 studies but unlike its other reviews, kept this one hidden and did not even reveal the fact that it had been conducted. The review’s existence was only discovered in emails obtained via the Freedom of Information Act (FOIA);
  • Five years later, for the 2020 guidelines, the USDA publicly reviewed the low-carbohydrate diet but could find no studies meeting its inclusion criteria on the topic;
  • For the upcoming 2025 guidelines, USDA has proposed ignoring low-carbohydrate diets altogether.

How could this happen?

A New Cycle Begins; Still No Recognition of Low-carb

In March, the USDA launched its process for the 2025 guidelines by publishing a draft list of scientific questions (no longer at its original URL), which did not include a single query on low-carb diets. If no question is asked, no review gets done, and this would mean that the guidelines would have no chance of including a low-carbohydrate option until the 2030 guidelines or later.

The public, given a month to comment, was clearly upset. Nearly 80% of the total comments, or some 1,200 individuals, urged the USDA-HHS to consider the extensive scientific literature on low-carb. The public comment period closed in mid-May, and the agencies have not yet responded.

Many commenters expressed frustration that they had suffered from obesity and other diet-related conditions for years without being told about the availability of a low-carbohydrate approach—which subsequently resolved their health problems. As one commenter wrote:

“I am a retired physician who personally struggled with overweight or obesity since childhood. I counseled patients on the same issues, using nutritional & exercise guidelines from government and medical experts. Those guidelines did not work for my patients or me. I would lose weight on calorie counting & exercise but could not sustain this when eating carbohydrates, including so-called healthy whole grains. Only when I discovered information about low carb/ketogenic way of eating at age 69 did my struggles end. I have been following low carb eating since then, feel wonderful, have excellent exercise endurance, saw my HDL increase to 104, and suffer no more joint pains.”

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