The next version of the U.S. Dietary Guidelines for Americans, which will be finalized later this year, is based on a non-rigorous assessment of the existing scientific literature on diet and health, according to a controversial article published Wednesday in The BMJ.

As a result of that lack of scientific rigor, this year’s update of the guidelines is likely to give Americans (and people around the world) “a misleading picture” of which types of foods are best for optimal health, writes journalist Nina Teicholz. 

The dietary guidelines, which were first issued in 1980, are revised every five years. Each update is based on a report issued by an advisory committee of 11 to 15 experts. The 14-member advisory committee for the 2015 guidelines published its report last February.

The report was met with immediate criticism, particularly for its proposals on the consumption of carbohydrates and red meat. 

As Teicholz notes, the advisers appear to have been reluctant “to consider any evidence that contradicts the last 35 years of nutritional advice.”

The importance of the dietary guidelines can’t be overstated. Although individuals may choose to ignore the recommendations, government officials cannot. The new guidelines will be used to set government policies on nutrition education, food labeling and research priorities for the next five years.

Industry influence

“Since its inception, the guidelines process has suffered from a lack of rigorous methods for reviewing the science on nutrition and disease, but a major effort was undertaken in 2010 to implement systematic reviews of studies to bring scientific rigor and transparency to the review process,” says Teicholz. “The US Department of Agriculture set up the Nutrition Evidence Library (NEL) to help conduct systematic reviews using a standardized process for identifying, selecting, and evaluating relevant studies.”

But the current committee “did not use NEL reviews for more than 70% of the topics, including some of the most controversial issues in nutrition,” Teicholz writes. “Instead, it relied on systematic reviews by external professional associations, almost exclusively the American Heart Association (AHA) and the American College of Cardiology (ACC), or conducted an hoc examination of the scientific literature without well defined systematic criteria for how studies or outside review papers were identified, selected, or evaluated. Use of external review by professional associations is problematic because these groups conduct literature reviews according to different standards and are supported by food and drug companies.” 

Industry provided the ACC with 38 percent of its revenue in 2012 and the AHA with 20 percent of its revenue in 2014, Teicholz reports.

In addition, the current committee’s 14 members have not been required to publicly list their own potential conflicts of interest.

“A cursory investigation shows several such possible conflicts,” writes Teicholz. “[O]ne member has received research funding from the California Walnut Commission and the Tree Nut Council, as well as vegetable oil giants Bunge and Unilever. Another has received more than $10,000 from Lluminari, which produces health related multimedia content for General Mills, PepsiCo, Stonyfield Farm, Newman’s Own, and ‘other companies.’ ”

(Critics of her article are arguing that Teicholz has her own conflict. She is the author of “The Big Fat Surprise: Why Butter, Meat & Cheese Belong in a Healthy Diet.”)

Saturated fats and carbohydrates

The “backsliding” on the scientific standards used during the committee’s review process can be seen most prominently in its recommendations regarding saturated fats and low-carbohydrate diets, says Teicholz.

On saturated fats:

Restrictions on saturated fats have been a foundation of nutrition policy since the first guidelines in 1980 and have had a dominant role in determining which foods, such as low fat dairy and lean meats, are considered “healthy.” Instead of requesting a new NEL review for the recent literature on this crucial topic, however, the 2015 committee recommended extending the current cap on saturated fats, at 10% of calories, based on a review by the AHA and ACC, a 2010 NEL review, and the 2015 committee’s ad hoc selection of seven review papers.

Several major papers published since 2010 have failed to find an association between saturated fats and heart disease, including the Women’s Health Initiative, a large controlled clinical trial involving almost 49,000 people, Teicholz points out. 

On low-carbohydrate diets:

Again, the 2015 committee did not request a NEL systematic review of the literature from the past five years … yet many studies of carbohydrate restriction have been published in peer review journals since 2000, nearly all of which were in US populations. These include nine pilot studies, 11 case studies, 19 observational studies, and at least 74 randomised controlled trials, 32 of which lasted six months or longer. 

“Given … the failure of existing strategies to make meaningful progress in fighting obesity and diabetes to date, one might expect the guidelines committee to welcome any new, promising dietary strategies. It is thus surprising that the studies listed above were considered insufficient to warrant a review,” writes Teicholz

A defense of the process

For her article, Teicholz interviewed the chair of the current advisory committee, Barbara Millen. She is a former nutrition epidemiologist at Boston University who is now president of Millenium Prevention Inc., a company that develops mobile applications and web-based platforms to promote healthy lifestyles. Millen defended the committee’s review process.

“The evidence base has never been stronger to guide solutions,” she told Teicholz. “You don’t simply answer these questions on the basis of the NEL. Where we didn’t feel we needed to, we didn’t do them. … That’s why you have an expert committee … to bring expertise,” including “our own original analysis.”

As for conflicts of interest, Millen pointed out that the federal government vetted all the committee’s members.

The report’s critics, she told Teicholz, “are coming from the point of view that they don’t like the answer.”

An urgent need for sound advice

Whether or not we agree with the “answer” that the committee came up with for its dietary recommendations, the process certainly raises some serious — and unanswered — questions.

“Given the ever increasing toll of obesity, diabetes, and heart disease, and the failure of existing strategies to make inroads in fighting these diseases, there is an urgent need to provide nutritional advice based on sound science,” writes Teicholz.

“It may be time,” she adds, “to ask our authorities to convene an unbiased and balanced panel of scientists to undertake a comprehensive review, in order to ensure that selection of the dietary guidelines committee becomes more transparent, with better disclosure of the conflicts of interest, and that the most rigorous scientific evidence is reliable used to produce the best possible nutrition policy.”

You can read Teicholz’s article in full on The BMJ’s website. For a contrarian viewpoint (and many have been posted since Teicholz’s article was released late Wednesday night), try Arielle Duhaime-Ross’ article on The Verge. She pulls no punches, calling Teicholz’s article “a bogus investigation” full of “erroneous errors.”

As I said, the importance of the new dietary guidelines can’t be understated. There’s a lot of money — and many professional reputations — riding on them.