By Sarah Reinhardt, Union of Concerned Scientists
Next week, a committee of top health, medical, and nutrition experts will gather in Houston, Texas to answer an age-old question: What should we eat?
This is the fourth of five public meetings the committee will hold as it develops the scientific basis for the 2020-2025 Dietary Guidelines for Americans, the nation’s leading set of evidence-based nutrition recommendations. Importantly, it’s also the last chance for stakeholders—from concerned citizens to health care providers to industry representatives—to deliver in-person comments to the committee. While we can expect many of the above to make an appearance, there is also reason to believe that the deck of stakeholder comments will be stacked with disciples of the low-carb diet.
Let’s get this out of the way: Carbohydrates are an essential part of human diets. Full stop. That being said, we’re far too often eating them in the form of highly processed foods with little nutritional value. So why do we seem to spend so much time talking about the quantity of carbs in our diets, and so little time talking about the quality?
Stop trying to make low-carb happen
Carbohydrates are the main source of energy for cells throughout our bodies, and are particularly important for our brains, which use about 120 grams of glucose (one of the end products of carbohydrates) every day. And while your brain does have a backup energy source—ketones, derived from fatty acids and the namesake of the popularized “keto diet”—this is a physiological pathway that’s intended to keep us alive under conditions of starvation. And not the six-hours-without-a-snack kind—we’re talking the two-weeks-in-the-wilderness-foraging-for-berries kind. Think of it as your metabolic spare tire: essential for emergencies, but pretty impractical for day-to-day use.
While there’s no single definition of a low-carb diet, most aim to limit carbs to no more than 25 percent of calories (for reference, the Dietary Guidelines recommends 45-65 percent). And though some research shows that low-carb diets can support weight loss and diabetes management, there is little evidence suggesting they deliver long-term health benefits. On the contrary, a recent studyfound that low-carb diets were linked to greater risk of early death. The short-term health benefits aren’t necessarily surprising: if a low-carb diet drives us to eat lower amounts of refined grains, the dominant form of carbohydrates in our diets and the leading ingredient in many highly processed and low-nutrient foods, it would stand to reason that our health may initially improve as a result. But how our health fares in the long run depends heavily on what we put on our plates in place of carbs—and our ability to maintain this diet over time. Meanwhile, study after study continues to confirm the numerous long-term health benefits of whole grains, including reduced risk of cardiovascular disease and type 2 diabetes.
To be clear, this isn’t to say that low-carb diets can’t or don’t help some people make positive lifestyle changes. In general, I’m a believer in the notion that the best diet is the one that works for you. But strong science-based dietary recommendations intended for large segments of the population can’t be built on personal success stories—just as they can’t be bought.
Meet the newest anti-carb advocates
So why is the low-carb diet coming up again (and again)?
The Low-Carb Action Network, a self-identified coalition of doctors, academics, and “average Americans with personal success stories,” is the latest group advocating for the inclusion of the low-carb diet in the Dietary Guidelines. Its website is home to articles and personal narratives touting the health benefits of low-carb diets, as well as a critique of the methodology being employed by the Dietary Guidelines scientific advisory committee to define the low-carb diet. Though the network, formally launched in December, is new, many of its talking points are familiar. Similar language has been used by the Nutrition Coalition, which has worked diligently to undermine confidence in the scientific process on which the Dietary Guidelines is based, including a 2015 British Medical Journal article by executive director Nina Teicholz that was sharply criticized by leading researchers for its portrayal of the process. And she’s not alone. In July of this year, more than 50 doctors were signatories of a full-page ad in the New York Times and Washington Postcalling for a total overhaul of the Dietary Guidelines—spearheaded by none other than Atkins Nutritionals, the company promoting the low-carb products of the Atkins diet. As reported by Politico, these groups have also found strange bedfellows in the livestock industry, whose interests would also benefit from the widespread adoption of diets that endorse foods low in carbs and high in fat—like beef.
By some measures, these groups have been successful in drawing public attention to this issue. In total, nearly 350 written comments on this particular topic have already been submitted to the federal agencies that publish the Dietary Guidelines, many of which align with Nutrition Coalition and Low-Carb Action Network talking points.
But comments don’t equal credibility. And it seems the Low-Carb Action Network has built its policy platform on low levels of that, too.
When credibility counts, low-carb groups come up short
It doesn’t take long to find faults in the Low-Carb Action Network.
For starters, in the December press release announcing its launch, the network points to a “large and rapidly growing body of strong scientific research” on the safety and effectiveness of carbohydrate restriction. To substantiate this claim, the press release links to a meta-analysis comparing the effects of weight loss diets. And while the results show that low-carb (and low-fat) diets produced the greatest weight loss after six months, it is a far cry from providing strong evidence in favor of going low-carb. By 12 months, the endpoint of the analysis, the effects of nearly all diets had decreased, and there were only small differences between diets with low and moderate amounts of carbohydrates. Where low-carb diets did stand out? Five clinical trials included in the meta-analysis reported negative side effects associated with the Atkins diet, including one study finding that more than a quarter of study participants following a low-carb diet experienced constipation, headache, halitosis, muscle cramps, diarrhea, and general weakness.
It’s also worth mentioning the lead author of this particular meta-analysis is Dr. Bradley Johnston. If that name rings a bell, it’s because he has gotten some publicity recently, and not the good kind. Late last year, Dr. Johnston authored a paper producing dubious dietary recommendations related to red and processed meat, and was soon after criticized for failing to report conflicts of interest in the form of funding from an influential industry trade group. Dr. Johnston had previously come under fire for industry ties after publishing a similar study discrediting international health guidelines on added sugar. While current or former industry ties certainly don’t invalidate this particular study’s conclusion, they’re certainly reason to take a closer look.
What else can we expect at next week’s meeting?
I, for one, will be sitting in the front row, taking a shot of grain alcohol every time a personal anecdote about low-carb diets is used to justify an overhaul of national dietary guidance. (Kidding! That’s not a whole grain!)
I will, however, be speaking on behalf of science. Specifically, I’ll be urging the committee to consider the rapidly expanding body of nutrition research that can simultaneously help us address the most pressing and costly challenges facing public health: chronic disease and climate change.
Even if you won’t be in Houston next week, there’s still plenty of time for you to do the same. The federal agencies publishing the 2020-2025 Dietary Guidelines for Americans are accepting public comments through May 1, 2020. For helpful tips and talking points on submitting public comments, see our comment guide—and check back on our blog soon.