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Dear Friends,
The
following is a post I wrote for Substack that I am reprinting here for
followers of the Nutrition Coalition. If you would like to subscribe to
my newsletter for posts on nutrition and health, you can do so here.
Nina
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Science review methods fall to new lows at USDA
As a new Trump era dawns on America, some of my friends are celebrating while many others are devastated. For the latter, I hope you can find a
slim silver lining in the possibility that we might finally see real progress in reversing our epidemics of chronic disease. This kind of revolution would have been near impossible under Harris, since her party has fully embraced the government’s status quo diet. (The historic
White House Conference on Hunger, Nutrition & Health in 2022, for instance, did not invite a single expert versed in the established science of reversing type 2 diabetes.) By contrast,
the super-fueled “Make America Healthy Again” campaign has catapulted chronic disease into the spotlight, and we can now, for the first time
in 40 years, glimpse an opening fortransformational change.
The immediate issue is the U.S. Dietary Guidelines for Americans, the single-most influential policy determining what we consider to be a healthy diet. I realize I sound like a broken record on this topic, but there’s a good reason. Given that these guidelines drive all federal
food-related programs, from school lunches to military mess halls, and are downloaded as the ‘gold standard’ by nearly all health professionals, we can’t emphasize their importance too often or too strongly. These guidelines are an important reason we’ve failed to meet
recruitment targets for the military for several years now, and why childhood disease rates, especially for obesity and pre-diabetes, are
now seen at unprecedented rates.
Less meat, less poultry, less eggs
Just weeks ago, we learned from a meeting of the experts reviewing the science, called the Dietary Guidelines Advisory Committee (DGAC), that
they recommended reducing red and processed meats for all Americans.Further, they propose cutting all animal foods--meat, poultry, and eggs--by 3 ½ - 4 ounce-equivalents per week for people eating 2,200 calories and over, as part of a “flexible”
dietary pattern.” This new versatility would allow schools to serve less of these foods to children.
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A bias against animal foods has been baked into the guidelines for a long time. In 2015, the U.S. Department of Agriculture (USDA) introduced a
“Vegetarian Dietary Pattern” for all Americans, even though its own systematic reviews found only “limited evidence” that this diet could prevent chronic diseases "(“Limited” is two notches below the “Strong” evidence needed to codify a recommendation).1 In this current cycle, the USDA went further by exploring a vegan option,
because it was “supported by the public interest,” according to one committee member.2 This inquiry hit a wall with the predictable finding that shifting from a
vegetarian to a vegan diet would cause many nutrient deficiencies, including:
- Protein, vitamins A, D, E, several B vitamins, choline, iron and zinc.
- Calcium and vitamin B12 across all life stages and calorie ranges.
- Several of these nutrients and nutrients of concern for certain life stages, for example protein and vitamin B12 for older adults, and calcium for adolescent girls.
A less biased staff acquainted with the well-known nutritional problems of veganism could have avoided this inquiry altogether. And while
reasonable people might conclude that animal foods seem pretty helpful for getting needed nutrients, the staff and committee members continued to refer to these foods as being of “lower nutrient density,” which is part of the agency’s frequent doublespeak (the guidelines also call water “nutrient dense” even though it contains zero nutrients).
More beans, peas, lentils
Following this flawed logic, the committee is pushing ahead with its proposed cuts to animal foods and replacing them instead with beans, peas, and lentils, by ½-1 cup weekly. This advice does not consider that plant-based proteins are not as complete as animal proteins—and therefore, not as digestible to people. Further, plant sources like peas and beans pack a hefty load of carbohydrates and calories for the same amount of protein, making them a far less healthy option.
There’s no doubt that these changes would exacerbate our disease epidemics. In addition to the greater carbohydrate load of more plant proteins, reductions in meat, eggs, and poultry would lead to further shortfalls in fiber, and vitamins D and E, the committee found. (The existing guidelines already fail to meet goals for vitamins D and E, folate,
choline, and iron.)3
- For nutrients with an Estimated Average Requirement (EAR), less than 10% of simulated diets are inadequate (< EAR) for each nutrient except vitamins D and E
- For nutrients with Adequate Intake (AI), median nutrient content of the distribution of simulated diets is adequate (≥ AI) for alpha linolenic acid, potassium, and vitamin K, but falls short on choline and fiber for select age-sex groups and for linoleic acid for foods consumed in Alaska Native diets
USDA defends refined, processed grains
These shortfalls were deemed acceptable by the DGAC, even though members had earlier in the meeting lamented the problem of the guidelines’
persistent nutrient deficits. For instance, there was serious concern about re-upping the recommendation of three daily servings of refined grains, understanding that these easily digested carbs are clearly bad for health. The rationale for retaining these grains was that only refined
(not whole) grains are enriched and fortified with iron and folate.4 “If we reduced refined grains, there would be nutritional inadequacies,” noted committee Chair Sarah Booth.5 Rather than accepting red meat is a great source of heme iron (the kind people absorb most readily) and a decent source of folate, the DGAC is letting us know that we will continue to see Lucky Charms served to kids K-12.
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Food, pharma conflicts are pervasive
Perhaps unsurprisingly, members of the expert committee include Christopher Gardner, a Stanford professorentirely underwritten by the fake-food company Beyond Meat, and Fatima Cody, a Harvard doctor who has taken tens of thousands of dollars from Wegovy and other GLP-1 manufacturers. The latter went on 60 Minutes to emphasize that obesity is a genetic disease.
Pervasive conflicts of interest are nothing new in the guidelines. Ninety-five percent of the committee for the current guidelines had a tie with a food or pharmaceutical company, according to the sole published systematic review of any guidelines committee (for which I was a co-author). These conflicts are not disclosed by the issuing agencies, the USDA and U.S. Department of Health and Human Services.
Science so weak it’s beneath mention
Worse, the justification for reducing poultry, red meat, and eggs was based on data simulations from computer modeling—evidence even weaker than the usual low-quality epidemiological data used to justify the guidelines.
As a refresher, here is the pyramid of evidence used by every internationally recognized methodology for scientific reviews:
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Randomized, controlled clinical trials (RCTs) are near the top, with all other forms of evidence falling below. The hypothetical computer modeling used by the USDA does not even appear on the chart for very good reason: it’s considered beneath consideration.
These models lack accuracy. For instance, the USDA simulations make no distinction between a tomato (< 5 grams of carbs per serving) and a
sweet potato (27 carbs); Both are part of the “red and yellow vegetables category.”6 The model did not control for portion size and did not include “mixed dishes,” such as lasagna and hamburgers, even though these are a major source of calories for Americans. The model also makes hundreds of questionable assumptions. If one assumes that saturated fats are bad for health, as the USDA does, then the model will downgrade all foods with those fats. The USDA office that conducted the modeling does not appear to provide any information on its methods or assumptions, so the project,
which reportedly produced 17,500 simulations, remains a virtual black box.
No less than the National Academies
of Sciences, Engineering, and Medicine reviewed the USDA’s overall methodology for reviewing the science and found in a 2017 report that it
“lacked scientific rigor” and did not have a “recognizable or verified” process. Congress had mandated and allocated 1 million dollars for this
high-level report and another $1 million for a follow-up in 2022. Still, the USDA did not fully adopt even one of the Academies’ 11 recommendations.
Similarly, a 2022 paper in PNAS Nexus that I co-authored with several former DGAC members detailed many problems with the guidelines, including the lack of strong evidence for numerous key recommendations. In a 2015 cover story for the BMJ, I reported that the USDA diets “are supported by a minuscule quantity of rigorous evidence that only marginally supports claims that these diets can promote better health than alternatives.” This year, the USDA-HHS
staff responded to our 2022 publication in a paper entitled “Addressing misinformation about the Dietary Guidelines.”
The USDA staff might say that they’re compelled to rely on weak evidence since data from clinical trials are sparse. Still, when the Academy
urged a process upgrade, no one could have imagined that the USDA would stoop lower by using evidence of even weaker quality than before.
It’s true that clinical trials of any meaningful duration are expensive to conduct. Still, the U.S. National Institutes of Health (NIH) and other countries have conducted many large, long-term diet trials—so the real
story is that the USDA has consistently ignored this rigorous evidence. For instance, I documented in the BMJ piece that the USDA did not incorporate results from any of the major, NIH-funded trials on the low-fat diet, including the Women’s Health
Initiative on some 49,000 women. This trial found that a low-fat diet similar to those now promoted by the USDA did not prevent diabetes, obesity, heart disease, or any type of cancer.
I also found that the USDA has ignored all the RCTs on saturated fats, which literature finds no effect of these fats on cardiovascular or
total mortality and little-to-no effect on heart disease.
The problem of overlooking clinical trials came up almost comically during Day One of the DGAC’s September meeting, when Gardner realized that his own three clinical trials had been omitted from the 36,000 papers culled by the USDA staff for an analysis on the health effects of replacing meat with vegetables. “I realized that there is no way that my trials would have come up,”7 given the search terms used in the literature review, he marveled, an admission that elicited nervous laughter around the room. If the USDA can’t even find the RCT data, they are clearly missing the most critical research evidence from the get-go.
The USDA systematic reviews also generally fail to prioritize RCTs over epidemiological data, and as we’ve often noted, this is a departure from
every known major methodology. It’s a significant reason why the Academies said that the USDA approach “lacks scientific rigor.”
The USDA also, once again, failed to consider clinical trials on low-carbohydrate diets, although there are now morethan 1,000 papers researching this approach. Suppressing the data on low-carb diets has been going on at the USDA for at least a decade, as I discovered through emails obtained through the Freedom of Information Act. “I was wondering if we should have a separate section on low-carb diets rather
than burying it,” Frank Hu, a Harvard professor on the 2015 DGAC, wrote to his fellow committee members and USDA colleagues.
One has to wonder what the rationale would be for burying evidence, but committee members throughout the years have consistently avowed that the high-carbohydrate guideline is a “healthy diet.” If this is your a priori assumption, fundamental questioning is not on the table.
The current DGAC did not ignore low-carbohydrate diets. Yet rather than consult those 1,000 papers on RCTS—actual experiments on real people—the committee instead simulated the diet using the USDA’s computer models. They discovered that when carbohydrates were removed (comprising some 52-54% of the USDA’s recommended calories per day), nutrient adequacy plummeted. But the
models didn’t replace those 50+% of calories with any other foods. So, of course, nutrients take a nose dive when caloric intake is halved!
Let’s remember what the guidelines recommend as a healthy diet:
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Further, the guidelines allow half of all fruit servings to be consumed as fruit juice, even though juice can impact blood sugar levels as much as sugar-sweetened beverages.
I wrote a whole book on how the Dietary Guidelines came into being and how they grew so entrenched. Resistance to change is endemic in every expert committee.
Further highlights from the September meetings include:
- People who questioned the healthfulness of seed oils were called “conspiracists”;
- Dierdre Tobias, a DGAC member, said, “Butter is not back”;
- Although DGAC members repeatedly talked about their focus on health equity and cultural diversity, many systematic reviews contained only data on
middle-class white people.
I have to admit that I’ve been put off watching these meetings. I find them agonizing. The tone in the room is one of treacly, cheerleader congratulations. “A great discussion!” and “Great job!” were often exclaimed, and Booth, the Chair, was perpetually upbeat, despite the grim reality that the guidelines have presided over this scenario.
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No one seemed to have any notion that basing population-wide dietary guidance on dubious computer models falls beneath any standard worldwide for clinical guidelines. No health professional association would issue broad advice based on this basement-level quality of evidence. The guidelines process is hard to fathom.
But to return to my post-election optimism, I hope the new administration’s commitment to reversing chronic diseases and using evidence-based science motivates them to turn this situation around. It’s not an understatement to say that the health of our nation depends on it.
Source material:
Meeting #6 of the DGAC, September 24-25: Day 1 of meeting, Day 2 of meeting
Meeting #7 of the DGAC: Presentation of the Final Report by the Dietary Guidelines Advisory Committee, Oct 21-22: Day 1 of meeting, Day 2 of meeting<
1 “Limited” evidence for preventing heart disease; “Limited” evidence for preventing type 2 diabetes. The evidence on obesity is not reported, at least in the top-line summary.
2 DGAC meeting, Sept., day 1, hour one.
3 The
use of “median nutrient content” implies half the people fell below this level and likely also had deficiencies in potassium and choline.
4 DGAC meeting, Sept., day 2, hour ~1:4
5 DGAC meeting, Sept., day 2, ~hour 1:39
6 DGAC meeting, Sept., day 1, hour one.
7 DGAC meeting, September 25th, minute 4:26
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