How healthy is Paleo and other diets that exclude entire food groups?

Chances are, back in grade school, you were taught healthy eating habits with the help of an illustration. There was the USDA’s “Basic Four food groups” — a chart as, um, basic as its name suggests — featuring dairy, meats, fruits and vegetables, and grains. If you’re a little younger, you studied one of the two food “Pyramids,” first published by the USDA in 1992, and revamped in 2005. Today, schools teach kids how to eat “right” with the USDA’s “MyPlate” visual, which breaks a plate of food up into four sections and leaves a small amount of dairy off to the side in a cup. But no matter the graphic you were brought up with, or which one you think was configured best, the USDA’s message about proper nutrition can arguably be summarized into a simple, two-word phrase that today’s extreme dieters (and vegans, really) disregard: “balanced variety.”

Proteins, carbohydrates, and fats are all important nutrients for the human body, but none of the foods that provide each of them should be eaten to excess. Yes, there’s more nuance people should grasp — the USDA recommends you consume more grains than dairy, for example, and certain carbs are healthier than others — but essentially you should include all kinds of healthy foods in your diet, through a responsibly balanced approach.

Though most of us acquired this knowledge when we still thought a graveyard shift-pulling fairy left us money under our pillows, millions of adults still engage in extreme dieting, and researchers continue to debunk these diets’ merits. Two recent studies, for example, cast scientific shade on the Paleo diet and veganism specifically, concluding that each could have unsavory side effects on the body.

The Paleo diet is inspired by what humans ate back in the Paleolithic era, which took place between 2.5 million and 10,000 years ago. Ignoring all new knowledge on the subject of nutrition from the past 10 millenia, Paelo diet devotees eat foods that were collected through hunting and gathering techniques — meats, fish, fruits, vegetables, nuts and seeds — while generally eschewing foods cultivated through agriculture — grains, dairy products, and legumes, among others. A new study, published last month in the European Journal of Nutrition, finds that Paleo dieters have higher levels of trimethylamine-n-oxide (TMAO), a compound produced in the belly, which is associated with an increased risk of heart disease.

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“Many Paleo diet proponents claim the diet is beneficial to gut health, but this research suggests that when it comes to the production of TMAO in the gut, the Paleo diet could be having an adverse impact in terms of heart health,” said Angela Genoni, the study’s lead researcher, in a statement. “We also found that populations of beneficial bacterial species were lower in the Paleolithic groups, associated with the reduced carbohydrate intake, which may have consequences for other chronic diseases over the long term.” Genoni and her team believe the lack of whole grains in the Paleo diet is to blame for the increased level of TMAO and other health issues in the bodies of Paleo subscribers.

On the other side of the spectrum are the people who go vegan, omitting from their diets anything sourced from animals, such as meats, cheeses and dairy products — you know, the good stuff. But a study released today, in the BMJ Nutrition, Prevention & Health online journal, says that vegan and even just plant-based diets “risks worsening an already low intake” of an “essential dietary nutrient” called choline. Described in a statement about the study as “critical to brain health, particularly during fetal development,” choline also has an impact on “liver function, with shortfalls linked to irregularities in blood fat metabolism as well as excess free radical cellular damage.”

The results of the study are “concerning” to Emma Derbyshire, a physician who specializes in nutrition and biomedical science, because “current trends appear to be towards meat reduction and plant-based diets,” as she told the American Association for the Advancement of Science.

“When we cut out food groups, we risk missing out on key nutrients or over-consuming other nutrients. It also sets the stage for binging and a disordered relationship with food by giving us a set of rules to follow and inevitably break.”

“More needs to be done to educate healthcare professionals and consumers about the importance of a choline-rich diet, and how to achieve this,” Derbyshire added. “If choline is not obtained in the levels needed from dietary sources per se then supplementation strategies will be required, especially in relation to key stages of the life cycle, such as pregnancy, when choline intakes are critical to infant development.”

But the knowledge is already out there for healthcare professionals and consumers to apply to their diets, and it always comes back to the same facts we were taught as a kid: “A balanced diet is a healthy diet,” says Lauren Cadillac, a New York-based registered dietician and personal trainer. “When we cut out food groups, we risk missing out on key nutrients or over-consuming other nutrients. It also sets the stage for binging and a disordered relationship with food by giving us a set of rules to follow and inevitably break.”

Cadillac explains that strict, extreme diets “teach us to listen to the rules of the diet rather than the feedback our body is giving us.”

Due to a drop in vitamins, like B12, going vegan can make you lethargic, with headaches, dizziness, and even anemia. There’s little research to support the idea that a Paleo diet helps you trim your waistline, and the ketogenic diet — very high in fat, very low in carbs — causes constipation. At best, all of this sounds unappealing, to say nothing of the mental toil that can be brought on by these diets’ shackling restrictions.

A balanced diet, Cadillac said, allows for “junk” or “comfort” foods to be enjoyed without guilt. “Making foods off limits is the fastest way to increase your desire for them,” she says. “It also induces shame when we do consume them possibly binging and leads people to believe they have no willpower. They then embark on the next diet since the previous one ‘didn’t work’ for them.”

On the question of whether or not the Paleo and vegan diets are viable options at all, Cadillac said that they both have “aspects” that can be applied to a healthy diet. “The focus on high quality animal products, veggies, and healthy fats are a positive for paleo, and increasing your vegetable intake is a good recommendation from vegan,” she said. “But again, anything too extreme one way or another isn’t healthy, for your physical or your mental health.”

So to all you Paleoheads, consider investing in a box of Cheerios. You'll thank me later.