Keto, Mediterranean or Vegan: Which Diet Is Best for the Heart?

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CHICAGO — In the room, physicians and nutritionists clung to their idea of an ideal diet like a parent clings to his or her child.

On Nov. 10, here at the American Heart Association's Scientific Sessions annual meeting, a group of panelists discussed which diets they thought were the best for heart health, pulling on already-published data from recent years. Though there wasn't a clear winner, the panelists agreed that an ideal diet is one that is high in vegetables, high in non-processed whole foods, and low in processed meat, added sugar and carbohydrates.

Though the best diet "depends on the individual … I also firmly believe that everyone should focus on a foundational diet that includes all of [these] agreed upon components," one of the panelists, Christopher Gardner, director of Nutrition Studies at Stanford Prevention Research Center, told Live Science afterwards. [Diet and Weight Loss: The Best Ways to Eat]

But even those agreed upon components would be a major dietary change for most Americans — and only once you get down to that "foundational diet" is there "room to 'biohack' your way to your own personalized diet," Gardner said.

What's more, the best diet is also "the one you can stick to," and more specifically, the "highest quality" one you can stick to, he said.

Veggies, meat and lots of olive oil

The panelists discussed three diets — vegan, Mediterranean and keto — and their effects on heart health.

The vegan diet

The vegan diet calls for the elimination of all meat and animal products from the diet, and focuses primarily on veggies.

"If you substitute animal protein with plant protein, you would decrease mortality… [and] cardiovascular risk factors" over a period of time, said Dr. Kim Williams, a cardiologist at Rush University Medical Center in Chicago, during the session. Past studies have shown that the risk decreases the most when you stop eating processed red meat, he added. Compared with a diet high in meat, a plant-based diet also reduces high blood pressure and there's evidence it also decreases levels of C-reactive protein, a marker of inflammation in the body, he said.  

But even without the vegan diet, "if everybody went from [eating] processed red meat to [eating] just regular red meat, we would dramatically decrease cardiovascular death in this country," Williams said.

Still, the vegan diet isn't perfect. The diet can lead to a vitamin B12 deficiency — a vitamin that's found in animal products. Vitamin B12 deficiency can lead to reduced red blood cell counts, or anemia. (Another cause of anemia is iron deficiency.) What's more, the vegan diet is not going to work if, along with your veggies, you're also eating plates of fried food, Williams added. [7 Tips for Moving Toward a More Plant-Based Diet]

The Mediterranean diet

The Mediterranean diet allows for animal protein, but fish is preferred over red meat. Extra-virgin olive oil takes a lead role in this diet, which also includes nuts, lots of vegetables, fruits and wine (in moderation). There's evidence that the Mediterranean diet reduces levels of "bad" cholesterol and is associated with a reduced risk of death from heart disease, according to the Mayo Clinic.

This summer, however, the Mediterranean diet took a hit when a major study touting its benefits was retracted because of problems with the methodology. Though some experts said that the retraction significantly weakened the claim that the Mediterranean diet is heart-healthy, others said there's enough other research showing it is beneficial, and that they'd continue to recommend it, Live Science reported in June.

The principal investigator of that trial, Dr. Miguel Martínez-Gonzalez, an epidemiologist at the University of Navarra in Spain, was also a panelist at Saturday's talk. He noted that even after the team retracted the study and reanalyzed the data, the findings, for the most part, held true: The diet is still heart-healthy.

The keto diet

Finally, in this non-exhaustive list of diets, the ketogenic diet. This is one that's low in carbohydrates and high in fat, with a moderate amount of protein. Dr. Sarah Hallberg, the medical director at Virta Health, stressed during the session that the keto diet "it is a whole food diet, .. [not] a hotdog and cheese diet." 

Carbohydrates can come from non-starchy vegetables, nuts and seeds, some berries, or dairy, but not from grains, potatoes or sugar, Hallberg said. According to Hallberg, this diet also decreases risk factors for cardiovascular disease. (Of note, Virta Health is a company that claims to be able to reverse type 2 diabetes without medications or surgery, instead by reducing carbohydrates in a person's diet.)

However, other experts have raised concerns that people on the keto diet are more prone than others to regain weight they've lost because the diet can be difficult to stick to in the long run, Live Science reported in May. What's more, the high levels of fat and cholesterol in the keto diet may be harmful for heart health.

Real food is better than processed

Though all the panelists felt strongly about the diet they advocated for, there was some common ground. The major point that the panelists agreed on is that whole foods are much better than processed foods. [11 Ways Processed Food Is Different from Real Food]

With that in mind, researchers don't need more studies to tell us what food is healthy and what isn't, but rather, they need to focus on how to get people to stick to healthy diets, Gardner said.

This can involve motivating people to prepare meals at home, educating people on the societal and planetary consequences of what they eat — such as the effect of eating meat on global warming and climate change, animal rights and human labor abuses — and by creating national health policies that can help make healthier food more affordable.

"Almost anything is better than the way most Americans are eating now," said panel moderator Dr. David Katz, a preventive-medicine specialist at Yale University's Yale-Griffin Prevention Research Center in Derby, Connecticut. "'America runs on Dunkin'' and multicolored marshmallows are 'part of a complete breakfast' — fix that, and things will tend to improve."

Originally published on Live Science.

Yasemin Saplakoglu
Staff Writer

Yasemin is a staff writer at Live Science, covering health, neuroscience and biology. Her work has appeared in Scientific American, Science and the San Jose Mercury News. She has a bachelor's degree in biomedical engineering from the University of Connecticut and a graduate certificate in science communication from the University of California, Santa Cruz.