Mediterranean and DASH are among the best diets for heart health, according to new American Heart Association rankings

• Cardiologists ranked 10 popular diets based on how healthy they are for your heart.
• The DASH and Mediterranean diets were top-ranked, with flexible choices and nutrient-rich foods.

Sorry, keto and paleo fans — low-carb, high-fat diets are among the worst for a healthy heart, while flexible, plant-based diets are among the best, according to cardiologists.

The diets went head-to-head in new rankings from the American Heart Association, based on analysis from doctors, dietitians, and nutrition researchers. The committee looked at 10 popular diets, evaluating them based on nine criteria for a heart-healthy diet such as inclusion of whole grains, a variety of veggies, healthy fats like those found in seafood and nuts, and avoidance of added sugar, oils, salt, and alcohol.

The diets were then grouped into four tiers from best to worst scores, in rankings published in scientific statement published April 27 in the AHA journal Circulation.

The rankings are intended to help guide people, including medical experts, to make heart-healthy eating choices in the midst of confusing and sometimes contradictory information online, according to Christopher D. Gardner, Ph.D in nutrition science, chair of the statement writing committee, and professor of medicine at Stanford University.

"The number of different, popular dietary patterns has proliferated in recent years, and the amount of misinformation about them on social media has reached critical levels," Gardner said in a press release. "The public — and even many health care professionals — may rightfully be confused about heart-healthy eating, and they may feel that they don't have the time or the training to evaluate the different diets."

Flexible, mostly vegetarian diets are best for your heart, doctors said

The highest ranking diet, with a perfect score, was the DASH diet. Specifically designed to lower high blood pressure and heart disease risk, the DASH diet emphasizes whole grains, lean proteins, and produce, while reducing red meat, salt, and sugar.

Other top ranking diets included the Mediterranean diet, based on traditional eating patterns in countries like Italy and Spain, and the mostly plant-based pescetarian and vegetarian diets with some fish, eggs, and dairy.

The high scores reflect the fact that these diets include plenty of plant-based nutrients and a variety of healthy options so people are more likely to stick to them regardless of their budget and preferences, Gardner said in the press release.

Vegan and low-fat diets can be healthy, but may be high in processed foods

Other plant-based eating styles like vegan and low-fat (or volumetric) diets were given similarly high marks for including lots of veggies and plant-based protein.

However, vegan diets have have higher certain nutrient deficiencies, particularly protein, amino acids, and B vitamins, and require careful planning, the committee noted.

Vegan and low-fat diets also run the risk of relying on foods that are highly processed to fit those dietary preferences which can include too much added sugar, salt, or oils.

Very low-fat diets ranked even lower on the list, since they also exclude heart-healthy foods like nuts and seafood.

Keto and paleo diets could be missing key nutrients for heart health

Low-carb diets ranked at the bottom half of the list, with the high-fat keto diet in dead last, followed by the paleo diet based on eating habits of pre-agricultural humans.

The diets clash with foundational AHA guidelines because they eliminate or severely restrict many of the foods recommended, such as whole grains, fruit, and vegetables. As a result, low-carb diets often lack fiber, a nutrient associated with myriad health benefits like lower risk of disease, healthy blood sugar, and reduced cholesterol.

Low-carb and paleo diets also tend to rely heavily on animal products, and therefore include more saturated fat and cholesterol than the AHA recommends for optimal heart health, the committee noted.

While people may see short-term benefits like weight loss and better blood sugar on low-carb and paleo diets, they may be ineffective over time, in part because people may struggle to follow them, according to Gardner.

"They are highly restrictive and difficult for most people to stick with long term," he said in the press release. "A diet that's effective at helping an individual maintain weight loss goals, from a practical perspective, needs to be sustainable."