Thinking about trying a new diet but not sure which way to go? An evidence-based analysis of 10 popular eating patterns shows some promote heart health much better than others.
A scientific statement from the American Heart Association published Thursday in its journal Circulation found the Mediterranean, DASH-style, pescetarian and vegetarian eating patterns strongly aligned with heart-healthy eating guidelines, while the popular paleo and ketogenic diets contradicted them.
"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," statement writing committee chair Christopher D. Gardner said in a news release. Gardner is the Rehnborg Farquhar Professor of Medicine at Stanford University in California.
"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," he said. "We hope this statement serves as a tool for clinicians and the public to understand which diets promote good cardiometabolic health."
The report evaluates how well each of 10 popular diets or eating patterns aligns with nine of 10 features of AHA's dietary guidance for heart-healthy eating: consuming a wide variety of fruits and vegetables; choosing mostly whole grains instead of refined grains; using liquid plant oils rather than tropical oils; eating healthy sources of protein, such as from plants, seafood or lean meats; minimizing added sugars and salt; limiting alcohol; choosing minimally processed foods instead of ultraprocessed foods; and following this guidance wherever food is prepared or consumed. The one feature not included in scoring was the energy balance needed to maintain a healthy weight, because it is influenced by factors other than dietary choices, such as physical activity levels.
The diets were rated on a scale of 1 to 100 for how well they adhered to AHA's guidance.
The statement did not review commercial dietary programs, those that are followed for fewer than 12 weeks, practices such as intermittent fasting or time-restricted eating, or diets used to manage non-cardiovascular health conditions.
The diets were divided into four tiers based on their scores, which ranged from 31 to 100. Only one – the DASH (Dietary Approaches to Stop Hypertension) eating plan – got a perfect score. This eating pattern is low in salt, added sugar, tropical oil, alcohol and processed foods and high in non-starchy vegetables, fruits, whole grains and legumes. Proteins mostly come from plant sources, such as legumes, beans or nuts, along with fish or seafood, lean poultry and meats and low-fat or fat-free dairy products.
The Mediterranean eating pattern had a slightly lower score (89) because unlike DASH, it allows for moderate alcohol consumption and does not address added salt. The pescetarian diet (92), which allows for seafood in addition to plant-based foods, and vegetarian diet (86) also were in the top tier.
"If implemented as intended, the top-tier dietary patterns align best with the American Heart Association's guidance and may be adapted to respect cultural practices, food preferences and budgets to enable people to always eat this way, for the long term," Gardner said.
Vegan and low-fat diets (78 each) fell into the second tier. While they emphasize fruits, vegetables, whole grains, legumes and nuts, while limiting alcohol and added sugars, the vegan diet is so restrictive it could be challenging to follow long-term or when eating out and may increase the risk of vitamin B-12 deficiency, which can lead to anemia.
There also are concerns that low-fat diets treat all fats equally, whereas the AHA guidance calls for replacing saturated fats with healthier fats. People eating low-fat diets also may overconsume less healthy sources of carbohydrates, such as added sugars and refined grains. But these concerns may be overcome with proper nutritional counseling and education.
Very low-fat (72) and low-carb diets (64) fall into the third tier. Both restrict foods that are emphasized in the AHA's dietary guidance. For example, very low-fat diets restrict nuts and healthy plant oils, and low-carb diets restrict consumption of fruits, grains and legumes, which can lead to eating less fiber and higher amounts of saturated fats.
Paleolithic (53) and very low-carb/ketogenic diets (31) fall into the fourth, or bottom, tier. Both, which are used for weight loss, align poorly with heart-healthy eating guidelines and have not been shown to be any more effective for weight loss than less restrictive diets over the long term. Both also are high in fat without limiting saturated fats.
The tier 4 diets, Gardner said, "are highly restrictive and difficult for most people to stick with long-term. While there will likely be short-term benefits and substantial weight loss, it isn't sustainable. A diet that's effective at helping an individual maintain weight-loss goals, from a practical perspective, needs to be sustainable."
Gardner cautioned that conflicting information about research into popular diets can confuse people trying to follow them.
"We often find that people don't fully understand popular eating patterns and aren't following them as intended," he said. "When that is the case, it is challenging to determine the effect of the 'diet as intended' and distinguish that from the 'diet as followed.' Two research findings that seem contradictory may merely reflect that there was high adherence in following the diet in one study and low adherence in the other."
The authors noted that more research and education are needed to show people how to follow eating patterns in ways that are culturally relevant to ensure their effectiveness. Efforts also need to be made to include historically marginalized groups in the research to reduce the impact of structural racism on diet-related diseases, and policies are needed to dismantle unjust practices that limit access to healthy foods in some communities, according to the report.