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food for thought

From low-carb to vegan to paleo, social media dishes out plenty of information (not all of it science-based) on countless diets to follow and different ways to follow them.

But which ones are best – or worst – for your heart?

A new scientific statement from the American Heart Association (AHA) answers this question. Here’s what to know, plus tips to increase the heart-health benefits of different dietary patterns.

About the evidence review

For the scientific statement, published in the journal Circulation, a team of nutrition scientists assessed how closely 10 popular eating patterns aligned with the AHA Dietary Guidance to Improve Cardiovascular Health.

Each eating pattern was ranked on a scale of one to 100; a higher score indicated greater alignment. Based on its score, the diet was assigned to one of four tiers.

Dietary patterns evaluated included DASH-style diets (e.g. Dietary Approaches to Stop Hypertension, Nordic), the Mediterranean diet, vegetarian-style diets (e.g., pescatarian, lacto-ovo, vegan), low-fat, very low-fat (e.g., Ornish, Pritikin, Esselstyn), low-carbohydrate (e.g., Zone, South Beach), very low-carbohydrate (e.g., ketogenic, Atkins 20) and paleolithic (e.g., paleo).

AHA’s dietary guidance for heart health

The AHA Dietary Guidance to Improve Cardiovascular Health, updated and published in 2021, provides evidence-based advice on dietary components that best promote cardiovascular health.

The guidance recommends eating a wide variety of fruits and vegetables, choosing whole grains over refined grains, emphasizing protein from plants (e.g., beans and lentils, soy foods, nuts) as well as fish and seafood, especially those plentiful in omega-3 fatty acids (e.g., salmon, trout, sardines, mackerel, herring).

The AHA advises limiting foods that are high in saturated fat (e.g., high-fat dairy, fatty meats, coconut oil, palm oil), salt and added sugars. Choosing minimally processed foods instead of ultra-processed foods is also recommended.

The organization doesn’t support drinking any amount of alcohol to improve heart health.

Scoring popular diet patterns

Diet scores ranged from 31 to 100. Only the DASH diet received a perfect score.

Dietary patterns ranked in “tier one” (score > 85) aligned closely with the 2021 AHA Dietary Guidance. These included the DASH, Mediterranean, pescatarian and lacto-ovo vegetarian diets (lacto-ovo vegetarian diets exclude animal foods except for dairy and eggs).

All eating patterns were plentiful in vegetables, fruit, whole grains and plant-protein sources.

The Mediterranean diet scored slightly lower (89) than the DASH diet because, unlike the DASH diet, it does not address salt intake and allows one alcoholic drink a day.

Vegan and low-fat diets fell into “tier two” (score 75-85) and can also support optimal cardiovascular health. These eating patterns emphasize vegetables, fruit, pulses (beans and lentils) and nuts and limit added sugars and alcohol.

Include these anti-inflammatory foods in a heart-healthy diet

The researchers noted, though, that vegan diets should focus on healthy plant proteins rather that processed meat alternatives. And since low-fat diets treat all fats equally, it’s important to choose heart-healthy unsaturated fats over saturated fats.

Low-carbohydrate and very low-fat diets were grouped in “tier three” (score 55 to 74). Both did well for recommending non-starchy vegetables, fruits and pulses. Low-carbohydrate diets also recommend eating nuts and fatty fish.

These eating patterns received lower scores because they limit AHA priority foods including whole grains, whole fruit and pulses (low-carbohydrate diets) and unsaturated plant oils (very low-fat diets).

AHA’s bottom tier diets

Very low-carbohydrate diets (e.g., ketogenic, paleo, Atkins 20) were ranked as “tier four” diets (score <55) because they aligned poorly with the AHA’s dietary guidance for cardiovascular health.

These eating patterns typically restrict carbohydrate intake to less than 10 per cent of daily calories and, in so doing, drastically limit or eliminate whole grains, fruit and pulses, healthy carbs known to benefit heart health.

Ketogenic diets that emphasize fat sources high in saturated fat (e.g., butter, cream, cheese, bacon) can also increase LDL (bad) cholesterol in the bloodstream.

To improve the nutritional benefits of a keto dietary pattern, the researchers recommend focusing on healthier plant-based fats such as plant oils, avocado, nuts and seeds.

They also suggest taking a daily multivitamin and mineral supplement that includes potassium and magnesium, nutrients which may be limited in these diets.

On the plus side, very low-carbohydrate diets emphasize non-starchy vegetables, nuts and fish and limit refined grains and added sugars.

This new scientific statement is intended to be used as a tool by doctors, who receive little training in nutrition, when discussing diet with their patients. The report includes practical tips to improve adherence or enhance the healthfulness of each dietary pattern.

Leslie Beck, a Toronto-based private practice dietitian, is director of food and nutrition at Medcan. Follow her on Twitter @LeslieBeckRD

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