Researchers analyzed nutrition studies in a new review published in the Journal of the American College of Cardiology, which intends to cut through the confusion about the best dietary patterns to reduce heart disease. The review concludes current evidence strongly supports eating plenty of fruits, vegetables, whole grains, legumes, and nuts in moderation. Although more controversial, some heart–healthy diets may also include very limited quantities of lean meat, fish, low–fat and nonfat dairy products, and liquid vegetable oils.

The review examined several of these dietary patterns as well as "hypes and controversies" surrounding nutrition to provide clinicians with information to aid in discussions with patients about dietary habits.

"There is a growing consensus that a predominantly plant–based diet that emphasizes green, leafy vegetables, whole grains, legumes and fruit is where the best improvements are seen in heart health," Freeman said.

Other nutrition topics covered in the review include:

• Eggs and cholesterol. Although a government report issued in 2015 dropped specific recommendations about upper limits for cholesterol consumption, the review concludes, "it remains prudent to advise patients to significantly limit intake of dietary cholesterol in the form of eggs or any high cholesterol foods to as little as possible."
• Vegetable oils. Coconut oil and palm oil should be discouraged due to limited data supporting routine use. The most heart–healthy oil is olive oil, though perhaps in moderation as it is still higher calorie, research suggests.
• Berries and antioxidant supplementation. Fruits and vegetables are the healthiest and most beneficial source of antioxidants to reduce heart disease risk. There is no compelling evidence adding high–dose antioxidant dietary supplements benefits heart health.
• Nuts. Nuts can be part of a heart–healthy diet. But beware of consuming too many, because nuts are high in calories.
• Juicing. While the fruits and vegetables contained in juices are heart–healthy, the process of juicing concentrates calories, which makes it is much easier to ingest too many. Eating whole fruits and vegetables is preferred, with juicing primarily reserved for situations when daily intake of vegetables and fruits is inadequate. If you do juice, avoid adding extra sugar by putting in honey, to minimize calories.
• Gluten. People who have celiac disease or other gluten sensitivity must avoid gluten—wheat, barley and rye. For patients who don't have any gluten sensitivities, many of the claims for health benefits of a gluten–free diet are unsubstantiated, the researchers conclude.
• The authors also addressed why there can be confusion surrounding nutrition studies. According to Freeman, many of these studies are funded and/or influenced by the food industry and may have some bias.

"In addition, it's very hard to separate the effects of specific nutrients in a food. For example, an apple contains many components including proteins, vitamins and fiber," he said.

Many people who eat a healthy diet also have other healthy lifestyle behaviors, such as regular physical activity, getting enough sleep, and not smoking, and it can be hard to pinpoint the diet's effect separate from these other behaviors.

"And some nutrition studies tend to be based on surveys that rely on people's memories of what they ate, which isn't always reliable," Freeman said.

"The founder of modern medicine, Hippocrates, said, 'Let food be thy medicine,'" Freeman said. "But the vast majority of doctors have little nutrition training. If we can get doctors, and especially cardiologists, to understand the value of nutrition in medical practice, we can have a greater impact on reducing heart disease, and it is certainly cost–effective."