A fascinating study published earlier this month in the Archives of Internal Medicine came to some surprising conclusions about some of the foods we normally consider to be heart-healthy (or unhealthy). It wasn’t a single clinical trial but rather a review article that looked at the results of more than 140 randomized and controlled human clinical trials—the research gold-standard—published between 1950 and 2007.

Based on the evidence provided by these studies, researchers from McMaster University in Ontario divided dietary interventions (or nutrients) into three categories: strong, moderate, or weak causal relationships between consumption and decreased—or increased—risk of developing heart disease.

The researchers concluded that only a few foods or dietary patterns have a significant impact on your risk for heart disease, whereas the vast majority of things that we dietitians typically recommend have only weak associations—or may even lack sufficient evidence to say that these foods impact heart disease at all.

For example, I’ve always recommended that individuals use fats and oils rich in polyunsaturated and monounsaturated fats in place of saturated fats to reduce risk of heart disease, but this study suggests that only monos have been sufficiently studied and reduce risk and at this time there’s not enough evidence around polys.

Another example is eggs, long thought to have a negative impact on our heart health due to high cholesterol levels. This analysis found insufficient evidence to suggest that.

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The only superfoods that did live up to their heart-healthy reputations included vegetables, nuts, monounsaturated fat, and a Mediterranean-style diet.  Unfortunately, the typical American-style diet was found to be equally bad as these items are good.

Bottom line: Isolating specific foods or nutrients is probably not the best way to eat yourself to a healthier heart. Instead, focusing on a Mediterranean-style diet rich in nuts, vegetables, seafood, and many nutrients suspected to reduce cardiovascular risk is probably the best advice until we know more.

Here are some of the foods with strong, moderate, or weak associations with heart disease, according to the new study:

Strongest heart healers
•    Vegetables
•    Nuts
•    Mediterranean-style eating
•    Monounsaturated fat

Strongest heart hurters
•    Trans fats
•    High glycemic index foods or high glycemic load diets
•    An “American” diet high in meat, dairy, and processed foods

Moderate heart healers
•    Seafood and marine omega-3 fatty acids
•    Whole grains
•    Fruit
•    Fiber
•    Diet rich in folate, beta-carotene, and vitamins E and C
•    Alcohol

Insufficient evidence of either helping or hurting
•    Vitamin E and C supplements
•    Total fat
•    Saturated fat
•    Polyunsaturated fat
•    Meat
•    Eggs
•    Milk