High Anthocyanin Intake Is Associated With a Reduced Risk of Myocardial Infarction in Young and Middle-Aged Women, Circulation, January 2013The study population was >93,000 women from the Nurses' Health Study 2. The benefit was seen in high consumers vs. low consumers and it was statistically adjusted for a number of covariates - behaviors or qualities that you think might result in this effect.1
Anthocyanins are merely pigments. They appear blue, purple, or red. They're found in many plants but are, as you'd guess, especially concentrated in blue, purple, and red plant tissues. Blueberries, cranberries, black and red raspberries, blackberries, cherries, eggplant skin, black rice, black soybeans, red and black grapes, and red cabbage are good sources.
Separately, they found:
"Combined intake of 2 anthocyanin-rich foods, blueberries and strawberries, tended to be associated with a decreased risk of [heart attack] in a comparison of those consuming >3 servings a week and those with lower intake."But that could have been because blueberries and strawberries are a major source of anthocyanins in the US diet, at least they were in this cohort.
There was also a dose-response effect. The more anthocyanins the women ate, the greater their benefit: "For every 15-mg increase in intake of anthocyanins, the relative risk of MI decreased by 17% in the multivariate model."
Interestingly, this reduction in heart attack risk was independent of total fruit and vegetable consumption. So, the adage "Eat your veggies." wouldn't do it here. Maybe "Eat your violet veggies."