CHICAGO (AP) -- What we know for sure about diet and what protects the heart is a relatively short list.

That's the conclusion of new research based on an analysis of nearly 200 studies involving millions of people.

Vegetables, nuts and the Mediterranean diet made the grocery list of "good" heart foods. On the "bad" list: starchy carbs like white bread and the trans fats in many cookies and french fries.

The "question mark" list includes meat, eggs and milk and many other foods where there's not yet strong evidence about whether they're good or bad for the heart.

"I do research. I also buy groceries for my family every week," said study co-author Dr. Sonia Anand of McMaster University in Hamilton, Ontario, who hopes the findings "decrease the confusion around what we should eat and what we shouldn't eat."

The study, appearing in Monday's Archives of Internal Medicine, doesn't actually read like a shopping list. It's a complicated explanation of how the researchers rated 189 prior studies on the topic.

In short, they used criteria developed by Sir Austin Bradford Hill, the late British scientist who helped establish a link between smoking and lung cancer. When multiple studies on a certain food or diet showed a strong link with better heart health, that put the food or diet at the top of the list.

Dr. JoAnn Manson, chief of preventive medicine at Harvard's Brigham and Women's Hospital, said the analysis underlines that there's a big gray area and a shorter list of foods with strong links to heart health.

Linda Van Horn, professor of preventive medicine at Northwestern University's Feinberg School of Medicine, said the analysis is more about the strengths and limits of previous studies than advice for consumers.

But she said the analysis reaffirms the benefits of a Mediterranean diet - rich in vegetables, nuts, whole grains, fish and olive oil - compared to a Western diet, heavy on processed meats, red meat, refined grains and high-fat dairy.

Beyond that, she found no reason to tear up your grocery list based on the findings.

"It's really about the totality of the usual eating pattern, rather than whether you ate a hot dog on opening day of baseball season," Van Horn said.

The Heart and Stroke Foundation of Canada and the Canadian Institutes of Health supported the research.

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