While it generally seems like a good idea to eat fruit and vegetables, a lot of research is still being done to figure out exactly how the plant foods improve your health. For this study, researchers used a long-term study to look at eating habits, cardiovascular disease, and cancer.

What the researchers wanted to know: What's the association between eating fruits and vegetables and major chronic diseases?

What they did: The researchers worked on the Nurses' Health Study, which recruited 121,700 female nurses in 1976 and has been going ever since, and the Health Professionals' Follow-up Study, which started in 1986 with 51,529 male health professionals. The participants filled out a health questionnaire at the beginning of the study and more questionnaires every two years—including, in some years, food frequency questionnaires.

What they found: People who ate a lot of fruits and vegetables, especially leafy green veggies, were less likely to develop cardiovascular disease. But fruits and vegetables didn't protect against cancer.

What the study means to you: Stop me if you've heard this before, but you probably should eat more fruits and vegetables.

Caveats: Getting people to report their own diets is notoriously difficult. They may forget. They may selectively remember the heaping plate of vegetables they ate last night while blocking out memory of those five milkshakes last week. The writers of an editorial published with this article say that all this makes it extremely difficult to really know how diet affects health and that there just isn't enough good evidence yet to say whether fruits and vegetables protect against cancer.

Find out more: The Centers for Disease Control and Prevention says to eat five fruits and vegetable servings a day and has recipes.

Read the article: Hung, H.-C., et al. "Fruit and Vegetable Intake and Risk of Major Chronic Disease." Journal of the National Cancer Institute. Nov. 3, 2004, Vol. 96, No. 21, pp. 1577–1584.

Abstract online: http://jncicancerspectrum.oupjournals.org