Searching for interesting nutritional information, the article below from Harvard School of Public Health crossed my way. It's worth reading!
"Eat your fruits and vegetables"
is one of the tried and true recommendations for a healthy diet. And for good reason. Eating plenty of vegetables and fruits can help you ward off heart disease and stroke, control blood pressure, prevent some types of cancer, avoid a painful intestinal ailment called diverticulitis, and guard against cataract and macular degeneration, two common causes of vision loss.
Over the past 30 years or so, researchers have developed a solid base of science to back up what generations of mothers preached (but didn't always practice themselves). Early on, fruits and vegetables were acclaimed as cancer-fighting foods. In fact, the ubiquitous 5 A Day message (now quietly changing to Fruits and Veggies: More Matters) seen in produce aisles, magazine ads, and schools was supported in part by the National Cancer Institute. The latest research, though, suggests that the biggest payoff from eating fruits and vegetables is for the heart.
Vegetables, Fruits, and Cancer
Numerous early studies revealed what appeared to be a strong link between eating fruits and vegetables and protection against cancer. But because many of these were case-control studies, where people who already have a certain health outcome (cases) are compared to people who do not have that outcome (controls), it is possible that the results may have been skewed by problems inherent in these types of studies; people with illnesses, for example, often recall past behaviors differently from those without illness, which can lead to potential inaccuracy in the information that they provide to study investigators.
Cohort studies, which follow large groups of initially healthy individuals for years, generally provide more reliable information than case-control studies because they don't rely on information from the past. And data from cohort studies have not consistently shown that a diet rich in fruits and vegetables prevents cancer in general. For example, in the Nurses' Health Study and the Health Professionals Follow-up Study, over a 14-year period, men and women with the highest intake of fruits and vegetables (8+ servings a day) were just as likely to have developed cancer as those who ate the fewest daily servings (under 1.5). (2)
A more likely possibility is that some types of fruits and vegetables may protect against certain cancers. A massive report by the World Cancer Research Fund and the American Institute for Cancer Research suggests that non-starchy vegetables—such as lettuce and other leafy greens, broccoli, bok choy, cabbage, as well as garlic, onions, and the like—and fruits "probably" protect against several types of cancers, including those of the mouth, throat, voice box, esophagus, and stomach; fruit probably also protects against lung cancer. (7)
http://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/vegetables-full-story/index.html