When scientists study human populations and their eating habits, they can draw some conclusions about different dietary habits and the link with certain diseases.
For example, populations that eat more fruits and vegetables with less fat suffer from fewer heart attacks and strokes. Sometimes it is tough to prove exactly how these foods work to prevent disease although we know they can.  
     At the 2007 Annual Meeting of the American Association of Cancer Research, researchers presented promising evidence that diet and lifestyle can help prevent cancer.
One of the studies presented dealt with prevention of cancers of the head and neck. Head and neck cancer is the sixth leading cause of cancer-related deaths worldwide, resulting in more than 350,000 deaths each year. This study was conducted by the National Cancer Institute with a half-million AARP members, men and women, over the age of 50. Those who ate six servings of fruits and vegetables for each 1000 calories consumed had 29 percent lower risk than the study participants who ate only one and a half servings per 1000 calories. Those members who ate just one additional serving of fruit and vegetables per day had a six percent reduction in cancer risk. The more servings they ate, the greater the reduction in risk.
     What is a typical serving of fruit and vegetables? One fruit serving would be a medium size whole fruit, one-half cup of cut fruit, or six ounces of fruit juice. A vegetable serving is one-half cup cooked or one cup raw. In this particular study, the vegetable intake appeared to have the strongest association with prevention of this type of cancer.  In a previous article, I discussed the new campaign called “Fruits and Veggies, More Matters,” and you can access information, recipes and other helpful tips at www.fruitsandveggiesmorematters.org .
     The Cancer Research Center of Hawaii presented information about diet and prevention of pancreatic cancer. The study involved more than 183,518 residents of California and Hawaii. The researchers were interested in dietary compounds known as flavonols which occur in many fruits and vegetables. The best sources of these compounds are broccoli, kale, berries, apples, onions, spinach, and some cabbages.
People who ate the greatest amount of flavonols had a 23 percent reduction in risk of developing pancreatic cancer compared to those who ate the least. If the participant was a  smoker, the benefit appeared to be greater, with a 59 percent reduction in risk compared to those who ate the least flavonols. Smokers are at a greater risk for pancreatic cancer already so other than stopping smoking, eating more fruits and vegetables may be a wise lifestyle change to consider.
    University of California researchers studied the effect of two different compounds on breast and ovarian cancer cells. The first compound is found in soy products and the other comes from the digestion of cruciferous vegetables such as broccoli, cauliflower, turnips, collards, brussel sprouts, and cabbage. In the lab, these compounds appeared to limit the movement of cancer cells and may prove useful in preventing the spread of cancer.