Just in case you didn't already know, the amount of fiber we eat prevents all chronic diseases including cancer and heart disease.
The American Journal of Clinical Nutrition just published a study (March 10, 2010) that found dietary fiber is associated with increased leukocyte telomere length. Recent studies have found leukocyte telomere length (or the length of specific white blood cells) as a strong predictor of inflammation and diseases of aging, including cancer. The longer the length, the lower the risk of chronic disease, and vice versa.
This study also found smaller waist circumference is associated with increased leukocyte telomere length. Good thing fiber helps with weight loss too!