Fiber may help keep  the heart healthy, possibly by lowering blood pressure.  In this study, 2,195 men and women visited doctors on days one and two, and again on days 21 and 22, reporting their diets, while doctors took multiple blood pressure and urine samples. Doctors considered differences in lifestyle and body mass index scores and found that increaing total fiber by 6.8 grams per 1,000 calories lowered systolic blood pressure (SBP) 1.69 mmHg.  Insoluable fiber was most efective, with an increase of 4.6 grams per 1,000 calories lowering SBP 1.81 mmHg.  Insoluble fiber helps food pass through the gut more quickly.