Effect of a very-high-fiber vegetable, fruit, and nut diet on serum lipidsand colonic function

We tested the effects of feeding a diet very high in fiber from fruit and v egetables. The levels fed were those, which had originally inspired the die tary fiber hypothesis related to colon cancer and heart disease prevention and also may have been eaten early in human evolution. Ten healthy voluntee rs each took 3 metabolic diets of 2 weeks duration. The diets were: high-ve getable, fruit, and nut (very-high-fiber, 55 9/1,000 kcal); starch-based co ntaining cereals and legumes (early agricultural diet); or Low-fat [contemp orary therapeutic diet). All diets were intended to be weight-maintaining ( mean intake, 2,577 kcal/d). Compared with the starch-based and low-fat diet s, the high-fiber vegetable diet resulted in the largest reduction in low-d ensity lipoprotein (LDL) cholesterol (33% +/- 4%, P < .001) and the greates t fecal bile acid output (1.13 <plus/minus> 0.30 g/d, P = .002), fecal bulk (906 +/- 130 g/d, P < .001), and fecal short-chain fatty acid outputs (78 <plus/minus> 13 mmol/d, P < .001). Nevertheless, due to the increase in fec al bulk, the actual concentrations of fecal bile acids were lowest on the v egetable diet (1.2 mg/g wet weight, P = .002). Maximum lipid reductions occ urred within 1 week. Urinary mevalonic acid excretion increased (P = .036) on the high-vegetable diet reflecting large fecal steroid tosses. We conclu de that very high-vegetable fiber intakes reduce risk factors for cardiovas cular disease and possibly colon cancer. Vegetable and fruit fibers therefo re warrant further detailed investigation. Copyright <(c)> 2001 by W.B. Sau nders Company.