Effects of dietary sucrose and fibers on blood pressure in hypertensive rats.

In spontaneously hypertensive rats (SHR), two separate studies examined effects on systolic blood pressure (SBP) and other cardiovascular parameters of different concentrations of sucrose compared to starches, soluble fibers (guar, psyllium), and insoluble fibers (cellulose, wheat bran). In the initial study, four diets were tested. The first diet was relatively high in sucrose calories (50%) and low in protein calories (17%)--"high sucrose"; the second diet was relatively low in sucrose (11%) and high in protein (56%) calories--"low sucrose". The third and fourth diets resembled the first and second diets respectively, but cornstarch replaced sucrose--"high and low starch". Initial SBP in each group averaged approximately 168 mmHg. After 2 weeks of ingesting the special diets, SBP of the high sucrose group rose rapidly and significantly, eventually rising above 200 mmHg by the termination of examination. The other 3 groups maintained the original SBP until after the 3rd week when the low sucrose group developed a rapid and significant SBP elevation approaching 200 mmHg. SBP of high starch and low starch remained below 181 mmHg for the two months of study. Platelets obtained at the termination of the study from the sucrose groups compared to the starch groups showed increased aggregatory responses to collagen and ADP. Further, significant elevations of triglycerides and cholesterol in the high sucrose group were found. The former parameter was also significantly elevated in the low sucrose group. In the second study, adding guar and psyllium to high sucrose diets delayed sugar-induced hypertension, while cellulose and wheat bran virtually showed no effects. Serum insulin concentrations correlated positively with SBP, serum triglycerides, and glucose--not cholesterol. Accordingly, sucrose compared to starch ingestion in SHR can adversely influence SBP and various other cardiovascular risk factors. These effects can be delayed by the presence of soluble fibers, but not insoluble fibers, in the diets.