Journal Name:
Am J Clin Nutr
Article Title:
Effect of psyllium in hypercholesterolemia at two monounsaturated fatty acid intakes
Date Written:
1997
Volume:
65
Number:
Page:
1524
Author(s):
Jenkins, D; Wolever, T.; Vidgen, E.; Kendall, C.; Ransom, T.; Mehling, C.; Mueller, S.; Cunnane, S.; O'Connell, N.; Stechell, K.; Lau, H.; Teitel, J.; Garvey, M.; Fulgoni, V.; Connelly, P.; Patten, R.; Corey, P.
Article:
It was demonstrated at least two decades ago that viscous soluble fibers, such as guar gum, beta-glucan, psyllium and mucilage, reduce serum total cholesterol levels, with primarily in LDL-C. A decreased risk of coronary artery disease (CAD) is associated with LDL-C lowering. However, many dietary interventions aimed at reducing LDL-C levels also result in a reduction in HDL-C levels, with no overall change in the ratio of LDL to HDL cholesterol. Research investigating a wide range of viscous fiber sources with background diets containing higher amounts of fat, report no significant reductions in HDL-C, unlike background diets containing very low fat levels. It is unclear whether the HDL-c lowering effect observed is due to the type of viscous fiber or the low amount of fat used in the background diets. The objective of this study was to investigate whether the lipid-lowering effect of psyllium, a soluble viscous fiber that has not been reported to lower HDL-C, can be modified by varying levels of monounsaturated fat in the diet.
Two separate studies were performed. Inclusion criteria for participants included an LDL-C concentration of >4.1mmol/L and body mass indices of 19-32 (kg/m2). The first study included 32 healthy subjects (15 men, 17 women) who consumed a 2-month run-in diet (NCEP Step-2 diet: <30% fat, <7% SFA, <200mg/dl cholesterol). In a random cross-over design, participants then consumed a metabolically controlled diet containing either psyllium (1.4g/MJ) or wheat bran (2.9 g wheat bran - control) for a one month period each. Each metabolic diet included 20% energy as fat (6% MUFA - derived from canola oil margarine and canola oil), and was separated by a return to an ad libitum, low-fat, low-cholesterol diet (NCEP-Step 2) for a 2-6 week period. The second study included 27 healthy subjects (12 men, 15 women) and commenced five months after conclusion of the first study. Protocol for the second study was identical to the first, but the metabolic diets contained 29% of dietary energy as fat, 12% of which was MUFA. Body weight, seated blood pressure, and blood samples were obtained at both baseline and during week four of each metabolic period for subsequent analysis.
Following both MUFA levels, dietary psyllium resulted in significant reductions in total, LDL-C and HDL-C when compared to the wheat bran control diet, with more marked reductions observed in women versus men. The psyllium diet at 6% MUFA compared to 12% MUFA resulted in total cholesterol decreases of 12.3 +/- 1.5% and 15.3 +/- 2.4%, respectively. During the control phase, the higher MUFA diet produced significant reductions in triacylglycerol values of 16.6 +/- 5.5%, while significant reductions in the ratio of LDL to HDL cholesterol were observed with psyllium intake 7.3 +/- 2.8%. When data was combined from both the psyllium and control phases, a significant association between the amount of MUFA consumed daily and percentage change in total cholesterol, ratio of total cholesterol to HDL-C, and ratio of LDL to HDL-C was observed. No differences were observed in blood pressure between the psyllium and control diets at either fat intake, and bile acid excretion did not differ significantly between these two diets.
Based on these data, the researchers concluded that the addition of psyllium to the diet lowered both LDL-C and HDL-C concentrations in a similar fashion as part of a low fat or moderate fat, as canola oil, supplemented diet. This study supports the role of soluble fiber inclusion in canola oil (high or low levels) based diets for individuals with high cholesterol concentrations.,
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