High Fiber Diet Effects on Serum Lipids in Adults

Introduction and Study Overview

This study addresses the question: "What effect does a high fiber diet have on serum lipids in adults?" The significance of this study lies in the additional information it contributes to the existing body of knowledge in this area, and in the synthesis of research on serum lipids and high fiber diet outcomes.

The study is a retrospective chart review of patients who followed a high fiber diet for a period of 12 weeks. Serum lipids were measured at the beginning of the diet and again at 12 weeks to evaluate any changes. The expectation is to observe a decrease in serum lipids among study participants who adhered to a high fiber diet.

Review of the Literature

A high fiber diet is one in which fiber intake is increased to 25 to 40 grams per day. This level of daily fiber intake has been linked to a "reduced risk of many chronic diseases, including cancer, heart disease, certain gastrointestinal conditions, and perhaps even obesity" (The Institute for Optimum Nutrition, 2009). Both soluble and insoluble fibers are included in a high fiber diet. Soluble fibers are found in beans, oats, and fruits, while insoluble fiber is found in "vegetables, whole grains, and fruit skins" (The Institute for Optimum Nutrition, 2009).

Fiber Intake, Lifestyle, and Serum Lipids in Adult Men

The work of Ballesteros et al. (2001), entitled "Dietary Fiber and Lifestyle Influence Serum Lipids in Free Living Adult Men," published in the Journal of Nutrition, reports a study with the objective of determining the effect of dietary fiber consumption and lifestyle on serum lipids in adult men following a non-restricted diet with unrestricted physical activity. The study involved two groups of 19 men classified as high and low fiber intake groups, consuming 48 grams per day and 27 grams per day of dietary fiber, respectively. For a seven-day period, "anthropometry, food frequency, daily weighed intakes, and physical activity were recorded. Fasting blood was collected and serum was analyzed for triglycerides, total cholesterol, and lipoprotein cholesterol fractions" (Ballesteros et al., 2001).

The findings of the study showed that:

"Total cholesterol was negatively associated with physical activity, total dietary fiber, and P/S ratio (r = −0.52; p < 0.001, r = −0.44; p < 0.01, r = −0.51, p < 0.001). LDL-C was also correlated negatively with total dietary fiber and P/S ratio (r = −0.34, p < 0.03; r = −0.53, p < 0.01). It was also positively associated with dietary cholesterol and body weight (r = 0.34, p < 0.03; r = 0.31, p < 0.05). Serum triglycerides had an inverse association with total dietary fiber and physical activity (r = −0.30; p < 0.05; r = −0.45, p < 0.004). After controlling for energy intake, total fat, saturated fat, dietary cholesterol, physical activity, and body mass index, LDL-C/HDL-C and TC/HDL-C remained significantly associated with dietary fiber (r = −0.34; p < 0.05 and r = −0.38; p < 0.02, respectively)." (Ballesteros et al., 2001)

The study demonstrates that in free-living men, "there is an association between fiber intake and favorable lipid status" (Ballesteros et al., 2001). It was also reported that consumption of dietary fiber — specifically the soluble type, such as pectins and guar gum — can result "in a decrease of serum cholesterol levels in healthy and hyperlipidemic subjects" (Ballesteros et al., 2001).