Metabolic Effects Of Lupine Kernel Fiber

Important metabolic effects of DF for reducing the risk of CVD, diabetes, and cancer were originally suggested by Burkitt (1969) in his DF-hypothesis. A number of reviewers have examined studies concerning the relationship between DF consumption and the incidence of CVD and gastrointestinal disease, and most of them have found protective effects for one or both classes of disease.

Lupine kernel fiber and the risk of cardiovascular disease

The first National Health and Nutrition Examination Survey Epidemiologic Follow-up Study on 9632 men and women who were free of CVD at their baseline examination indicated that legume consumption is significantly and inversely associated with the risk of CVD. Legume consumption four times or more per week, compared with less than once a week, was associated with a 22% lower risk of coronary heart disease (CHD) and an 11% lower risk of CVD (Bazzano et al., 2001). A meta-analysis of 11 intervention trials involving legumes found overall a 6.2% lowering of low-density lipoprotein (LDL) cholesterol and a 22% lowering of triacylglyceroles.

In two randomized crossover studies, the lipid-lowering effects of LKFiber (Lupinus angustifolius Boregine) were compared in normo- and hypercholesterolemic humans. In the first study, healthy subjects consumed 25 g of pure LKFiber daily. The moderate hypercholesterolemic subjects of the second trial consumed a high-fiber diet containing 25 g LKFiber per day over 4 weeks (Table 42.2) (Fechner and Jahreis, 2011).

The blood lipids did not change in normocholesterolemic subjects. In contrast, the 4-week intervention with LKFiber-enriched food, studied in hypercholesterolemic subjects, led to a decrease of total plasma cholesterol by 12% (p < 0.001). The LDL concentration was lowered by 15% (p < 0.001), but high-density lipoprotein (HDL) cholesterol remained unchanged, which resulted in a 12% decline in the LDL:HDL ratio (Fechner and Jahreis, 2011). The reduction of total cholesterol and LDL was similar to the effects of soluble viscous fiber such as psyllium (Anderson et al., 2000). The work group of Johnson also showed only a cholesterol-lowering effect of LKFiber in hypercholesterolemic patients (Hall et al., 2005).

The hypocholesterolemic effect of legumes is primarily attributed to the soluble DF fraction and appears related to its ability to bind bile acids (BAs). The BA binding could lead to a higher BA excretion and thereby a lowering of plasma cholesterol by interrupting the enterohepatic circulation (Eastwood, 1992). The supplementation of LKFiber increased the daily excretion of

TABLE 42.2 Parameters for Two Human Intervention Studies with Lupine Kernel Fiber

Study 1

Study 2

Intervention LKFiber (g/day) Duration (weeks) No. of subjects Age (years) Cholesterol concentration (mmol/l) Standardized diet

Pure LKFiber product

25 2

LKFiber-enriched food

Normocholesterolemia: X = 4.9 Hypercholesterolemia: X = 6.6 No Yes aTwo randomized, crossover studies were conducted to investigate the lipid-lowering effects of LKFiber in normo- and hypercholesterolemic subjects.

the primary BAs significantly, but the secondary BA excretion was slightly decreased. Presumably, the observed reduction in the pH value (Fechner et al., 2009) is responsible for the rise in the excretion of primary BAs due to LKFiber. A reduction in pH inhibits the activity of the bacterial enzymes that are involved in the conversion of primary to secondary BAs (Bingham et al., 2003). Another possible mechanism for the beneficial effect of LKFiber on blood lipids may be via inhibition of dietary cholesterol absorption. The cholesterol excretion was increased significantly in both studies. Furthermore, a significantly higher output of short-chain fatty acids (SCFAs) was observed during the LKFiber intervention (Fechner et al., 2009). Therefore, the inhibition of hepatic cholesterol production via propionate-mediated effects can also help to explain the modified blood lipid profile (Anderson and Chen, 1979).

In addition to the previously mentioned lipoproteins, a relationship between CVD and other risk factors such as triacylglyceroles and C-reactive protein is described. The C-reactive protein is a marker of vascular diseases but is also believed to play an active role in atherogenesis. The LKFiber-enriched diet led to a significant decrease in the triacylglyceroles by 12% (p = 0.03) and in the high-sensitivity C-reactive protein by 19% (p = 0.02) (Fechner and Jahreis, 2010). Currently, the underlying mechanisms are unknown.

Furthermore, the intake of legumes can also reduce the risk of CVD due to favorable effects on blood pressure, glycemia, and the risk of diabetes (Anderson and Major, 2002). Consuming a high amount of fiber-enriched food has been reported to increase the perception of satiety and to modify nutritional behavior (lower intake of energy, fat, protein, and cholesterol), which supports long-term weight loss and protects against diet-induced obesity (Blundell etal., 1994).

Lupine kernel fiber and colonic health

468 DF from different plant sources often possesses unique physicochemical properties, which results in various changes to bowel function. Some epidemiological studies have supported the hypothesis that increased DF intake leads to a reduced risk of colon cancer (Burkitt, 1969). Insoluble DF is considered to reduce the risk because the exposure of colonocytes to potential carcinogens is decreased by enhancing the fecal bulk and reducing the transit time. The fermentation of soluble DF produces SCFAs, of which butyrate has been linked to a reduction in the risk of colon cancer.

LKFiber is a novel food ingredient containing both soluble and insoluble fiber fractions. The objective oftwo human intervention studies was to examine the broader physiological effects of LKFiber (L. angustifolius Boregine) on different stool and digestive parameters in humans. The administration of the tested LKFiber at a dose of 25 g DF/day over 2 weeks (study 1, pure LKFiber) or 4 weeks (study 2, LKFiber-enriched food) was well tolerated by the subjects. The LKFiber interventions resulted in a significantly higher daily fecal mass and daily fecal dry matter. Consequently, the frequency of defecations was increased, the consistency of the stool was improved, and the orofecal transit time was shortened after LKFiber intervention (Fechner et al., 2009). Similar results were obtained by the research group of Johnson. The consumption of a high-fiber diet containing 17—30 g/day LKFiber over 4 weeks increased the frequency of defecation by 0.13 events/day and fecal output by 21 % while decreasing transit time by 17% (Johnson et al., 2006). The increased stool weight is caused by the ability to bind water, the promotion of bacterial growth, and the stimulation of intestinal peristalsis. Thus, the contact of harmful substances, especially carcinogens, with the enterocytes is reduced (Cummings et al., 1992).

It is suggested that DF, depending on its structure, is of benefit for the formation of SCFAs in the colon and therefore lowers the pH value, which decreases the formation of carcinogenic substances. The consumption of LKFiber led to enhanced formation of SCFAs whereby the total SCFA excretion as well as the excretion of the main SCFAs (acetate, propionate, and n-butyrate) increased significantly. Due to the enhanced formation, the SCFA concentration in

FIGURE 42.3

Schematic summary of the physiological effects of lupine kernel fiber (LKFiber) in the colon. Lupine kernel fiber has a positive impact on the putative risk factors of colon cancer, such as transit time, short-chain fatty acid (SCFA) production, pH value, and the concentration of secondary bile acids.

FIGURE 42.3

Schematic summary of the physiological effects of lupine kernel fiber (LKFiber) in the colon. Lupine kernel fiber has a positive impact on the putative risk factors of colon cancer, such as transit time, short-chain fatty acid (SCFA) production, pH value, and the concentration of secondary bile acids.

the feces was elevated and the pH value decreased (Fechner et al., 2009). SCFAs, especially butyrate, are an important energy source for colonocytes. In addition, butyrate is able to reduce the risk of malignant changes through regulation of colonocyte differentiation (Johnson et al., 2006; Topping and Clifton, 2001).

Moreover, the LKFiber intake lowered the fecal concentration of total BAs, especially the secondary BAs (Fechner et al., 2009). The decrease in BA concentration is due to the increase in the daily fecal mass and fecal dry matter. Acid steroids, especially the secondary BAs, are potential risk factors for colorectal cancer (Reddy et al., 1989).

In summary, the results of the studies show that LKFiber has a positive impact on the putative risk factors of colon cancer, such as transit time (daily fecal mass), SCFA production, pH value, and concentration of secondary BAs (Figure 42.3). LKFiber has a positive impact on the function of the colon and on health in general.

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