Tracing metabolites of starch digestion and fermentation in relation to colon cancer
The occurrence of colon cancer is increasing in both man and women and an important cause of death in the western society. Starch components are thought to play an essential role in the prevention of colon cancer. The potential beneficial effects of starch in the diet probably depend on its digestion and fermentation characteristics (Topping et al., 2003). Part of the starch, the resistant starch (RS), escapes from digestion and is fermented in the large intestine into short chain fatty acids (SCFA's) like acetate, propionate, and butyrate. A high rate of SCFA production, especially butyrate, is associated with health promoting activities in the colon. RS may cause these prebiotic effects in the colon by stimulating the growth of specific probiotic bacteria like Lactobacillus acidophilus and Bifidobacterium spec. (Fig. 1).
Figure 1. Bifidobacterium longum, a probiotic bacterium in human intestins (Schell, 2002).
Stable Isotope Solution: 13C-labelled starches
One of the problems to investigate the effects of prebiotics like RS is to follow the dynamics of its metabolites e.g. in the blood plasma and to distinguish them from other internal or external sources. The use of [1-13C]-labelled SCFA's and recent developments in solid phase microextraction coupled to gas chromatography–mass spectrometry now much better facilitate the detection of SCFA dynamics in plasma (Moreau et al, 2004). The use of uniformly labelled 13C-starch enables even better the tracing of metabolites, either in vivo or in vitro systems like TIM (TNO gastro-Intestinal Models; www.tno.nl) during a long period.
Stimulation of prebiotic effects of starch may be optimised by using the right forms of starch that are linked to prevention of colon cancer. Using uniformly 13C-labelled starches, digestion and fermentation characteristics and SCFA levels can be accurately determined in vivo in humans or animals. Starches from different sources (corn, wheat, rice, potato etc.), purified or in the natural food matrix, natural or modified, will reveal their own specific fermentation characteristics, resulting in identification of starch-specific prebiotic effects on colon cancer.
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