Dried Plums & Digestive Health
Short Chain Fatty Acids
The portion of dietary fiber that is not digested and passes into the colon becomes available for fermentation.
Fermentation of dietary fiber increases the production of short chain fatty acids (SCFAs) including acetate,
propionate and butyrate.6 These SCFAs lower the pH of the colon.4 By acidifying the colonic environment,
SCFAs play an important role in both colonic and systemic physiology. Butyrate has received scientificattention for its ability to regulate genes that control cell proliferation and differentiation, which has
implications for prevention of colon cancer. Both colon cancer and inflammatory bowel disease have been
associated with decreased concentrations of butyrate, and some studies have shown that administration ofbutyrate may be useful for prevention or treatment of experimental colitis. Furthermore, animal studies haveshown that administration of fructo-oligosaccharides decreased tumor formation and/or the formation ofaberrant crypt foci, a marker for colon cancer risk.4
Another mechanism potentially affecting cancer risk is the reduction of secondary bile salts, which occurs
as a result of the lowered pH of the colonic environment. The conversion of primary bile salts to secondary
bile salts is inhibited when the pH is below 6.5. One team of investigators showed recently that chronic
administration of fructo-oligosaccharides increased the excretion of primary bile salts in people with colon
polyps and suggested that fructo-oligosaccharides may be useful in colon cancer prevention.4
In another experiment with human volunteers, fecal concentration of secondary bile acids was significantly
lower after ingesting 100 g/day of dried plums for four weeks.1All three SCFAs serve as fuel sources for different cells, with butyrate being the preferred fuel of colonocytes.
Proprionate is absorbed from the colonic lumen and transported to the liver, where it is thought to reducecholesterol production. Acetate is transported to various tissues for fuel.4,6 Multiple physiological roles ofbutyrate and other SCFAs produced during fermentation of prebiotics in the colon are shown in Figure 1.
Figure 1. Physiological effects of butyrate and other SCFAs produced in the colon 4

Nutrition of coloncyte (butyrate)
Energy salvage
Increase sodium absorption

Increase musocal blood flow

Butyrate and other SCFAs
produced during fermentation of prebiotics
Regulate cell proliferation
Effect on cell differentationand carcinogenesis

Decrease blood cholesterol(propionate)
Immunomodulation

Dried Plums & Digestive Health
The Cholesterol Connection
There are basically two ways to reduce cholesterol — either to increase excretion or to suppress productionof cholesterol in the liver. Cholesterol can be reabsorbed from the intestines and cycled back to the liver via
the enterohepatic circulation; in the liver it can be catabolized, and the bile acids which are the metabolitesof this process can be measured in the feces. The soluble fiber pectin, which accounts for 40-60% of thetotal fiber content of dried plums, has been shown to reduce plasma cholesterol levels.7,8 Viscous fibers
including pectin have been shown to increase fecal bile acid losses, and this has been proposed as one
mechanism by which soluble fiber lowers serum cholesterol.8 However, the effect has not been seen in all
studies.7 Soluble fiber may reduce hepatic free cholesterol and triaglycerol while also upregulating theactivity of the enzyme responsible for cholesterol catabolism.9 Pectin has also been shown in laboratory
animals to decrease the susceptibility of low density lipoprotein cholesterol (LDL) to oxidation, and this may
be another mechanism by which soluble fiber protects cardiovascular health.10
Furthermore, the production of SCFAs in the gut may decrease serum cholesterol levels by inhibiting hepaticcholesterol synthesis and/or redistributing cholesterol from plasma to the liver.11 It has been suggested thatsome bacteria present in the GI microflora may have the ability to assimilate cholesterol directly, or tointerfere with cholesterol absorption from the gut by deconjugating bile salts and therefore affecting themetabolism of cholesterol.11
Whatever the mechanism, it is clear that an interplay exists between the GI system and the cardiovascularsystem, so in a sense the impact of fiber on cholesterol levels may be seen as an “indirect effect” ofdigestive health.
Laxation
Dried plums have been consumed by humans for centuries for their positive effects on laxation. In
recent human experiments, ingestion of 12 dried plums daily increased fecal bulk by about 20%,7 andconsumption of a very high fruit and vegetable diet for two weeks significantly increased fecal weight,
bulk and water content.8 Fiber has a known osmotic quality, but may also alleviate constipation by
improving the GI microflora.12 Both sorbitol and phenolics may increase the amount of glucose passing
into the bowel, making it available for fermentation.1 Additionally, phenolics influence the electrolyte
balance in the intestinal tract and were shown to induce contractions in isolated intestinal sections fromlaboratory animals.1 Thus, the laxative effect of dried plums is likely due to the combined action of fiber,sorbitol and phenolic compounds.
Prune juice also produces a laxative effect similar to whole dried plums, although most brands of prune
juice are nearly devoid of fiber. This is attributed to its sorbitol and phenolic content.1 However, somebrands of prune juice now have added pulp and may provide about 2 g of dietary fiber per serving; onebrand, in fact, has almost as much fiber per serving as dried plums.
Summary
The impact of dried plums on digestive health extends beyond their laxative effects and invites a holistic
perspective encompassing the multifaceted, systemic impact of GI health on the entire body. Increased
production of SCFAs may have beneficial effects on both cardiovascular health and the resistance tocancer. Other potential health benefits of dried plums related to their nutrient profile and phenolic content,
while important and impressive, are beyond the scope of the present discussion.

Dried Plums & Digestive Health
References
1. Stacewicz-Sapuntzakis M, Bowen PE, Hussain EA, et al, 2001. Chemical Composition and Potential HealthEffects of Prunes: A Functional Food? Crit Rev Food Sci Nutr 41(4):251-286.
2. Mercenier A, Pavan S and Pot B, 2002. Probiotics as biotherapeutic agents: present knowledge andfuture prospects. Curr Pharmaceut Design 8:99-110.
3. Bezkorovainy A, 2001. Probiotics: determinants of survival and growth in the gut. Am J Clin Nutr 73(Suppl):399S-405S.
4. Marteau P, Seksik P, Lepage P, Dore J, 2004. Cellular and physiological effects of probiotics andprebiotics. Mini-Rev in Med Chem 4:889-896.
5. Gibson GR, Wang X, 1994. Regulatory effects of bifidobacteria on the growth of other colonic bacteria.
J Appl Bacteriol 77(4):412-420.
6. Priebe MG, Vonk RJ, Sun X, et al, 2002. The physiology of colonic metabolism. Possibilities forinterventions with pre- and probiotics. Eur J Nutr 41 (Suppl 1):1/2-1/10.
7. Tinker LF, Schneeman BO, Davis PA, et al, 1991. Consumption of prunes as a source of dietary fiber inmen with milk hypercholesterolemia. Am J Clin Nutr 53:1259-1265.
8. Jenkins DJA, Kendall CWC, Popovich DG, et al, 2001. Effect of a very-high-fiber vegetable, fruit, and nut
diet on serum lipids and colonic function. Metabolism 50(4), 494-503.
9. Roy S, Freake HC, Fernandez ML, 2002. Gender and hormonal status affect the regulation of hepaticcholesterol 7alpha-hydroxylase activity and mRNA abundance by dietary soluble fiber in the guinea pig.
Atherosclerosis 163(1):29-37.
10.Vergara-Jimenez M, Furr H, Fernadez ML, 1999. Pectin and psyllium decrease the susceptibility ofLDL to oxidation in guinea pigs. J Nutr Biochem 10(2):118-124.
11.Pereira DI, Gibson GR, 2002. Effects of consumption of probiotics and prebiotics on serum lipid levels
in humans. Crit Rev Biochem Mol Biol 37(4):259-281.
12.Marteau P, Boutron-Ruault MC, 2002. Nutritional advantages of probiotics and prebiotics. Brit J Nutr
86 (Suppl.2)S153-S157.