Digestion

Digestion

by Jennifer Mueller

Everyone is aware of the importance of the foods we eat; certain foods contain specific nutrients, and if we don't get enough of them, we can become ill. However, not many people are aware of the importance of the digestive tract, the place where food is predigested and nutrients are absorbed. The healthiest diet is useless if the body cannot digest the food and utilize it efficiently.

Probiotics
The gastrointestinal tract consists of the mouth, esophagus, stomach, small intestine, and colon (large intestine). (Fig. 1) It plays an important role in health and nutrition. The colon is especially important for the absorption of water and certain essential minerals such as calcium, iron, and magnesium. But perhaps more importantly, the colon serves as the home for nearly 50 different species of bacteria. These beneficial bacteria, known as 'probiotics,' play a critical role in maintaining healthy digestion, and ultimately, good overall health.(1)
The health of the body depends on the health of the digestive tract. Signs of an unhealthy digestive tract include diarrhea, bloating, and gas, any of which can be brought about by stress, illness, malnutrition, and antibiotic therapies. Over time, an unhealthy digestive tract can lead to ulcerative colitis, Crohn's disease, or even colorectal cancer. Obviously, it is in your best interest to keep your gut healthy.

The two main families of beneficial bacteria found in the colon are lactobacillus and bifidobacteria. The healthful effects of probiotics (beneficial bacteria) and prebiotics (the food sources for those bacteria) have been studied extensively for over a century, demonstrating that the ratio of these bacteria to other species in the gut can play a significant role in health.(1, 2)

Lactobacillus
Lactobacillus supplementation has numerous benefits including: (1) reduced serum cholesterol levels, (2) inhibition of pathogenic (disease causing) bacteria, (3) production of enzymes which assist with the digestion of proteins and fats, and (4) the production of natural antibiotic compounds which inhibit certain pathogenic compounds. Lactobacillus treatment provides relief for some very common ailments, including lactose intolerance. Lactobacillus relieves the symptoms of lactose intolerance (bloating, cramps and flatulence) by providing enzymes to digest the lactose in milk.
Other studies have demonstrated that lactobacillus may play a role in the reduction of urinary and vaginal tract infections. Studies have shown that the incidence of recurring vaginal infections (caused by candida) is greatly reduced in women who regularly consume lactobacillus in yogurt or supplement form.3 Other studies suggest that lactobacillus treatment (via suppositories) may also reduce the recurrence of urinary tract infections.4

Diarrhea is the most common sign of a troubled digestive tract, and lactobacillus treatment has been used effectively for a number of causes of diarrhea. Antibiotic-associated diarrhea (AAD) is the most common side effect of antibiotic therapy. Supplementation with L. acidophillus and L. bulgaricus (via yogurt) during antibiotic therapy significantly reduced the incidence of diarrhea caused by clostridium, (5) while supplements of L. casei-fortified yogurt have shown some protective effects against 'travelers' diarrhea,' caused by E. coli. (6) Supplementation with yogurt containing bifidobacteria has also been shown to help prevent AAD. (7)

Bifidobacteria
For adults bifidobacteria accounts for almost 25% of the colonic bacterial population and for new-borns accounts for nearly 95%.1 Bifidobacteria produce lactate and acetate, which lower the intestinal pH, thereby restricting the growth of some pathogenic bacteria.8 Its beneficial effects also include reduction of blood ammonia levels (helpful with patients with liver disease), reduction in blood cholesterol, production of folic acid and the B vitamins, and stimulation of the immune system to attack carcinogenic cells. (1)

Prebiotics
Prebiotics are just as important as probiotics. These are non-digestible food ingredients that stimulate the growth and/or activity of colonic bacteria.(10)

The primary food source for the colonic bacteria is carbohydrates. While most simple sugars and digestible carbohydrates are broken down and absorbed before leaving the small intestine. A small percentage pass through to the large intestine where they are fermented by the colonic bacteria. The main source of carbohydrates for the colonic bacteria come from non-digestible sources: starches, polysaccharides, pectins and gums, plant cell walls, and oligosaccharrides. Most of these are non-specifically fermented, meaning that they can be used by both the harmful and the beneficial bacteria. However, some oligosaccharides are species-specific food sources -- only usable by the beneficial bacteria. One of these is fructooligosaccharides, or FOS.
FOS is a mix of oligosaccharides, consisting of glucose-linked-to-fructose units. It is produced naturally by synthesis of sucrose and can be found in small quantities in such foods as onions, rye, wheat, and asparagus.(10) FOS is used in food preparation as a sweetening and bulking agent in some dairy products and pastries.(11) It is the main food source for bifidobacteria and lactobacillus, but cannot be used by harmful bacteria such as E. coli, clostridium, or staphylococci. Thus, a rich source of FOS allows the beneficial bacteria to grow, effectively 'crowding out' the harmful varieties.(12) Numerous studies, link an increased ingestion of FOS to an increased concentration of bifidobacteria and lactobacillus and significantly lower concentrations of the pathogen-producing bacteria. (12, 13, 14)

In one study, human volunteers ingested 12.5 grams of FOS per day for 12 days, and stools were collected for measurement of bacterial enzymes.(10) In another study, male volunteers ingested either 0, 5, or 15 grams of FOS per day. Results in both studies showed increased bifidobacteria populations in the colon in proportion to the amount of FOS ingested.(15) It is important to note that these increases in beneficial bacteria levels dropped after FOS supplementation was stopped. Levels of lactobacillus remained elevated longer than bifido levels, but lactobacillus eventually dropped back down to their previous levels. FOS is completely fermented in the gut; very little is excreted in the feces.(15)

Studies in laboratory animals confirm that the concentrations of bifidobacteria in the gut can play a role in the absorption of certain essential minerals. In one study, rats given FOS supplements showed a significant increase in absorption of calcium, magnesium, and phosphorus.(16) In another, FOS supplementation led to significantly increased absorption rates for calcium, magnesium, phosphorus, and zinc. FOS supplementation also resulted in increased excretion of fecal nitrogen, with a corresponding decrease in urinary nitrogen excretion (nitrogen is one of the body's waste products and can be harmful if levels are too high).(4)These beneficial effects appear to apply to humans as well.

While results are still preliminary, some studies suggest that supplementation with FOS can result in a reduction in colorectal tumors. In one such study, mice were given milk containing either a placebo, bifidobacteria alone, or bifidobacteria with FOS, and then exposed to a known carcinogen. The mice who had received the bifidobacteria alone showed a lower incidence of abnormal intestinal cells. This effect was even more pronounced in the group which had received the bifidobacteria with FOS.(2) While it is still too early to tell if these results will apply to humans, the implications are, nonetheless, quite exciting, as the composition of the Western diet (high fat, high protein) has been linked to an increased risk of colorectal cancers.
The bacterial population of the gut plays a role in everything from the proper absorption of nutrients, to the prevention of disease. Supplementation with probiotics and prebiotics can assist in maintaining a healthy gut, and ultimately, a healthy you. JM

References

1. Gibson, G.R, Roberfroid, M.B. Dietary modulation of the human colonic microbiota: introducing the concept of prebiotics. J Nutr. 125: 1401-12, 1995
2. Gallaher, D.D., Stallings, W.H., Blessing, L.L., et al. Probiotics, cecal microflora, and aberrant crypts in the rat colon. J Nutr. 126: 1362-71, 1996
3. Delzenne, N., Aertssens, J,. Verplaetse, H., et al. Effect of ferm-entable fructo-oligosaccharides on mineral, nitrogen and energy digestive balance in the rat. Life Sciences 57(17):1579-87, 1995
4. Reid, G., Bruce, A.V., Taylor, M. Influence of three-day antimicrobial therapy and Lactobacillus vaginal suppositories on recurrence of urinary tract infections. Clin Ther. 14:11-16, 1992
5. Hilton, E., Isenberg, H.D., Alperstein, P., et al. Ingestion of yogurt containing Lactobacillus acidophilus as prophylaxis for candidal vaginitis. Ann Int Med. 116: 252-57, 1992
6. Gotz, V., Romankiewicz, J.A., Moss, J., et al. Prophylaxis against ampicillin-associated diarrhea with a lactobacillus preparation. Am J Hosp Pharm 36: 754-57, 1979
7. Oksanen, P.J., Salminen, S., Saxelin, M., et al. Prevention of travelers' diarrhea by Lactobacillus GG. Ann Med. 22: 53-56, 1990
8. Columbel, J.F., Corlot, A., Neut, C., et al. Yogurt with Bifidobacterium longum reduces erythromycin-induced gastrointestinal effects. Lancet. 2-43, 1987
9. Bornet, F.R.J. Undigestible sugars in food products. Am J Clin Nutr. 59(suppl): 763S-9S, 1994
10. Bouhnik, Y., Flourie, B., Riottot, M., et al. Effects of fructo-oligosaccharides ingestion on fecal bifidobacteria and selected metabolic indexes of colon carcinogenesis in healthy humans. Nutr Cancer 26(1): 21-29, 996
11. Poch, M., Bezkorovainy, A. Growth-enhancing supplements for various species of the genus bifidobacterium. J Dairy Sci. 71: 3214-21, 1988
12. Howard, M.D., Gordon, D.T., Garleb, K.A., et al. Dietary fructooligosaccharide, xylooligosaccharide and gum arabic have variable effects on cecal and colonic microbiota and epithelial cell proliferation in mice and rats. J Nutr. 125: 2604-9, 1995
13. Buddington, R.K., Williams, C.H., Chen, S.C., et al. Dietary supplement of neosugar alters the fecal flora and decreases activities of some reductive enzymes in human subjects. Am J Clin Nutr. 63: 709-16, 1996
14. Howard, M.D., Gordon, D.T., Pace, L.W., et al. Effects of dietary supplementation with fructooligosaccharides on colonic microbiota populations and epithelial cell proliferation in neonatal pigs. J Ped Gast Nutr. 21(3)297-302, 1995
15. Alles, M.S., Hautvast, J.G., Nagengast, F.M., et al. Fate of fructo-oligosaccharides in the human intestine. Brit J Nutr. 76: 211-21, 1996
16. Ohta, A., Ohtsuki, M., Baba, S., et al. Calcium and magnesium absorption from the colon and rectum are increased in rats fed fructooligosaccharides. J Nutr . 125: 2417-24, 1995

The information in this article is not intended to provide personal medical advice, which should be obtained from a medical professional, and has not been approved by the U.S. FDA.

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