Fiber

Overview

Fiber is found in the stems, seeds and leaves of plants. Fiber is made up of long chains of sugar, but as humans, we lack the digestive enzymes to break down these complex polysaccharides (although a small amount of ingested fiber can be partially broken down by enzymes produced by bacteria in the intestines). Most of the fiber, however, is not broken down and exits the body in the feces. “Fiber” is a very broad term. More precise terms are soluble and insoluble fiber. Soluble fiber dissolves in water and can be broken down by bacterial enzymes, while insoluble fiber cannot. The distinction is important because the solubility of the fiber determines its health benefit. Fiber found in food is usually a mixture of both types of fiber, while purified fiber supplements may contain just one type of fiber.

Dietary sources of fiber are plentiful. Fruits, vegetables, seeds and legumes (dried peas and beans such as lentils, split peas, red beans and pinto beans) contain both types of fiber. Barley, oats, oat bran and rye contain predominantly soluble fiber. Wheat bran, brown rice and whole grains (grains that have not been refined) are excellent sources of insoluble fiber.

Supplemental sources of fiber include psyllium, methylcellulose or polycarbophil as well as fiber extracted from fruits, vegetables and grains. Psyllium is a concentrated source of fiber from the husks of the psyllium plant. Methylcellulose and polycarbophil are chemically altered forms of cellulose (the cell wall of many plants). The chemical alterations make them resistant to bacterial breakdown. The United States Food and Drug Administration (FDA) has approved health claims for 2 dietary fibers, beta-glucan (0.75g/serving) and psyllium (1.78g/serving), based on evidence that 4 servings/day can reduce cardiovascular disease risk – reducing total cholesterol by an average of 2% and overall cardiovascular disease risk by about 4% (Jenkins et al. 2002).

General health recommendations call for a daily consumption of 20-40 grams of fiber, but the average American consumes less than 15 grams. Although the amount of soluble and insoluble fiber is not specified, it is assumed that people will receive both types of fiber. In general, claims made for supplemental forms of dietary fiber are based on scientific evidence showing that soluble fiber reduces the risk of heart disease (by lowering total and LDL cholesterol levels) and that insoluble fiber reduces the risk of colon cancer (by reducing the concentrations of fecal bile acids).

Comments

There is no question that adequate fiber is necessary for good health. Consumption of 20 to 40 grams of fiber per day is possible from food sources alone – but this entails a high consumption of legumes and whole grains. However, it is recognized that in the U.S., the average fiber intake is less than 15 grams per day. In light of average intake, fiber supplements are often recommended and warranted.

Scientific Support

Soluble Fiber and Heart Disease Risk

Hundreds of studies have been conducted to examine the role of soluble fiber in reducing the risk of heart disease by lowering cholesterol levels. Although it is difficult to compare the studies because of differences in the type and amount of soluble fiber, the number of people studied and the initial cholesterol levels of the subjects, some general conclusions can be drawn. It is generally accepted by nutrition scientists that approximately 2-10 grams of soluble fiber daily appears to reduce blood cholesterol and LDL cholesterol (Jenkins et al. 1993, Jenkins et al. 2001, Jenkins et al, 2002). The reduction is small, but makes a substantial contribution to reducing heart disease risk. The source of the fiber (oats, pectin found in fruits or psyllium) seems to make little difference, as all types have been shown to be effective (Jenkins et al. 2002, Lampe et al. 1992). The inclusion of soluble fibers in the diet is both practical and safe as long as the individual is not allergic to the source of the fiber.

Soluble fiber reduces the risk of heart disease by lowering cholesterol and LDL (Jenkins et al. 1993, Jenkins et al. 2001). Although the mechanism is not entirely known, soluble fiber is thought to decrease the absorption of bile. Bile, which contains cholesterol, is necessary for the digestion of fat. It is secreted into the intestine in response to food intake and most is reabsorbed after digestion is complete. When soluble fiber is present in the digestive tract, not as much bile is reabsorbed and more must be made by the liver. Some of the cholesterol that would have circulated in the blood is used to make the bile. In addition, soluble fiber can be partially broken down by intestinal bacteria which produce fatty acids that keep the liver from making cholesterol. It is generally accepted by nutrition scientists that soluble fiber intake can help reduce cholesterol levels. In one study, a high-fiber fruit and vegetable diet was shown to reduce LDL cholesterol levels by 33% within 1 week (Jenkins et al. 2001) – and a number of studies have shown that the drop in total and LDL cholesterol from a diet high in fiber is nearly 50% greater than would be predicted by differences in dietary fat and cholesterol (Haack et al. 1998, Jenkins et al. 1993, Jenkins et al. 1997).

Insoluble Fiber and Colon Cancer Risk

For nearly 30 years, researchers have been studying the effect of fiber on colon cancer. People who consume diets high in fiber tend to also consume diets that are low in total fat, low in animal fat and high in fruits and vegetables – all of which are factors that might reduce colon cancer risk. Fiber is also a vehicle for other compounds, such as phytic acid, an antioxidant thought to prevent colon cancer. Researchers are trying to determine whether fiber should be considered an independent factor in reducing colon cancer risk or whether the effect of fiber is due to a combination of other factors. Results of human studies have been mixed but a number of recent large studies suggest that fiber is not protective against colon cancer (Hung et al. 2004, McCullough et al. 2003, Michels et al. 2000, Sellers et al. 1998). In particular, McCullough (2003) and Michels (2000) looked at very large populations (cohorts from the 62,609-men and 70,554-women Cancer Prevention Study II Nutrition Cohort, the 88,764-women Nurses Health Study and the 47,325-men Health Professionals Follow-up Study) – finding that higher intakes of plant foods or fiber were not related to lower risk of colon cancer (but that low intakes were related to a higher cancer risk).

There are, however, numerous studies that have suggested that diets high in insoluble fiber reduce the risk of colon cancer (Alberts et al. 1996, Kesaniemi et al. 1990, Lampe et al. 1992) – but not all studies have supported these findings (McCullough et al. 2003, Michels et al. 2000). If, and how, fiber reduces the risk of cancer is not completely known and is undoubtedly complicated. The theory that supports the role of a high fiber diet in the prevention of colon cancer is controversial. It is suggested that insoluble fiber may work by helping to excrete bile from the body. Bile, which is necessary for the digestion of fat, is also thought to promote tumor growth. Insoluble fiber may bind with the bile – thus preventing it from being a promoter. Insoluble fiber also reduces the amount of time that fecal material is in the colon. Exposure to potential cancer-causing compounds is reduced because the fiber binds and removes these compounds quickly. Researchers who question whether or not insoluble fiber actually reduces colon cancer risk do so because they are not convinced that the fiber itself is responsible. They suggest that foods that contain insoluble dietary fiber also contain substances such as antioxidants, folate or dozens of other phytonutrients that protect the body from colon cancer (McCullough et al. 2003, Slattery et al. 1997, Voorrips et al. 2000). They argue that it is these compounds, rather than the dietary fiber, that help to protect against colon cancer.

Constipation

Constipation is a condition where bowel movements (feces) are hard and dry. The strain of trying to pass the hard, dry feces may result in hemorrhoids (swollen veins in the rectum). Adequate fiber, fluid and exercise help prevent constipation. Both soluble and insoluble fibers help the feces stay moist because fiber attracts water. Insoluble fiber also has a laxative effect and helps speed up the time it takes for feces to move out of the body. This theory is well accepted. Scientific studies support the role of dietary fiber to relieve constipation. Fluid and exercise are also mentioned as important factors. Both dietary fiber and fiber supplements are beneficial.

Safety/Dosage

The intake of dietary fiber or fiber supplements within the recommended doses (see below) is considered safe. To prevent dehydration, adequate fluid must be consumed. Side effects such as excessive gas or bloating may occur. Some individuals may be allergic to the source of the fiber, for example, wheat or psyllium.

Total daily fiber consumption should be within the range of 20-40 grams – with supplemental sources of fiber advised when dietary sources (fruits, vegetables, whole grains, legumes, and nuts) are below recommended levels. Popular fiber supplements (all with 8 ounces of water) may include, psyllium (7 grams – up to 3 times daily), methylcellulose (10 grams – up to 3 times daily), and polycarbophil (1 gram – up to 4 times daily).

References

1.Alberts DS, Ritenbaugh C, Story JA, Aickin M, Rees-McGee S, Buller MK, Atwood J, Phelps J, Ramanujam PS, Bellapravalu S, Patel J, Bextinger L, Clark L. Randomized, double-blinded, placebo-controlled study of effect of wheat bran fiber and calcium on fecal bile acids in patients with resected adenomatous colon polyps. J Natl Cancer Inst. 1996 Jan 17;88(2):81-92.

2.Anderson JW, Smith BM, Gustafson NJ. Health benefits and practical aspects of high-fiber diets. Am J Clin Nutr. 1994 May;59(5 Suppl):1242S-1247S.

3.Correa P. Epidemiological correlations between diet and cancer frequency. Cancer Res. 1981 Sep;41(9 Pt 2):3685-90.

4.Dietary fiber and health. AMA council on Scientific Affairs. Conn Med. 1989 Sep;53(9):529-34.

5.Haack VS, Chesters JG, Vollendorf NW, Story JA, Marlett JA. Increasing amounts of dietary fiber provided by foods normalizes physiologic response of the large bowel without altering calcium balance or fecal steroid excretion. Am J Clin Nutr. 1998 Sep;68(3):615-22.

6.Hung HC, Joshipura KJ, Jiang R, Hu FB, Hunter D, Smith-Warner SA, Colditz GA, Rosner B, Spiegelman D, Willett WC. Fruit and vegetable intake and risk of major chronic disease. J Natl Cancer Inst. 2004 Nov 3;96(21):1577-84.

7.Jacobs DR Jr, Meyer KA, Kushi LH, Folsom AR. Whole-grain intake may reduce the risk of ischemic heart disease death in postmenopausal women: the Iowa Women's Health Study. Am J Clin Nutr. 1998 Aug;68(2):248-57.

8.Jenkins DJ, Kendall CW, Popovich DG, Vidgen E, Mehling CC, Vuksan V, Ransom TP, Rao AV, Rosenberg-Zand R, Tariq N, Corey P, Jones PJ, Raeini M, Story JA, Furumoto EJ, Illingworth DR, Pappu AS, Connelly PW. Effect of a very-high-fiber vegetable, fruit, and nut diet on serum lipids and colonic function. Metabolism. 2001 Apr;50(4):494-503.

9.Jenkins DJ, Kendall CW, Vuksan V, Vidgen E, Parker T, Faulkner D, Mehling CC, Garsetti M, Testolin G, Cunnane SC, Ryan MA, Corey PN. Soluble fiber intake at a dose approved by the US Food and Drug Administration for a claim of health benefits: serum lipid risk factors for cardiovascular disease assessed in a randomized controlled crossover trial. Am J Clin Nutr. 2002 May;75(5):834-9.

10.Jenkins DJ, Popovich DG, Kendall CW, Vidgen E, Tariq N, Ransom TP, Wolever TM, Vuksan V, Mehling CC, Boctor DL, Bolognesi C, Huang J, Patten R. Effect of a diet high in vegetables, fruit, and nuts on serum lipids. Metabolism. 1997 May;46(5):530-7.

11.Jenkins DJ, Wolever TM, Rao AV, Hegele RA, Mitchell SJ, Ransom TP, Boctor DL, Spadafora PJ, Jenkins AL, Mehling C, et al. Effect on blood lipids of very high intakes of fiber in diets low in saturated fat and cholesterol. N Engl J Med. 1993 Jul 1;329(1):21-6.

12.Kesaniemi YA, Tarpila S, Miettinen TA. Low vs high dietary fiber and serum, biliary, and fecal lipids in middle-aged men. Am J Clin Nutr. 1990 Jun;51(6):1007-12.

13.Kritchevsky D. The role of dietary fiber in health and disease. J Environ Pathol Toxicol Oncol. 1986 Mar-Apr;6(3-4):273-84.

14.Lampe JW, Slavin JL, Melcher EA, Potter JD. Effects of cereal and vegetable fiber feeding on potential risk factors for colon cancer. Cancer Epidemiol Biomarkers Prev. 1992 Mar-Apr;1(3):207-11.

15.McCullough ML, Robertson AS, Chao A, Jacobs EJ, Stampfer MJ, Jacobs DR, Diver WR, Calle EE, Thun MJ. A prospective study of whole grains, fruits, vegetables and colon cancer risk. Cancer Causes Control. 2003 Dec;14(10):959-70.

16.Michels KB, Edward Giovannucci, Joshipura KJ, Rosner BA, Stampfer MJ, Fuchs CS, Colditz GA, Speizer FE, Willett WC. Prospective study of fruit and vegetable consumption and incidence of colon and rectal cancers. J Natl Cancer Inst. 2000 Nov 1;92(21):1740-52.

17.Sandler RS, Lyles CM, Peipins LA, McAuliffe CA, Woosley JT, Kupper LL. Diet and risk of colorectal adenomas: macronutrients, cholesterol, and fiber. J Natl Cancer Inst. 1993 Jun 2;85(11):884-91.

18.Sellers TA, Bazyk AE, Bostick RM, Kushi LH, Olson JE, Anderson KE, Lazovich D, Folsom AR. Diet and risk of colon cancer in a large prospective study of older women: an analysis stratified on family history (Iowa, United States). Cancer Causes Control. 1998 Aug;9(4):357-67.

19.Slattery ML, Potter JD, Coates A, Ma KN, Berry TD, Duncan DM, Caan BJ. Plant foods and colon cancer: an assessment of specific foods and their related nutrients (United States). Cancer Causes Control. 1997 Jul;8(4):575-90.

20.Stampfer MJ, Hu FB, Manson JE, Rimm EB, Willett WC. Primary prevention of coronary heart disease in women through diet and lifestyle. N Engl J Med. 2000 Jul 6;343(1):16-22.

21.Voorrips LE, Goldbohm RA, van Poppel G, Sturmans F, Hermus RJ, van den Brandt PA. Vegetable and fruit consumption and risks of colon and rectal cancer in a prospective cohort study: The Netherlands Cohort Study on Diet and Cancer. Am J Epidemiol. 2000 Dec 1;152(11):1081-92.

22.Wolk A, Manson JE, Stampfer MJ, Colditz GA, Hu FB, Speizer FE, Hennekens CH, Willett WC. Long-term intake of dietary fiber and decreased risk of coronary heart disease among women. JAMA. 1999 Jun 2;281(21):1998-2004.

EDITOR'S NOTE: This monograph can be found in The Health Professional's Guide to Dietary Supplements (Lippincott, Williams & Wilkins) by Shawn M. Talbott, PhD and Kerry Hughes, MS.

Prebiotics

Overview

Fructo-oligosaccharides (FOS) also called “prebiotics” are a group of non-digestible compounds that stimulate the growth of beneficial microflora (note: this is different than PRO-biotics, or the actual beneficial bacteria such as acidophilus and bifidum). In terms of chemistry, a fructo-oligosaccharide (FOS) is a glucose molecule bonded to multiple fructose molecules. These bonds cannot be broken down by enzymes in the human small intestine - allowing the FOS to reach the large intestine intact, where it becomes a substrate for colonic bacteria. The effects of short-chain FOS have been studied for nearly two decades. Groups of oligosaccharides can be found in foods such as beans, blueberries, and onions; a liquid supplement is available in Japan, and FOS is available in capsule form in the U.S.

Comments

Prebiotics have been shown to selectively stimulate the growth and activity of benefical bacteria in the colon. The prebiotic, fructooligosaccharide (FOS), is found naturally in many foods, such as wheat, onions, bananas, honey, garlic, and leeks – and FOS can also be isolated from chicory root or synthesized enzymatically from sucrose (both more commonly found in FOS dietary supplements). Fermentation of FOS in the colon results in a large number of physiologic effects including increasing the numbers of bifidobacteria in the colon, increasing calcium absorption, increasing fecal weight, shortening of gastrointestinal transit time, and possibly lowering blood lipid levels.

Based on the available scientific evidence, FOS supplements are generally claimed to boost levels and activity of beneficial gut bacteria and thus promote general gut health, reduce serum lipids, increase intestinal calcium absorption, alleviate antibiotic-induced diarrhea, and reduce both the severity of irritable bowel syndromes and the risk of colon cancer.

Scientific Support

Short-chain FOS is metabolized in the colon (by colonic bacteria) into short-chain fatty acids (Giacco et al. 2004). These short-chain fatty acids cause a drop in pH, which may inhibit the growth of pathogenic bacteria, facilitate intestinal calcium absorption, and act as an energy substrate for colonic epithelial cells (Bouhnik et al. 1999, Tahiri et al. 2001). By manipulating colonic pH and microflora content, FOS may also play a protective role against colon cancer (Giacco et al. 2004, Swanson et al. 2002, Ten Bruggencate et al. 2003 and 2004). Research also points to a reduction in liver fatty acid synthesis as a possible mechanism for serum lipid reduction (Giacco et al. 2004, Swanson et al. 2002).

Human studies have shown significant increases in bifidobacteria (beneficial bacteria in the gut) from ingestion of as little as 6-8 grams of short-chain FOS per day (Chow 2002). Research has also shown decreases in pathogenic colonic bacteria from FOS ingestion (Chow 2002). There is evidence that short-chain FOS can lower cholesterol and triglycerides, but most of this research has involved animal models. Colon tumors and indicators of cancer have also been reduced in animal models. Although animal studies have given promising results, relatively few human studies have shown that mineral absorption can be enhanced from FOS ingestion (Tahiri et al. 2001).

Safety/Dosage

Since the bonds of FOS are not digestible, bacterial metabolism in the large intestine produces gas and bloating. Flatulence is a common symptom associated with FOS ingestion and can be worse in people who are lactose intolerant (depending on how the FOS is processed). Studies have shown that the severity of symptoms is dose-dependent (less FOS = less symptoms). Ingestion of 20-30 grams per day has been associated with the onset of severe discomfort – but symptoms may be alleviated by starting with a small dose and increasing gradually to the desired amount (Bouhnik et al. 1999). Ten grams of FOS per day appears to be the “optimal” dose, since this amount produces a significant increase in bifidobacteria and is fairly well-tolerated.

References

1.Alles MS, Hautvast JG, Nagengast FM, Hartemink R, Van Laere KM, Jansen JB. Fate of fructo-oligosaccharides in the human intestine. Br J Nutr. 1996 Aug;76(2):211-21.

2.Bouhnik Y, Flourie B, Riottot M, Bisetti N, Gailing MF, Guibert A, Bornet F, Rambaud JC. Effects of fructo-oligosaccharides ingestion on fecal bifidobacteria and selected metabolic indexes of colon carcinogenesis in healthy humans. Nutr Cancer. 1996;26(1):21-9.

3.Bouhnik Y, Vahedi K, Achour L, Attar A, Salfati J, Pochart P, Marteau P, Flourie B, Bornet F, Rambaud JC. Short-chain fructo-oligosaccharide administration dose-dependently increases fecal bifidobacteria in healthy humans. J Nutr. 1999 Jan;129(1):113-6.

4.Chow J. Probiotics and prebiotics: A brief overview. J Ren Nutr. 2002 Apr;12(2):76-86.

5.Djouzi Z, Andrieux C. Compared effects of three oligosaccharides on metabolism of intestinal microflora in rats inoculated with a human faecal flora. Br J Nutr. 1997 Aug;78(2):313-24.

6.Flickinger EA, Hatch TF, Wofford RC, Grieshop CM, Murray SM, Fahey GC Jr. In vitro fermentation properties of selected fructooligosaccharide-containing vegetables and in vivo colonic microbial populations are affected by the diets of healthy human infants. J Nutr. 2002 Aug;132(8):2188-94.

7.Giacco R, Clemente G, Luongo D, Lasorella G, Fiume I, Brouns F, Bornet F, Patti L, Cipriano P, Rivellese AA, Riccardi G. Effects of short-chain fructo-oligosaccharides on glucose and lipid metabolism in mild hypercholesterolaemic individuals. Clin Nutr. 2004 Jun;23(3):331-40.

8.Gibson GR. Dietary modulation of the human gut microflora using prebiotics. Br J Nutr. 1998 Oct;80(4):S209-12.

9.Luo J, Van Yperselle M, Rizkalla SW, Rossi F, Bornet FR, Slama G. Chronic consumption of short-chain fructooligosaccharides does not affect basal hepatic glucose production or insulin resistance in type 2 diabetics. J Nutr. 2000 Jun;130(6):1572-7.

10.Moore N, Chao C, Yang LP, Storm H, Oliva-Hemker M, Saavedra JM. Effects of fructo-oligosaccharide-supplemented infant cereal: a double-blind, randomized trial. Br J Nutr. 2003 Sep;90(3):581-7.

11.Piche T, des Varannes SB, Sacher-Huvelin S, Holst JJ, Cuber JC, Galmiche JP. Colonic fermentation influences lower esophageal sphincter function in gastroesophageal reflux disease. Gastroenterology. 2003 Apr;124(4):894-902.

12.Rao AV. Dose-response effects of inulin and oligofructose on intestinal bifidogenesis effects. J Nutr. 1999 Jul;129(7 Suppl):1442S-5S.

13.Roberfroid M. Dietary fiber, inulin, and oligofructose: a review comparing their physiological effects. Crit Rev Food Sci Nutr. 1993;33(2):103-48.

14.Roberfroid MB, Van Loo JA, Gibson GR. The bifidogenic nature of chicory inulin and its hydrolysis products. J Nutr. 1998 Jan;128(1):11-9.

15.Roberfroid MB. Prebiotics and synbiotics: concepts and nutritional properties. Br J Nutr. 1998 Oct;80(4):S197-202.

16.Schaafsma G, Meuling WJ, van Dokkum W, Bouley C. Effects of a milk product, fermented by Lactobacillus acidophilus and with fructo-oligosaccharides added, on blood lipids in male volunteers. Eur J Clin Nutr. 1998 Jun;52(6):436-40.

17.Swanson KS, Grieshop CM, Flickinger EA, Bauer LL, Wolf BW, Chow J, Garleb KA, Williams JA, Fahey GC Jr. Fructooligosaccharides and Lactobacillus acidophilus modify bowel function and protein catabolites excreted by healthy humans. J Nutr. 2002 Oct;132(10):3042-50.

18.Tahiri M, Tressol JC, Arnaud J, Bornet F, Bouteloup-Demange C, Feillet-Coudray C, Ducros V, Pepin D, Brouns F, Rayssiguier AM, Coudray C. Five-week intake of short-chain fructo-oligosaccharides increases intestinal absorption and status of magnesium in postmenopausal women. J Bone Miner Res. 2001 Nov;16(11):2152-60.

19.Ten Bruggencate SJ, Bovee-Oudenhoven IM, Lettink-Wissink ML, Katan MB, Van Der Meer R. Dietary fructo-oligosaccharides and inulin decrease resistance of rats to salmonella: protective role of calcium. Gut. 2004 Apr;53(4):530-5.

20.Ten Bruggencate SJ, Bovee-Oudenhoven IM, Lettink-Wissink ML, Van der Meer R. Dietary fructo-oligosaccharides dose-dependently increase translocation of salmonella in rats. J Nutr. 2003 Jul;133(7):2313-8.

21.van Dokkum W, Wezendonk B, Srikumar TS, van den Heuvel EG. Effect of nondigestible oligosaccharides on large-bowel functions, blood lipid concentrations and glucose absorption in young healthy male subjects. Eur J Clin Nutr. 1999 Jan;53(1):1-7.

EDITOR'S NOTE: This monograph can be found in The Health Professional's Guide to Dietary Supplements (Lippincott, Williams & Wilkins) by Shawn M. Talbott, PhD and Kerry Hughes, MS.

Probiotics

Overview

“Probiotics” is a term used to refer to a group of “beneficial” bacteria that help maintain the health and function of the gastrointestinal tract. Probiotics have been defined as viable microorganisms that (when ingested) have a beneficial effect in the prevention and treatment of specific pathologic conditions. These microorganisms are believed to exert biological effects through a phenomenon known as colonization resistance, whereby the indigenous anaerobic flora limits the concentration of potentially pathogenic (mostly aerobic) flora in the digestive tract. Other modes of action, such as supplying enzymes or influencing enzyme activity in the gastrointestinal tract, may also account for some of the other physiologic effects that have been attributed to probiotics.

Acidophilus (Lactobacillus acidophilus) and Bifidus (Bifidobacterium lactis) of varying strains are popular forms of “good” bacteria found in dietary supplements. By displacing other bacteria and yeast, Acidophilus and other lactic acid bacteria may also play an important role in immune system function and prevention of gastrointestinal problems, including cancer. A wide variety of beneficial bacterial strains can be found in cultured yogurts and in freeze-dried form as dietary supplements. Claims for these products are generally made to reduce cholesterol levels (marginal evidence), support immune system function (solid evidence), maintain a healthy digestive system (solid evidence), and prevent colon cancer (preliminary evidence).

Comments

Dietary supplements providing Acidophilus in combination with some of the other beneficial probiotic bacteria are fairly inexpensive. Given the strong evidence for their beneficial effects on immune system function and the possibility that regular consumption may reduce colon cancer risk, these supplements would be a good choice for anybody looking for a general immune system booster.

Scientific Support

The digestive system is home to millions of bacteria that help digest, modify and convert the food we eat. Any alteration in the gastrointestinal environment is likely to influence the activity of these beneficial bacteria – sometimes posing health problems. Maintaining the “normal” populations of these good bacteria in the intestines, through consuming them as supplements or in cultured yogurt, can help displace disease-promoting bacteria and yeast that may gain a foothold when the levels of good bacteria drop.

Acidophilus and other beneficial bacteria are both acid- and bile-resistant, and thus capable of surviving transit through the gastrointestinal tract after they are ingested. These bacteria are sometimes called “probiotics” because regular consumption is linked to health benefits such as reducing cholesterol, preventing microbial growth, modulation of the immune system and, possibly, prevention of colon cancer.

Both human and animal studies have shown direct benefits of regular consumption of acidophilus and other beneficial bacteria on immune system function (Arunachalam et al. 2000, Gill et al. 2000 and 2001, Shieh et al. 2001). Overall, the probiotic bacteria tend to result in an enhanced ability of the immune system to recognize and destroy invading organisms. Several key components of the immune system, including macrophages, immunoglobulins and cytokines are altered by regular intake of beneficial bacteria. Populations of white blood cells are known to increase in number and activity following 1-2 weeks of consuming beneficial bacteria (Gill et al. 2001, Shieh et al. 2001). Importantly, resistance to viral and bacterial infections is significantly improved following regular intake of probiotics.

Epidemiological studies support the possibility that consumption of beneficial bacteria (from fermented milk and yogurt) may play a role in the prevention of colon cancer and inflammatory conditions (Gill et al. 2000 and 2001, Isolauri et al. 2000, Shieh et al. 2001). Test tube studies have shown that Acidophilus can decrease the cancer-causing potential (mutagenic activity) of various carcinogens – possible due to a direct interaction between the carcinogens and the bacteria. Consumption of acidophilus (and other lactic acid bacteria) has also been shown to reduce levels of cancer-causing enzymes in the digestive tract, supporting the possibility that probiotics do indeed play a role in the prevention of colon cancer.

Safety/Dosage

There are no safety issues associated with regular consumption of Acidophilus or other probiotic bacteria at recommended levels, although those individuals with severe gastrointestinal ailments (Crohn’s disease or ulcerative colitis) should consult with their personal physician prior to consuming probiotic supplements. Most probiotic products will typically list the type of bacteria and the number of “live cells” on the label or side panel. There are no strict guidelines for dosage intake, but 1-10 billion CFUs (colony forming units) is a general rule of thumb and corresponds to effective levels used in human studies.

References

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19.Friedrich MJ. A bit of culture for children: probiotics may improve health and fight disease. JAMA. 2000 Sep 20;284(11):1365-6.

20.Gibson GR, Fuller R. Aspects of in vitro and in vivo research approaches directed toward identifying probiotics and prebiotics for human use. J Nutr. 2000 Feb;130(2S Suppl):391S-395S.

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EDITOR'S NOTE: This monograph can be found in The Health Professional's Guide to Dietary Supplements (Lippincott, Williams & Wilkins) by Shawn M. Talbott, PhD and Kerry Hughes, MS.