New Findings on FiberMay 2005
By Stephen Laifer
Natural Cancer Weapon
Medical researchers estimate that 30-40% of all cancers are preventable by lifestyle and dietary measures alone. Fiber-depleted processed foods are viewed as significant contributors to excess cancer risk.36
Recent studies have examined the role of a high-fiber diet—typically supplying more than 34 grams of fiber a day—in preventing cancer. Most of these studies have focused on colorectal cancer. A high-fiber diet reduced the risk for rectal cancer by a remarkable 56% in one study, while eating more that three servings a day of whole-grain products was associated with a 31% reduced risk. By contrast, consumption of refined grain products in excess of 4.5 servings a day was associated with a 42% greater risk of rectal cancer.37 A similar study by a consortium of health groups, including the National Cancer Institute, showed that high intake of vegetables, fruits, and whole-grain foods—all high in dietary fiber—reduces the risk of distal colon adenomas (precancerous growths of the colon). Patients who consumed the most fiber had a 27% lower risk of adenomas than those who consumed the least fiber.38
The 2003 European Prospective Investigation into Cancer and Nutrition (EPIC) was the largest study ever to investigate the association between diet and cancer risk. Spanning 10 countries, the EPIC study followed 519,978 participants, aged 24 to 75, for nearly five years. The study results indicate that abundant intake of dietary fiber is highly protective against colorectal cancer. Participants who consumed the most dietary fiber had a 40% lower risk of developing colon cancer than those who ate the least fiber. The study authors proposed that if populations with a low average dietary intake of fiber doubled their fiber consumption, they could slash their risk of colorectal cancer by 40%.39
The Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial compared the fiber intake of 33,971 patients who tested negative for polyps to 3,591 patients who had at least one verified adenoma in the distal large bowel. The study found that patients consuming the most fiber had a 27% lower risk of adenomas than those who consumed the least fiber. Interestingly, the researchers further noted that fiber “might serve as a marker for unmeasured substances that have anti-carcinogenic effects.”40
Diabetes and Insulin Control
The obesity epidemic in America has dramatically increased the incidence of type II diabetes by exacerbating insulin resistance.41 For those who have tried unsuccessfully to lower cholesterol with a high-carbohydrate, low-fat diet, refined carbohydrates that are low in fiber may be to blame.
Refined, fiber-depleted carbohydrates tend to have a high glycemic index, and thus cause a rapid increase in blood sugar. Following their consumption, a “glucose spike” prompts the pancreas to release insulin, which in turn signals the liver to pump more triglycerides into the bloodstream. Dietary fiber slows the absorption of food so that blood sugar does not rise as rapidly, while also reducing insulin secretion.42 This was demonstrated in a study published in 2004 in which a high fiber intake led to improved glycemic control, along with reduction of blood pressure and serum cholesterol and triglyceride levels.43
Fiber’s positive effects on blood glucose and insulin concentrations are most evident in people diagnosed with diabetes mellitus. In a randomized study, researchers compared the effects of a diet high in fiber (50 grams/day) to those of a moderate-fiber diet (24 grams/day) recommended by the American Diabetes Association. They found that a high intake of dietary fiber, particularly soluble fiber, significantly improves glycemic control, decreases hyperinsulinemia (a disorder associated with aberrant blood sugar control), and lowers plasma lipid concentrations in diabetic patients.44
In one study, guar gum improved metabolic control and decreased serum lipids of nine patients with type II diabetes.45 In another promising research trial, three weeks of supplementation with guar gum lowered both fasting and after-meal blood glucose levels. In addition, the attenuation of insulin levels suggests that guar gum slowed the rate of carbohydrate absorption. Cholesterol levels dropped 14% on average in the diabetic subjects.46 Thus, supplementation with soluble fibers like guar gum appears to improve glycemic control and lipid profiles in people with type II diabetes.
Selecting the Best Fibers
Dietary fibers, which are resistant to digestion by enzymes in the gastrointestinal tract, can be classified as either water soluble or insoluble. Soluble fiber in particular helps lower cholesterol levels by binding to cholesterol in the intestinal tract and increasing its elimination from the body. Good sources of soluble fiber include beans, peas, rice bran, oats, barley, citrus fruits, and strawberries. Adding two to three servings of high-fiber fruit or cereal could provide powerful added protection for your heart.
Oat bran and oatmeal, both of which contain the fiber beta-glucan, have been the subject of growing attention.47 In 1997, the FDA approved the health claim that “a diet high in soluble fiber from whole oats and low in saturated fat and cholesterol may reduce the risk of heart disease.”48 Researchers have debated beta-glucan’s mechanism of action in the body. While some speculate that beta-glucan may act as a physical barrier in the intestinal tract by blocking the absorption of bile acids and cholesterol, others have theorized that soluble fibers are bacterially fermented in the colon, leading to the production of short-chain fatty acids that may lower cholesterol synthesis.49
According to a German study published in 2004, different sources of dietary fiber confer various benefits.50 Food sources of dietary fiber like whole-grain bread, vegetables, and fruit are particularly useful in preventing and treating colon conditions and cancers. Purified dietary fibers such as cellulose, guar gum, psyllium, and beta-glucan help promote healthy blood sugar levels. All water-soluble fibers help maintain normal blood lipid levels, according to the study authors, but oat bran is especially effective.
The Importance of Fiber Supplements
The average American currently consumes only 12-17 grams of fiber a day from dietary sources, far below the 20-35 grams recommended by the American Dietetic Association and the 30 grams or more suggested by both the American Heart Association and the National Cancer Institute.51,52
Since many people do not want to change or cannot change their diets, supplements and natural fiber products can help them benefit from fiber’s many beneficial effects. Supplemental fiber products can provide optimal combinations and amounts of fiber, as well as complementary nutrients such as calcium. Incorporating increased fiber intake into a daily plan for healthy living can help you lower your risk of heart attack and cancer, as well as prevent or manage such common conditions as hypertension and diabetes mellitus. Moreover, fiber is a valuable tool in achieving optimal weight.
With increased fiber intake, some people may experience gastrointestinal discomfort or changes such as increased or loose bowel movements. This is simply the body’s period of adjustment to the introduction of greater amounts of dietary fiber. Medical professionals recommend adding fiber to the diet gradually until the body adjusts. Moreover, because soluble fibers form a gel with water, it is important to drink plenty of water with fiber supplements. Abundant water intake will help to optimize fiber’s actions in the body and prevent ill effects such as dehydration or constipation.
1. Hipsley EH. Dietary “fibre” and pregnancy toxaemia. Br Med J. 1953 Aug 22;16(4833):420-2.
2. Cleave TL, Campbell GD, Painter NS. Diabetes, Coronary Thrombosis and the Saccharine Disease. 2nd ed. Bristol: Wright; 1969.
3. Burkitt DP. Related disease—related cause? Lancet. 1969 Dec 6;2(7632):1229-31.
4. Burkitt DP, Trowell HC, eds. Refined Carbohydrate Foods and Disease. Some Implications of Dietary Fibre. New York: Academic Press; 1975.
5. Pereira MA, O’Reilly E, Augustsson K et, al. Dietary fiber and risk of coronary heart disease: a pooled analysis of cohort studies. Arch Intern.Med. 2004 Feb 23;164(4):370-6.
6. Available at: http://www.cdc.gov/nccdphp/dnpa/obesity/trend/index.htm. Accessed March 4, 2005.
7. Flegal KM, Carroll MD, Ogden CL, Johnson CL. Prevalence and trends in obesity among US adults, 1999-2000. JAMA. 2002 Oct 9;288(14):1723-7.
8. de Leeuw JA, Jongbloed AW, Verstegen MW. Dietary fiber stabilizes blood glucose and insulin levels and reduces physical activity in sows (Sus scrofa). J Nutr. 2004 Jun;134(6):1481-6.
9. Yao M, Roberts SB. Dietary energy density and weight regulation. Nutr Rev. 2001 Aug;59(8 Pt 1):247-58.
10. Pasman WJ, Saris WH, Wauters MA, et al. Effect of one week of fibre supplementation on hunger and satiety ratings and energy intake. Appetite. 1997 Aug;29(1):77-87.
11. Howarth NC, Saltzman E, Roberts SB. Dietary fiber and weight regulation. Nutr Rev. 2001 May;59(5):129-39.
12. Rolls BJ. The role of energy density in the overconsumption of fat. J Nutr. 2000 Feb;130(2S Suppl):268S-71S.
13. Pereira MA and Ludwig DS. Dietary fiber and body-weight regulation. Observations and mechanisms. Pediatr Clin North Am. 2001 Aug;48(4):969-80.
14. Gonzalez Canga A, Fernandez Martinez N, Sahagun AM, et al. Glucomannan: properties and therapeutic applications. Nutr Hosp. 2004 Jan-Feb;19(1):45-50.
15. Birketvedt GS, Shimshi M, Thom E, Florholmen J. Experiences with three different fiber supplements in weight reduction. Med Sci Monit. 2004 Dec 22;11(1):I5-8.
16. Walsh DE, Yaghoubian V, Behforooz A. Effect of glucomannan on obese patients: a clinical study. Int J Obes.1984;8(4):289-93.
17. Vuksan V, Sievenpiper JL, Owen R, et al. Beneficial effects of viscous dietary fiber from Konjac-mannan in subjects with the insulin resistance syndrome: results of a controlled metabolic trial. Diabetes Care. 2000 Jan;23(1):9-14.
18. Vuksan V, Jenkins DJ, Spadafora P, et al. Konjac-mannan (glucomannan) improves glycemia and other associated risk factors for coronary heart disease in type 2 diabetes. A randomized controlled metabolic trial. Diabetes Care. 1999 Jun;22(6):913-9.
19. Kim E, Vuksan V, et al. The relationship between viscosity of dietary fibers and their hypoglycemic effects. Kor J Nutr. 1996;29:615-21.
20. Cifuentes M, Riedt CS, Brolin RE, Field MP, Sherrell RM, Shapses SA. Weight loss and calcium intake influence calcium absorption in postmenopausal women. Am J Clin Nutr. 2004 Jul;80(1):123-30.
21. Bowen J, Noakes M, Clifton PM. A high dairy protein, high-calcium diet minimizes bone turnover in overweight adults during weight loss. J Nutr. 2004 Mar;134(3):568-73.
22. Zemel MB, Thompson W, Milstead A, Morris K, Campbell P. Calcium and dairy acceleration of weight and fat loss during energy restriction in obese adults. Obes Res. 2004 Apr;12(4):582-90.
23. Jacobsen R, Lorenzen JK, Toubro S, Krog-Mikkelsen I, Astrup A. Effect of short-term high dietary calcium intake on 24-h energy expenditure, fat oxidation, and fecal fat excretion. Int J Obes Relat Metab Disord. 2005 Mar;29(3):292-301.
24. Zemel MB. Role of calcium and dairy products in energy partitioning and weight management. Am J Clin Nutr. 2004 May;79(5):907S-12S.
25. Moyad MA. The potential benefits of dietary and/or supplemental calcium and vitamin D. Urol Oncol. 2003 Sept-Oct;21(5):384-91.
26. Tucker KL. Dietary intake and coronary heart disease: a variety of nutrients and phytochemicals are important. Curr Treat Options Cardiovasc Med. 2004 Aug;6(4):291-302.
27. Trowell, HC, Burkitt DP. Concluding considerations. In: Burkitt DP, Trowell HC, eds. Refined Carbohydrate Foods and Disease. New York: Academic Press; 1975:333-45.
28. Burkitt D. Don’t forget the fibre in your diet, to help avoid many of our commonest diseases. London: Martin Dunitz Limited; 1983:8.
29. Khaw KT, Barrett-Connor E. Dietary fiber and reduced ischemic heart disease mortality rates in men and women: a 12-year prospective study. Am J Epidemiol. 1987 Dec;126(6):1093-1102.
30. Erkkila AT, Sarkkinen ES, Lehto S, Pyorala K, Uusitupa MI. Dietary associates of serum total, LDL, and HDL cholesterol and triglycerides in patients with coronary heart disease. Prev Med. 1999 Jun;28(6):558-65.
31. US Food and Drug Administration. Health claims: soluble fiber from certain foods and risk of heart diseases. Code of Federal Regulations. 2001;21:101.81.
32. Lupton JR, Turner ND. Dietary fiber and coronary disease: does the evidence support an association? Curr Atheroscler Rep. 2003 Nov;5(6):500-5.
33. Ballesteros MN, Cabrera RM, Saucedo Mdel S, et al. High intake of saturated fat and early occurrence of specific biomarkers may explain the prevalence of chronic disease in northern Mexico. J Nutr. 2005 Jan;135(1):70-3.
34. Chan WB, Tong PC, Chow CC, et al. Triglyceride predicts cardiovascular mortality and its relationship with glycaemia and obesity in Chinese type 2 diabetic patients. Diabetes Metab Res Rev. 2004 Jul 27.
35. Ajani UA, Ford ES, Mokdad AH. Dietary fiber and C-reactive protein: findings from national health and nutrition examination survey data. J Nutr. 2004 May;134(5):1181-5.
36. Donaldson MS. Nutrition and cancer: A review of the evidence for an anti-cancer diet. Nutr J. 2004 Oct 20;3(1):19.
37. Slattery ML, Curtin KP, Edwards SL, Schaffer DM. Plant foods, fiber, and rectal cancer. Am J Clin Nutr. 2004 Feb;79(2):274-81.
38. Available at: http://www.physiciansweekly.com/article.asp?issueid=68&articleid=604. Accessed March 2, 2005.
39. Bingham SA, Day NE, Luben R, et al. Dietary fibre in food and protection against colorectal cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC): an observational study. Lancet. 2003 May 3;361(9368):1496-501.
40. Peters U, Sinha R, Chatterjee N et al. Dietary fibre and colorectal adenoma in a colorectal cancer early detection programme. Lancet. 2003 May 3;361(9368):1491-5.
41. Rendel M. Advances in diabetes for the millennium: nutritional therapy of type 2 diabetes. Med Gen Med. 2004 Sep 1;6(2):10.
42. Anderson JW, Akanji AO. Treatment of diabetes with high fiber diets. In: Spiller GA, ed. Dietary Fiber in Human Nutrition. 2nd ed. Boca Raton, FL: CRC Press; 1993:443-70.
43. Nizami F, Farooqui MS, Munir SM, Rizvi TJ. Effect of fiber bread on the management of diabetes mellitus. J Coll Physicians Surg Pak. 2004 Nov;14(11):673-6.
44. Chandalia M, Garg A, Lutjohann D, et al. Beneficial effects of high dietary fiber intake in patients with type 2 diabetes mellitus. N Engl J Med. 2000 May 11;342(19):1392-8.
45. Uusitupa M, Sodervik H, Silvasti M, Karttunen P. Effects of a gel forming dietary fiber, guar gum, on the absorption of glibenclamide and metabolic control and serum lipids in patients with non-insulin-dependent (type 2) diabetes. Int J Clin Pharmacol Ther Toxicol. 1990 Apr;28(4):153-7.
46. Smith U, Holm G. Effect of a modified guar gum preparation on glucose and lipid levels in diabetics and healthy volunteers. Atherosclerosis. 1982 Oct;45(1):1-10.
47. Braaten JT, Wood PJ, Scott FW, et al. Oat beta-glucan reduces blood cholesterol concentration in hypercholesterolemic subjects. Eur J Clin Nutr. 1994 Jul;48(7):465-74.
48. Available at: http://www.cfsan.fda.gov/~lrd/tpoats.html. Accessed March 2, 2005.
49. Thacker PA. Influence of propionic acid on cholesterol metabolism of pigs fed hyper-cholesterolemic diets. Can J Anim Sci. 1981;61:969-75.
50. Trepel F. Dietary fibre: more than a matter of dietetics. II. Preventative and therapeutic uses. Wien Klin Wochenschr. 2004 Aug 31;116(15-16):511-22.
51. Available at: http://www.americanheart.org/presenter.jhtml?identifier=4574. Accessed March 4, 2005.
52. Available at: http://5aday.nci.nih.gov/tools/faqs.html. Accessed March 4, 2005.