Are your patients with risk of CVD getting the viscous soluble fiber they need?

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Applied Evidence

Are your patients with risk of CVD getting the viscous soluble fiber they need?

J Fam Pract. 2006 September;55(9):761-768

By

Tatyana A. Shamliyan, MD

Few patients eat the right amount of fiber known to reduce CVD risks and events.

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References

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8. The definition of dietary fiber. Cereal Foods World 2001;46:112-127.

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11. US Food and Drug Administration, Department of Health and Human Services. Food labeling: health claims; soluble dietary fiber from certain foods and coronary heart disease. Final rule. Fed Regist 2003;68:44207-44209.

12. Andersson M, Ellegard L, Andersson H. Oat bran stimulates bile acid synthesis within 8 h as measured by 7alpha-hydroxy-4-cholesten-3-one. Am J Clin Nutr 2002;76:1111-1116.

13. Jenkins DJA, Wolever TMS, Vidgen E, et al. Effect of psyllium in hypercholesterolemia at two monounsaturated fatty acid intakes. Am J Clin Nutr 1997;65:1524-1533.

14. Marlett JA, Hosig KB, Vollendorf NW, et al. Mechanism of serum cholesterol reduction by oat bran. Hepatology 1994;20:1450-1457.

15. Marcil V, Delvin E, Seidman E, et al. Modulation of lipid synthesis, apolipoprotein biogenesis, and lipoprotein assembly by butyrate. Am J Physiol Gastrointest Liver Physiol 2002;283:G340-346.

16. Wolever TM, Mehling C. High-carbohydrate-low-glycaemic index dietary advice improves glucose disposition index in subjects with impaired glucose tolerance. Br J Nutr 2002;87:477-487.

17. Ripsin CM, Keenan JM, Jacobs DR, Jr, et al. Oat products and lipid lowering. A meta-analysis. JAMA 1992;267:3317-3325.

18. Brown L, Rosner B, Willett WW, et al. Cholesterol-lowering effects of dietary fiber: a meta-analysis. Am J Clin Nutr 1999;69:30-42.

19. Olson BH, Anderson SM, Becker MP, et al. Psyllium-enriched cereals lower blood total cholesterol and LDL cholesterol, but not HDL cholesterol, in hypercholesterolemic adults: results of a meta-analysis. J Nutr 1997;127:1973-1980.

20. Anderson JW, Allgood LD, Lawrence A, et al. Cholesterol-lowering effects of psyllium intake adjunctive to diet therapy in men and women with hypercholesterolemia: meta-analysis of 8 controlled trials. Am J Clin Nutr 2000;71:472-479.

21. Davidson MH, Dugan LD, Burns JH, et al. The hypocholesterolemic effects of beta-glucan in oatmeal and oat bran. A dose controlled study. JAMA 1991;265:1833-1839.

22. Van Horn L, Emidy LA, Liu KA, et al. Serum lipid response to a fat-modified, oatmeal-enhanced diet. Prev Med 1988;17:377-386.

23. Van Horn LV, Liu K, Parker D, et al. Serum lipid response to oat product intake with a fat-modified diet. J Am Diet Assoc 1986;86:759-764.

24. Van Horn L, Liu K, Gerber J, et al. Oats and soy in lipid-lowering diets for women with hypercholesterolemia: is there synergy? J Am Diet Assoc 2001;101:1319-1325.

25. Moreyra AE, Wilson AC, Koraym A. Effect of combining psyllium fiber with simvastatin in lowering cholesterol. Arch Intern Med 2005;165:1161-1166.

26. Ascherio A, Rimm EB, Giovannucci EL, et al. A prospective study of nutritional factors and hypertension among US men. Circulation 1992;86:1475-1484.

27. Burke V, Hodgson JM, Beilin LJ, et al. Dietary protein and viscous soluble fiber reduce ambulatory blood pressure in treated hypertensives. Hypertension 2001;38:821-826.

28. Saltzman E, Das SK, Lichtenstein AH, et al. An oat-containing hypocaloric diet reduces systolic blood pressure and improves lipid profile beyond effects of weight loss in men and women. J Nutr 2001;131:1465-1470.

29. Chobanian AV, Bakris GL, Black HR, et al. Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. National Heart, Lung, and Blood Institute; National High Blood Pressure Education Program Coordinating Committee. Seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. Hypertension 2003;42:1206-1252.

30. Pins JJ, Geleva D, Keenan JM, et al. Do whole-grain oat cereals reduce the need for antihypertensive medications and improve blood pressure control? J Fam Pract 2002;51:353-359.

31. Cavallero A, Empilli S, Brighenti F, et al. High (1 -> 3,1 -> 4)-β-glucan barley fractions in bread making and their effects on human glycemic response. J Cereal Science 2002;36:59-66.

32. Urooj A, Vinutha SR, Puttaraj S, et al. Effect of barley incorporation in bread on its quality and glycemic responses in diabetics. Int J Food Sci Nutr 1998;49:265-270.

33. Thorburn A, Muir J, Proietto J. Carbohydrate fermentation decreases hepatic glucose output in healthy subjects. Metabolism 1993;42:780-785.

34. Pick ME, Hawrysh ZJ, Gee MI, et al. Barley bread products improve glycemic control of type 2 subjects. Int J Food Sci Nutr 1998;49:71-78.

35. Anderson JA, Randles KM, Kendall CW, et al. Carbohydrate and fiber recommendations for individuals with diabetes: A quantitative assessment and meta-analysis of the evidence. J Am Coll Nutr 2004;23:5-17.

36. Liu S, Buring JE, Sesso HD, et al. A prospective study of dietary fiber intake and risk of cardiovascular diseases among women. J Am Coll Cardiol 2002;39:49-56.

37. Rimm EB, Ascherio A, Giovannucci E, et al. Vegetable, fruit, and cereal fiber intake and risk of coronary heart disease among men. JAMA 1996;275:447-451.

38. Bazzano LA, He J, Ogden LG, et al. Dietary fiber intake and reduced risk of coronary heart disease in US men and women: the National Health and Nutrition Examination Survey I Epidemiologic Follow-up Study. Arch Intern Med 2003;163:1897-1904.

39. Li BW, Andrews KW, Pehrsson PR. Individual sugars, soluble, and insoluble dietary fiber contents of 70 high consumption foods. J Food Composition Analysis 2002;15:715-723.

40. Marlett JA. Content and composition of dietary fiber in 117 frequently consumed foods. J Am Diet Assoc 1992;92:175-186.

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42. National Cholesterol Education Program, National Heart, Lung, and Blood Institute, National Institutes of Health. Food sources of soluble fiber. Available at: www.nhlbi.nih.gov/chd/Tipsheets/solfiber.htm. Accessed on April 28, 2006.

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Practice recommendations

A diet that includes 5 to 10 g/d of viscous soluble fiber reduces cardiovascular disease (CVD) events and death independent of baseline risk (A).
Consuming foods rich in viscous soluble fiber reduces low-density lipoprotein cholesterol (LDL-C) blood levels 10% to 15% with expected reduction in CVD events by 10% to 15% (A).
Routinely counsel adults at risk of CVD to promote a healthy diet: assess dietary fiber consumption; recommend specific foods rich in viscous soluble fiber; monitor LDL-C levels and encourage increased dietary fiber intake at follow-up visits; motivate patients to comply with recommendations (A).

The Adult Treatment Panel III and the Dietary Guidelines for Americans recommend that adults eat a healthy diet as defined in TABLE 1—including more than 20 to 30 g of dietary fiber per day, 5 to 10 g of which should be viscous soluble fiber.^1,2,3 The benefits of such a diet are supported by growing epidemiologic data:

Risk of CVD drops by 20% to 30%
Morbidity and mortality from cardiovascular diseases fall by more than 10%
Foods rich in viscous soluble fiber, at a dose of 5 to 10 g/d, can reduce LDL-C levels by 10% to 15%, improve insulin sensitivity, and decrease blood pressure
Pooled analysis of 10 prospective cohort studies showed that, for adults at low risk of heart attack (estimated with Framingham scores), every additional 10 g of fiber consumed daily may prevent 1 coronary death in 74 adults (95% confidence interval [CI], 51–154), and 1 in 19 adults at high risk (95% CI, 13–38).⁴

Despite these hopeful findings, the average American adult eats less than half the recommended amount of fiber: 10 to 15 g/d; just 2.4 g of viscous soluble fiber.^2,5Healthy People 2010 has set a national objective to reduce coronary heart disease (CHD) mortality from 208 deaths to 166 deaths per 100,000 people.⁶ The US Preventive Services Task Force (USPSTF) recommends that primary care clinicians intensively counsel adults with elevated risk of CVD to improve daily intake of essential components of a healthy diet, including dietary fiber.⁷

In this article, we review practical approaches you can use in motivating patients to eat more fiber, types of dietary fiber and their sources, and the evidence for fiber’s impact on CVD risk factors and prevention of CVD events.

TABLE 1
Recommended ATP-III dietary change reduces risk of CVD by 20% to 30%

DIETARY COMPONENT	RECOMMENDED DAILY LEVELS*	EXPECTED LDL-C REDUCTION⁴
Total fat	25%-35%	8%-10%
Saturated fat	<7%
Polyunsaturated fat	≤10%
Monounsaturated fat	≤20%
Dietary cholesterol	<200 mg	3%-5%
Carbohydrates	50%–60%
Dietary fiber	20–30 g
Viscous soluble fiber	5–10 g	3%–5%
Protein	15%
Plant stanols/sterols	2 g	6%–15%
Cumulative estimate		20%–30%
* % of total calorie intake

Making sure patients get the right dietary fiber

Dietary fiber (nondigestible non-starch polysaccharides) is classified as insoluble or viscous soluble, based on its solubility in water and other fluids in the digestive tract.⁸

Insoluble fibers, present in most fruits, vegetables, and whole grain products, constitute over 80% of the total fiber in the typical US diet. Insoluble fibers shorten bowel transit time and produce a laxative effect but have no significant impact on blood lipids.⁹

FAST TRACK

A diet rich in viscous soluble fiber drops LDL-C blood levels by 10%–15%, with expected reduction in CVD events by 10%–15%

Viscous soluble fiber is present in smaller quantities in foods, but is responsible for the fiber-related physiological effects such as decreased blood cholesterol.⁵ The US Food and Drug Administration (FDA) has also approved health claims for 2 such fibers—beta-glucan from whole oat sources and psyllium—to be used as supplements in reducing CVD risk.^10,11

Viscous soluble fiber absorbs and holds water in the gastrointestinal tract, forming a thick gel. Viscous soluble bulk reduces reabsorption of bile acids from the ileum. Consequently, the liver shifts sterol metabolism from cholesterol production to replacement of bile acids lost in the stool. Fecal excretion of total bile acids increases in conjunction with serum cholesterol reduction when diets high in viscous soluble fiber are eaten.^12-14

Moreover, when viscous soluble fiber is fermented by colonic microflora, it produces short-chain fatty acids that directly inhibit intestinal fat absorption, and cholesterol transport and synthesis.¹⁵ Viscous soluble fiber may delay the absorption of simple sugars from the gut, thus decreasing postprandial glucose level and the demand for insulin secretion, and increasing insulin sensitivity.¹⁶

Viscous soluble fibers reduce CVD risk factors: The evidence

The goal of the cholesterol-lowering diet is to prevent CVD events by reducing LDLC, blood pressure, and glucose intolerance. Evidence from observational studies and randomized controlled trials confirms that foods rich in viscous soluble fiber lower blood lipids and arterial blood pressure and enhance insulin sensitivity.

Soluble fiber reduces LDL-C and may allow lower drug doses. In randomized controlled trials, 2 viscous soluble fiber sources at different doses resulted in a modest but clinically significant reduction in LDLC.^17,18 In addition, the reduction was seen in healthy men and women and in those with hypercholesterolemia (TABLE 2).^19-24 A 1% decrease in LDL-C reduces the risk of CVD events by 1%.¹