The Use of Psyllium and Soy for Hypercholesterolemia
The Use of Psyllium and Soy for Hypercholesterolemia
By Susan T. Marcolina, MD
Hyperlipidemia is a major risk factor for coronary heart disease (CHD), the leading cause of death among American adults.1,2 In the United States, 32% of adult men and 27% of adult women have hyperlipidemia according to the National Cholesterol Education Program (NCEP).3 Because diet is the main environmental determinant of plasma lipid concentrations, dietary modification is an important therapeutic tool whereby physicians can alter patient risk profiles.
Current initial treatment for hyperlipidemia recommended by the Adult Treatment Panel III include the following therapeutic lifestyle changes: 1) reduced intakes of saturated fats (fewer than 7% of total calories) and cholesterol (less than 200 mg/d); 2) use of therapeutic dietary additions, such as plant stanols/sterols (2 g/d) and increased soluble dietary fiber intake (10-25 g/d); 3) weight reduction; and 4) increased physical activity.4 Many patients need additional cholesterol lowering beyond what can be achieved with these interventions. Lipid-lowering medications, although efficacious in reducing serum cholesterol and the incidence of CHD, are expensive and can cause severe adverse reactions.5
Dietary measures, such as addition of soluble fiber and substitution of soy protein for meat and dairy products, can help patients achieve lower cholesterol levels. On a population-wide basis, each 1% reduction in serum cholesterol can reduce heart disease mortality by 2%.6 These interventions, therefore, can provide valuable additions to a patient’s cholesterol-lowering menu.
Dietary Fiber
The U.S. population, with one of the lowest dietary fiber intakes in the world, has much to gain from supplementation.7 Dietary fibers are the complex carbohydrates in fruits, vegetables, grains, nuts, and legumes that human digestive enzymes cannot break down. Soluble dietary fibers, shown to have cholesterol-lowering effects, include pectins, gums, psyllium, and algal polysaccharides; insoluble fibers include cellulose, lignin, and hemicellulose.8 Psyllium is a source of soluble fiber derived from the husks of blond psyllium seed, Plantago ovata, cultivated primarily in India.9 Table 1 lists some psyllium-containing fiber supplements.
Mechanism of Action
Two major hypotheses have been presented to explain the lipid-lowering action of psyllium. In the first, soluble fiber physically entraps bile acids, resulting in increased fecal loss.10,11 The second theory postulates that soluble fiber produces a decrease in cholesterol absorption and bile acid reabsorption by physical disruption of intraluminal micellar formation. In both mechanisms, interruption of the enterohepatic circulation causes increased conversion of cholesterol into newly synthesized bile acids in the liver. This reduction in cholesterol biosynthesis leads to an up-regulation of the low-density lipoprotein (LDL) receptor. This in turn leads to an enhanced plasma LDL uptake and reduced serum LDL-cholesterol (LDL-C) and total cholesterol levels.12
Soluble fibers have other lipid effects. They are fermented by colonic bacteria to short-chain fatty acids, which suppress cholesterol synthesis by limiting the action of HMG-CoA reductase, the enzyme that catalyses the rate-limiting step of cholesterol biosynthesis.13 Soluble fiber decreases gastrointestinal lipid and cholesterol absorption and serum insulin secretion, and in-creases peripheral insulin sensitivity.14 Marckmann et al showed in an eight-month study of healthy young men that a low-fat, high-fiber diet increases fibrinolysis.15
Watts et al demonstrated that 27 men with CHD who were treated with a low-fat, high-fiber diet (about 5 g pectin per day) showed improvement in angiographic patency of stenosed segments and a significant decrease in clinical cardiac events in comparison to controls.16
The mechanism by which soybean products lower cholesterol levels is not certain. Huff et al suggest that turnover of very low-density lipoprotein apoprotein (apo) B is increased in humans when soy protein is substituted for meat and dairy protein.17 Lovati et al noted an eightfold increase in the LDL-receptor activity of monocytes in human subjects who regularly consumed soy products compared to those eating control diets.18
Table 1
Cost of common psyllium-containing fiber
supplements
Yerba Prima
1 tsp (3.5 g) $0.13Psyllium husk powder
Nature’s Way
5 capsules (3.1 g) $0.45Psyllium husk seed
Nature’s Herbs
5 capsules (2.8 g) $0.45Psyllium husk
Adapted from: Bennett WG, et al. Benefits of dietary fiber:
Myth or medicine? Postgrad Med 1996;99:169-175.
Regulation
In February 1998, the Food and Drug Administration (FDA) authorized manufacturers of foods containing soluble fiber from psyllium seed husk (PSH) to claim a benefit for the treatment of CHD. Foods carrying this health claim must provide 1.7 g/serving of soluble fiber from PSH.19
In October 1999, the FDA authorized the use of health claims about the reduction of CHD risk on the labeling of foods containing soy protein. Based on the results of clinical studies, the FDA recommends daily ingestion of 25 g or more of soy protein to achieve optimal reduction in total cholesterol and LDL-C levels.20
Clinical Studies
Anderson et al published a meta-analysis that included five published studies of the hypocholesterolemic effects of 10.2 g psyllium per day adjunctive to an American Heart Association (AHA) Step I diet.9 All patients in these studies had been on the low-fat diet for a lead-in of 8-12 weeks and were randomized to their specific groups. Duration of treatment was from eight to 12 weeks. All studies had a cellulose placebo. Psyllium was associated with significant reductions in serum total cholesterol and LDL-C concentrations, total to high-density lipoprotein-cholesterol (HDL-C) ratios, and apoB/apoA-1 ratio compared with placebo. Psyllium intake did not significantly affect serum HDL-C concentrations. No significant differences were found in serum triglyceride (TG) concentrations between the psyllium and placebo groups.
Jensen et al conducted a six-month, double-blind, randomized, placebo-controlled, parallel comparison of 15 g/d of a supplemental, water-soluble dietary fiber (WSDF), which was a mixture of psyllium, pectin, guar gum, and locust bean gum with an inactive WSDF control (acacia gum).21 Changes in the mean plasma lipids and lipoprotein measures did not differ significantly from baseline to each of the follow-up periods for the control group. For the treated group, the mean plasma total cholesterol concentration declined by 6.4% and LDL-C declined by 10.5% (P < 0.05); these reductions were sustained throughout the study period. Mean plasma HDL-C and TG concentrations did not significantly change over the course of the study. The TG levels were quite variable and tended to be higher over the course of study in the treatment group. All of the subjects maintained their typical eating, physical activity, and medication patterns throughout the study.
Anderson et al performed a meta-analysis that included 29 articles on the effects of ingesting 31-47 g of soy protein on serum cholesterol concentrations.22 All studies were controlled with a parallel or crossover design. In the majority of the studies, dietary fat content was similar in the control and experimental groups. The use of soy in the experimental group diet caused a net decrease in total cholesterol of 9.3%, a net decrease in LDL-C of 12.9%, a net increase in HDL-C of 2.4%, and a net decrease in TG of 10.5%. The initial serum cholesterol level was the most significant predictor of change.
Wong et al evaluated the effects of the substitution of approximately 50 g/d of soy protein for animal protein in a NCEP Step 1 diet with a fixed fiber content of 25 g/d and similar amounts of saturated, monounsaturated, and polyunsaturated fatty acids.23 Thirteen hypercholesterolemic and 13 normocholesterolemic men were enrolled in this randomized, two-part crossover study with a washout of 10-15 weeks between diets. All participants completed the study. The investigators found that the cholesterol-lowering effect of the soy protein diet was independent of age, weight, pretreatment plasma lipid concentrations, and sequence of dietary treatment. The soy protein diet was associated with a statistically significant decrease in the plasma LDL-C concentrations of 6% (P = 0.029), as well as a decrease of 11% in the ratio of plasma LDL-C to HDL-C (P = 0.005).
Lewis et al found the effects of dietary saturated fat reduction and fiber supplementation to be additive in causing a decrease in serum total cholesterol of 29.2%, a decrease in LDL-C of 34.5%, and a decrease in serum TG of 20.8%, compared with Western diet controls.24
Adverse Reactions
Anderson et al assessed the safety of psyllium by pooling data from 19 clinical studies using psyllium. The amounts of psyllium varied from 5.1 to 20.4 g/d across the studies. A total of 966 patients were treated with psyllium. The most common symptoms presented more frequently in treated patients and included flatulence and bloating. No serious or unexpected psyllium-related adverse events occurred.
Psyllium always should be taken with at least 8 ounces of water per teaspoon.9 Psyllium-containing products should not be given to persons with gastrointestinal strictures or impaired gastrointestinal motility.25 Psyllium should be avoided by persons with known or suspected allergy; allergy symptoms include allergic rhinitis, conjunctivitis, urticaria, and asthma. Psyllium is safe to use during pregnancy and lactation when taken with adequate amounts of fluid.
The most common side effects after introduction of soy protein to a soy-naïve diet are flatulence, bloat- ing, abdominal cramping, and increased stool freq-uency, all of which often resolve with time and gradual re-introduction.
Conclusion
Multiple dietary manipulations, such as the addition of soluble fiber supplements and soy proteins, contribute significantly, individually, and in the aggregate to cholesterol lowering and may alleviate the need for pharmacotherapy in patients at risk for CHD. Physicians need to tailor carefully the interventions as appropriate to the patient’s clinical situation.
| Table 2 | |||
|
Examples of good dietary sources of fiber |
|||
| Food | Serving | Fiber | Soluble |
| Content | Fiber | ||
| Kidney beans | ½ cup | 4.5 g | 1.0 g |
| Spinach | ½ cup | 2.0 g | 0.5 g |
| Potato with skin | 1 medium | 4.0 g | 1.0 g |
| Apple | 1 medium | 3.0 g | 0.5 g |
| Oatmeal | ¾ cup | 3.0 g | 1.0 g |
| Source: American Dietetic Association. Available at: | |||
| Table 3 | ||
|
Examples of good dietary sources of soy protein |
||
| Foods | Serving |
Soy Content |
| Soy flour | ¼ cup | 8 g |
|
Soy breakfast links |
2 links | 6.5 g |
|
Soy burger |
1 patty | 10 g |
|
Green soybeans |
½ cup | 7 g |
|
Soynut non-dairy butter |
2 tbsp | 8 g |
|
Source: Soy Protein Partners. 2001 Soyfoods Guide. |
||
|
Available at: www.soyfoods.com/SoyfoodsGuide.pdf. |
||
Recommendation
Psyllium and soy protein are useful adjuncts for patients on a low-fat, AHA diet who have not reached their goal cholesterol level. They can be incorporated into a healthy lifestyle, which includes daily exercise and weight reduction to decrease cholesterol levels, specifically LDL-C.
The recommended daily intake for lowering cholesterol is 10.2 g of psyllium seed husk, or approximately 7 g of soluble fiber. In adults, a single serving size of 1.7 g should be consumed with at least 8 ounces of water and can be increased gradually to four times daily to produce the cholesterol-lowering effect.20 Consumption of soluble fiber supplements with meals is important for cholesterol-lowering efficacy.22 Because it may interfere with the absorption of other medications, particularly oral anticoagulants, PSH should be taken either one hour before or three hours after medications.
Soy protein should be introduced gradually to the diet to avoid side effects. A gradual increase to 25 g of soy protein daily over several weeks can produce the desired cholesterol-lowering effects.21 Tables 2 and 3 summarize common sources of soy protein and fiber.
Dr. Marcolina is a board-certified internist and geriatrician in Issaquah, WA.
References
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2. Keys A. Seven Countries: A Multivariate Analysis of Death and Coronary Heart Disease. Cambridge, MA: Harvard University Press; 1980.
3. Adult Treatment Panel II. National Cholesterol Education Program: Second Report of the Expert Panel on Detection, Evaluation and Treatment of High Blood Cholesterol in Adults. Circulation 1994;89:1333-1445.
4. Executive Summary of the Third Report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III). JAMA 2001;285:2486-2497.
5. FDA Talk Paper. Bayer Voluntarily Withdraws Baycol. Available at: http://www.fda.gov/bbs/topics/ answers/2001/ans01095.html. Accessed Sept. 2, 2001.
6. Lipid Research Clinics Program. The lipid research clinics coronary primary prevention trial results. 1. Reduction in incidence of coronary heart disease. JAMA 1984;251:351-364.
7. Spiller GA, ed. CRC Handbook of Dietary Fiber in Human Nutrition. 2nd ed. Boca Raton, FL: CRC Press; 1993.
8. Chu WW, et al. Dietary fiber and coronary artery disease. WMJ 2000;99:32-36.
9. Anderson JW, 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.
10. Everson GT, et al. Effects of psyllium hydrophilic mucilloid on LDL-cholesterol and bile acid synthesis in hypercholesterolemic men. J Lipid Res 1992;33: 1183-1192.
11. Matheson HB, et al. Cholesterol 7 alpha-hydroxylase activity is increased by dietary modification with psyllium hydrocolloid, pectin, cholesterol and cholestyramine in rats. J Nutr 1995;125:454-458.
12. Story JA. The role of dietary fiber in lipid metabolism. Adv Lipid Res 1981;18:229-246.
13. Anderson JW. Short-chain fatty acids and lipid metabolism. In: Cummings JH, et al, eds. Physiological and Clinical Aspects of Short Chain Fatty Acids. New York: Cambridge University Press; 1995:509-523.
14. Jenkins DJ, 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;329:21-26.
15. Marckmann P, et al. Favorable long-term effect of a low-fat/high-fiber diet on human blood coagulation and fibrinolysis. Arterioscler Thromb 1993;13:505-511.
16. Watts GF, et al. Effects on coronary artery disease of lipid-lowering diet or diet plus cholestyramine in the St. Thomas’ Atherosclerosis Regression Study (STARS). Lancet 1992;339:563-569.
17. Huff MW, et al. Turnover of very low-density lipoprotein-apoprotein B is increased by substitution of soybean protein for meat and dairy protein in the diets of hypercholesterolemic men. Am J Clin Nutr 1984;39: 888-897.
18. Lovati MR, et al. Soybean protein diet increases low density lipoprotein receptor activity in mononuclear cells from hypercholesterolemic patients. J Clin Invest 1987;80:1498-1502.
19. FDA Talk Paper. FDA Allows Foods Containing Psyllium to Make Health Claim on Reducing Risk of Heart Disease. Available at: http://www.cfsan.fda.gov. Accessed July 17, 2001.
20. FDA Talk Paper. FDA Approves New Health Claim for Soy Protein and Coronary Heart Disease. Available at: http://www.cfsan.fda.gov. Accessed Aug. 28, 2001.
21. Jensen CD, et al. Long-term effects of water-soluble dietary fiber in the management of hypercholesterolemia in healthy men and women. Am J Cardiol 1997;79:34-37.
22. Anderson JW, et al. Meta-analysis of the effects of soy protein intake on serum lipids. N Engl J Med 1995; 333:276-282.
23. Wong WW, et al. Cholesterol-lowering effect of soy protein on normocholesterolemic and hypercholesterolemic men. Am J Clin Nutr 1998;68(6 Suppl): 1385S-1389S.
24. Lewis B, et al. Towards an improved lipid-lowering diet: Additive effects of changes in nutrient intake. Lancet 1981;2:1310-1313.
25. Shulman LM. Perdiem causing esophageal obstruction in Parkinson’s disease. Neurology 1999;52:670-671.
26. Graedon J, Graedon T. Guide to Herbal Therapies—Psyllium. In: Graedon J, Graedon T, eds. The People’s Pharmacy Guide to Home and Herbal Remedies. New York: St. Martin’s Press; 1999.
Marcolina ST. The use of psyllium and soy for hypercholesterolemia. Altern Med Alert 2001;12:136-140.Subscribe Now for Access
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