Oat Ingestion Reduces Systolic and Diastolic Blood Pressure in Patients with Mild or Borderline Hypertension: A Pilot Trial

,

Original Research

Oat Ingestion Reduces Systolic and Diastolic Blood Pressure in Patients with Mild or Borderline Hypertension: A Pilot Trial

J Fam Pract. 2002 April;51(4):1

By

Joseph M. Keenan, MD

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References

1. He J, Klag M, Whelton P, et al. Oats and buckwheat intakes and cardiovascular disease risk factors in an ethnic minority of China. Am J Clin Nutr 1995;61:366-72.

2. Lichtenstein M, Burr M, Fehily A, Yarnell J. Heart rate, employment status, and prevalent ischemic heart disease confound relation between cereal fibre intake and blood pressure. J Epidemiol Community Health 1986;40:330-3.

3. Ascherio A, Rimm E, Giovannucci E, et al. A prospective study of nutritional factors and hypertension among US men. Circulation 1992;86:1475-84.

4. Hallfrisch J, Tobin J, Muller D, Andres R. Fiber intake, age, and other coronary risk factors in men of the Baltimore Longitudinal Study (1959-1975). J Gerontol 1988;43:M64-8.

5. Ascherio A, Hennekens C, Willett W, et al. Prospective study of nutritional factors, blood pressure, and hypertension among US women. Hypertension 1996;27:1065-72.

6. Schlamowitz P, Halberg T, Warnoe O, Wilstrup F, Ryttig K. Treatment of mild to moderate hypertension with dietary fiber. Lancet 1987;2:622-3.

7. Eliasson K, Ryttig K, Hylander B, Rossner S. A dietary fiber supplement in the treatment of mild hypertension. A randomized, double-blind, placebo-controlled trial. J Hypertens 1992;10:195-9.

8. Ryttig K, Tellnes G, Haegh L, Boe E, Fagerthun H. A dietary fiber supplement and weight maintenance after weight reduction: a randomized, double-blind, placebo-controlled long-term trial. Int J Obes 1989;13:165-71.

9. Dodson P, Stephenson J, Dodson L, et al. Randomised blind controlled trial of a high fiber, low fat and low sodium dietary regimen in mild essential hypertension. J Hum Hypertens 1989;3:197-202.

10. Little P, Girling G, Hasler A, Trafford A. A controlled trial of a low sodium, low fat, high fibre diet in treated hypertensive patients: effect on antihypertensive drug requirement in clinical practice. J Hum Hypertens 1991;5:175-81.

11. Rossner S, Andersson I, Ryttig K. Effects of a dietary fiber supplement to a weight reduction program on blood pressure. Acta Med Scand 1988;223:353-7.

12. Sandstrom B, Marckmann P, Bindslev N. An eight-month controlled study of a low-fat high-fiber diet: effects on blood lipids and blood pressure in healthy young subjects. Eur J Clin Nutr 1992;46:95-109.

13. Kestin M, Moss R, Clifton P. Comparative effects of three cereal brans on plasma lipids, blood pressure, and glucose metabolism in mildly hypercholesterolemic men. Am J Clin Nutr 1990;52:661-6.

14. Swain J, Rouse I, Curley C, Sacks F. Comparison of the effects of oat bran and low-fiber wheat on serum lipoprotein levels and blood pressure. N Engl J Med 1990;322:147-52.

15. Sciarrone S, Beilin L, Rouse I, Rogers P. A factorial study of salt restriction and a low-fat/high-fibre diet in hypertensive subjects. J Hypertens 1992;10:287-98.

16. Margetts B, Beilin L, Vandongen R, Armstrong B. A randomized controlled trial of the effect of dietary fiber on blood pressure. Clin Sci 1987;72:343-50.

17. el Zein M, Areas J, Knapka J, et al. Influence of oat bran on sucrose-induced blood pressure elevations in SHR. Life Sci 1990;47:1121-8.

18. Gondal J, MacArthy P, Myers A, Preuss H. Effects of dietary sucrose and fibers on blood pressure in hypertensive rats. Clin Nephrol 1996;45:163-8.

19. Krotkiewski M. Effect of guar gum on the arterial blood pressure. Acta Med Scand 1987;222:43-9.

20. Singh R, Rastogi S, Singh N, Ghosh S, Gupta S, Niaz M. Can guava fruit intake decrease blood pressure and blood lipids? J Hum Hypertens 1993;7:33-8.

21. Weidmann P, de Courten M, Bohlen L. Insulin resistance, hyperinsulinemia and hypertension. J Hypertens 1993;11:S27-38.

22. Tuck M. Obesity, the sympathetic nervous system, and essential hypertension. Hypertension 1992;19:I67-77.

23. Sowers J. Insulin resistance, hyperinsulinemia, dyslipidemia, hypertension, and accelerated atherosclerosis. J Clin Pharmacol 1992;32:529-35.

24. Braaten J, Wood P, Scott F, Riedel K, Poste L, Collins M. Oat gum lowers glucose and insulin after an oral glucose load. Am J Clin Nutr 1991;53:1425-30.

25. Braaten J, Scott F, Wood P, et al. High ß-glucan oat bran and oat gum reduce postprandial blood glucose and insulin in subjects with and without type 2 diabetes. Diabet Med 1994;11:312-8.

26. Hallfrisch J, Scholfield D, Behall K. Diets containing soluble oat extracts improve glucose and insulin responses of moderately hypercholesterolemic men and women. Am J Clin Nutr 1995;61:379-84.

27. Fukagawa N, Anderson J, Hageman G, Young V, Minaker K. High-carbohydrate, high-fiber diets increase peripheral insulin sensitivity in healthy young and old adults. Am J Clin Nutr 1990;52:524-8.

28. Welch S, Gebhart S, Bergman R, Phillips L. Minimal model analysis of IVGTT-derived insulin sensitivity in diabetic subjects. J Clin Endocrinol Metab 1990;71:1508-18.

29. Bergman R, Ider Y, Bowden C, Cobelli C. Quantitative estimation of insulin sensitivity. Am J Physiol 1979;236:E667-77.

30. Appel LJ, Moore TJ, Obarzanek E, et al. A clinical trial on the effects of dietary patterns on blood pressure. N Engl J Med 1997;336:1117-24.

31. Appel LJ. The role of diet in the prevention and treatment of hypertension. Curr Atheroscler Rep 2000;2:521-8.

32. Song YJ, Sawamura M, Ikeda K, Igawa S, Yamori Y. Soluble dietary fiber improves insulin sensitivity by increasing muscle GLUT-4 content in stroke-prone spontaneously hypertensive rats. Clin Exp Pharm Physiol 2000;27:41-5.

33. Taddei S, Salvetti A. Pathogenic factors in hypertension. Endothelial Factors. Clin Exp Hypertens 1996;18:323-35.

34. Krum H, Viskoper R, Lacourciere Y, Budde B, Charlon V. The effect of an endothelium-receptor antagonist, Bosentan, on blood pressure in patients with essential hypertension. N Engl J Med 1998;338:784-90.

35. Anderson T, Meredith I, Yeung A. The effect of cholesterol-lowering and antioxidant therapy on endothelium-dependent coronary vasomotion. N Engl J Med 1995;332:488-93.

36. Vogel R, Corretti M, Plotnick G. Changes in flow-mediated brachial artery vasoactivity with lowering of desirable cholesterol levels in healthy middle-aged men. Am J Cardiol 1996;77:37-40.

37. Crago M, West S, Hoeprich K, Michaelis K, McKenzie J. Effects of hyperlipidemia on blood pressure and coronary blood flow in swine. FASEB J 1998;12:A238.-

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ABSTRACT

OBJECTIVES: We assessed the short-term antihypertensive effects of soluble fiber-rich whole oat cereals when added to a standard American diet. In addition, multiple assessments of insulin sensitivity were conducted.

STUDY DESIGN: This was a randomized, controlled, parallel-group pilot study designed to compare an oat cereal group (standardized to 5.52 g/day beta-glucan) to a low-fiber cereal control group (less than 1.0 g/day total fiber) over 6 weeks.

POPULATION: A total of 18 hypertensive and hyperinsulinemic ( ≥10 μU/mL) men and women completed the trial.

OUTCOMES MEASURED: Primary study outcomes were changes in systolic blood pressure (SBP) and diastolic blood pressure (DBP). Secondary outcomes included blood lipid, fasting glucose, and insulin levels and side effects related to elevated blood pressure and increased dietary fiber intake.

RESULTS: The oat cereal group experienced a 7.5 mm Hg reduction in SBP (P < .01) and a 5.5 mm Hg reduction in DBP (P < .02), while there was virtually no change in either SBP or DBP in the control group. In the oat cereal group, a trend was observed for a lower total insulin response to a glucose load, suggesting improved insulin sensitivity. However, this could not be confirmed using estimates from the Bergman Minimal Model, perhaps because of our small sample size. As expected and reported in previous trials, the oats group experienced a significant reduction in both total cholesterol (9%) and low-density lipoprotein cholesterol (14%).

CONCLUSIONS: The addition of oat cereals to the normal diet of persons with hypertension significantly reduces both systolic and diastolic blood pressure. Soluble fiber-rich whole oats may be an effective dietary therapy in the prevention and adjunct treatment of hypertension.

Interest is growing in the use of nonpharmacologic methods for the prevention and management of hypertension. Specifically, the effect of dietary fiber on the incidence and treatment of hypertension has been explored. Epidemiologic studies show that the amount of dietary fiber ingested is inversely related to the incidence of hypertension as well as to systolic blood pressure (SBP) and diastolic blood pressure (DBP) in both hypertensive and normotensive patients.^1–5 The results obtained from clinical trials, however, are inconsistent; some report modest blood pressure reductions after increased fiber intake,^6–12 while others fail to demonstrate any effect of dietary fiber on blood pressure.^13–16 Some animal trials^17,18 and human trials^19,20 have shown a consistent lowering of blood pressure upon consumption of larger amounts of soluble fiber, suggesting that the antihypertensive effects of fiber may be caused by the soluble fraction and that these effects may be contingent upon the intake of a sufficiently large quantity.

Hypertension often occurs in association with obesity, impaired glucose tolerance, and dyslipidemia. Hyperinsulinemia and insulin resistance are thought to be key pathogenic links among these disturbances.^21–23 Studies show that soluble fiber from oats reduces both postprandial blood glucose and insulin levels.^24–27 Therefore, we conducted the following pilot trial to investigate the antihypertensive and insulin-modifying effects of oat cereal supplementation in a population of mild and borderline hyperinsulinemic and hypertensive men and women.

Methods

Study protocol

The study participants in this 6-week, randomized, parallel-group, active-controlled pilot trial were recruited by means of local community screenings and mass media advertising. The study protocol was reviewed and approved by the University of Minnesota Institutional Review Board. All participants provided informed consent before official enrollment in the study. One hundred nine men and women aged 20 to 70 were screened for eligibility with a physical exam, medical history, and chemistry and lipid profile (see Table 1 for exclusion criteria). Only generally healthy, untreated hypertensives with average SBP of 130 to 160 mm Hg and DBP of 85 to 100 mm Hg and with at least 1 reading greater than 140/90 as well as moderately elevated levels of fasting insulin (≥10μU/mL) were considered for enrollment. Participants were determined to be eligible only after 2 sets of hypertensive (SBP > 130, DBP > 85) baseline blood pressure readings had been taken 7 days apart and only if all inclusion criteria were fulfilled.

Ultimately, 22 men and women were randomized to either an oat cereal treatment group (standardized to 5.52 g/day beta-glucan) or a low fiber cereal control group (<1 g/day total fiber). Four of these individuals (1 in the treatment and 3 in the control group) discontinued participation because of time constraints. Eighteen healthy, nonsmoking men and women aged 27 to 59 years (44 ± 18; mean, SD) completed the trial. Cereal treatments were isocaloric. Participants were instructed to consume all their cereal (treatment, 137 g; control, 146 g) daily for the next 6 weeks but were allowed to prepare and consume the cereal however and whenever they wished.