The effect of fiber-rich carbohydrates on features of Syndrome X☆

https://doi.org/10.1053/jada.2003.50005Get rights and content

Abstract

There has been much debate among nutritionists and scientists regarding the optimal dietary approach for the treatment of the Insulin Resistance Syndrome, also called Syndrome X. This condition, which may affect as many as 47 million individuals in the United States, significantly increases risk of coronary heart disease and stroke. Major health organizations have historically recommended high-carbohydrate, low-fat (HCLF) diets to reduce chronic disease risk. However, there is evidence that a high intake of carbohydrates may adversely affect one or more of the abnormalities associated with this syndrome. Studies in this area have often had limitations. For example, some studies showing adverse effects of an HCLF diet have not taken into account the dietary fiber content of the diet. This article describes abnormalities often associated with Syndrome X, reviews the beneficial effects of fiber-rich carbohydrates, discusses the effect of fiber-rich carbohydrates on features of this syndrome, and concludes with applications of these findings for those involved in treating individuals with features of this disorder. This review indicates that an HCLF dietary pattern such as that used in the DASH trial, with a level of dietary fiber consistent with the recommendations of the American Dietetic Association (eg, 20-35g/day), containing from 3 to 10 g soluble fiber/day, may be beneficial for treating those with Syndrome X. J Am Diet Assoc. 2003;103:86-96.

Section snippets

Description of Syndrome X

Syndrome X refers to a condition in which several specific abnormalities (Figure 1) are clustered together with insulin resistance as the primary defect.Increased intra-abdominal adipose tissue (eg, visceral obesity) may be the initial culprit in the development of this syndrome ((11)). Elevated stress-related cortisol secretion ((12)), abnormal uric acid metabolism, and polycystic ovary syndrome ((1)) have also been associated with this syndrome. Recently, elevated concentrations of C-reactive

Prevalence and significance of Syndrome X

Estimates of the prevalence of Syndrome X in the United States vary depending on the source and criteria used to diagnose this condition. Prevalence has been reported to be 16% among white persons ((14)); 7% in white and African American men and women ((15)); and 10% and 6% in Native American men and women, respectively ((16)). In 2002, findings from the Third National Health and Nutrition Examination Survey ((17)) reported much higher overall prevalence rates (age-adjusted) of 24% for men and

Genetics versus behavior

The development of Syndrome X is likely caused by interactions between and among genetic and behavioral factors, eg, diet and physical activity ((20)). There is evidence of familial aggregation with respect to features of this syndrome ((21)). Abdominal obesity is strongly heritable ((20)), with estimates ranging from 25% to 40%. It has been estimated that 50% of the variability in insulin-mediated glucose disposal in nondiabetic individuals is attributable to genetic factors, with the

Insulin resistance and abnormal glucose metabolism

A primary feature of Syndrome X is insulin resistance. Specifically, the ability of insulin to promote glucose disposal in peripheral tissues such as skeletal muscle is impaired. This can be detected clinically by reduced insulin sensitivity (SI) (eg, less than normal insulin-mediated glucose disposal), hyperinsulinemia, impaired glucose tolerance, and an elevation in fasting blood glucose concentration (Table 1). Although insulin resistance is usually defined based on impaired glucose

Beneficial effects of fiber-rich carbohydrates

There is a vast body of literature supporting the beneficial effect of fiber-rich carbohydrates for optimal health and disease prevention. It is generally accepted that consumption of fiber-rich carbohydrates is important for gastrointestinal health by decreasing constipation and reducing risk of diverticular disease [41], [42]. A high intake of fiber-rich carbohydrates is beneficial for weight management [42], [43] and for reducing risk of cardiovascular disease [44], [45], diabetes [42], [46]

Benefits of fiber-rich carbohydrates for weight management

Weight loss, specifically the reduction of body fat, may be the most effective strategy for improving abnormalities associated with Syndrome X in overweight individuals [1], [20]. The degree of insulin resistance and/or hyperinsulinemia does not alter weight loss response to a hypocaloric diet ((108)). A moderate weight loss of ∼10% can significantly enhance insulin clearance, thereby reducing hyperinsulinemia, although greater degrees of weight loss may be required to reduce insulin secretion

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    ☆

    The authors received funding for research cited in this review (references 10, 105) from The Quaker Oats Company, Barrington, IL.

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    Copyright © 2003 American Dietetic Association. Published by Elsevier Inc. All rights reserved.