Obesity, Metabolic Syndrome, and the Benefits of ... - ACS Publications

Chapter 16

Downloaded by NANYANG TECHNOLOGICAL UNIV on September 18, 2017 | http://pubs.acs.org Publication Date: June 9, 2006 | doi: 10.1021/bk-2006-0936.ch016

Obesity, Metabolic Syndrome, and the Benefits of Citrus Ken Fujioka and Michael W. Lee Nutrition and Metabolic Research Center, Scripps Clinic Division of Endocrinology, Diabetes, and Metabolism, 12395 El Camino Real, Suite 317, San Diego, C A 92130

Background on Obesity The World Health Organization estimates that there are currently over 300 million obese adults worldwide. In the United States, the prevalence of obesity among adults has doubled over the past twenty years, and is now at 31%. Even more troubling is the tripling (to 16%) of obesity (commonly called pediatric overweight) among American children over the same twenty years. Modernity has created the growing epidemic of obesity; left unchecked, this societal scourge of the 21 century threatens to undo and even reverse the gains made thus far in lifespan and health. Up to 365,000 adult deaths per year in the U.S. have been attributed to excess weight. Obese individuals are more likely to develop a variety of medical conditions, such as coronary artery disease, stroke, sleep apnea, type II diabetes, osteoarthritis, and certain malignancies (e.g., breast and prostate cancer). Total costs attributable to obesity in the United States amounted to nearly $100 billion in 1995. Among adults, obesity is associated with a decline in health-related quality of life that is greater than the decline associated with 20 years of aging. 1

2

3

st

4

5

6

7

8

Metabolic Syndrome Concurrent with the increase in obesity is the rise in prevalence of a condition known as metabolic syndrome. As a multidimensional risk factor for both cardiovascular disease and type II diabetes, the diagnosis of metabolic syndrome is extremely useful in predicting which individuals will develop obesity-related medical conditions and complications. Nearly 1 in 4 adult © 2006 American Chemical Society

Patil et al.; Potential Health Benefits of Citrus ACS Symposium Series; American Chemical Society: Washington, DC, 2006.

211

212 Americans has metabolic syndrome, and the prevalence is even higher in those over the age of 50 and in certain ethnic populations (e.g., Hispanic Americans). Metabolic syndrome is due in part to abdominal obesity and the concept of insulin resistance, which result in characteristic changes in waist circumference, blood pressure, glucose homeostasis, and cholesterol levels. In 2001, the third Adult Treatment Panel (ATP III) of the National Cholesterol Education Program (NCEP) stated that the diagnosis of metabolic syndrome is established when 3 or more of the following risk factors are present (Table l ) : 9


10

10

Table 1: ATP III Definition of Metabolic Syndrome (Diagnosis is established when >3 risk factors are present) RISK FACTOR

DEFINING LEVEL

Abdominal Obesity fWaist Circumference) Men

>40 inches (>102 cm)

Women

>35 inches (>88 cm)

Triglyceride Level

>150 mg/dL

HDL (High Density Lipoprotein) Cholesterol Men

85 mm Hg >110 mg/dL (revised to > 100 mg/dL in 2004)

11

In 2005, the International Diabetes Federation published similar criteria for the diagnosis of metabolic syndrome, placing a more stringent emphasis on central/abdominal obesity. 12

Treatment of Metabolic Syndrome The principal therapy for metabolic syndrome is weight loss and increased physical activity. Weight reduction and exercise improve every element of metabolic syndrome: they lower triglyceride levels, raise HDL cholesterol, and improve blood pressure and glucose. The landmark Diabetes Prevention Program study showed that 7% weight loss and regular physical activity reduced the risk of type II diabetes by 58% over a period of four years. 11

13


213

Benefits of Citrus on Metabolic Syndrome Risk Factors There is also evidence that specific dietary changes will improve the individual risk factors of metabolic syndrome. Both reduced sodium intake and the DASH (Dietary Approaches to Stop Hypertension) eating plan, which emphasizes fruits, vegetables, and lowfat dairy foods, have been shown to reduce blood pressure in clinical studies. Incorporation of monounsaturated fats and moderation in alcohol consumption are recommended in order to decrease elevated triglyceride levels. Consumption of citrus foods has beneficial effects on metabolic syndrome risk factors as well; this chapter will now focus on the available evidence from human studies thus far.


14

15

Flavonoids and Citrus Flavonoids are the products of plant metabolism and provide much of the color and flavor to fruits and vegetables. Due to their antioxidant properties, there is growing interest in the potential health benefits of flavonoids. Several epidemiologic studies have shown a protective effect of flavonoid consumption in cardiovascular disease and cancer. The six major classes of flavonoids are listed in Table 2. Citrus foods are a major source of flavanones, such as hesperetin (oranges) and naringenin (grapefruit). 16

17,18

Table 2: Major Classes of Flavonoids FLAVONOID CLASS Flavones Flavonols Flavanones Catechins/Flavanols Anthocyanidins Isoflavones

EXAMPLES

FOOD SOURCES

Apigenin Luteolin Quercetin Myricetin Naringenin Hesperetin Epicatechin Gallocatechin Cyanidin Pelargonidin Genistein Daidzein

Parsley, thyme, celery Onions, broccoli, apples Berries, tea Citrus fruit Tea, apples, cocoa Cherries, grapes Soya beans


214

Orange Juice In healthy subjects with hypercholesterolemia, consumption of 750 mL of orange juice was shown to increase HDL-cholesterol levels by 21% over a fourweek period. According to a pilot study at the Cleveland Clinic, intake of 16 ounces of orange juice daily for six weeks significantly reduced blood pressure. 19


20

Grapefruit Since being introduced in the 1930s as part of the "Hollywood Diet," grapefruit has developed a reputation in the general public as a weight loss food. Due to its inhibition of the CYP3A family of P-450 enzymes in the liver and small intestine, grapefruit affects the metabolism of a variety of medications, including felodipine, cyclosporine, atorvastatin, and erythromycin. At the Scripps Clinic Nutrition and Metabolic Research Center, a three month study was conducted to investigate the effects of grapefruit on weight and metabolic factors. Ninety-one subjects were randomized to the following groups: • Vi of a fresh grapefruit three times a day • 500 mg grapefruit capsules three times a day • 8 ounces of grapefruit juice three times a day • Placebo capsules three times a day Thirty-one patients (34%) had metabolic syndrome according to ATP III criteria. Weight and blood pressure were measured at monthly intervals. Laboratory work included a 75-gram two-hour glucose tolerance test at the start and end of the study; elevated insulin and/or glucose levels during such testing signifies insulin resistance, which is a key feature of metabolic syndrome. 21

22

23

Results Compared to the placebo group, subjects who consumed fresh grapefruit had a statistically significant 1.6 kilogram weight loss over three months (Figure 1). Of particular interest was the finding that subjects who had metabolic syndrome and received any form of grapefruit product (fresh fruit, capsules, or juice) also lost significantly more weight (0.9-2.5 kilograms) than subjects on placebo (Table 3). In addition, subjects with metabolic syndrome and intake of fresh grapefruit had a significant reduction in 2-hour insulin level compared to the placebo group, suggesting that insulin resistance was decreased by fresh grapefruit. Grapefruit juice also decreased 2-hour insulin levels, but this finding did not reach statistical significance relative to placebo. Interestingly, grapefruit capsules did not improve insulin resistance in this study (also Table 3).



215

—•— -O— C —v-

A. Grapefruit Capsule (A, E, or I) & Placebo B. Placebo Capsule (H, R, or S) & Placebo . Placebo Capsule (H, R, or S) & grapefruit D. Placebo Capsule (H, R, or S) & Fresh

Figure 1: Weight Loss With Grapefruit Intake (All Subjects, Regardless of Metabolic Syndrome Status) (Reproduced with permission from reference 23. Copyright 2005.) 23


216 Table 3: Weight and Insulin Changes in Subjects Over 12 Weeks of Treatment (Metabolic Syndrome Subgroup)' Metabolic Syndrome Subgroup


Weight (kg) 2-hour insulin (mcg/ml)

A (Capsule)

B (Placebo)

C (Juice)

D (Fruit)

-1.9*

1.8

-2.5*

-0.9*

44

44

-59**

-76*

* Statistically significant relative to placebo (p

Obesity, Metabolic Syndrome, and the Benefits of ... - ACS Publications

Recommend Documents