Dietary Strategies for the Prevention & Treatment of Metabolic Syndrome

Abstract

Obesity and the metabolic syndrome are epidemic health problems that are the root of many of the chronic diseases in our society. The increase in obesity in western societies can be largely attributed to changes in diet associated with modern civilization. Dietary strategies to reduce postprandial glucose and triglyceride spikes, and to increase the intake of dietary antioxidants, potassium, and omega-3 fatty acids will be helpful for improving health and reducing metabolic syndrome and obesity.

Introduction

Approximately two-thirds of American adults are overweight (have a body mass index [BMI] of 25.0–29.9) or obese (BMI ≥30).¹ Metabolic syndrome is characterized by the presence of several metabolic abnormalities including abdominal obesity, high blood pressure, impaired fasting blood glucose, and dyslipidemia.² The metabolic syndrome (MetSyn), according to the revised National Cholesterol Education Program Adult Treatment Panel (ATP) III definition, is present in 34% of individuals ≥20 years of age and in about 50% of individuals ≥60 years of age.²

Over the years from 1971 to 2000, daily calorie intake increased by 168 kilocalories (Kcal) in men and by 335 Kcal in women.³ Studies indicate that the epidemic of obesity can be largely accounted for by the increase in calorie intake.⁴ Intake of a diet high in caloriedense processed foods and beverages can result in increased insulin resistance,⁵ abdominal obesity,⁵ and the MetSyn.⁵ Thus, the most important dietary change for improving MetSyn is to reduce daily calorie intake. This will help eliminate excess intra-abdominal fat, improve all of the other features of MetSyn, and reduce systemic oxidative stress.

Postprandial Spikes in Glucose Cause Oxidative Stress and Inflammation

The high calorie, high glycemic diet, prevalent in America and increasingly throughout the world, predisposes to MetSyn and acute and chronic generalized systemic inflammation. A high glycemic-load meal, rich in sugars and starches which are easily digested and quickly absorbed into the bloodstream, results in a rapid and steep rise in blood glucose levels. By overwhelming the mitochondria and leading to the formation of free radicals,⁶ postprandial hyperglycemia may trigger an acute systemic inflammatory response, especially in subjects with diabetes.⁷ In addition, high glucose and high fat meals result in increased markers of inflammation and oxidative stress, and reduced endothelial function.⁸ Moreover, the combination of a high fat and high glucose load causes worsening in markers of inflammation (such as C-reactive protein), oxidative stress and endothelial function that is similar in direction but greater in magnitude compared to high fat or high glucose load alone.⁸ Importantly. the generalized inflammatory response to a high calorie, high glycemic diet is exacerbated by excess weight,⁹ and sedentary lifestyle.^{9, 10} When this is repeated regularly multiple times each day, as it is for many Americans, oxidative stress may ultimately lead to chronic degenerative diseases and premature aging.¹¹

Dietary Strategies to Reduce Metabolic Syndrome, Inflammation, and Chronic Degenerative Diseases

Strategies to reduce diet-induced oxidative stress should include blunting the excessive rises in postprandial glucose and triglyceride levels,⁸ and increasing the intake of dietary antioxidants in the form of plant-based phytonutrients.¹² The antioxidants in colorful plant foods and beverages such as berries, spinach, carrots, tomatoes, apples, kiwi, peach, citrus fruits, tea, coffee, and red wine can help reduce meal-generated free radicals and oxidative stress.^12–14 Additionally, antioxidants found in plant based foods may confer anti-inflammatory benefits by favorably altering genetic transcription factors.¹⁵ Given the relatively short duration of the anti-oxidant activity from ingested foods,¹³ an individual should ideally consume antioxidant-rich foods and/or beverages with each meal and snack to ensure that the body has a steady supply of blood-borne anti-oxidants to help buffer and eliminate postprandial oxidative stress throughout the day.

Glycemic index reflects the degree of increase in glucose after ingesting a certain type of food.^16,17 To examine the effect of the glycemic index of food on the antioxidant capacity of blood, a recent cross-over study randomly assigned 12 overweight or obese men, to either a diet with a low glycemic index rating or one with a high glycemic index rating.¹⁶ The total antioxidant capacity of blood and standard cardiovascular risk factors were measured at baseline and again after the subjects followed these diets.¹⁶ The low glycemic index diet resulted in a significantly higher level of total antioxidant capacity than the high glycemic index diet.¹⁶ Thus, a diet low in sugars and refined starches (low carbohydrate diet) may help to reduce the endogenous production of free radicals, and thereby reduce inflammation and lower the incidence of many chronic degenerative diseases.

The Hunter-Gatherer Diet

Studies suggest that eating patterns such as the hunter-gatherer style of diet or the Mediterranean style of diet are helpful, both for the prevention and the treatment of the MetSyn. Compared to our modern diet, the hunter-gatherer diet, which is the type of diet humans used to eat prior to agriculture and domestication of animals, had much higher amounts of lean protein (and hence dietary cholesterol), omega-3 fatty acids, beneficial plant-based compounds such as vitamins and antioxidant phytonutrients, fiber, and potassium, but contained much lower levels of sugar, sodium, and saturated fat.^17–20 See Table 1.

Table 1.

Comparison of modern diet and the hunter gatherer diet.¹⁷–²⁰

	Modern Diet	Hunter-Gatherer
Fat	33% of Energy	28–58% of Energy
Saturated Fat	11–12% of Energy	10–15% of Energy
Monounsaturated Fat	13% of Energy	16–25% of Energy
Omega-3	110 mg/day	660 mg/day
Carbohydrate	52% of Energy	22–40% of Energy
Protein	15% of Energy	19–35% of Energy
Sodium	2.3–6.9gm/day	0.7gm/day
Potassium	3.1gm/day	10.9gm/day
Fiber	15 gm/day	43 gm/day

Features of modern civilizations including sedentary life style, tobacco use, and the widespread availability of calorie-dense nutritionally-depleted foods, certainly magnify the risk of cardiovascular disease. However, the nutritional seeds of atherosclerosis had sprouted and were already discernible among ancient Egyptians who had transitioned away from the indigenous diet for which humans were, and remain today, genetically adapted.²¹ In fact, a recent study by Allam et al²¹ showed a high prevalence of calcified plaques in the aortas of 3,000 year-old mummies. This fascinating study was widely misinterpreted by the general media as evidence that atherosclerosis is a common and natural age-related human condition. Available data suggest that atherosclerosis is a disease of civilization whereby the abandonment of the hunter-forager lifestyle and the adoption of agriculture is associated with the development of cardiovascular disease.²² In contrast to the native hunter-forager diet, the diet of individuals living in agricultural societies, even ancient ones such as the Egyptians imaged in the Allam et al study, is likely to be based on grains and domesticated animals, resulting in reduced intake of cardioprotective dietary elements such as omega-3 fatty acids, folic acid, vitamins B6, antioxidants, phytochemicals and lean protein.^{17, 22} Accordingly, prospective dietary intervention studies have shown that a Paleolithic (Stone Age) -type diet is effective for weight loss and for improving multiple CV risk factors, including blood pressure, blood glucose, LDL and HDL cholesterol, and triglycerides.^{23, 24} In addition, a recent three-month randomized crossover trial demonstrated that a modern day “Paleolithic” diet improved multiple indices of MetSyn and cardiovascular risk in type 2 diabetic individuals when compared to a standard “diabetic” diet.²⁴

The major drawback of the hunter-gatherer diet relates to the high consumption of animal protein advocated by this eating plan.²⁰ Evidence suggests that most hunter-gatherer cultures consumed more than 50% of their calories from animal sources.²⁰ A modern diet high in fatty meat and/or highly processed animal foods tends to be atherogenic.²⁰ However, compared to modern sources of food, the omega-3 fatty acid content of the hunter gatherer diet was higher, and commonly used modern preservatives and salt were not used.²⁰ As such, the most reasonable approach would be to consume modest serving sizes of healthy forms of animal foods, such as fish and seafood, skinless chicken breasts, game meats, and lean red meat. It is also very important to consume, in conjunction with the healthy animal foods, a large variety of colorful produce on a daily basis. The other potential problem with the hunter gatherer eating style as practiced today relates to inadequate calcium intake and increased calcium excretion.²⁰ Thus, a calcium supplement may be necessary for individuals following the hunter gatherer diet.

The Mediterranean Diet

The Mediterranean cuisine is not a specific diet but instead a set of eating habits that are traditionally followed by the inhabitants of the Mediterranean region. Several nations surround the Mediterranean Sea, and although the eating traditions vary widely from one country to the next, these cultures typically follow the following general dietary principles:^25–27

• A high intake of fruits, vegetables, nuts, and cereal grains.

• Olive oil preferred for cooking and dressings.

• Moderate amounts of fish and seafood but sparse intake of meat.

• Low to moderate amounts of full fat cheese and yogurt.

• Moderate consumption of wine, typically with meals.

Several large studies suggest that following a Mediterranean-type diet is associated with good long-term health and longevity. A four-year study of a large cohort of people living in Greece reported that following the Mediterranean diet conferred protection against both heart disease and cancer.²⁶ In addition, data from 2,730 non-diabetic participants in the Framingham Heart Study Offspring Cohort followed for an average of seven years suggested several metabolic benefits for following a Mediterranean-type diet.²⁷ A higher compliance with the Mediterranean diet principles was associated with significantly lower levels of insulin resistance, waist circumference, fasting glucose, and triglycerides, and higher HDL cholesterol levels.²⁷ A controlled dietary trial randomized 215 patients with newly-diagnosed type 2 diabetes to either a Mediterranean diet or a low-fat diet. After four years, with ongoing dietary counseling, only 44% of newly diagnosed diabetic patients randomized to the Mediterranean diet versus 70% of those randomized to the low-fat diet required glucose-lowering drug therapy for control of their diabetes.²⁸ Individuals following the Mediterranean diet also had greater improvement in several cardiovascular risk factors.²⁸ Moreover, an epidemiological study of over 13,000 people found that those who followed a Mediterranean-style diet, despite having a worse diabetes risk factor profile, were less likely to develop new-onset diabetes during the four-year follow up period.²⁹

Studies have evaluated the specific components of the Mediterranean diet to see which ones were most important for conferring the health benefits associated with the consumption of this diet. Vogel and colleagues identified the anti-oxidant rich foods and beverages such as vegetables, fruits, olive oil and red wine, along with omega-3 rich foods including fish and nuts as the important dietary factors responsible for improving CV risk factors and endothelial function.³⁰ Additionally, in a more recent epidemiological study of 23,349 Greek adults followed for eight and a half years, the proportion of the overall improvement in longevity attributable to each of the specific components of the Mediterranean diet was determined. ³¹ About quarter of the benefit was provided by moderate ethanol consumption, whereas low consumption of meat and meat products and high vegetable consumption contributed about 16% each. ³¹ High fruit and nut consumption, high monounsaturated to saturated lipid ratio, and high legume consumption contributed 10–11% each. ³¹ The contributions of high fish and seafood consumption, high cereal consumption and low dairy consumption were not significant.³¹

Conclusion

Elimination of excess calorie intake is the single most important dietary factor for preventing or treating the MetSyn. Additionally, avoidance of high glycemic-index foods and beverages, and other easily digestible, highly processed, calorie-dense foods and beverages, is important. The consumption of foods and beverages with added sugar, high-fructose corn syrup, and artificial sweeteners should be minimized. Ideally, a modest-sized serving of lean fresh animal protein should be eaten at two meals daily and vegetable protein such as nuts or legumes should be consumed at least once daily. Two or three servings of vegetables and fruits (ideally those high in antioxidants and low in calories) should be eaten at each of the three daily meals. One alcoholic drink daily (four to six ounces of red wine with or before the evening meal) may be beneficial. ³³ Other foods and beverages that may be useful in preventing or treating MetSyn include coffee, cinnamon, vinegar, fish and fish oil, whole grains and other high-fiber foods, and olive oil.³³ See Table 2.

Table 2.

Suggested Dietary Recommendations Based on the Hunter-Gatherer and Mediterranean Diets. ²², ³², ³³

Protein	2–3 portions of lean protein daily.
Carbohydrates	Avoid simple/processed sugars. Consume fruits, and vegetables (2 servings with each meal).
Fat	Limit saturated fats. Avoid trans-fats. Increase omega-3 fatty acids (fatty fish, fish oil, nuts).
Salt	No salt added to food. Avoid high sodium foods.
Alcohol	Limited to light-to-moderate intake of red wine (4–6 ounces daily).
Physical Activity	Exercise for 30–60 minutes daily most days of the week.

Biography

James H O’Keefe, MD, MSMA member since 2003, and Mohammad Abuannadi, MD, practice at the Mid America Heart Institute/University of Missouri-Kansas City.

Contact: jhokeefe@cc-pc.com