Recomendations

Lifestyle has a strong influence on the development and outcome of T2D and MetS. The goal of nutritional intervention should include dietary modifications that promote improved glycemic control and reduce diabetic complications. The most important consideration should be a lifestyle and dietary pattern that a patient chooses to follow over the long term. Common threads among successful diets in T2D include high vegetable and fruit intake, higher protein, and healthy fat intake, along with the avoidance of high carbohydrate loads, high glycemic index foods, and processed foods. These general rules should lead to reduction in the consumption of fructose and saturated fat. Although there is likely to be no single, optimal dietary pattern, the Mediterranean diet and the NND serve as model examples for the successful treatment and prevention of T2D and the MetS.

Diabetes Mellitus Type 2

The addition of micronutrient supplements can be considered but remain controversial and should only be taken as part of a more comprehensive approach to T2D. Avoidance of ED compounds, such as by thoroughly washing foods during preparations or by minimizing use of plastic food containers, may benefit T2D, although strong evidence for this recommendation is not currently available. Similarly, avoidance of artificial sweeteners may also be beneficial, although further study is necessary. Along with physical activity, dietary modification as part of an intensive lifestyle should be recommended universally to patients with T2D.

Summary of nutritional recommendations:

  • Follow a healthful dietary pattern, such as the Mediterranean diet or NND
  • Maintain lower carbohydrate intake, approximately 30% to 40% of calories
  • Consume copious fruits, vegetables, and nuts
  • Avoid/minimize high glycemic index foods, such as sugar-containing beverages, desserts, and easily digestible starches, such as white bread and crackers
  • Minimize fructose intake by avoiding processed foods
  • Take care to minimize ED exposure – wash foods, wash hands, and use organic
  • foods, fertilizers, and cleaning products wherever possible.
  • Glycemic Index of Local Foods and Diets: The Mediterranean Experience

The Mediterranean diet represents a healthful eating pattern associated with the prevention of coronary heart diseases (CHD), the major cause of premature death and disability in industrialized countries. The main features of this dietary model are a moderate intake of total fat — with liberal intake of monounsaturated fat and low intake of saturated fat and cholestero l— and a high consumption of foods rich in starch. Although this type of diet has beneficial effects on lipid metabolism, its high carbohydrate content might not be ideal for diabetic patients, who are known to be at particularly high risk for CHD. A diet high in carbohydrate can have detrimental effects on glycemic control in patients with diabetes, particularly people treated with insulin or people who have more severe forms of type 2 diabetes. Moreover, this type of diet may exacerbate metabolic abnormalities associated with insulin resistance (i.e., metabolic syndrome) and increase the risk of diabetes in the general population. Not all carbohydrate-rich foods are equally hyperglycaemic; different postprandial blood glucose responses to isoglucidic amounts of various carbohydratecontaining foods have been observed in healthy subjects and people with diabetes. Carbohydrate-rich foods are therefore classiffed as foods with high or low glycemic index.

For individuals at risk for type 2 diabetes mellitus (T2D) or the metabolic syndrome (MetS), adherence to an idealized dietary pattern can drastically alter the risk and course of these chronic conditions:

  • Target levels of carbohydrate intake should approximate 30% of consumed calories.
  • Healthy food choices should include copious fruits, vegetables, and nuts while minimizing foods with high glycemic indices, especially processed foods.

Insulin resistance manifesting as T2D, the MetS, polycystic ovary syndrome, or hypertriglyceridemia, is a major public health problem. Approximately 10% of the United States population is diagnosed with T2D, and the prevalence of MetS is approximately 22% to 30%, depending on the defining criteria used. Modern lifestyles have long been suspected as the major influence of this trend, with the implication that modification of daily routines can prevent or substantially alter the course of these conditions. Prior to the therapeutic use of insulin, lifestyle intervention was the only effective option for the treatment of insulin resistance syndromes. Resistance to insulin is present for years prior to the development of T2D and drives the multiple components of MetS, including increased abdominal girth (waist circumference >102 cm in men and >88 cm in women), hypertension (systolic blood pressure >130 mm Hg and diastolic blood pressure >85 mm Hg), elevated circulating triglycerides (>150 mg/dL), reduced circulating high-density lipoprotein (HDL) levels (100 mg/dL). Individuals with at least 3 of these 5 components are considered to have MetS, although more precise definitions exist from multiple professional medical organizations.

Several large clinical trials demonstrate the effectiveness of lifestyle modification for the treatment and prevention of T2D and MetS. Despite the wide array of medication classes presently available, lifestyle modification focused on dietary change and enhanced physical activity remains a cornerstone of disease management in T2D, MetS, and other insulin resistance syndromes. Individuals develop insulin resistance over prolonged periods of time, secondary to alterations in multiple metabolic and energy regulatory pathways. This culminates in hyperglycemia and other metabolic abnormalities, such as hypertriglyceridemia, hypertension, and obesity as well as the emergence of MetS or T2D. Obesity is the most significant factor contributing to insulin resistance and T2D, and, subsequently, weight loss through dietary caloric restriction has been shown to be the most important treatment in patients with T2D who are overweight or obese.

Metabolic Syndrome

Dietary components affecting type 2 diabetes melitus

:

Carbohydrates

Carbohydrates, in the form of starch, glycogen, or other polysaccharides, as well as simple sugars (monosaccharides and disaccharides) comprise approximately 40% to 50% of the calories of most diets. Polysaccharides are hydrolyzed within the gastrointestinal tract to glucose monosaccharides for absorption. Most other absorbed dietary monosaccharides are converted to glucose for systemic use.

Fructose

Long-term consumption of fructose in high amounts is associated with worsening insulin resistance and T2D. Fructose intake is also associated with the development of common diabetes-associated complications. Dietary fructose should be kept at a minimum in T2D and MetS, which may be achieved by elimination of processed foods and sugar-containing beverages as well as reduction in dessert intake. The World Health Organization recommends that sugar intake, including fructose, be kept at less than 5% of total calorie consumption.

Fiber

Another class of carbohydrate, dietary fiber, includes polysaccharides and modified

polysaccharides that are not easily digested in the stomach or intestine. These substances, produced by plants and fungi, provide structure to intestinal chyme and stool, slow gastric emptying, and delay the absorption of dietary carbohydrates, leading to improved serum glucose concentrations in individuals with diabetes.

Glycemic index and load

The rapidity and extent to which dietary carbohydrates enter circulation in the form of glucose is described as the glycemic index, which is given as the total area delineated by the change in blood glucose concentration over time after food consumption. Foods with a high glycemic index often contain high amounts of monosaccharides or easily digestible polysaccharides and are low in dietary fiber. In T2D, consumption of high glycemic index foods can lead to profound and rapid increases in blood glucose concentrations, worsening the disease state. Foods are often consumed, however, as part of a meal, mixed with multiple other food items. Mixing can affect the glycemic index of specific foods, commonly dampening and prolonging the degree of glycemic excursion in large mixed meals. In this manner of real-world food consumption, the glycemic load, or simply the total amount of digestible carbohydrates consumed, is the more important factor contributing to postprandial glycemic excursions.

Accordingly, patients with T2D should completely avoid or at least minimize high glycemic index foods and minimize intake of foods that deliver high glycemic loads.

Dietary patterns

For individuals with T2D, dietary considerations should minimize carbohydrate load, especially fructose; contain high amounts of fiber; and contain a favorable fat content, antioxidants, and vitamins. Most importantly, diet should be palatable for long-term adherence. Dietary patterns consistent with these general principles are briefly described.

The Mediterranean Diet

The Mediterranean diet has long been recognized to promote overall health and improve markers of metabolism. Approximately 30% to 40% of calories are carbohydrate based, and 35% to 40% calories in the form of fats and oils. In a randomized trial in which overweight subjects were given prepared meals daily, those on the Mediterranean diet had the greatest weight loss over the planned 2 years of follow-up compared with a low-fat diet and a very-low-carbohydrate diet. This difference was sustained over a 4-year extension among those who chose to remain in the study. The Mediterranean diet group also had reductions in LDL cholesterol and triglycerides and induced the greatest reduction in fasting glucose and fasting insulin among the subset of subjects with diabetes who were included in the trial.

Components of the Mediterranean diet:

  • Fruits, 3 to 4 servings per day
  • Vegetables, 3 to 4 servings per day
  • Poultry
  • Fish, 2 to 3 servings per week
  • Whole grains
  • Olive oil for consumption and food preparation
  • Nuts, 5 to 7 nuts per day
  • Cheese
  • Wine, 1 to 2 glasses per day

To date, the Mediterranean diet is the only diet shown to reduce cardiovascular events and mortality among individuals who are overweight. A large randomized trial that used a low fat diet as comparison demonstrated an approximate 30% reduction in cardiovascular events and cardiovascular mortality over 6 years. A post hoc analysis of subjects with diabetes who were included in this trial demonstrates an approximate 40% reduction in new-onset retinopathy. Another analysis of the subjects without T2D at baseline showed a 30% reduction in the incidence of T2D in the Mediterranean diet group. Wine serves as a source of dietary polyphenols, with a 7-fold higher polyphenol content in red wine compared with white wine. A 2-year randomized trial in which 224 subjects with T2D who already were following the Mediterranean diet were provided either 150 mL of red wine, white wine, or water daily and asked to abstain from other alcohol was recently published. Both groups given wine showed reduction in fasting insulin, although only the white wine group had an average reduction in fasting plasma glucose by 18 mg/dL. HDL levels increased by an average of 2 mg/dL in the red wine group. These results are consistent with many other small trials that show improved levels of cholesterol, reduced markers of inflammation, and reduced insulin resistance with moderate consumption of alcohol, mainly wine. Although still controversial, wine is an important component of the Mediterranean diet. These results support moderate wine consumption as beneficial to individuals with diabetes.

The New Nordic Diet

Although the concept for the New Nordic Diet (NND) was developed based on local Scandinavian cuisine, many of the components are similar to the Mediterranean diet, which include intake of copious fruits, vegetables, whole grains, and fish.

Content of the New Nordic Diet:

  • Organic foods
  • Fruits, especially berries
  • Vegetables – cabbage, root vegetables, legumes
  • Fresh herbs
  • Wild mushrooms
  • Nuts
  • Fish
  • Seaweed
  • Meats

Currently, there are no large published studies of the NND conducted specifically in subjects with diabetes; however, a recent trial shows promise for treatment of T2D and MetS. This study was performed in Denmark and randomly assigned individuals with obesity to the NND or a typical Danish diet – similar to the Western diet. At 6 months of follow-up, the NND group lost 6 kg compared with a 2-kg weight loss in the control group. Average fasting insulin levels declined by 3 mU/L, fasting glucose decreased by 5 mg/dL, and triglycerides decreased by 18 mg/dL in study subjects assigned to the NND. These improvements in markers of insulin resistance support recommendation of the NND lifestyle intervention in T2D and MetS.

The Ornish Diet

The central principle of the Ornish diet (OD) is a significant reduction or elimination of ingested animal fat and products derived from animal fat. As a result, the OD necessarily includes increased carbohydrates in the form of whole grains. This diet demonstrates significant improvement in circulating LDL levels and is beneficial in the treatment and prevention of atherosclerotic disease.

Ornish diet components:

  • Fruits
  • Vegetables
  • Whole grains
  • Reduced fish
  • Minimal meats
  • Ornish diet calorie content
  • 15% Daily calories from fat
  • 10% Daily calories from protein
  • 75% Daily calories from complex carbohydrates

The effects of the OD on insulin resistance has not been well characterized. One uncontrolled cohort study included subjects at high risk for cardiovascular disease who were directed to follow the OD as a lifestyle intervention. The subset of subjects with diabetes within the study showed a reduction in average fasting glucose of 16 mg/dL and a 0.4% reduction in HbA1C levels after 3 months of follow-up. Although promising, longer-term follow-up is needed. Although the tradeoff of reduced animal products for increased whole grains seems beneficial in atherosclerotic disease, the increased carbohydrate load of the OD may make this dietary pattern less effective than the Mediterranean diet or NND.

Potentially beneficial micronutrients in insuline resistance

  • Chromium (as chromium picolinate 500–1000 mg/d)
  • Amplifies insulin signaling
  • Induces weight loss and lowers serum glucose levels in some studies
  • Selenium (approximately 200 mg/d)
  • Use in selenoproteins/redox reactions
  • Reduces production of AGEs
  • May improve insulin resistance
  • Vitamin D (2000–5000 U/d – targeting normal circulating levels)
  • Pancreatic b-cell activity
  • Reduces insulin resistance in animal trials
  • Minimal effect in T2D and MetS, may be most effective as preventive measure