Growing evidence is demonstrating that the Mediterranean diet is effective in certain disease states. Although several variants exist, the common components are high intakes of monounsaturated fat, moderate levels of alcohol consumption (mainly of red wine), high intakes of fruits, vegetables, legumes and grains, and low consumption of meat and meat products (especially red meat). The macronutrient composition is roughly 40% fat (20% from monounsaturated fat), 40% carbohydrate, and 20% protein. These characteristics, whether individual or collective, are demonstrating healthful benefits. In the Lyon Diet Heart Study (1), a Mediterranean diet high in alpha-linolenic acid showed a major reduction of risks of coronary recurrences. In addition, this trial suggested that the diet might reduce cancer risks.

Because of past findings, the Mediterranean diet is currently being studied at our center in patients with heart disease who have already endured at least one myocardial infarction. Subjects are randomized to a standard low fat diet or the Mediterranean diet. This multi-center 6-month, outpatient trial aims to show 3 things, that dietary compliance, serum lipid panels and cardiac events while on a Mediterranean diet is similar to results found while on the low fat diet. Since the results have been successful in meeting these objectives, it can perhaps serve as a second medical nutrition therapy option for patients with cardiovascular disease. We are hoping this population is more willing to comply with a diet if given more than one choice to fit their lifestyle. Although statistical comparisons of diet compliance and clinical parameters are pending, findings thus far suggest that subjects are compliant with the Mediterranean diet and lipid panels are improving.

The diet’s usefulness in cancer and cardiovascular disease trials has directed our attention to the treatment of type 2 diabetes, whose incidence ranks South Carolina second in the US. The diet’s characteristics (rich in monounsaturated fats and fiber, generally lower in refined sugars and overall carbohydrate composition) may have similar, if not improved effects on lipid panels, glycemic control, and adherence than does the typical American diabetic diet. Our literature search revealed three studies investigating lipid and glycemic control subjects with type 2 diabetes.

These peer-reviewed studies reported their findings in diet-induced lipid changes. Subjects were placed on either a HMLC (high-monounsaturated fat, low CHO) diet or a LFHC (low-fat, high-CHO) diet. Using similar diabetic populations, two studies showed no change in lipid profiles (2,3), whereas one showed a dramatic decrease in triglyceride levels from the Mediterranean diet. Rasmussen et al. (2) observed no differences in fasting levels of TG, total cholesterol, LDL cholesterol, HDL cholesterol or LDL/HDL ratio in patients randomly assigned to either 3-week diet treatment. Calle-Pascual et al. (3) in a similar study also found no significant change in the lipoprotein profile. In the third study, however, Lerman-Garber et al. (4) found that both the LFHC and HMLC diets had a minor hypocholesterolemic effect with no major changes in HDL cholesterol. The HMLC diet was associated with a greater decrement in plasma triglycerides (20% vs. 7% in the LFHC diet). The differences suggest that the major hypotriglyceridemic effect resulted in patients with higher basal triglyceride values. The group with lower baseline triglyceride values had generally no changes on either diet (4).

These studies have also researched differences in glycemic control in LFHC diet compared to HMLC diets in subjects with DM. Lerman-Garber et al. (4) showed that glycemic control was similar in both diets. However, Calle-Pascual et al. (3) found that HMLC diet improved insulin sensitivity and glucose tolerance, without modifications in insulin secretion. Finally, Rasmussen et al. (2) observed that the HMLC diet showed evidence of lower fasting blood glucose, lower average blood glucose and peak blood glucose responses when compared to the LFHC diet. Whether the improvement in glycemic control is specific to monounsaturated fatty acids or the change is macronutrient density is not clear. In summary, the HMLC demonstrated similar, if not better outcomes in lipid and glycemic control.

If our preliminary data shows that the Mediterranean diet is generally well accepted by patients with CVD while at least maintaining lipid control, and if published studies find that this diet is at least as effective in lipid and glycemic status in diabetic patients, could this diet be offered as a dietary treatment choice in patients with type 2 diabetes? In recognizing the need for more research in this area, our GCRC hopes to answer this question. We are proposing a 6-week pilot study to investigate the effects of a Mediterranean diet on compliance, metabolic control, and weight status in type 2 diabetics. Subjects will be randomized to one of a three-armed design: 1) a LFHC diet (typical diabetic diet) taught to be prepared at home, 2) HMLC diet taught to be prepared at home, or 3) a HMLC diet in which patients will receive daily meals from the GCRC kitchen. Having two HMLC diet groups will help to measure dietary adherence variations and will be a major determinant in justifying a larger-scale study. Baseline and incremental anthropometric measurements, vital signs, labs (HgbA1c, pre- and postprandial blood glucose, lipid panels) and 3-day diet records and will be prospectively collected and analyzed to monitor safety, compliance and clinical changes. If the pilot study deems feasible in terms of compliance and at least the same glycemic and lipid control, then additional dependant variables will be measured for a larger study. Such variables will include changes in body composition using DEXA scans and bioelectrical impedance, metabolic rate using room calorimetry, and insulin sensitivity using clamp and glucose tolerance testing.

All facts considered, the Mediterranean diet has demonstrated at least the same, if not more beneficial health outcomes in controlled research trials. Its differences in nutrient sources and composition, as well as the overall difference in the culture of the Mediterranean lifestyle mandates further research to determine its mechanism in improving chronic disease outcomes. This diet can not only be classified as "alternative" medicine, but could one day be an "alternative" choice in medical nutrition therapy for certain disease states.

References1. de Lorgeril, M. MD et al. Mediterranean dietary pattern in a randomized trial Prolonged Survival and Possible Reduced Cancer Rates. Archives of Internal Medicine 1998 June 8;(11)1181-1187.

2. Rasmussen, O. et al. Effects of blood pressure, glucose, and lipid levels of a high-monounsaturated fat diet compared

with a high carbohydrate diet in NIDDM subjects. Diabetes Care 16: 1565-1571, 1993

3. A.L. Calle-Pascual et al. Changes in nutritional pattern, insulin sensitivity and glucose tolerance during weight loss

in obese patients from a Mediterranean area. Horm Metab. Res. 27 499-502, 1995

4. Lerman-Garber, I. et al. Effect of a high-monounsaturated fat diet enriched with avocado in NIDDM patients.

Diabetes Care 17: 311-315, 1994.