1. What would constitute a typical high-carbohydrate diet in terms of real food? What would constitute a diet of 40% monounsaturated fatty acids (MUFAs)?
In this study, we did not want any interference on the experiment by dietary fibre (which exerts a beneficial effect on blood glucose and plasma lipid metabolism) since this might have obscured the effects of dietary carbohydrate per se. Therefore, we selected for the high-carbohydrate diet food items which did not contain large amounts of vegetable fibre (white bread, spaghetti and other types of pasta dishes, rice and potatoes). These starchy foods were consumed every day in generous servings. The diet containing 40% monounsaturated fatty acids was based on a high consumption of virgin olive oil (five to six tablespoons per day), a typical source of monounsaturated fats in Mediterranean cuisine. This was utilized for salad dressing, on toasted bread together with garlic and tomatoes (bruschetta), and for cooking meat and fish.
2. What are the best natural sources of carbohydrate and of MUFAs?
The best natural sources of carbohydrate are foods rich both in carbohydrate and in fibre, since the latter counteracts most of the undesired metabolic effects of a high-carbohydrate diet. In particular, we advise our diabetic patients to consume often legumes (beans, lentils and peas), cereals (whole-grain bread, porridge and barley), and all types of vegetables and fresh fruit (apples, oranges, grapefruit, peaches, pears and plums). Other sources of carbohydrate, but not particularly rich in fibre, are the starchy foods employed in our experiment (white bread, spaghetti, rice, potatoes), which should be utilized often but in limited amounts, since they can increase the post prandial blood glucose concentration in some diabetic patients. The best source of monounsaturated fatty acids is represented by virgin olive oil which contains significant amounts of antioxidants (polyphenols) useful for prevention of cardiovascular diseases. Other suitable sources of MUFAs are peanut and rapeseed oil and margarine.
3. Up to what limit of glucose intolerance would you recommend a high-carbohydrate diet?
A high-carbohydrate and high-fibre diet is recommended for any type of glucose intolerance, even for insulin-dependent diabetes. The only limitation is represented by the presence of hypertriglyceridemia, which is usually exacerbated by a high-carbohydrate intake. Conversely, a high-carbohydrate diet constituted in large part by starchy foods should not be recommended to diabetic patients treated with hypoglycemic drugs and insulin, and in general to patients with unsatisfactory blood glucose control and/or hypertriglyceridemia.
4. Is one type of diet best for obese NIDDM patients, and another for lean ones?
High-fat diets are more energy-dense, and therefore they are not suitable for overweight patients. Conversely, these patients will certainly benefit from a high-carbohydrate, high-fibre diet which has a low-energy density, a low energy-sparing ability, and moreover has a very good satiating effect. Therefore it might facilitate weight reduction in patients who can benefit from this therapeutic manoeuver.