Does a high-carbohydrate diet have different effects in NIDDM patients treated with diet alone or hypoglycemic drugs?
Monounsaturated fatty acids (MUFAs) have become the latest dietary revelation in the management of diabetes. Dietary diabetes control has progressed a good deal over time, and a lot is now known about the effect of various drug regimens on the different indicators of metabolic well-being. MUFAs, when consumed as part of a diet that provides a caloric deficit (in other words, less calories in food than calories burned in activity), have been found to offer benefits in improving lipid and cholesterol profiles beyond those offered by low-calorie/high-carbohydrate diets.
Suspecting that different diets might have different effects on people with less serious glucose intolerance, a group of Italian specialists decided to compare a group of NIDDM (non-insulin-dependent diabetes mellitus) patients with reasonably mild hyperglycemia who were controlled by diet alone and a group of more hyperglycemic NIDDM patients who needed oral hypoglycemic drugs (in this case, glibenclamide) in addition to dietary control. The patients were isolated in the metabolic ward and fed rigourously controlled diets in which calories came either mostly from carbohydrate (carbohydrate 60%, fat 20%, protein 20%) or equally from fat and carbohydrate (carbohydrate 40%, fat 40%, protein 20%). The fat portion of the diet consisted mostly of MUFAs, and this being a Neapolitan study, was supplied by olive oil. The carbohydrate portion of the diet was based heavily on bread which is rich in starch, a complex carbohydrate that is better for metabolic control than simple monodisaccharides. After 15 days the two groups switched diets and continued for another 15 days; glucose and insulin monitoring continued throughout.
No difference was found between the two regimens in fasting glucose concentrations or body weight, which remained unchanged. However, glucose levels after meals were higher in the high carbohydrate regime, but only in the drug-treated patients. The patients treated with diet alone showed higher insulin levels after meals on the high-carbohydrate diet. Both glibenclamide-treated patients and diet-managed patients showed a tendency to higher triglyceride levels following meals on the high-carbohydrate diet.
The reason appears to be that in patients with less severe glucose intolerance (including all borderline non-insulin-dependent diabetes mellitus cases, but probably none of those that require hypoglycemic drugs) there is a natural insulin secretory response to the intake of carbohydrates that keeps glucose following meals at controlled levels. A high-fat, low-carbohydrate diet does not seem to present any problem for people with milder cases of diabetes either, provided most of the fats are unsaturated and total caloric intake does not increase. In conclusion, dieticians should be flexible to the particular profile of each patient, looking at body weight, cholesterol levels, triglyceride levels and glucose intolerance before prescribing any particular regimen.