Nutrient interaction in relation to glycaemic and insulinaemic response.

Although it is known that protein, fat and fibre reduce the postprandial glycaemia following an oral carbohydrate load, the nature and extent of interaction of different nutrients with one another in this respect is not well understood. The present study was designed to explore systematically the glycaemic and insulinaemic response to glucose (G) alone, or in combination with one or more of the following: casein (CS), maize oil (MO), cellulose (CL) and pectin (P). Besides 100 g G, eleven isoenergetic and six isocarbohydrate meals were studied on healthy adult males using an incomplete block design. Addition of other nutrients to G led to a lowering of the glycaemic response. The lowest glycaemic responses were seen in case of meals containing the largest number of nutrients. P was more effective in reducing postprandial glycaemia than CL. As in case of glycaemic response, low insulinaemic responses were also associated with P-containing meals, and meals containing the largest number of nutrients. But unlike in case of glycaemic response, there was a tendency for elevation of the insulinaemic response in case of CL-containing meals. The degree of attenuation of glycaemic response observed with meals containing several nutrients was roughly predictable on the basis of the attenuation observed with meals in which only one nutrient had been added at a time to G. But the glycaemic response of natural foods is unlikely to be predictable on the basis of their nutrient composition because of the overriding influence of several other factors such as physical form, cooking, processing, storage and antinutrient content of the food.

Modulation of postprandial glycaemia and insulinaemia by dietary fat.

The present study was designed to examine the effect of corn oil (Co) on postprandial glycaemia and insulinaemia when ingested with glucose (G), casein (Cs), cellulose (Cl) and pectin (P) in various combinations. The study was conducted on six healthy male volunteers, on each of whom six meal tolerance tests were performed. The meals were isocaloric and consisted of G; G and Co; G, Co and Cs; G, Co and P; G, Co, Cs and P; and G, Co, Cs and Cl. The meals were administered after an overnight fast. In addition to a fasting blood sample, blood was collected 0.5, 1.0, 1.5 and 2.0 h after ingestion for measurement of serum glucose and insulin levels. The glycaemic response to GCo was comparable to that to G, but the insulinaemic response was significantly lower. The glycaemic response to GCoCs was significantly lower than that to G but the insulinaemic response to both was comparable. The cellulose containing meal GCoCsCl showed a further reduction in the glycaemic response but not in the insulinaemic response. The pectin containing meals GCoP and GCoCsP gave the lowest glycaemic and insulinaemic responses, the responses to the latter being lower. Corn oil by itself has only a modest effect on the postprandial metabolic response to glucose. Addition of protein and fibre, specially pectin, leads to significant attenuation of glycaemic and insulinaemic responses.

Nutrient interaction in relation to glycaemic response in isocarbohydrate and isocaloric meals.

The present study was designed to examine the effect of casein (Cs) on postprandial glycaemia when ingested with glucose (G) alone or in combination with corn oil (Co), cellulose (Cl) or pectin (P). The study was conducted on a pool of ten healthy male volunteers in two sets of five volunteers each. The meals administered in the two sets were similar in composition but were isocarbohydrate (100 g G) in one set, and isocaloric (400 kcal) in another set. The meals in each set consisted of G, G Cs, G Cs Co, G Cs Cl and G Cs P. Each of the five volunteers in a given set underwent five meal tolerance tests (MTT), once with each meal, in a Latin Square design. During the MTT, the meal was administered after an overnight fast. In addition to a fasting venous blood sample, blood was collected 0.5, 1.0, 1.5 and 2.0 h after ingestion for measurement of serum glucose and insulin levels. In both sets, the highest glycaemic response was that to G. In the isocarbohydrate set, G Cs gave a significantly lower glycaemic and insulinaemic response than G. Further addition of Co made no essential difference but both the fibre containing meals gave significantly lower glycaemic responses. The insulinaemic response was attenuated only in case of G Cs P but not in case of G Cs Cl. In the isocaloric set, Cs as G Cs was observed to stimulate insulin secretion rather than attenuate postprandial glycaemia G Cs Co gave a reduction in glycaemic as well as insulinaemic response as compared to G. Both fibre containing meals led to further reduction in both responses, P being somewhat more effective than Cl. Addition of other nutrients to G, in general, reduces postprandial glycaemia.

Modulation of postprandial glycaemia and insulinaemia by pectin in mixed nutrient combinations.

The present study was designed to examine the effect of pectin (P) on postprandial glycaemia and insulinaemia when ingested with glucose (G), casein (Cs) and corn oil (Co) in various combinations. The study was conducted on five healthy male volunteers, on each of whom five meal tolerance tests were performed. The meals were isocaloric and consisted of G; G and P; G, Cs and P; G, Co and P; and G, Cs, Co and P. The meals were administered after an overnight fast. In addition to a fasting blood sample, blood was collected 0.5, 1.0, 1.5 and 2.0 h after ingestion for measurement of serum glucose and insulin levels. The glycaemic and insulinaemic response to GP did not differ significantly from that to G. All the other meals, viz. GCsP, GCoP and GCsCoP, gave a significant reduction in postprandial glycaemia as compared to G. The corn oil containing meals, viz. GCoP and GCsCoP, in addition, gave a significant reduction in postprandial insulinaemia as compared to G. Pectin alone is not a dependable dietary constituent for reducing postprandial glycaemia. Its combination with protein and fat significantly lowers the postprandial glycaemic as well as insulinaemic response to orally administered glucose.