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1. A formula breakfast containing protein, carbohydrate and fat was given on two occasions to nine middle-aged male convalescent patients and to ten young men. The meals differed only in the type of carbohydrate given; sucrose or an isocalorific amount of glucose. 2. After the formula meal containing sucrose; (a) the alimentary lipaemia was cleared more slowly; (b) insulin response was smaller, and (c) there was a lower blood sugar curve than after the glucose meal. 3. The degree of lipaemia showed a significant positive correlation with insulin response which was, as expected, lower after sucrose than glucose. While attempting to confirm a report (Schilling, Hashim & Leonardy, 1964) that serum triglycerides are not significantly elevated after the ingestion of a small mixed meal, it was noticed that the triglyceride concentrations seemed to depend on the type of carbohydrate given (Mann & Truswell, 1971). Albrink, Fitzgerald & Mann (1958) and Sullivan (1960) have shown that the lipaemia which occurs after a fatty meal is diminished by the addition of glucose to the meal. Krut & Barsky (1964) found that postprandial lipaemia in patients with ischaemic heart disease is decreased by intravenous infusion of glucose and insulin. These considerations led us to examine the effects of glucose and sucrose and subsequent insulin release on alimentary lipaemia.

1. Each of nine volunteers was fed three different diets. The percentage of total daily energy provided by fat, carbohydrate and protein remained constant, but the nature of the fat and carbohydrate was altered. The first diet contained ordinary amounts of sucrose and predominantly saturated fat. During the second dietary period, fat remained saturated, but the quantity of sucrose was increased at the expense of complex carbohydrate. In the third dietary period, the sucrose intake remained high, but fat was supplied chiefly in the polyunsaturated form. 2. A small but statistically significant increase of serum fasting cholesterol and triglyceride was observed during the second dietary period, but on the third diet levels of both lipids fell to concentrations not significantly different from those seen on the first diet.

1. Fasting serum cholesterol and triglyceride, and post prandial insulin secretion and lipaemia were measured in human subjects in a metabolic ward, who were given an ordinary diet (diet 1) in which the sucrose was isocalorically replaced by starch (diet 2) or vice versa. The subjects were nine healthy normolipaemic adult males. In eight of these subjects the effect of sucrose calorie reduction (diet 3) on fasting serum lipids was also studied.2. When starch replaced sucrose, there were no singnificant differences in fasting serum lipid concentrations or immunoreactive insulin or in the insulin response and alimentary lipaemia after a standard mixed breakfast.3. Serum triglyceride concentration fell and cholesterol concentration rose during the period of sucrose (and calorie) restriction.4. After lunch and supper on the first two diets (when different carbohydrates were given) the lipaemic response was larger and the insulin response smaller after meals containing sucrose.5. Thus, there was no difference between concentrations of fasting serum lipids when starch replaced sucrose at 23% total calories, but the concentrations of serum triglycerides were higher after individual mixed meals containing sucrose.6. There were no significant differences in the fatty acid patterns of serum lipids on the different diets.

We compared plasma glucose and insulin responses to an Aboriginal bushfood and its western equivalent in healthy Aborigines and Caucasians. Bush potato (Ipomoea costata), an Aboriginal bushfood which is slowly digested in vitro, and potato (Solanum tuberosum), which has a high glycemic index, were studied. The areas under the glucose and insulin curves for Aborigines were 34% and 42% smaller, respectively, after bush potato than after potato (p less than 0.05). In Caucasians only the insulin response to bush potato was lower (by 19%) than that to potato (p less than 0.05). Compared with Caucasians, Aborigines produced 2.5 times greater glucose and insulin responses to potato (p less than 0.025). Their insulin responses to bush potato were also twice as large (p less than 0.05) although glucose responses were not significantly different. These findings add weight to the hypothesis that rapidly digested carbohydrate in western diets may be one of the factors in the lifestyle change which precipitates diabetes in indigenous populations.

Our aim was to determine the in vivo glycemic and insulin responses and in vitro starch digestibility of seven processed wheat products (shortbread biscuits, custard, quick-cooking wheat, wholemeal bread, water biscuits, puffed wheat, and puffed crispbread). The degree of starch gelatinization in the foods was measured. Fifty-gram carbohydrate portions of the foods were fed to eight volunteers after an overnight fast. The calculated glycemic indices (GI) (mean +/- SEM) ranged from 43 +/- 10 for custard to 81 +/- 9 for puffed crispbread. Insulin responses paralleled the glycemic responses. The GI correlated positively with the percentage of starch digested in vitro (p less than 0.05). The degree of starch gelatinization ranged from 0.4 to 60% and correlated positively with the percentage starch digested in vitro (p less than 0.05). Differences in the glycemic and insulin responses to wheat products may be explained in part by the extent of processing and the degree of gelatinization achieved.

The in vivo glycemic and insulin responses and in vitro starch digestibility were determined for six staple foods (corn, lima beans, white and yellow teparies, mesquite, and acorns) traditionally consumed by Pima Indians. Equivalent carbohydrate portions (25 g) of the foods were fed to eight healthy Caucasian volunteers. The calculated glycemic indices (GIs) (mean +/- SEM with glucose as the standard) were all low, ranging from 16 +/- 2 for acorns to 40 +/- 5 for corn. Insulin responses and in vitro starch digestibilities correlated with the GI. These results provide further support for the hypothesis that the slow digestion and absorption of starch in traditional foods was a factor that helped protect susceptible populations from developing diabetes.

We compared the effects on the ratio of plasma tryptophan to large neutral amino acids (trp:LNAA) of two different carbohydrate meals (sucrose or starch, 120 g) and a contrasting meal of fat + protein given at breakfast to 10 healthy adults. Plasma glucose and insulin were also measured. The trp:LNAA ratio rose after both carbohydrate meals (p less than 0.001). Glucose and insulin peaks were higher after sucrose than starch, and trp:LNAA rose correspondingly higher (sucrose +34% and starch +20%, p less than 0.05). The ratio declined 45% after the fat + protein meal. At 180 min, absolute ratio values were twofold higher after carbohydrate (sucrose 0.133 and starch 0.127) than after fat + protein (0.057). Similar results were found with the same meals given in the evening. Our results suggest that high-carbohydrate meals have an influence on serotonin synthesis. We predict that carbohydrates with a high glycemic index would have a greater serotoninergic effect than carbohydrates with a low glycemic index.

To assess the effect of religious dietary practices and social customs on the vitamin D status of Asian immigrants, we kept records of the dietary intake and time spent out of doors of 81 Ugandan Asian men, women, and girls (9-19 years old). Sera were analysed for 25-hydroxycholecalciferol (25-OHD3), and 28% of the subjects were found to have levels below the lower limit of normal. The (vegetarian) Hindus had the lowest dietary intakes, least time out of doors, and lowest serum 25-OHD3. The Goan (Roman Catholic) Asians, despite more pigmentation, had 25-OHD3 levels similar to those found among indigenous British people and had the most satisfactory vitamin D intakes. Among Asians, whose exposure to sunlight may be limited, dietary vitamin D becomes the major determinant of serum 25-OHD3.