On the causation of diabetes mellitus (effect of saliva on blood glucose levels in oral glucose tolerance tests)

Abstract

17 male patients, aged 25 - 58, completed four sets of blood glucose estimations, fasting at 30 minutes, 60 minutes and 120 minutes after a 50 g. oral glucose load. The study was so designed that saliva was added to the glucose meal in one set of observations and excluded from the other. Results based on 136 observations on blood glucose showed that at the time intervals, namely, 30 minutes and 60 minutes, the blood glucose levels were significantly lower when the glucose meal was admixed with saliva than when it was excluded, although there was no significant difference in the mean fasting levels. The difference at 120 minutes did not reach 1% level of significance. The differences in blood glucose levels may be due to the saliva retarding gastric emptying. In the case of meals with no saliva, a rapid "dumping" of glucose takes place as a result of increased gastric emptying rate and this may give rise to sucrose-induced hyperinsulinism, which, if prolonged over extended periods, may result in insulin-resistance. The slower rise of blood glucose after meals admixed with saliva will not have this effect because insulin-release and glycaemia would go hand in hand. This may possibly explain the increased incidence-rates of diabetes mellitus in individuals used to "meal-scamping" as noted in the companion study (1), as compared with "meal-chewers". It has been proposed that a sudden and rapid rise of insulin levels in the blood, whether due to a sudden hyperglycaemia due to rapid gastric emptying and resultant "dumping" of sucrose, or due to secretin-release, may give rise to insulin anti-body production (1), setting up the vicious cycle - hurried meals-rapid gastric emptying accompanied by hyperglycaemia and hyperchlorhydria (2,3) -secretin-release (4) - hyperinsulinism (5,6) -hypoglycaemia, persistence of insulin - insulin resistance and insulin antibodies (7,8) -islet over-activity and islet-cell exhaustion (7-9). Yudkin et al (10) observed that out of their 13 subjects, only 6 showed hyperinsulinism after a sucrose meal. They did not find out the reasons for this susceptibility of only some persons to develop hyperglycaemia and hyperinsulinism after a high sucrose diet. It has been propsed by me (1,11) that this susceptibility may be due to the pattern of eating: persons who masticate their food well, so that a mucus-rich saliva mixes with the meal, do not develop this and those who do not masticate their food well, so that saliva does not mix with the meal, develop hyperglycaemia and resultant hyperinsulinism to counteract the high glucose levels, because swallowing a mucus-rich saliva with the meals delays gastric emptying (12).