Richardson and Feldman (1986) studied the effects of food on salivary secretion and the impact of saliva on gastric acid secretion (pp. G85-91). They carried this experiment on 59 individuals who were informed of the procedures.
The objectives involved in this study were to observe various implications related to salivary secretion. It was mainly quantitative research. They wanted to measure the increase in salivary secretion in response to food intake. Also, they focused on the effects of saliva on gastric secretions. They claimed that their research was different from other previous studies in that most of the previous studies used alternatives to natural food to observe changes in salivary secretion (Richardson & Feldman, 1986, p. G85). Instead, they opted for modified sham feeding using meals containing steak, french-fried potatoes and water, and chewing gum for their study.
It has been observed that the ages of the subjects ranged between 20 and 52years, with the average being 41 years (Richardson & Feldman, 1986, p. G85). It was not clear whether any consideration had been given to age-related changes in respective individuals. Though it can be assumed that all the selected individuals were healthy, no particular mention of this can be found in their explanation of the subjects except for some sub-stages. For, the health status of an individual is vital for any experiment, and a failure to mention it may give the chance of considering the results as biased.
They chose two methods to collect saliva from the subjects- one is expectoration and the other is aspiration using a dental catheter (Richardson & Feldman, 1986, p. G85). Though, the intended results seemed to be similar for both the methods, clarification for adopting two collection techniques was not provided. Also, the result might have been apparently similar, but the effect of a foreign object connected to a suction device on the production of saliva remains unclear. Nevertheless, within the scope of this study, it does not make much difference, as the focus should be on salivary response to food intake than collection modalities.
The authors paid great attention to considering the effects of temperature changes on the food weight and adjusting the values accordingly (Richardson & Feldman, 1986, p. G85). However, it would have been better, if they had tried with a substance that does not show many temperature-related variations in the short duration of the particular stage, i.e., chewing of food and the later collection of saliva mixed food. Further, the use of devices that can collect the saliva at the releasing points of ducts should be considered, which seems impossible with the existing techniques.
As the authors themselves had mentioned, their technique of calculating the weight of chewed food would allow only quantitative assessment (Richardson & Feldman, 1986, p. G89). However, analysis of the secreted saliva is important to know the concentrations of various ingredients in response to food and chewing gum. For, the number of electrolytes and enzymes may produce certain consequences, though of minor importance.
The comparisons of the basal salivary flows with those of food and/or chewing gum induced indicated that there was four to six-fold increased secretion in the latter case (Richardson & Feldman, 1986, p. G89). The variation was identical in both men and women (Richardson & Feldman, 1986, p. G86). Nevertheless, it needs to be observed there was a general tendency of comparatively less salivary secretion in women than men under all conditions (Richardson & Feldman, 1986, p. G86).
The authors followed a systematic approach in presenting the data of salivary secretion in all the individuals. They included all the details from averages of values to value correlations. However, we are not informed about individualized changes to food (or gum) chewing. While it is understandable that providing minute details can be cumbersome, information on it becomes essential when it comes to detailed evaluation.
The effect of saliva on the secretion and acidity of the gastric content was also observed in schematic approaches (Richardson & Feldman, 1986, p. G88). Anyway, the observation remained superficial, as there was no actual analysis of the saliva secreted except for the known presence of urogastrone. Though it was mainly intended for the evaluation of the amount of salivary secretion, the focus was also given on the role of secretion inducers by using bethanechol.
Moreover, the impact of gastric contents on salivary flow was also observed by two methods- infusions of an amino acid meal and saline into the stomach and also through a separate infusion of gastrin and somatostatin (Richardson & Feldman, 1986, p. G87-8).
The authors had mentioned that the mechanical act of chewing stimulated salivary secretion (Richardson & Feldman, 1986, p. G89). In such cases, adapting to a single collection method seems important, as very minute changes from mistakes of catheter manipulation in the oral cavity are possible.
The provision of line graphs and data charts has increased the understandability of various stages of the experiment. However, no data was provided on values for gum chewing and sham feeding except for an inference that there was no much difference (Richardson & Feldman, 1986, p. G87). Nonetheless, we have values of tube chewing and sham feeding for comparison.
All in all, it is clearly evident that the number of subjects is relatively less to reach any conclusion on the observations. Moreover, individual stages in the experiment included hardly 6-15 subjects that make the credibility of results uncertain (Richardson & Feldman, 1986, p. 86-9). Even then, the authors seem to have followed a systematic and well-oriented approach throughout their experiment. Minor drawbacks that have been mentioned here might have occurred due to natural experimental inevitabilities or the intended scope of the experiment. It must be noted that they provided substantial data with standard calculations at various levels.
Reference
Richardson, C. T. & Feldman, M. (1986). Salivary Response to Food in Humans and its Effect on Gastric Acid Secretion. American Journal of Physiology, 250 (Gastrointest. Liver Physiology, 13.). G85-91.