Responses of salivary glands to intake of soft diet

Modernization has made individuals prefer processed and cooked foods (soft food), but this eating habit may have negative effects on the oral cavity. However, laboratory animals fed with soft diet are commonly used in an attempt to clarify this issue, and various oral tissues, including the salivary glands have been examined. In this review, we summarize the findings of previous studies concerning the responses of salivary glands to daily intake of soft diet.

The weight of the parotid glands decreased in rodents fed with soft diet (liquid or powder). In atrophic parotid glands, acinar cell shrinkage is histologically observed and the DNA content is reduced, showing that the atrophy is caused by a decrease in the size and number of acinar cells. Immunohistochemical examinations showed that the decrease in the acinar cell number was induced by suppression of acinar cell proliferation and acceleration of apoptosis. The atrophic parotid glands recovered following a change from soft to pellet diet. Other salivary glands, such as the submandibular, sublingual, and palatine glands, responded only slightly to the soft diet feeding.

Accumulated research data showed that a soft diet negatively affects the parotid glands much more than other salivary glands and that atrophic parotid glands are able to recover by switching to a hard diet. Therefore, it should be emphasized that good eating habits are important for not only digestion but also the health of oral tissues, including the salivary glands.