Effects of cooking plant oils on recurrent aphthous stomatitis: a randomized, placebo-controlled, double-blind trial

OBJECTIVE: One-third of the total population seems to develop minor recurrent aphthous stomatitis (RAS) during their lifetime. However, well-controlled dietary intervention studies to prevent minor RAS are very rare. The objective of the present study was to investigate whether the prevalence of RAS decreased with perilla oil (rich in alpha-linolenic acid). METHODS: Thirty subjects (8 men and 22 women) who had minor RAS at least once a month were randomly allocated to a soybean oil group or a perilla oil group in a double-blind manner (experimental phase) after a run-in phase of 4 mo during which subjects used a reference oil, the most popular cooking oil in Japan, or a 50/50 mixture of soybean oil and rapeseed oil. During the experimental phase, subjects were asked to use soybean oil or perilla oil as the sole cooking oil for 8 mo. Blood samples were collected at the start and end of the experimental phase for fatty acid analysis of total plasma phospholipid fraction. Occurrence and needed days for healing of minor RAS were recorded during the two phases and compared. RESULTS: alpha-Linolenic acid concentrations in the plasma phospholipid fraction increased significantly in both groups during the experimental phase to a similar extent. The prevalence of minor RAS in the experimental phase decreased significantly in both groups compared with the run-in phase to a similar extent, without intergroup differences. CONCLUSION: Perilla oil, which is rich in alpha-linolenic acid, was not superior to soybean oil in preventing minor RAS. There was a possibility that avoiding rapeseed oil might be beneficial for prevention of minor RAS.