There are currently a variety of different cooking oils sold in stores, such as canola oil, soybean oil, corn oil, safflower oil, cottonseed oil, olive oil, sesame oil, perilla oil, flaxseed oil, shiso oil, and coconut oil. Lard and fish oils are also well-known dietary fats. One of the main differences between these oils is their fatty acid composition. For example, the main fatty acid component of olive oil and canola oil is oleic acid, while corn oil is mainly linoleic acid, perilla oil and flaxseed oil are mainly alpha-linolenic acid, and coconut oil is mainly medium-chain triglycerides. In addition, fish oil contains fatty acids such as DHA and EPA. From a nutrition science standpoint, fats are one of the three main macronutrients, and linoleic acid and alpha-linolenic acid are essential fatty acids for humans. This is because human physiology cannot produce the delta-12 desaturase required to convert oleic acid to linoleic acid or the omega-3/delta-15 desaturase required to convert linoleic acid to alpha-linolenic acid. Linoleic acid we consume is metabolized within the body and becomes arachidonic acid, and these omega-6 fatty acids have all been reported to play a role in bodily functions such as inflammation response and blood clotting. On the other hand, alpha-linolenic acid is converted to EPA and DHA in the body, and these omega-3 fatty acids have been reported to have anti-inflammatory effects.

What happens to fats that are not absorbed? Up until now, these fats were thought to be excreted as is, but in order to exit the body, they must first pass through the colon, where intestinal bacteria live. When we focused on how unsaturated fatty acids are metabolized by the intestinal bacteria and analyzed these processes, the results uncovered a variety of new metabolites. For example, linoleic acid is metabolized into multiple hydroxy fatty acids, oxo fatty acids, conjugated fatty acids, and partially saturated fatty acids. Since these metabolites cannot be created by other processes within the body, these results prove that we are dependent on intestinal bacteria for their production. In our research, we produced these modified fatty acids produced by the intestinal bacteria in the lab through the application of enzymes derived from intestinal bacteria, then refined them to 95% or higher purity and used them for physiological value analysis testing related to functions such as regulation of the intestinal barrier, fatty acid composition and metabolism, and immunity, as well as anti-inflammation and antioxidant properties. We discovered a variety of fascinating functions. For example, hydroxy fatty acid HYA (10-hydroxy-cis-12-18:1) assists with repair of the epithelial barrier of the intestine, oxo fatty acid KetoA (10-oxo-cis-12-18:1) may have a role in lipid metabolism regulation via the PPARγ nuclear receptor, and KetoC (10-oxo-trans-11-18:1) exhibited antioxidant properties via Nrf2, an oxidative stress response transcription factor. All of these compounds are modified fatty acids derived from linoleic acid. These results suggest that the fatty acid molecular species human hosts depend on intestinal bacteria to produce within the intestinal tract may have an impact on health. This would mean that vegetable oils may be the raw materials used for the production of modified fatty acids with physiological functions in the body.