Fatty15C 15 or pentadecanoic acid is the first essential fatty acid discovered in nearly 90 years, and it has some pretty amazing reported effects in the research literature, and in practice. C15: 0 (also called pentadecanoic acid) is a healthy fat naturally present in dairy products, as well as some types of fish and plants. Dozens and dozens of studies from around the world have linked higher C15: 0 in our bodies to healthy metabolism, balanced immunity,