Docosahexaenoic Acid Synthesis from Plant-Based Omega-3 Polyunsaturated Fatty Acids

Plant-based omega-3 (n-3) polyunsaturated fatty acids (PUFAs), such as alpha-linolenic acid (ALA, 18:3n-3), are by far the most abundant n-3 PUFAs in the Western diet. It has long been accepted that docosahexaenoic acid (DHA, 22:6n-3) synthesis from plant-based n-3 PUFAs such as ALA is low in mammals, particularly humans. Another lesser-known plant-based n-3 PUFA, stearidonic acid (SDA, 18:4n-3), is found in high amounts in Ahiflower oil and represents a relatively novel alternative to potentially increasing DHA synthesis in humans as it bypasses the putative rate-limiting step in the DHA synthesis pathway. Percent conversion of dietary ALA to plasma DHA has been reported between 0 – 9.8% but is most often reported to be less than 1%, a value that is assumed to be low. However, given that these models tend to measure conversion to plasma DHA only, they may not be representative of whole-body DHA synthesis. Using compound-specific isotope analysis (CSIA) to detect small variations in the carbon-13 content of the diet to measure tissue-specific and whole-body DHA synthesis and turnover, our research program has discovered that 1) DHA synthesis from dietary ALA is much higher than previously believed, 2) Ahiflower oil, via it’s uniquely high SDA content, may be able to provide DHA at rates higher than flaxseed and similar to preformed DHA, and 3) Ahiflower oil may be able to overcome slower n-3 PUFA synthesis resulting from enzymatic competition relating to high n-6 PUFA intake. The ability of plant-based n-3 PUFAs to support whole-body DHA requirements has massive implications for alleviating the currently stressed marine ecosystem.