Aaron Deere is a sports nutritionist, functional medicine consultant and advanced personal trainer. He is based in London.
It has long been established that omega-3 fats have powerful anti-inflammatory properties, which revolve around these fats being the building blocks of eicosanoids, which are signalling molecules that play a key role in the regulation of inflammation.
Eikosi is the Greek word for 20, and it is these 20-carbon long eicosanoids, which are derived from n-6 polyunsaturated fatty acids (PUFAs), better known as omega-6, that have pro-inflammatory and immunoactive functions, and n-3 PUFAs – such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and better known as omega-3 fatty acids – which have anti-inflammatory properties largely related to their ability to inhibit the formation of omega-6 derived eicosanoids.
Strong evidence exists that shows an increase in the ratio of omega-3 to omega-6 fatty acids in the diet results in reductions in the incidence of many chronic diseases that involve inflammatory processes, such as cardiovascular diseases, inflammatory bowel disease, some cancers and rheumatoid arthritis. But do plant-based sources of omega-3 offer the same potential anti-inflammatory properties as animal-based sources?
Plant-based sources, such as flax seeds, walnuts and chia, contain a form of omega-3 known as alpha-linolenic acid (ALA). This form has a chain length of 18 carbon atoms. Through the actions of an enzyme named delta-6-desaturase it is able to be converted into different forms of omega-3, such as stearidonic acid and eicosatetraenoic acid.
Delta-5-desaturase then acts on the eicosatetraenoic acid to convert it to EPA, with further actions resulting in the formation of DHA. These continuing modulatory actions imparted on ALA result in a clear conversion pathway which facilitates the conversion of plant based omega-3 to the animal-based form, which largely demonstrates anti-inflammatory properties. Unfortunately this conversion process is largely inefficient: research suggests that conversion rates of ALA through to EPA is approximately 6%, with DHA conversion rates approximated to be as low as 3.8%. Therefore, plant-based sources of omega-3 are poor choices for imparting anti-inflammatory effects.
Gender appears to play an important role in the capacity for synthesis of EPA and DHA from ALA, with evidence showing the conversion rate to be reduced by up to 47% in males versus females. The evidence suggests testosterone plays a key role in the reduced conversion rates, with estrogen and progesterone having the opposite effect and up-regulating the conversion rates, with research showing women using an oral contraceptive pill having increased DHA status compared to those who did not, and the increased DHA status associated with pregnancy.
The mechanism behind the increased rate of conversion seen in females versus males, and the specific up-regulation during pregnancy, is theorised to revolve around the increased maternal needs for DHA. The up-regulation of this pathway offers a method for the mother to pass the required DHA to the developing foetus, if dietary sources of DHA are unavailable.
1, 2 Wall, R., Ross, R. P., Fitzgerald, G. F., & Stanton, C. (2010). Fatty acids from fish: the anti-inflammatory potential of long-chain omega-3 fatty acids. Nutrition reviews, 68(5), 280-289.
3 Goyens, P. L., Spilker, M. E., Zock, P. L., Katan, M. B., & Mensink, R. P. (2006). Conversion of Alpha-linolenic acid in humans is influenced by the absolute amounts of Alpha-linolenic acid and linoleic acid in the diet and not by their ratio.The American journal of clinical nutrition, 84(1), 44-53.
4 Gerster, H. (1997). Can adults adequately convert alpha-linolenic acid (18: 3n-3) to eicosapentaenoic acid (20: 5n-3) and docosahexaenoic acid (22: 6n-3)?.International journal for vitamin and nutrition research. Internationale Zeitschrift fur Vitamin-und Ernahrungsforschung. Journal international de vitaminologie et de nutrition, 68(3), 159-173.
5 Decsi, T., & Kennedy, K. (2011). Sex-specific differences in essential fatty acid metabolism. The American journal of clinical nutrition, 94(6 Suppl), 1914S-1919S.
6 Sibbons, C. M., Brenna, J. T., Lawrence, P., Hoile, S. P., Clarke-Harris, R., Lillycrop, K. A., & Burdge, G. C. (2014). Effect of sex hormones on n-3 polyunsaturated fatty acid biosynthesis in HepG2 cells and in human primary hepatocytes. Prostaglandins, Leukotrienes and Essential Fatty Acids (PLEFA),90(2), 47-54.