Our bodies convert the DHA (docosahexaenoic acid) in fish oil into a compound called resolvin D2, which helps down regulate inflammation. This discovery, by investigators in London and at Harvard, may explain why fish oil helps with conditions such as rheumatoid arthritis, heart disease, and many other disorders that are linked to inflammation. The clinicians suggested that resolvin D2 could lead to new treatments for inflammatory conditions - they found that when they added it to white blood cells that stick to the inner lining of blood vessels (the endothelium) the cells making up this lining produced small amounts of nitric oxide, which discourages the white blood cells from adhering. The result: reduction of inflammation. Another advantage: unlike other anti-inflammatory drugs, resolvin D2 doesn't suppress the immune system. The researchers also found that resolvin D2 is a powerful chemical, and that effects can be measured with very small quantities. The study was published in the journal Nature on October 29, 2009.