Eicosapentaenoic acid (EPA) compositions and EPA-rich polar lipids for prophylactic or therapeutic applications are described. Production from certain cultured micro-organisms (like Nitzschia laevis) promotes synthesis of EPA, including polar lipids including EPA. The EPA-rich polar lipids themselves may be used as polar compounds. EPA can be selectively hydrolysed from particular positions in isolated polar lipids by lipase activity, then optionally further purified. The process bypasses reliance on diminishing fish stocks and on physico-chemical processes that may not adequately separate desirable n-3 HUFAs from unwanted products like DHA also found in fish oil and cultured organisms.