EPA and DHA
Alpha-linolenic Acid is converted in the body to EPA (eiocosapentaenoic acid) usually found in marine oil and DHA (docosahexaenoic acid) usually found in marine fish oil. Many factors affect the rate of conversion and one factor seems to be a high food intake of linoleic acid which is typical of vegan diets and may suppress the body's ability to convert alpha-linolenic acid to DHA. Vegans can achieve a better balance of PUFAs in their body tissues by using less sunflower, safflower and corn oils and more oils containing alphalinolenic acid such as rapeseed (canola) oil, or soya bean and walnut oils. This would encourage their tissues to make more DHA.
http://www.vegansociety.com/lifestyl...tty-acids.aspx