[PerfectElement]

It's likely that vegans don't suffer from EPA and DHA deficiency because the body gets better at converting them from ALA. As this study have found: http://www.ncbi.nlm.nih.gov/pubmed/20861171

From the study: "Despite having significantly lower intakes of EPA and DHA (from fish or fish oil), blood levels of EPA and DHA in vegans and vegetarians were approximately the same as regular fish eaters.

The results indicate that the bodies of vegetarians and other non-fish-eaters can respond to a lack of dietary omega-3 EPA and DHA by increasing their ability to make them from omega-3 ALA.

And as they said, "The implications of this study are that, if conversion of plant-based sources of n-3 PUFAs were ... sufficient to maintain health, it could have significant consequences for public health ..."

To be safe, I occasionally take an omega-3 supplement from algae.

[mrob]

Humans vary in their ability to elongate fatty acids. It's possible that poor elongaters fail to thrive on a vegan diet and revert to a omnivorous diet, biasing the sample. We'd need a randomized controlled study to see if this is important.