Flax seeds are Paleo friendly, so long as you consume them in moderation. Flax seed oil can also be included as part of a Paleo diet, but we recommend keeping it to a minimum.
Paleo and PUFAs
The bad news is that flax seed oil is mostly polyunsaturated fats (PUFA), which are very unstable and tend to oxidize when exposed to heat and light. Oxidized fats are bad because consuming them leads to oxidized cholesterol in our blood, and it is the oxidized cholesterol that latches onto our arteries, causing inflammation and plaque build-up.
Not All Omega-3s Are Created Equal
The good news is that the PUFAs in flax seed oil are mostly omega-3 PUFAs, which are anti-inflammatory. However, the omega-3s come from alpha linolenic acid (ALA) rather than Docosahexaenoic acid (DHA) and Eicosapentaenoic acid (EPA), which are more bioavailable sources of omega-3. Our bodies aren’t very good at converting ALA into DHA or EPA, which is why we’re better off getting DHA and EPA in our diet as much as possible.
DHA and EPA are found largely in meat and fish, so strict vegetarians/vegans might want to use flax seed oil for their omega-3 supplement, but the rest of us would be better off with a fish oil supplement or just eating meat and eggs.
Mark Sisson includes flax seed oil in his assessment of various oils.