john Do you know of any studies that actually manage to induce clinical symptoms of EFA deficiency in humans (ie dermatitis etc)? I've only seen one, conducted in infants who received a completely fat-free diet, and very few studies seem to actually investigate whether the symptoms could rather be due to depletion of some nutrient due to the increased metabolism.
I went through some of the literature on EFA-deficient mice, and its really true as Peat says that EFA-deficiency seems to be highly protective against many different toxins and auto-immune diseases.
There's half a dozen papers on how EFA-deficienct mice are immune against streptozotocin and cyclosporin-induced diabetes, EFA-deficiency prevents autoimmune diabetes, toxin-induced renal failure and autoimmune kidney disease, makes mice strongly resistant to endotoxic shock, infectious disease and almost completely eliminates the edema associated with arthritis.
Seeing as how the main purported role of PUFAs is to modulate the immune system, if they were truly essential, it just seems very odd to me that EFA-deficient animals actually show many signs of having superior immune function. Some refs: Diabetes
http://www.ncbi.nlm.nih.gov/pubmed/3045812 http://www.ncbi.nlm.nih.gov/pubmed/7667243 http://www.ncbi.nlm.nih.gov/pubmed/9389417 http://www.ncbi.nlm.nih.gov/pubmed/7579534 http://www.ncbi.nlm.nih.gov/pubmed/2307932 Arthritis http://www.ncbi.nlm.nih.gov/pubmed/2307932 Endotoxic shock http://www.ncbi.nlm.nih.gov/pubmed/394879 Kidney disease http://www.ncbi.nlm.nih.gov/pubmed/2212002 http://www.ncbi.nlm.nih.gov/pubmed/2809195 Trypanosoma infection http://www.ncbi.nlm.nih.gov/pubmed/1342611 Antimicrobial activity http://www.ncbi.nlm.nih.gov/pubmed/2649598 http://www.ncbi.nlm.nih.gov/pubmed/9119445