Letter: Defective essential-fatty-acid metabolism in cystic fibrosis.

Mr Rivers and Mr Hassam propose that the subnormal levels of linoleic 
acid (18:2) found in the plasma-phospholipids of patients with cystic fibrosis 
are due to malabsorption. To substantiate their hypothesis they deduce that 
the remarkable remission observed in a cystic-fibrosis patient given intravenous 'Intralipid' 
was due not to the 18:2 content of the 20% triglyceride 
component of the fat emulsion but to the 20:4 content of 
its 1.2% phospholipid component (not 6% as they state). This explanation 
seems unlikely in view of the relatively small proportion of 20:4 
in intralipid phospholipid, especially since intravenous administration of intralipid phospholipid to 
healthy subjects decreases both the 18:2 and 20:4 content of their 
plasma-phospholipids. Comparison of the effects of complete intralipid versus intralipid phospholipid 
on the level of 20:4 in the plasma-phospholipids of patients with 
cystic fibrosis would soon determine whether they lack the ability to 
desaturate 18:2 to 20:4. 