My cat has lost weight since going on a special “I’m inbred and my kidneys don’t want to kidney” diet. He’s also wheezing a lot. My vet has recommended fish oil to get him some extra calories, and to fight the wheezing, if the wheezing is something something allergy something something prostaglandin. She didn’t explain it very well, so I’m consulting with Dr. Internet.
Prostaglandins are lipids that send signals from a cell to itself or its close neighbors. Prostaglandins take their name from the prostate gland, signifying the fact that they are produced and have effects in almost every tissue of the body. This is what happens when you name things after the first place they’re discovered. “Local signalling” covers a lot of ground, including constricting blood vessels, dilating blood vessels, inducing a fever, making you more sensitive to pain, digestive muscle contraction, digestive muscle relaxation, airway contraction, and airway relaxation. So they could definitely either cause or cure my cat’s wheezing.
What about fish oil? Prostaglandins are made from fats, but less so from omega-3 than any other fat, and their prostaglandins are less active than others. Fish oil is rich in omega-3s, but it’s not the only source, as soylent has been working so diligently to demonstrate. That’s an argument for swapping omega-6 for omega-3, but it doesn’t mean adding additional omega-3s will be any help. What is an argument for straight up supplementation is that all fats are converted to prostaglandins by the same enzyme, which exists in limited quantities regardless of the amount of fat available. Omega-3’s slow conversion rate effective blocks the conversion of the more inflammatory omega-6s. So while I don’t see any reason fish oil would do better than other sources of omega-3s, this certainly seems like a plausible treatment with limited downsides.
Now is as good a time as any for a general omega-3 vs. omega-6 lesson. 3 and 6 are different in ways I can’t be bothered to look up because it doesn’t matter; your body absolutely needs both of these to survive. Presumably we adapted, more or less, to whatever ratio was available in the evolutionary relevant time period. Unfortunately 6s have a much longer half life than 3s before going rancid, and everything in our modern food system pushes this- olive oil bred for shelf life, cows are fed grains, which have more omega-6s than grown plants because they don’t want their seed energy going bad either. The end result is that the intake ratio of omega-6:omega-3 is extremely different than what our bodies expect, and this causes various problems, like maybe prostaglandin-mediated allergies and inflammation (source).