Metabolism of propanoate begins with its conversion to propionyl coenzyme A (propionyl-CoA), the usual first step in the metabolism of carboxylic acids. Since propanoic acid has three carbons, propionyl-CoA can directly enter neither beta oxidation nor the citric acid cycles. In most vertebrates, propionyl-CoA is carboxylated to D-methylmalonyl-CoA, which is isomerised to L-methylmalonyl-CoA. A vitamin B 12 -dependent enzyme catalyzes rearrangement of L-methylmalonyl-CoA to succinyl-CoA, which is an intermediate of the citric acid cycle and can be readily incorporated there.

Do you find milk addictive? If so, assume an opioid-like peptide reaction. Does milk make you sneeze? If so, assume an intolerance to the immunological compounds and/or opioids, or a genuine allergic reaction – particularly if milk makes your throat itch. Does milk make you gain weight? If so, assume an opioid-like peptide reaction and/or sensitivity to IGF. Does milk provoke seizures? If so, you may need to test your reaction to calcium.
For suspected opioid-like peptide responders, individuals should test A1 milk (regular cow’s milk) versus officially branded A2 milk (Guernsey cow, buffalo, goat’s and sheep’s milk). People who are intolerant of opioids usually tolerate goat’s and sheep’s milk unless they are super-responders. See the gluten and casein responders page . Cream and Butter