Well sure, but like I said, I do not find the risk of rancidity to likely be terribly increased. They're also in a sealed container while sitting on store shelves, and by the time someone's bought them (which for this kind of thing tends to be pretty quickly; ads for this kind of thing obviously abound, and with the American attitude toward pharmaceuticals...), not much has happened to the product in all likelihood. Add to this the likely speed of consumption (one a day, sealed almost all the time), and fish oil pills going rancid doesn't seem to be a going concern, to me at least. One thing that would certainly affect this: how many pills are generally in each bottle?kinnision wrote:Even if the capsule shell and the bottle are both completely impervious to oxygen - doubtful over a several-year timescale, the usual shelf life of supplements - one still has to deal with the oxygen introduced into the oil during processing. While it is undoubtedly possible to nitrogen-purge the oil itself, do all the processing and capsule-filling in an inert atmosphere and fill the bottle with nitrogen before sealing - somehow I doubt that most manufacturers go to all that trouble.
You are correct. However, what I said was also correct. Basically, atoms and molecules have a range of energies in any given situation; some have more than others, and there will be a well defined peak that is the most probable energy for one to have (see the Maxwell-Boltzmann distribution for a basic application of the concept). Some of the free radicals will have enough energy that they will never bond with the Vitamin E molecules, while others will bond only relatively loosely, and others will bond more tightly. Every once in a while, an already bonded E/radical molecule will be hit by another molecule or atom hard enough to break the bond between the E and radical molecules. Given a set of initial conditions (generally, an average temperature, density, and starting amounts of the reactants), you will settle into a certain equilibrium state, where the rate at which bonds are forming equals the rate at which bonds are breaking. Thus, you will never get rid of all the oxygen, no matter how much vitamin E you put in.As for the business about vitamin E/oxygen reaction - well, maybe. Two things; simplification on my part - and frankly I doubt it. As I understand it, most antioxidants work by reacting with highly-reactive free radicals (thus making another free radical, but a much less active one) and thus getting rid of them. Eventually, two of the tocopheryl radicals floating around will join with each other and then there are none. Free-radical damage is often more of a problem because it is a chain reaction, and antioxidants are chain-stoppers.
Another example of this that might be easier to understand: consider a pot of water with the lid on. Assume the seal is perfect; nothing can get in or out, and the pot is in contact with a heat reservoir at temperature T (that is, nothing we do will change the temperature of the system). As you know, water evaporates at room temperature and one atmosphere of pressure. However, in our system, not all the water will evaporate. Why? Just like in an ideal gas, or our previous situation, the water molecules have a range of energies. Some of them have enough energy to escape the surface of the water, and evaporate. However, some of the water molecules in the air have very little energy, and they will at some point hit the water and form hydrogen bonds, subsuming into the liquid. With our initial conditions, at first evaporation will dominate; however, as more and more water finds its way into the air, more and more water molecules will lose enough energy through collisions and such to go back to the liquid. Eventually, the two rates will be the same, and nothing more will seem to happen. So it is with the vitamin E and oxygen in our pill.
I didn't know they only worked in aqeuous media; interesting, but it doesn't really matter, since the cell membrane damage due to free radicals is easily repaired by the cell, IIRC. The places to worry about are the mitochondria, ribosomes, and nucleus, which are aqueous environments, and all of them contain high concentrations of glutathione and SOD.Finally - vitamin E vs. other antioxidants like SOD and glutathione? Again, I am quite prepared to be proved wrong; but AFAIK both of those work in an aqueous medium and the cell wall is not such a medium. The body contains quite a lot of fat enclosed in some sort of vacuole, too - especially mine, unfortunately.
