Your claim, as I understand it, is that Target, Costco, and Walmart stock substandard vitamins compared to those you can find if you are "very very careful". This is an extraordinary claim: and you are asked to provide extraordinary proof. Do you have any?
It's not an especially extraordinary claim. There are multiple ways to formulate a lot of supplements (e.g. α-tocopherol vs. γ-tocopherol, or any of the zillion ways to put a mineral like calcium or iron into edible form). Some of these are more effective than others. Some of these are cheaper to manufacture than others. All he's claiming is that in cases where the cheapest formulation is not the most effective one, you'll often not find the more effective form unless you know what to look for and go out of your way to find it.
Well, magnesium oxide and calcium carbonate (worst form possible) without vitamin K and D3 (at least!) to direct your calcium to your bones and not arteries is pure crap, sorry!
Let me give you one simple example: you can find magnesium oxide at those stores, which is the worst form of magnesium on the market. For similar amount of money though you can buy magnesium glycinate, orotate, malate, taurate, and other chelated forms of magnesium that absorb better, have additional benefits, and save you the digestive system discomfort. Of course, the best prices and convenience (autoship) is available online, of course, plus, most stores offer additional 5-20% discounts. I can add a lot more examples of the various forms of vitamin E, B vitamins, vitamin D, vitamin K, folate/folic acid, vitamin A, etc. The formulation of the mass market brands are not only worse in terms of absorption, but are often harmful like folic acid and vitamin A. Even basic supplements like calcium not taken with vitamin K and D3 and dangerous, but anyway. There was a recent study that omega-3 EFAs increase prostate cancer risks, which was so poorly conducted that it's not even funny! There are many people with hidden agendas in "science" and especially when it comes to nutrition, it's not hard to engineer a study that will give you the desired outcome. It's been done many times in the past, Big Pharma is on a war against supplements, so, take all these with a grain (or chunk) of salt!
Well, I can't post a bunch of links. You can google yourself about the 8 forms of vitamin E (4 tocopherols and 4 tocotrienols) and why taking only one is harmful. Also, many supplements mix tocopherols and tocotrienols, which nulls the effect. Same with taking resveratrol with quercetin, which is the most common formulation.
