I see you try out a lot of supplements, just letting you know if you’re buying off Amazon/ebay or off smaller less reputable local brands then there is a big chance you are getting something different to what’s being advertised: either a much smaller amount of the supplement than has been advertised, poor quality, or the supplement may not even contain the thing it is labelled as.
The best quality and most trust worthy brands are Life Extension, Thorne, Now foods, Nootropics Depot all these brands are reputable and have been lab tested for purity. Best place to buy these brands (excluding ND) is from iherb where you can get 22% off your first order. Amazon does sell fake Now foods products so be careful.
I would have preferred to avoid mentioning brands as the situation with POIS is quite complex as it is without adding further uncertainty elements. So far I haven’t bought anything from ebay, amazon or China if that counts anything. Unfortunately my budget is rather limited so I can’t always buy the more expensive stuff. Not to mention that some things can only be bought from a sole source which doesn’t make it easy to be picky. I prefer to buy in-country to avoid international shipping prices, but I think our country’s quality control is rather strict especially as part of the EU. You may be partially right about local brands, but it doesn’t mean they can’t have good products. For example I bought the alfalfa pills and licorice pills form the same local brand and they worked rather well which proves their quality. Astaxanthin and L-theanine also came from another local company both of which were quite beneficial. I also bought indole-3-carbinol from them. As this product has to be kept cool they sent it with a freeze casket and it was still cool by the time it arrived. Such care must imply that they are also a trustworthy company. I bought many stuff from fitness stores. The two most notable ones here are BioTechUSA and GymBeam. I think they are also present in at least a few other countries. They have a wide range of products and I think they are relatively trustworthy regarding product quality. The maca capsules I use come from GymBeam, but I also bought Tribulus, Ecdysterone and Cordyceps from them. Not all of their products were beneficial, e.g synephrine, but it is unlikely to be a quality issue. The L-tryptophan I tested the most came from BioTechUSA. I also bought medicinal mushrooms from a variety of sources. The best so far came from another local brand. They also sell many nutritional supplements in bags. I bought triphala from their selection. Of course not all of their supplements work similarly well, but it is hard to believe to be a quality issue. I bought damiana from yet another local brand that makes it possibly trustworthy. I ordered saffron from a reform food store that also sells exotic spices. I heard there are many fake saffron products, but fortunately this one isn’t one of them. I bought No-Spa at the pharmacy and it comes from Sanofi, thus it must be authentic. Mexican Wild Yam Root came from Nature’s Way and the similar Diosgenin is from a UK company. Mangosteen came from Terra Elements which is a German company. The only other product I have from them is pine pollen, but I haven’t tested that as of yet.
More towards international products it is strange you haven’t mentioned Swanson, but from experience I can tell that it has quality products. Some of the better things I tried from them are Resveratrol, Catuaba bark, Muira puama, Magnolia and Chinese skullcap. There were several other things I have tried from them and most were at least a little beneficial. I also bought some stuff from Nowfoods, but I haven’t had time to test most of them. My Relora came from them, but I couldn’t see a particular benefit over Swanson’s Magnolia. The beta-glucan (Maitake) supplement was also from them, however it wasn’t the best amongst the medicinal mushrooms and a common "noname" bagged reishi was possibly better. I think the only supplement I have from Life Extension is calcium d-glucarate, but I haven’t had time to test that. I don’t have any Thorne and Nootropics Depot products as they are either not available here or too expensive for me.
It is true though that I also suspected some products may be of lower quality. One example is another local brand where I bought black maca, black cumin and DHM. All of these were actually beneficial for me, however I am not altogether sure if another brand wouldn’t be better. Another more problematic issue is an Eastern European brand that I bought from via a local market. Some of their products were actually beneficial (lion’s mane and tongkat ali), however I can’t shake the thought that their products are possibly of lower quality. I bought yohimbe from them which didn’t really work. However if catuaba bark’s active component is really yohimbine than it should have worked better. The quercetin supplement I tried was also from them and it was barely effective for me. I also bought DHEA from them and although I only tested it little so far it doesn’t seem to be that great which doesn’t agree with my current theory. I will probably need to buy quercetin and DHEA from another source as well to see what is the real deal with them.
Nevertheless thank you for the recommendation about iherbs! I was actually considering to buy some stuff there that I can’t buy anywhere else. I was also going to order there when I decided to switch to treatment as their prices seem quite good and buying in bulk could reduce the shipping overhead.
I hope these facts lessen some of the concerns towards the reliability of my findings.