Yes, brands are not all the same even if the ingredient seems the same on the package. I found that with SAMe a long time back and have also read about quality differences especially with Melatonin. Years back I was taking a B-complex that had Niacin in it. I couldn't figure out what was going wrong with me everytime I took it. Ended up talking to my gastroenterologist who told me to change the type of Niacin I was taking because my liver wasn't dealing with it well. Ended up changing to niacinamide instead of the nicotinic acid. Gosh, I think I got that the right way around. Long time ago.