I can't be too critical of taking supplements, since I do try to drink 8 ounces of grapefruit juice every day to lower my cholesterol, but I am deeply skeptical of anything that comes in a supplement form. It's just basically companies capitalizing on this finding or that finding by packaging and selling "good health" like snake oil. Many foods have health benefits, but eating whole foods and taking a pill are two different things. Since we don't always know what it is in a certain food that is good for us — or if it's actually a combination of more than one thing, acting together — the idea that we can cram good health into a little plastic capsule is ludicrous.
Take cinnamon, for example. It has long been claimed that cinnamon helps to lower blood sugar, and while that sounds like a fine excuse for enjoying a little cinnamon and sugar on your toast, many supplement nuts pop cinnamon capsules like Valium.
Well, the claims weren't actually backed up by solid research — apparently there were a lot of conflicting findings, and the studies on cinnamon tended to be too small to make any good conclusions. Finally someone did a large study, however, and found that cinnamon has no effect on diabetics' sugars.
I'm sure there will be people who stubbornly insist that cinnamon works, and if you want to continue taking it, more power to you — as long as you eat right and exercise as well. There is simply no substitute for a low fat, whole foods diet and an active lifestyle!