Do you take vitamins or dietary supplements? Sure they’re working? Information is Beautiful has a wonderful chart that shows graphically the effectiveness of various dietary supplements. The chart shows me two major things: first, there’s way too much money spent on ineffective supplements and second, our diets are way out of whack if we’re needing (or even thing we’re needing) all these extras.
I’m personally in the camp of no supplements. Find the vitamins or supplements you are told you are lacking and find a real food that gives what you’re missing. 9 times out of 10 when it comes to food science they find down the road that they were wrong with the supplement and you need the whole food / whole diet to get the best effect. Plus why on earth would you take a green tea pill when green tea is so yummy
For a better look at why food science is constantly changing it’s mind when it comes to healthy and harmful ingredients (a lot of the time these are harmful ingredients food science introduced in the first place) and why isolating particular ingredients from foods might not provide all that you’re needing check out In Defense of Food by Michael Pollan.