In my humble opinion, I think they work most of the time. I would put it on a sliding scale, maybe 10-20% at worst, 80-90% at best. I think it depends upon
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the amount of food/water you have on your stomach when taking the pill.
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how quickly your body metabolizes the capsule/pill
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the excercise done afterward that would change conditions for (1) and (2)
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taking multivitamins before bed, when it would be absorbed slower into the body.
This is pure speculation on my part, what do you think?