Does grapefruit prevent the absorption of vitamins when taken at the same time? Vitamins, not medicines!

Acid generally helps absorb vitamins and minerals. So grapefruit juice and other acidic juices like orange juice should improve absorption. The danger with medicine is you can get dosed too much at once, because of the quick absorption, I would never take any medicine with any citric juices. By contrast milk reduces stomach acids and inhibits absorption. Things like iron should be taken with orange juice for better absorption because iron absorbs better with vitamin C.