My dad used to tell me grapefruit juice can potentiate some prescription drugs. Although I did not take him seriously then, it seems to be true, in an evil sort of way.OK. So the story of how this works, begins with a class of enzymes called the Cytochrome p450 (see pictures), which removes foreign molecules (e.g. drugs) from your body by adding oxygen atoms to them. Most of the time this makes the foreign molecule soluble in water and thus “flushable” from the body.Some unknown Chemical X (think power puff girls), present in grapefruit inhibits the ability of this enzyme to oxidate foreign chemicals. This increases the biological half-life (i.e. the time required for half of that substance to be removed from an organism by either a physical or a chemical process) and hence increases the drug potency.Sadly for anthropocentric creationists (SFAC) Cytochrome p450 enzymes are found in all organisms. Bacteria have 20 types of p450 and human beings have around 60. Plants, SFAC have a hundred of them. This is because plants make exotic toxins and pigments to protect them.References: here. here.