Was saddened to read a memorial about this doctor. He was the first Canadian to run a mile in under four minutes. He went on to discover a great deal about how the liver metabolizes certain medicines, and how some common foods can have a huge effect on how the human body reacts to certain drugs. This research, expanded by others, also helped make taking medicine safer, by suggesting likely drug-drug interactions.
Article is paywalled.
So he’s the reason I can’t have Grapefruit! 
(Joking. He seems like a good guy. And I’d prefer my medicine to actually work.)
I’m sorry to read of his passing. Due to his citrus discovery, a whole lot of other interactions between medicine and food has come to light.
An excerpt…
“David Bailey improved countless lives because of a discovery he made by accident.
In the late 1980s, Dr. Bailey, an Olympic runner-turned-pharmacologist, was researching the effects of alcohol on a blood-pressure medication… Seeking to disguise the alcohol’s taste in his experiment, he tried combining it with grapefruit juice and stumbled upon the fact that his subjects’ consumption of the juice resulted in a greater concentration of the drug in their bloodstreams. He went on to discover that grapefruit juice has this effect because it inhibits an enzyme in the human gut that breaks down the medication, so the body consequently absorbs a larger than normal amount of the medication…
In 1991, Dr. Bailey’s findings were published in the prestigious international medical journal The Lancet and reported by several other academic publications… The phenomenon he identified came to be known as the grapefruit effect.
Over the years, Dr. Bailey’s follow-up research determined that grapefruit juice has harmful interactions with some 100 oral medications, with the potential either to cause an overdose or, in some cases, to do the opposite and reduce the drug’s benefit.
As a result, many prescription medicines now carry labels warning patients not to consume grapefruit juice with them.”
Thank you, doctor. Your discovery may have saved my life.