In May 1961, President John F. Kennedy traveled to the Vienna Summit to meet with Soviet Premier Nikita Khrushchev for talks crucial to the relationship between the two nuclear superpowers. As part of his entourage, Kennedy brought an unlikely figure; a man whose colleagues would later describe as "out of his mind", known as "Dr Feelgood".

Dr Feelgood – real name Dr Max Jacobson – was a German physician to the rich and famous. Over his lifetime, he treated clients from Ingrid Bergman and Humphrey Bogart to Nelson Rockefeller and Elvis Presley. Judy Garland and Marilyn Monroe feature among his most famous clients, who flocked to him for his suspiciously invigorating (and addictive) "vitamin shots".

The shots contained everything from animal placenta and bone marrow to vitamins and steroids, plus one or two secret ingredients that added a little extra spring to the step. Truman Capote, another client, explained that the treatment makes you feel "like Superman. You're flying. Ideas come at the speed of light. You go 722 hours straight without so much as a coffee break."

At this point, you may have taken a wild stab in the dark and guessed correctly that his secret ingredients were methamphetamine and speed.

As the New York Times reported in 1972: "Dr Jacobson uses unusually large amounts of amphetamine in his practice. The doctor's office reported that Dr Jacobson buys amphetamine at the rate of 80 grams a month. This is enough to make 100 fairly strong doses of 25 milligrams every day."

Kennedy had experienced back pain for some time when he came across Dr Jacobson. Kennedy concealed the pain he was in from the public, refusing to let on that he was suffering not just from spinal issues, but also chronic stomach, colon, and prostate problems. 

Dr Jacobson began to treat Kennedy, who was a fan of the relief provided by the "vitamin mix" compared to other painkillers. When it came time to meet with Khrushchev – who saw the opportunity to intimidate the inexperienced president – he wanted to be at his best. He took Jacobson with him, telling Feelgood “Khrushchev is supposed to be on his way over. See to it that my back won’t give me any trouble.”

As much as you don't want to worry about back pain during a meeting with the leader of the Soviet Union, it's probably not a great idea to be shot full of a mystery drug either. Side effects of amphetamines include everything from nervousness to impaired judgement – arguably worse than a back twinge when the other guy has access to a short temper and nuclear weapons.

The meetings did not go well. Rather than deescalate tensions, the talks were tense and meandering on the first day, before ending in threats of war.

“He just beat the hell out of me,” Kennedy told a journalist for The New York Times. “It was the worst thing in my life. He savaged me.”

The President did not know what the vitamin mix contained at first, though he continued to take it several times a day. Eventually, he submitted the concoction for analysis by the Centers for Disease Control and Prevention. When he was told that the mixture contained amphetamines and steroids, he reportedly replied, "I don't care if it's horse piss. It’s the only thing that works."

The regime continued unabated until Kennedy's official doctor – official White House physicians do not generally have the title "feelgood" – put an end to his contact with Jacobson. Though correlation doesn't equal causation, this cessation of amphetamines occurred at roughly the same time his performance as president notably improved.