Mary Poppins sang its praises in the 1964 film and yesterday a scientist insisted she was right - a spoonful of sugar really does help the medicine go down.
Experts discovered that infants who are given sugar feel less pain during injections than those who go without.
Dr Paul Heaton, one of Britain's leading paediatricians, says a tiny amount of sugar can ease the suffering babies and toddlers feel when receiving jabs or blood tests.
A few drops of sucrose solution put on their tongues before an injection was found to act as an analgesia, effectively blocking the pain they felt in their arms or bottoms.
Dr Heaton said: 'The sweet taste works through nerve channels in the tongue that perceive sweetness in the brain.
'The brain reacts by producing endorphins, a pain reliever. In babies a second pain-relieving compound is created by the action of sucking, called endocanabinoids.'
Once they taste the solution, Dr Heaton noticed babies cried less and recovered more quickly from the procedures.
Boiled sweets have long been given to tots in a bid to distract them from the pain, but tests have never been carried out to see if sugar alone can reduce it.
Dr Heaton, 53, has spent more than 15 years researching ways to alleviate pain in children during injections at Yeovil District Hospital in Somerset.
He claims his practical studies have revealed what mothers and fathers have known for generations - that a sweet treat works best.
It really works: The film and stage character Mary Poppins sings 'a spoonful of sugar helps the medicine go down'
The married father-of-two, whose findings have been published in medical journals over the years, is now spearheading a campaign to encourage other doctors to follow his lead.
Dr Heaton said: 'The association of sweetness as making nasty things less nasty is a common practice in every day life.
'It didn't start with Mary Poppins - historic texts refer to Jews being given honey before they were circumcised.
'But we only started researching using sugar to relieve babies' pain in 1992.
'And since then, we have noticed incredible results, with the majority of youngsters crying less and recovering more quickly after receiving a sugar solution.'
His research began 16 years ago when he started treating babies in New Zealand. He has continued the study since moving to Yeovil District Hospital in 2002.
Studies have shown that young babies experience pain more easily and sharply than adults during injections or blood tests.
He has given thousands of babies half a millimetre of sucrose solution, and recorded their reactions.
They are given 'just enough to taste but not enough to swallow', which sparks a physiological reaction that numbs small amounts of pain.
Dr Heaton said: 'Pain is not a natural feeling for babies. Their heart rate and blood pressure rise and very small babies can sometimes stop breathing.
'However, sweet tasting substances reduce their response to pain.
'They release natural substances which minimise the pain and enable quick and effective short-term relief.'
Dr Heaton's research has even shown that babies who are saved the pain of early injections could enjoy a higher pain threshold later in life.
He added: 'Research has also shown that if babies experience pain in the very early stages their nervous system becomes more sensitised to pain and this sensitivity can persist for a prolonged period.'
Now he plans to spread the use of sugar being used to reduce pain in babies in hospitals, doctors' surgeries and medical centres across the UK and beyond.
He said: 'Each baby born in the UK gets at least three or four jabs in the first six months of their lives.
'There are 750,000 babies born each year, so that's over three million injections which could be given in a more painless way.
'It costs almost nothing and could have long-term health benefits for generations to come.
'There are so many scientific discoveries every day, but unless they are put into practice they are all rendered useless.'
He said that sugar could have similar effects in adults.
'There is some evidence that sweetness acts in a similar way to relieve pain in adults.
Perhaps this explains why women find chocolate so comforting during times of need.'