Evidence from studies of almost half a million people suggested that "supplementing the diet of well-nourished adults... might even be harmful", despite one in three Britons taking vitamins or mineral pills.
The conclusions were made by academics from the University of Warwick and the Johns Hopkins School of Medicine in Baltimore, the US, and published in the Annals of Internal Medicine.
The scientists also suggested that firms selling supplements were fuelling false health anxieties to offer unnecessary cures, after examining research papers.
One analysing 24 trials involving 450,000 people found no beneficial effect on mortality from taking vitamins. Another examined 6000 elderly men and found no improvement on cognitive decline after 12 years of taking supplements, while a third saw no advantage of supplements among 1700 people with heart problems.
The experts said: "These vitamins should not be used for chronic disease prevention. Enough is enough."
Edgar Miller, of the Johns Hopkins School of Medicine, said: "Our diet is completely adequate."
The NHS advised recently that other than women taking folic acid to help them conceive and the elderly and children under five benefiting from vitamin D, supplementary vitamins would be surplus to that already gained through diet.
The Health Food Manufacturers' Association said supplements gave people "nutritional insurance".