Vitamin D and fish based omega-3 supplements do not prevent cancer or heart disease, a new study has suggested.
During the five-year experiment, researchers at Harvard Medical School found no significant difference in the rates of diagnosis of disease between those taking supplements and those taking a placebo.
More than 26,000 people of various ethnicities who were over the age of 50 and had no history of cancer, heart attack, stroke or other forms of heart disease took part in the trial.
The research comes after a similar study by the University of East Anglia was published earlier this year, which concluded that omega-3 supplements did little to help the heart and consumers were better off spending money on vegetables.
But the latest research, which was funded by the United State's National Institute of Health, has produced some of the clearest evidence yet about the usefulness of taking the supplements.
Following the study, Naveed Sattar, a professor of metabolic medicine at the University of Glasgow, urged the public not to "waste time" on vitamin D supplements.
"By and large the marketing of supplements is done very cleverly, but it’s not backed up by evidence," he told The Independent.
"Don’t waste your time on vitamin D. There are thousands of people still popping it, but this is the biggest trial in the world to date, so forget vitamin D, draw a line under it."
What did the trial look at and what were the results?
The Harvard trial, known as Vital, sought to settle the question of what benefits the public might gain from these supplements and asked 26,000 healthy over-50s to take either double their minimum daily requirement of vitamin D, 1g of fish oil, or both.
Around 820 people were in the placebo group
After the study ended, researchers found just 905 participants developed problems such as stroke, heart attack or death from heart disease.
Of them, 396 were taking vitamin D supplements daily; the placebo group had 409 cases of a major cardiovascular event.
The researchers concluded the difference was too small and said there was no link between vitamin D and a lowered risk of major heart disease or invasive cancers.
Despite the findings, the study did reveal some evidence that fish oil supplements could benefit some patients in preventing heart disease or cancer.
But researchers stressed the "positive" results needed to be interpreted with caution.
The results were presented at the American Heart Association Scientific Sessions in Chicago and released online on Saturday by The New England Journal of Medicine.