Dundee University scientists suspect high doses of vitamins may help treat Hepatitis C sufferers.
Current treatments for the condition, which can cause serious liver damage and even lead to cancer, are only successful with 60% of patients.
It can also take up to a year to cure patients, who often suffer debilitating side-effects.
Now researchers are to work with the voluntary sector organisation Hepatitis Scotland and health boards, including NHS Tayside and NHS Forth Valley, to see if taking vitamin D can improve cure rates when used with current therapies.
Leon Wylie of Hepatitis Scotland welcomed the trial of 100 patients.
He said: “This study could have significant impact on the future of Hepatitis C treatment, both here and internationally.
“If this study replicates other findings then a very cheap and safe method of increasing treatment success rates could be available.
“When we first saw the early research it seemed very exciting and I am extremely pleased that our partnership working has helped achieve the start of this research.”
The £250,000 project is being funded by the Scottish Government’s Chief Scientist Office.
Around 38,000 people in Scotland, and 150 million people globally, suffer from the illness.