New research has found that Vitamin D supplements will not protect from catching the common cold, flu, and other respiratory illnesses, ABC News reported.

For the study, the researchers carried out a five-year clinical trial, led by Brisbane's QIMR Berghofer Medical Research Institute. The study involved 16,000 Australians aged between 60 and 84.

The trial is considered to be the largest of its kind to study the link between vitamin supplements and respiratory infections.

The researchers of the study asked each to take a capsule once a month for five years — half were given a vitamin D supplement, while the other half were given a placebo or sugar tablet.

By the end of every year, the participants reported their medical events throughout that particular year.

The researchers also asked around 2,600 participants to keep a daily diary during winter and observe their health, particularly if they had cold or flu symptoms.

Lead researcher, Professor Rachel Neale said that they have found that Vitamin D supplements had not helped the participants in preventing cold and other flu. However, the supplements shortened the length of illness and reduced the severity of the infection.

"The key message is that if you are not vitamin D deficient, taking vitamin D is unlikely to stop you from getting a head cold or the flu," Professor Neale said.

She added: "It may reduce the length of it a little bit, but not enough to really warrant taking vitamin D if you're not already vitamin D deficient."

"The findings of this, which suggest that more is not better, would indicate that we shouldn't just go out and routinely supplement the whole Australian population. It does tell us that being aware of avoiding vitamin D deficiency is important,” she noted.

"But if you're not vitamin D deficient — if you're out and about and getting a bit of sun exposure particularly during summer — you don't need to run out and get a supplement," she further added.