Taking vitamin D supplements could help more than three million people a year stave off colds and flu, according to new research.

Scientists at Queen Mary University of London claim that taking the so-called "sunshine vitamin" may have benefits beyond bone and muscle health and could protect against acute respiratory infections.

They analysed data from 11,000 people across 25 trials in 14 countries, including the UK, and concluded that vitamin D can help prevent infections.

"Assuming a UK population of 65 million and that 70% have at least one acute respiratory infection each year, then daily or weekly vitamin D supplements will mean 3.25 million fewer people would get at least one acute respiratory infection a year," said report author Professor Adrian Martineau.

Experts said the study had implications for public health policy, including the possibility of fortification of foods with vitamin D to tackle high levels of deficiency in the UK.

Mr Martineau added: "The bottom line is that the protective effects of vitamin D supplementation are strongest in those who have the lowest vitamin D levels and when supplementation is given daily or weekly rather than in more widely spaced doses.

"Vitamin D fortification of foods provides a steady, low-level intake of vitamin D that has virtually eliminated profound vitamin D deficiency in several countries."

But baker John Townshend said he believes that vitamin D should not be added to bread, regardless of any purported health benefits.

"Bread should be made from flour, water and salt and nothing else, that's my view," he told Sky News from his Kennington bakery in central London.

"I don't agree with adding in vitamins. It's the wrong approach and it's really not necessary. We need to get back to taking ingredients out, not adding more in."

The supplements have been a hot topic in medical circles in recent years, with some experts arguing their usefulness remains uncertain.

Last year, Public Health England said people were generally not getting the recommended 10 micrograms of vitamin D a day from sunlight in winter.

Professor Louis Levy, head of nutrition science at PHE, said: "The evidence on vitamin D and infection is inconsistent and this study does not provide sufficient evidence to support recommending vitamin D for reducing the risk of respiratory tract infections."

The study's results fit with the observation that colds and flu are most common during winter and spring, when levels of vitamin D are at their lowest.

Respiratory tract infections affect the sinuses, throat, airways or lungs and can last up to 30 days.

At least 70% of the population gets at least one acute respiratory infection every year. And about a quarter of the UK population will visit the GP each year to get treatment.(SKY)