Adding vitamin D supplements to your diet can protect against colds, flu and other respiratory infections, according to a new study published in the British Medical Journal (BMJ) which will no doubt, reopen a debate on the usefulness of over-the-counter supplements.

The team behind the paper say their results show there is an advantage to taking vitamin D supplements daily or weekly.

For the new study, researchers from the Queen Mary University of London conducted the biggest ever survey of trials involving nearly 11,000 people.

The paper suggests the ‘sunshine vitamin’ can help reduce the risk of respiratory infections, including colds and flu – especially among people who don’t get enough of the vitamin from diet or exposure to sunlight.

Louis Levy, head of nutrition science at Public Health England, has added a note of caution about the findings, stating “this study does not provide sufficient evidence to support recommending vitamin D for reducing the risk of respiratory tract infections,” he said via the Science Media Centre in London.

While the paper proclaims in favour of adding supplements to our diets, lots of foods are already rich in vitamin D.

The most natural way to get vitamin D is from sunlight on our skin, the best source being summer sunlight.The vitamin forms under the skin in reaction to sunlight. However, of course, if you are out in the sun, take care not to turn red or get burnt.

Vitamin D is also found in a small number of foods. Here are just some of the good food sources that can boost your level of vitamin D:

• oily fish, such as salmon, sardines, herring and mackerel
• eggs
• fortified fat spreads
• fortified breakfast cereals
• powdered milk

According to the HSE, Vitamin D has several important functions. For example, it helps regulate the amount of calcium and phosphate in the body. These substances are needed to keep bones and teeth healthy.