Taking vitamin D supplements can lower your risk of acute respiratory infections such as influenza or the common cold, latest research shows.

The findings are part of an international research study involving the world’s leading infectious disease and vitamin D experts.

University of Otago, Christchurch, Professor David Murdoch is one of the authors of the study, recently published in the British Medical Journal.

The study pulled together data from 25 of the most robust studies done on vitamin D supplementation’s effect on preventing acute respiratory infections. The ‘big data crunch’ analysed individual results of more than 11,000 patients from four continents, including New Zealanders. All participants took some form of vitamin D2 or D3 supplementation.

Professor Murdoch says the study found vitamin D supplementation was safe and reduced the risk of acute respiratory infection overall. However, those people very deficient in vitamin D experienced the greatest benefit, he says.

The study found regular supplement use resulted in a 12 per cent reduction in the number of people suffering an acute respiratory tract infection. For people with the lowest levels of the vitamin, supplements cut their risk by 50 per cent.

Professor Murdoch, is a Christchurch–based infectious disease specialist who is involved in many of the world’s best and largest research studies in that field. Murdoch and his colleagues provided data from a study of healthy adult Cantabrians who had taken vitamin D supplements monthly. The other New Zealander involved in the study, Associate Professor Cameron Grant from Auckland University, provided data from a study of children and infants.

Professor Murdoch says the many individual studies done on vitamin D’s effect on serious respiratory conditions produced conflicting results. The study recently published in the British Medical Journal accessed all individual patient data from relevant studies done at the highest scientific level – randomised control trials – to get this latest finding on the vitamin’s effectiveness.

Professor Murdoch says different doses of the vitamin were given to participants in individual trails, so the study was not able to determine the ideal dose to protect against infections.

Professor Murdoch says many people get adequate amounts of the vitamin through exposure to sunlight. Vitamin D is in oily fish, such as canned tuna and salmon, eggs, lean meat and dairy products.