Dogs really are man’s best friend as owning one can slash the risk of premature death by one-third, according to major new research.

The landmark study of more than 3.4 million older people found the animals reduce the likelihood of heart disease and combats loneliness.

Those living alone were 33 percent less likely to die over the next 12 years if they owned a dog.

The biggest impact was seen on cardiovascular disease, the world’s biggest killer, reducing mortality rates by 36 percent.

Scientists from Uppsala University, Sweden, said the companionship was key, along with the physical activity in taking it for a walk. Hunting breeds such as Golden Retrievers, Irish Setters and Beagles achieved the best results.

The findings come in the wake of warnings that loneliness is as dangerous as high blood pressure, diabetes and depression.

Senior author Professor Tove Fall said: “We know dog owners in general have a higher level of physical activity, which could be one explanation to the observed results.

“Other explanations include an increased wellbeing and social contacts or effects of the dog on the bacterial microbiome (gut bacteria) in the owner.”

The study was published in Scientific Reports.

Dr Mike Knapton, associate medical director at the British Heart Foundation, said: “Owning a dog is associated with reduced mortality and risk of having heart disease.

“Previous studies have shown this association but have not been as conclusive - largely due to the population size studied here.

“We cannot infer a causal relationship, however, dog ownership is associated with increased physical activity, improved psycho-social wellbeing and socialisation, all of which are associated with reduced CVD mortality- so it is plausible the effect is mediated though these mechanisms.

“Alternatively it could be reverse causality – people who are fitter and more active are more likely to own a dog.”