A 'flexitarian' diet which includes one portion of meat a day has a lower carbon footprint than a vegetarian diet that includes dairy, according to a major new study.

The research by Johns Hopkins University (JHU) in Baltimore, America, could turn recent advice about diet and climate change on its head.

It modeled the environmental impact of all major diets across some 140 countries and concludes that those who switch to a vegetarian diet may be doing more harm than good.

By giving up meat and supplementing their intake with dairy products such as Halloumi cheese, yogurt and crème fraîche, vegetarians are only fractionally improving their carbon footprint.

The research shows they would be better cutting down on diary products, increasing their fruit and vegetable intake and eating meat once a day for protein and energy. They call this a "two thirds vegan" diet.

Here in the UK, the average healthy two-thirds vegan diet contributes the equivalent of 762.7 kg of Carbon Dioxide emissions (CO2e) per-person, compared with 1,265.2 kg for a vegetarian diet that includes dairy.