Eating a vegan or vegetarian diet can reduce the risk of developing diabetes by almost a quarter, according to new research.

An analysis of more than 300,000 people found those whose diets were mainly plant based were 23 percent less prone to the Type 2 form linked to obesity.

The foods are rich in antioxidants that protect against the potentially fatal disease, say scientists.

They improve sensitivity to insulin - the hormone that controls blood sugar - and reduce weight gain. They also combat inflammation, explained the US team.

The study is the first of its kind because it also differentiated between healthy and less healthy plant based foods.

The former included fruits, vegetables, whole grains, nuts, and legumes and the latter potatoes, white flour, sugar and modest amounts of animal products.

It also found the association was strengthened for those who ate diets emphasising healthy plant-based foods and lower consumption of unhealthy ones.

Senior author Professor Qi Sun, a nutritionist at the Harvard T.H. Chan School of Public Health, Boston, said: "Overall, these data highlighted the importance of adhering to plant-based diets to achieve or maintain good health.

"People should choose fresh fruits and vegetables, whole grains, tofu, and other healthy plant foods as the cornerstone of such diets."