Vegetarians have been delivered some "very good news" in an Australian study of a group of strict vegan Buddhist nuns.

Bone density among the 105 nuns, who live in temples and monasteries across Vietnam's Ho Chi Minh City, was found to be the same as non-vegetarian women matched in every physical respect.

Sydney-based Professor Tuan Nguyen, from the Garvan Institute of Medical Research, collaborated with Dr Ho-Pham Thuc Lan from the Pham Ngoc Thach Medical University to undertake the research.

"We showed that although the vegans studied do indeed have lower protein and calcium intakes, their bone density is virtually identical to that of people who eat a wide variety of foods, including animal protein," Professor Nguyen says.

"For the five per cent of people in Western countries who choose to be vegetarians, this is very good news.

"Even vegans who eat only plant-based foods appear to have bones as healthy as everyone else."

Although Professor Nguyen and Dr Thuc Lan do not advocate a vegan diet, they say the study shows how fruits and vegetables are likely to have positive effects on bone health.

The nuns came from 20 temples and monasteries while the control group, 105 non-vegetarian women of exactly the same age, were recruited from the same localities.

The study found the nun's calcium intake was very low, only about 370mg a day while the recommended level was 1,000 mg.

Their protein intake was also very low at around 35g a day, compared with the non-vegetarian group, which was 65g.

Professor Nguyen says Buddhist nuns were chosen because their faith requires them to observe strict vegan diets all their lives.

"We didn't study vegetarians from the West because many are lacto-vegetarians, so could have considerable calcium in their diets," he says.

"It would have compromised the results."

They also caution the study did not measure the nun's levels of vitamin D - as important for healthy bones as calcium - or lifestyle factors which could curb the application of the finding to vegetarians living in the West.

The research is published in the online journal Osteoporosis International.

No drawbacks ... a plant based diet found to be healthy for bones despite the lack of calcium.