A new Australian study has busted some commonly held beliefs about the importance of meat, particularly for pregnant women and children.

The findings, published today in the Medical Journal of Australia Open, show a well-planned, plant-based diet can meet the nutritional needs of all adults and children, whatever their age.

Traditional thinking has long supported the idea growing bodies need nutrients, such as protein and iron, that have usually been associated with eating meat.

The research was prepared by a team of three Australian dieticians from Sanitarium, a private Sydney practice and the University of Newcastle, who worked with local and international academics.

Nutritionist Dr Rosemary Stanton supports the findings, saying it is a break from traditional thinking.

"I've been aware that you can have an adequate vegetarian diet for many years, but I think this new research really puts everything together so that people can understand why," she told ABC's Radio National.

"As long as you've had a variety of plant-based foods over the course of a day or so, your body will take the amino acids as it needs them. And so we don't need to fuss about having seeds and nuts together, or particular foods together, the way we used to."

Dr Stanton says there has always been a push to track iron intake and concern of iron deficiency in those who do not eat meat, but advice has been confused.

"I think we've mixed up the people who are vegetarian because they can't afford meat, or can't afford enough food to eat, with those who can eat a variety of plant-based foods," she said.

"If you take meat off the plate, you need to put something else there, in the way of some legumes or grains or seeds or nuts."

During pregnancy, she says, the iron in plant-based foods is more easily absorbed simply because the body needs more of it.

Dr Stanton also says grains contain twice as much protein as the typical meat serving does.

As a nutritionist, she recommends moving towards a plant-based diet, although not necessarily removing all meat products.

"You always need a variety. Variety is important," she said.

"People always say to me, 'what's the most nutritious vegetable?' Well it's a variety of vegetables - no one food has it all."

Dr Stanton says in order to get vitamin B12, which is found only in animal products, dairy and eggs will fill that need.

But she says vegans - who eat no animal products whatsoever - will need a supplement of B12, which is particularly important during pregnancy and for small children.