A Sydney naturopath will face trial over a raw food diet she allegedly devised for a breastfeeding mother, whose baby nearly starved to death.

Marilyn Bodnar, 60, has appeared in Campbelltown Local Court charged with recklessly causing grievous bodily harm and aiding or abetting failure to provide necessities of life to a child.

She is yet to enter a formal plea, however has indicated she will plead not guilty.

The prosecution alleges that in February 2015 a 33-year-old maternity ward nurse, who cannot be identified, went to the naturopath seeking advice for her baby son's eczema.

It is alleged Bodnar told the woman, who was still breastfeeding, the eczema was caused by toxins, which needed to be eliminated.

The court was told the naturopath devised a raw food diet for the woman, before advising her to subsist solely off water and watermelon for three days.

When relatives expressed concern over the woman's weight loss, Bodnar allegedly told her she was "fat and needed to lose weight".

The court heard the naturopath also said the baby boy's weight loss was his body's way of eliminating toxins.

The baby boy became sick and when the mother told Bodnar her child was projectile vomiting, the naturopath allegedly said it was good because he was "deeply eliminating" the toxins.

The court heard the eight-month-old boy was "just days" away from death when his mother ultimately took him to Westmead Hospital in May 2015.

Upon arrival at the hospital he weighed just 6.4 kilograms, was severely malnourished and dehydrated, had sunken eyes, dangerously low sodium levels, and flexed hands and feet.

He was also developmentally delayed, showing the equivalent skills of a three-month-old.

Mother ignored naturopath's advice, defence alleges

In court, Bodnar's lawyer Alex Walker argued the blame lay with the child's mother, not the naturopath.

"It was the actions taken by the mother that directly inflicted harm on the infant," Ms Walker told the court.

"Whilst unconventional advice may have been given by Marilyn as to how to cure the infant's eczema, it is the reckless and negligent actions of the infant's mother, a former registered nurse, that directly impacted the child's health."

Ms Walker told the court Bodnar advised the mother to eat healthily and continue to breastfeed.

However she said the woman ignored the advice.

"We submit the mother ceased breastfeeding," she said.

The prosecutor, Alex Brown, said there was no evidence the woman had stopped breastfeeding her child.

Magistrate David Degnan told the court he was satisfied there was evidence Bodnar was an active participant in the child's "failure to thrive" and the mother had been encouraged to act the way she did by the naturopath.

Bodnar was committed to stand trial at Parramatta District Court, where she will appear next month.

She has remained on bail since her arrest on the condition she not provide naturopathy services to anyone under the age of 16.