Dr Libby Weaver has recalled 20,000 copies of her book What Am I Supposed to Eat? in which she has used the term "mongolism".
And medical experts now say her use of the term in the book in connection with the consumption of folate also has no scientific basis.
Weaver said she was horrified after learning the term was offensive when she received a phone call from a mother of a child with Down syndrome.
The nutritional biochemist apologised to the mother after being informed the meaning of the term.
"It has since been brought to my attention it is a word that is used in a derogatory way," she said.
"I am very, very sorry to have caused anyone any distress through this error, particularly children with Down syndrome and their families."
Weaver said she thought the word was used in the medical world.
The term mongolism is an offensive term used to describe Down syndrome people.
In Weaver's book, What Am I Supposed to Eat? it suggests pregnant women consume folate to reduce the risk of "neural tube defects, spina bifida, deformed limbs and mongolism".
IHC, an organisation that advocates for children with intellectual disabilities, was "thrilled" Weaver had pulled the book from shelves.
Director of advocacy, Trish Grant, said the connection made between Down syndrome and folate had an "extraordinary lack of basic science".
"Down syndrome has nothing to do with folate.
"I think the comments are not only inaccurate but also distressing. They have potential to cause a lot of unnecessary harm," Grant said.
She said the gaffe was the kind of misinformation that added to poor attitudes around Down syndrome.
Weaver is expected to publicly apologise for the mistake, and has said anyone who bought a copy of the book can return it for a refund.