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.