“I say it’s spinach, and I say the hell with it”

The famous New Yorker cartoon was on December 8, 1928, with a drawing by Carl Rose and text by E. B. White:

Young Mother: "It's broccoli, dear."
Young Daughter: "I say it's spinach, and I say the hell with it."

I discovered the following interesting passage about this.

Dumbbells and Carrot Strips
The Story of Bernarr MacFadden

by Mary MacFadden & Emile Gauvreau
New York, NY: Henry Holt & Company
1953
Pg. 197:
Her name was Nanette Kutner. She had come to our carrotcastle with her parents. She was never to forget the experience although she was not ten years old. She was thin but wiry, with inquisitive dark eyes that took in everything.
Pg. 198:
Her spinach and carrots always disappeared from her plate as if by magic. I knew she despised the stuff. While the boarders at the tables stowed it away in their stomachs she dumped it, by some sleight-of-hand, into a big reticule in which she carried reading matter. Later, sometimes in the middle of the night, in her bare feet, she got out of the house quietly and cast the food of health into the ocean. She is supposed to have been the originator of the phrase, "It's spinach, and the hell with it!" A cartoonist for The New Yorker was to make it famous.