Start with high-confidence kids' nutrition books, then narrow by subgenre or adjacent topics.
Eating the Alphabet Board Book
Lois Ehlert
The Digestive System
Christine Taylor-Butler
Kid Smoothies: a Healthy Kids' Cookbook
Erin Fletter
How Did That Get in My Lunchbox?
Chris Butterworth
Brushing Teeth
Mari Schuh
How Does Soap Clean Your Hands?
Madeline J. Hayes
What the World Eats
Faith D'Aluisio
Kids Cook Gluten-free
Kelli Bronski, Peter Bronski
Busy Little Hands: Food Play!
Amy Palanjian
Chopchop I Made This! Snacks
Sally Sampson