GIVE THEM MILK! DRINK MILK!!
EXCERPT FROM "NUMBERS DON'T LIE"
"And which nation has the tallest citizens? For males the record holders are the Netherlands, Belgium, Estonia, Latvia, and Denmark; for females it is Latvia, the Netherlands, Estonia, the Czech Republic, and Serbia; and the tallest cohort (whose average surpasses 182.5 centimeters) is that of the Dutchmen born during the last quarter of the 20th century.
Milk has been a key growth factor, be it in Japan or in the Netherlands.
Before the Second World War, Dutch males were smaller than American men, but post-1950 US milk consumption declined while in the Netherlands it rose until the 1960s—and it remains higher than in the US.
The lesson is obvious: the easiest way to improve a child’s chances of growing taller is for them to drink more milk."
Numbers Don't Lie by Vaclav Smil
Brother!! On the other hand, milk as part of a diet might be one way to quantify the quality of childhood or childhood living standards, discounting for cultural norms for example (like Japan where milk is not a customary part of the diet)
https://www.j-milk.jp/report/study/h4ogb400000011y2-att/h4ogb40000003f7e.pdf
https://academic.oup.com/ajcn/article/80/4/1088/4690374#:~:text=Several%20previous%20studies%20showed%20an,height%20was%20prominent%20during%20puberty.