Average heights of american men and women have increased steadily since the 1940s. what is the best explanation for this observation?

Average heights of American men and women have increased steadily since the 1940s because of the interaction of genes with environmental changes especially in the diet consumed over time. Thus, the healthier an individual, the taller they are based on their rich lifestyles.  In contrast, individuals who are malnourished tend to appear short in height. It is correct to infer that the living standards of individuals affect the aspect height with time.

Ithink its trade and commernce let me know if im wrong