Vitamin D Status In The United States, 2011–2014, American Journal of Clinical Nutrition, 10 May 2019

First, the Vitamin D situation is not getting worse, it’s getting better:

This report provides the most recent estimates for the US population of the prevalence of at risk of deficiency or inadequacy of vitamin D.
…
The prevalence of at risk of vitamin D deficiency in the United States remained stable from 2003 to 2014; at risk of inadequacy declined.

And older adults (aged 60yrs or older) have a LOWER risk of Vitamin D deficiency (2.9%) and inadequacy (12.3%) than younger adults. Everyone older than 11 years (aged 12 to 59) have a HIGHER risk. Those aged 20-39 have the highest risk for deficiency (7.6%) and inadequacy (23.8%).

But…

Researchers at Northwestern University are saying that Vitamin D deficiency is more prevalent in “elderly populations.”
NU Researchers Discover Strong Correlation Between Vitamin D Deficiency And Covid-19 Mortality Rates

The abstract for their study says that Vitamin D insufficiency is greater with “advanced age.”
Vitamin D Insufficiency Is Prevalent In Severe COVID-19, 28 April 2020

If it is true that Vitamin D deficiency or inadequacy increases the risk for dying of COVID-19, you would expect people aged 20 to 39 years to be more affected, since they have the highest prevalence of deficiency and inadequacy. But…

Source: Business Insider

These researchers are perpetuating the myth that people’s health (in this case, Vitamin D status) declines based merely upon age. Discrimination against people based upon their age is ageism. Just as societies should not tolerate racism, they should not tolerate ageism.