You're begging the question by labeling vitamin deficiencies in this population as "rare." But that's not true.
"Vitamin D deficiency occurred in 50.5% of blacks, 29.3% of whites, and 14.3% of Asian inmates (p = 0.007). Black inmates had significantly lower serum 25(OH)D level than white inmates at the maximum security level (p = 0.015), medium security level (p = 0.001), but not at the minimum security level (p = 0.40). After adjusting for covariates black inmates at a maximum security level had a four-fold higher risk for vitamin D deficiency than white inmates at the same security level (OR 3.9 [95% CI 1.3–11.7]."
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3944727/
Why Vitamin D? Because the 600 IU RDA (the amount prisons must legally put in their food) is way too low.
Considering how cranky I get if I miss my vitamin D, it's not hard to posit a link between deficiency and increases in aggressive/violent behavior, especially in populations with a high rate of pre-existing mental illness.
Athletes and those who don't get enough sun, like most in the northern parts of the United States with the abrupt switch to being indoors far more than usual in the last 100 years?
It's not that rare. If you mean the bullshit industry, sure, but this attitude of "all vitamins are obtained through food" is simply not true and been proven repeatedly false - especially for athletes.
Thank you!
This is a webpage about "orthomolecuar medicine". This isn't a real thing, it's a quack theory that vitamins are some wonder drug that help against everything. It's been largely discredited.
The evidence for vitamin supplements is extremely clear: Except for some rare circumstances (special deficiencies and illnesses) they are largely a waste of money.