Don't trust the NIH with your health. They're the reason the mass majority of Americans are deficient in vitamin d, potassium, magnesium and a bunch of other vital vitamins/minerals, primarily due to faulty research done 50 years ago and never updated.
Humans spent thousands of years out in the sun on a daily basis growing crops and hunting. They never got a vitamin D overdose and were in fact much healthier than you and I.