That's the best source of Vitamin D.
I’ll second the “Sun” motion.
It’s been a very rainy winter in N. California. There has been no sun.
This morning it was sunny, and I told her at lunch to take off her jacket role up her sleeves and hang out in the sun.
We do have skin cancer that runs in our family, but I don’t have them wear sunscreen to school. She has PE outside 4 days a week, and then they eat outside if it isn’t raining.
However, her levels were low in August, and we have a pool and spend lots of time outside.