> Looks like adequate sunlight is necessary for health.

There was a study in Sweden about ten years ago when they looked into the
different circumstances in child daycare, ages 1-7 years old. They wanted to
find out why some children were so often sick and staying home. The point is
that parents in Sweden can stay at home during 60 days each year for looking
after sick children and they are then being payed out of health security
money.
What they found was that the one thing that made a difference to the amount
of days staying home was the amount of time spent outdoor, nothing else.