I am so fond of Vitamin D3. It’s clearly a fad that is refusing to die; and, like most medical fads, the journals overflow with evidence in favor of the snake oil cure of the day. I have to admit, though, that while I try to be skeptical, the tsunami of articles and studies make it hard to deny something is going on.
Vitamin D is not a vitamin, it is a very biologically active hormone–a neurohormone, for us–that appears to treat everything from cancer to depression to seasonal blues.
The recommended amounts have changed in the last five years and most conservative estimates suggest 1000IU a day is the minimum.
Others suggest up to 2000IU if you are deficient, and the Health Canada toxic dose limit is 4000IU a day.
Nutrition scientists across the world beg to differ: there have been no cases of toxicity at doses 10000IU or less.
So take you pick, and get a Vitamin D (OH, 25) level to see if you need a higher dose.
The targeted blood level is 75 nmol/L with optimal health achieved more like 80-100 nmol/L. Toxic blood levels start around 200 nmol/L.
Below is a good link written by a psychiatrist from Northern California, Dr. John Cannell.