Power Thesaurus. 1969. unsolicited thesaurus http://www.powerthesaurus.org/unsolicited/synonyms (accessed August 29, 2017). Harvard. Power Thesaurus 1969, unsolicited thesaurus, Power Thesaurus, viewed 29 August, 2017, <http://www.powerthesaurus.org/unsolicited/synonyms>.
The AAP also recommends 400 IU/day of vitamin D for children and teens who drink less than a quart of vitamin D-fortified milk per day. The Vitamin D Council recommends that healthy adults take 2,000 IU of vitamin D daily -- more if they get little or no sun exposure. There's evidence that people with a lot of body fat need more vitamin D than lean people.
I take 3,000 IU daily, but I skip it in the summer. I feel markedly better after I've taken about 1,000 IU consistently for over a week. Tolerable upper intake limit (that is, max to safely take every day) is listed on wikipedia at 4,000 IU for adults. Wikipedia tells me that Vitamin D is fat-soluble, not water-soluble.