Vitamin D3

http://www.vrp.com/bone-and-joint/vitamin-d3-higher-doses-reduce-risk-of-common-health-concerns

http://www.rejuvenation-science.com/n_vitamin-d-upper-limit.html

Vitamin D3 is one of the most useful nutritional tools we have at our disposal for improving overall health. This vitamin is unique because cholecalciferol (Vitamin D3) is a vitamin derived from 7-dehyrocholesterol; however, Vitamin D3 acquires hormone-like actions when cholecalciferol (Vitamin D3) is converted to 1,25-dihydroxy Vitamin D3 (Calcitriol) by the liver and kidneys. As a hormone, Calcitriol controls phosphorus, calcium, and bone metabolism and neuromuscular function. Vitamin D3 is the only vitamin the body can manufacture from sunlight (UVB). Yet, with today’s indoor living and the extensive use of sunscreens due to concern about skin cancer, we are now a society with millions of individuals deficient in life-sustaining bone building and immune modulating 1,25-dihydroxy Vitamin D3.
For more than a century, scientists have recognized that Vitamin D3 is involved in bone health. Research has continued to accumulate, documenting Calcitriol’s role in the reduction of the risk of fractures to a significant degree. The latest research, however, shows that 1,25-dihyroxy Vitamin D3 deficiency is linked to a surprising number of other health conditions such as depression, back pain, cancer, both insulin resistance and pre-eclampsia during pregnancy, impaired immunity and macular degeneration.

I can personally attest to the 10,000 IU range with zero side affects, of course your mileage may vary.

I take one Vitamin D3 daily that has Vitamin K2, I also supplement with Magnesium as well. If you decided to go this route consider incorporating Magnesium as  just encase of Nausea or Flu type symptoms arise.

I have noticed a considerable difference in my mood as well as my over all well being..Something Big Pharma or even your GP will not tell you.

I like this brand, but of course you can find it cheaper..

http://www.amazon.com/gp/product/B00ECH40MQ?psc=1&redirect=true&ref_=oh_aui_detailpage_o03_s00