I live in the Pacific Northwest and the dark, dreary winters have really taken their toll on me in the past. I was researching what I could do about it and learned about vitamin D deficiency and its effects. I thought why not supplement with Vitamin D and see what happens. I read that Vitamin D3 Cholecalciferol was most efficacious for supplementation so I ordered Bluebonnet's product and have been exceptionally well pleased. This is the second winter that I have taken it and I've noticed a tremendous difference in my outlook. I would recommend this for anyone living in a northern climate. Also, last winter iHerb shipped me a bottle that was damaged during shipment. They replaced the product at no charge. I highly recommend doing business with them.