I agree with both posts. I live more North then South here in the US. My state is usually cloudy and the winters last for 7 months. Working 55 hours per week, (inside), I have a real difficult time getting the amount of sun I need. Every chance I get, I get sun on my body. Last year, I had my doctor pull blood and check my vitamin d levels. The test showed I was far below minimum. My doc put me on 10,000 iu per day. After one year I am in the normal range. I now take 5000 iu per day. I feel great, look great, sleep great.