Obviously, the very best way to get adequate levels of vitamin D is to expose yourself to sunlight for 5 to 10 minutes a day, several times per week. However, given today's work and home environments, many of us simply do not have the time or cannot remember to get outside. That's why most of us should keep a supply of high quality vitamin D supplements handy.
How much to take? That is a very highly individualized question. Different people need differing amounts. How much time do you spend outside, collecting sun on your skin? Is your skin lighter or darker in nature? How strong is your immune system? Do you have a history of cardiovascular problems? Are you prone to catching the common cold and/or flu? All of these questions should be considered as you determine the proper dosage for yourself. It's very difficult to obtain too much vitamin D, I err on the side of "more is better." Personally, I take every opportunity to get outside as often as possible to drink in the sun. I'll take phone calls and occasional breaks outside for the sole purpose of sun exposure. I also supplement with about 2,000 IU first thing in the morning, followed by another 2,000 IU around lunch time. Dr. Mercola recommends a blood level of 50 to 70 ng/ml, for those of us who like to get technical about it.
With a solid strategy of vitamin D supplementation in hand, you can ensure healthier bones and teeth, promote good cardiovascular health, and probably decrease your chances of contracting very serious diseases, all while strengthening your mitochondria, thereby increasing the chances that you'll live a longer, happier life - naturally!