From the time we are infants to the time we become elderly, we need vitamin D for a healthy skeleton. Some research indicates that Vitamin D may be very important in maintaining healthy vessels, too.
In our Wisconsin climate—our high latitude, it is difficult to get enough vitamin D from sun exposure. We are also often advised to use sunscreen, and this blocks Vitamin D absorption through the skin. People with dark skin absorb less Vitamin D than those with fair skin.
It is difficult to get Vitamin D from foods, although fatty fish and eggs do contain some. Some foods are fortified with Vitamin D, such as milk, but many people do not drink much milk.
Many health conditions affect our ability to absorb Vitamin D. For example, if you do not absorb fats well, have celiac disease, have Crohn’s disease, or have liver disease, you will probably not absorb Vitamin D very well and supplementation is needed.
It is possible to take too much Vitamin D. Generally speaking, most people do well with 1000-2000 IU per day. Ask your doctor how much Vitamin D you should take daily, and if you should have your Vitamin D level checked with a blood test.