Vitamin D is a nutrient found in some foods that is needed for health and to maintain strong bones. It does so by helping the body absorb calcium (one of bone’s main building blocks) from food and supplements. People who get too little vitamin D may develop soft, thin, and brittle bones, a condition known as rickets in children and osteomalacia in adults.
Vitamin D is important to the body in many other ways as well. Muscles need it to move, for example, nerves need it to carry messages between the brain and every body part, and the immune system needs vitamin D to fight off invading bacteria and viruses. Together with calcium, vitamin D also helps protect older adults from osteoporosis. Vitamin D is found in cells throughout the body. Very few foods naturally have vitamin D. Fortified foods provide most of the vitamin D in American diets. Fatty fish such as salmon, tuna, and mackerel are among the best sources. Beef liver, cheese, and egg yolks provide small amounts and mushrooms provide some vitamin D. In some mushrooms that are newly available in stores, the vitamin D content is being boosted by exposing these mushrooms to ultraviolet light. Almost all of the U.S. milk supply is fortified with 400 IU of vitamin D per quart. But foods made from milk, like cheese and ice cream, are usually not fortified. Vitamin D is added to many breakfast cereals and to some brands of orange juice, yogurt, margarine, and soy beverages; check the labels. As you can see, it is difficult to get enough vitamin D from food.
The body makes vitamin D when skin is directly exposed to the sun, and most people meet at least some of their vitamin D needs this way. Skin exposed to sunshine indoors through a window will not produce vitamin D. Cloudy days, shade, and having dark-colored skin also cut down on the amount of vitamin D the skin makes.
People who avoid the sun or who cover their bodies with sunscreen or clothing should include good sources of vitamin D in their diets or take a supplement. Recommended intakes of vitamin D3 are set on the assumption of little sun exposure. Most doctors who practice holistic medicine are recommending between 3000-5000 iu/day of a vitamin D3 supplement to maintain levels of vitamin D in the blood. The best measure of one’s vitamin D status is blood levels of a form known as 25-hydroxyvitamin D. Levels are described in either nanomoles per liter (nmol/L) or nanograms per milliliter (ng/mL), where 1 nmol/L = 0.4 ng/mL. In general, levels below 30 ng/mL are too low for bone or overall health, and levels above 100 ng/mL are probably too high. Levels of 50 ng/mL or above are recommended for optimal health in most people. By these measures, a large percentage of Americans are vitamin D deficient and almost no one has levels that are too high. When supplementing with Vitamin D3 it is important to also have vitamin K2 present, otherwise the increased calcium absorption from vitamin D ends up staying in your blood stream instead of getting moved to the bones.
In Summary, the combination of D3 and vitamin K2 taken daily is needed by most to maintain adequate blood levels of 50 or higher. Failure to have enough K2 can result in diminished bone building results and in the long run could be harmful to your health.