Vitamins D2 and D3 and Osteoporosis

Vitamin D is important to bone health. Most milk products are supplemented with Vitamin D, and everyone is urged to get ten minutes of sun exposure daily so that their body will produce this healthy nutrient. Many people do not know that there are several different subgroups within the Vitamin D category. While there are many forms of Vitamin D, only two are critical to the proper functioning of the human body.

Vitamin D2, or ergocalciferol, is synthesized by plants. It is the compound used in most over-the-counter and prescription Vitamin D supplements. The problem with Vitamin D2 is that it is not absorbed very well by the human body. Many people incorrectly believe that they are receiving an adequate amount of this nutrient to protect their bone health when they supplement their diet with a pill that is reported to contain the recommended daily allowance (RDA) of Vitamin D. (The parathyroid glands and vitamin D.)

On the other hand, Vitamin D3, or cholecalciferol, is the substance that is produced by the human body when it is exposed to ultraviolet-B (UVB) rays. Studies show that each person should be able to produce enough Vitamin D3 if they expose their unprotected skin to the sun for about ten minutes each day. While this isn't a problem for most people, some are not able to do so because of their local weather, their health condition, or some other reason. Skin color can also affect natural Vitamin D3 levels; darker skin does not produce Vitamin D3 as easily as fairer skin. Because this is the type of Vitamin D that the human body prefers, it is readily absorbed even when taken as a supplement.

Both Vitamin D2 and Vitamin D3 can be used to fortify food products, although the current labeling requirements do not indicate which one has been added. Vitamin D is typically added to milk, soymilk, some orange juice, and most cereals. It is naturally part of fatty fish, egg yolks, and beef liver. Due to the limited types of food that contain Vitamin D, it is essential that humans receive an adequate supply from sunlight or from high-quality supplements that can be readily absorbed.

For prevention of osteoporosis, the National Osteoporosis Foundation (NOF) recommends that each person under 50 years of age include 400 to 800 international units (IUs) of Vitamin D in their diet daily, while those over 50 should have 800 to 1,000 IUs. A recent study of nursing home residents found Vitamin D successful in lowering risk of hip fractures.

To treat severe bone disease, the current recommendations are either 2,800 or 5,600 IU's daily depending on the extent of bone loss. A doctor should be consulted before consuming such high levels. Excessive levels of Vitamin D can cause kidney problems.