It is estimated that as many as half of Americans are deficient in or have insufficient levels of vitamin D in their bodies in the winter. However, taking any nutrition supplement poses some risk for toxicity, and vitamin D is no exception. The primary concern with overconsumption of vitamin D is an abnormal increase in blood calcium, which may lead to hardening of soft tissues and issues such as kidney stones. Because the question of the necessity and safety of vitamin D supplementation is currently controversial, it is wise to discuss testing and whether and how much to supplement with your doctor.
Keep in mind that this test may or may not be covered by your insurance plan, and out-of-pocket costs will vary greatly among labs. Also be aware that there is not yet a standard definition of vitamin D deficiency (as there is for iron, for example), nor is there currently a standard protocol to correct suspected deficiency, so the advice you get will depend on your caregiver. Even the laboratory tests have proven almost as controversial as the vitamin itself. Some analyses have shown that results vary greatly among different labs and testing methods, which means some people might be advised to take vitamin D unnecessarily, and others will have their deficiencies go undiagnosed.
Although there is no unanimous agreement about what optimal vitamin D levels are — and it’s possible that optimal levels may be different for people with diabetes — it is generally accepted that a level above 30 ng/ml is sufficient. Keep in mind that vitamin D status may change seasonally, particularly if you live above 35 degrees latitude, or in the northern two-thirds of the United States, so take note of what month you are checked. Levels will most likely be lowest in the spring and highest in the early fall. According to Dr. Holick, the body can store sun-derived vitamin D for about one month and the supplemental form for only two weeks, so he believes that supplementation is necessary in the fall, winter, and spring months in northern states. He points out that even in the southernmost states, vitamin D production drops drastically in winter months.
If you choose to take vitamin D supplements, be aware that you will find it available in both the inactive D2 form and the active D3 form. It is arguable whether one is better utilized or safer than the other, but most experts suggest seeking the D3 form in a supplement. Dr. Holick suggests either taking a daily dose of up to 2,000 IU or taking up to 20,000 IU once every two weeks, since single doses this large have not been found to be toxic, and the body can store a two-week supply.
The jury is out on whether vitamin D is a miracle cure-all for sure, but the message is clear that everyone needs it and many people do not get enough. Getting your vitamin D is yet another good reason to eat more fish and to get out and enjoy the outdoors.