Vesteroid -- yes, Vitamin D is the flavor of the month in medicine. You've probably seen this before. I remember that when I was growing up, Vitamin C was the miracle vitamin that would cure everything; then Vitamin E. And when studies were conducted looking at what happened when people took supplements for these vitamins, it turns out that not only did the studies not support any benefit to using them -- it seemed that the supplements also increased the risk of certain problems.

Vitamin D got "on the radar" when studies started coming out of Australia looking at skin cancer. Malignant melanoma is a big problem in Oz, and researchers expected to find that people who used sunscreen consistently would have a reduced risk of skin cancer.

Sure enough, people who used sunscreen or otherwise avoided the sun had lower rates of skin cancer. But, oddly, they didn't have lower rates of DEATH from skin cancer -- as if the folks who were in the sun were getting something that helped keep the cancer survivable/manageable/less nasty.

"WTF?" said researchers. (OK, they probably said something closer to, "This anomalous result suggests the need for further investigation.")

So then came studies looking at cancer rates among people given vitamin D supplements. There were a few old studies lying around, designed to look mainly at osteoporosis, where folks were given calcium, Vitamin D, both, or neither. Hmm, when folks went back to look at the old data, they found lower cancer rates in the vitamin D groups.

Then rheumatologists got in the act, and tried giving vitamin D to people who had been told they had fibromyalgia and/or chronic fatigue. A lot of those folks started saying they had more energy.

Prospective studies designed to see the effects of vitamin D supplementation will have a lot more weight than chart reviews of studies already conducted that were designed to look at other things. Many of those are under way now. Still, it's easy to be hopeful about vitamin D even after being disappointed about other vitamins in the past: you can see that the effects of foods that contain certain vitamins can be different than the vitamin taken as a supplement. But vitamin D generally comes from sunlight -- and "what else can there be in sunlight?"

(Digression: there IS something else in sunlight that we haven't tracked down yet. Multiple sclerosis is a lot more common the farther you get from the equator -- but giving folks [and experimental animals] vitamin D doesn't keep them from getting MS)

There can be. Vitamin D is a fat-soluble vitamin. It gets stored in the body -- which makes sense for something that comes from sunlight. Your body literally stores it for a rainy day (or a long winter). If you take too much for too long, you can seriously damage yourself. It starts off with nausea and vomiting; if you don't catch it at that stage, your muscles, um, stop. Including the heart.

So, how much is too much? For MOST people, 2000-4000 units daily is OK. People with serious deficiencies may be prescribed 50,000 units once a week for several weeks, and then switch to a 2000 unit daily dose. Folks with kidney or liver problems can reach toxic levels more quickly.

Interestingly, you can't get too much vitamin D from sunlight; your skin just stops making it. But it is possible to overdose when taken as a dietary supplement or in food.

Disclaimers apply; I'm a doctor, but I'm not your doctor. It pays to get checked out by a doctor before beginning any health regimen....