When he examined the young lifeguard, he saw that almost every square inch of her body was well tanned. She had been wearing practically nothing when she worked at the beach.
Neil Binkley, M.D., told me about his patient because she had the highest physiologic level of vitamin D in her system of anyone he ever saw. Her level was 80 ng/ml.
I had to look up the word "physiologic" to make sure what Dr. Binkley meant. Physiologic in the sense that he's using it is "something that is normal, neither due to anything pathologic nor significant in terms of causing illness," according to a medical dictionary.
Her level of 80 ng/ml is about the "maximum human physiologic level of vitamin D," he told me when I interviewed him yesterday. "And it doesn't make sense to push vitamin D beyond the physiologic level."
Dr. Binkley is now associate professor of medicine at the University of Wisconsin in Madison. The technical name for vitamin D in our systems is 25 hydroxyvitamin D. And Dr. Binkley is "an expert in the assays for 25 hydroxyvitamin D and how they can be applied clinically in the most accurate manner."
He spoke yesterday morning to a general session of the annual meeting and clinical congress of the American Association of Clinical Endocrinologists in Houston. I'm in Houston to report on the AACE convention.
Dr. Binkley spoke on "Vitamin D -- Beyond Bone." After his speech, he gave a press briefing in the AACE's media room, where I caught up with him. I had the opportunity to talk with him before and after his briefing as well as question him during the briefing.
Like Dr. Binkley's lifeguard patient, the natural way for humans to get enough vitamin D is from exposure to the sun. That's one of three ways we can get vitamin D. The other ways are from supplements and from fortified foods.
I asked him if it wasn't safer to get the vitamin D level that we need from supplements. "Yes," he replied. "Vitamin D supplements don't give you skin cancer."
So what level of vitamin D do we need to reach? All of us need a vitamin D level of at least 40 ng/ml, he says. That's in line with the recommendations of GrassrootsHealth, which I wrote about here.
His level usually runs "in the 40s and 50s," he told me. To reach that level he takes 1,000 IU of vitamin D every day.
I have been taking 10,000 IU of vitamin D daily for the past couple of years. GrassRoots Health reported my total Vitamin D level as 83 ng/ml.
On the basis of the lifeguard's experience, Dr. Binkley says that my level is a bit too high -- a bit higher than normal. Still, he acknowledges that every quantitative test has variability.
"They are not perfect," he says. "Every quantitative test is done by a human being -- an imperfect entity -- using instrumentation that is also imperfect."
So if I cut back on my vitamin D supplementation, it will be only a little. Aside from having a level somewhat above normal, I have no reason to stop.