Too much of a good thing can be downright disastrous. After taking 8 to 12 drops of concentrated Vitamin D every day for two-and-a-half years, a 54-year-old man in Canada has inadvertently and permanently damaged his kidneys.
He used it as prescribed by a naturopath at a dose well above the recommended daily allowance, and now it has taken a year of treatment for the patient's blood to return to normal, while some organs never will - he is ultimately burdened with stage 3B chronic kidney disease.
The physicians who published his case in a medical journal are worried that others might fall into the same innocent trap.
"Our experience informs us that patients and clinicians should be better informed about the risks regarding the unfettered use of vitamin D," the authors suggest.
"Given new findings from the US Preventive Services Task Force, current Canadian guidelines regarding its use in low-risk individuals should be revisited."
Vitamin D toxicity is a rare but potentially serious condition usually caused by megadoses of supplements, not by diet or excessive sun exposure.
In this particular case though, sun exposure was probably what broke the camel's back. Upon returning home from a holiday during which the man had sunbathed daily for eight hours or more, the middle-aged patient's family physician noticed a worrying sign.
It appeared that in his two week trip to Southeast Asia, the patient's creatine levels had suddenly skyrocketed, shooting from 100 μmol/L to 132 μmol/L. Given that the kidneys usually filter excess creatine out, the results suggested some sort of malfunction.
At first, the doctor thought his patient was simply suffering from heat stroke and dehydration, but even after stopping the use of his antihypertensive and diuretic medication, the patient's creatine levels continued to climb.
When the reading reached 376 μmol/L and his physician still had no idea what was going on, the patient was referred to a kidney specialist.
It was only then that doctors first heard about the naturopath - the 'specialist' responsible for prescribing a mega dose of vitamin D, despite the fact that the man had no known deficiency or any medical condition that would necessitate such a supplement.
The rest of the story is a series of unfortunate yet understandable mistakes.
"The recommended brand contained 500 IU per drop. Unknowingly, the patient obtained another vitamin D preparation that contained 1,000 IU per drop," the authors explain.
"The patient was not counselled about toxicity risks and, over a period of 2.5 years, he took 8–12 drops of vitamin D daily, for a total daily dose of 8000–12 000 IU."
Obviously, everyone's body is slightly different, but the literature generally suggests that a dose greater than 1,000 IU per day for several months is not recommended to anyone.
The patient in this case was unknowingly taking 8 to 12 times that amount, and with few symptoms to serve as a warning, he continued doing so for several years.
The result was a dangerous buildup of vitamin D and calcium in his blood that ultimately left his kidneys functioning at an seriously impaired filtration rate. In the future, this sets him at a higher risk of needing dialysis.
"And his logic, which one can understand looking back, is that the more vitamin D I take, the stronger the bones will be."
This study has been published in Canadian Medical Association Journal.