A case study recently published in the Canadian Medical Association Journal has highlighted the danger of taking too many vitamin D supplements.
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Known as the healthy "sunshine" vitamin, vitamin D is synthesized by the skin upon exposure to sunlight. However, in the case of one Canadian man, taking excessive doses vitamin D supplements proved to have disastrous health consequences that medical experts are calling a warning to consumers.
A team of physicians in Toronto reported on the case of a 54-year old man they had assessed after he returned from a trip to Southeast Asia, where he had spent much of his time in the sun. After the man was found to have elevated blood creatinine levels, which is a marker for kidney disease or malfunction, he was referred to a kidney specialist for additional testing.
Dr. Bourne Auguste from Toronto General Hospital and colleagues found that the man had been prescribed high doses of over-the-counter vitamin D supplements by a naturopathic doctor. The patient had no medical history of vitamin D deficiency or bone loss, which the supplement is sometimes prescribed for.
The naturopath had recommended a dose of 8 drops daily and over the course of 30 months, the man took between 8 to 12 drops or 8000 to 12,000 International Units (IUs) per day. This compares with a recommended daily allowance of 400 to 1,000 IUs per day for healthy individuals and a dose of 800 to 2,000 IUs for older individuals or people at increased risk for osteoporosis.
Taking this excessive dose resulted in the man having extremely high levels of calcium in his blood, which had triggered significant kidney damage, reports Auguste and team.
The authors say patients and clinicians should be better informed about the risks associated with unfettered use of vitamin D.
"Although vitamin D toxicity is rare owing to a large therapeutic range, its widespread availability in various over-the-counter formulations may pose a substantial risk to uninformed patients," writes Auguste.
On reading the case report, nephrologist Maria DeVita (Lenox Hill Hospital, New York) warns that, as is the case with many supplements, overuse of vitamin D can result in dire adverse effects:
Vitamin D is necessary for the development and maintenance of strong bones, [but] the take-home message is too much of a good thing is not good.”
Use of vitamin D drops leading to kidney failure in a 54-year-old man. CMAJ. 8 Apr 2019. 191 (14) E390-E394. DOI: https://doi.org/10.1503/cmaj.180465.