A lot of Canadians take vitamin D, particularly during the dark winter months. But you can get too much of a good thing — one man developed permanent kidney damage after taking high doses of the “sunshine vitamin,” according to a recent case study.
The case report, published Monday in the Canadian Medical Association Journal, highlights the risks of too much vitamin D.
According to the report, a 54-year-old man had his kidneys examined after a routine blood test found he had very high levels of creatinine — a waste product produced during normal muscle function. High levels of creatinine in the blood can indicate kidney trouble, since the product is normally filtered out by the kidneys.
Doctors were baffled at first, as the man’s kidney function was at less than 15 per cent for no apparent reason, according to Dr. Bourne Auguste, a clinical fellow in nephrology at Toronto General Hospital and a co-author of the report.
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After a few tests and a kidney biopsy, Auguste said, the doctors found calcium deposits in his kidney, which helped them narrow down what was going on. After a few more questions, the man said that he had seen a naturopath, who had prescribed high doses of vitamin D. He actually took even more than was prescribed, since he accidentally bought the wrong strength of vitamin D drops, and was taking about 8,000-12,000 IU of vitamin D daily for two and a half years.
Healthy adults under age 50 should have only 400-1,000 IU daily, according to Osteoporosis Canada. A dose of 800-2000 IU is recommended for people at high risk of bone fractures and osteoporosis. This patient was not a high-risk individual.
“There is a recommendation to give people high doses of vitamin D, but you need to have a documented deficiency,” said Auguste. “Then you can get these high doses but only for a very short period of time.”
No one would ever be on these doses for years at a time, he said.
“His simple logic was that he was not aware there was such a thing as vitamin D toxicity.”
“He thought that vitamins are harmless. And his logic, which one can understand looking back, is that the more vitamin D I take, the stronger the bones will be.”
Unfortunately, even after treatment, the man was left with chronic kidney disease as a result of his vitamin D intake, and his kidney function is still only at about 30 per cent, meaning he is at higher risk of needing dialysis someday, Auguste said.
The sunshine vitamin
Vitamin D helps the body to absorb calcium and phosphorus to maintain strong bones and teeth, said Nardine Nakhla, a pharmacist and clinical lecturer at the University of Waterloo’s School of Pharmacy.
Having too little vitamin D can make your bones weaker, she said. But now, “The focus has been on too little vitamin D for so long that individuals are kind of overdoing it. Too much of a good thing is what’s happening.”
People can produce their own vitamin D when their skin is exposed to the sun — but in Canada, where the days are short for much of the year, we often don’t get enough sun to produce as much vitamin D as we need, Osteoporosis Canada says.
That’s why they often recommend supplementation, although their website notes that many common foods like milk, margarine and infant formula are fortified with vitamin D.
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Fat-soluble vitamins, like vitamins A, D, K and E, can build up in the body if you have too much, Nakhla said.
Too much vitamin D can cause symptoms like frequent urination, thirst, confusion, constipation and itchiness, Auguste said. “Vitamin D toxicity is very rare, but if you are able to take significant amounts of it over a sustained period of time, you can get toxic levels which can lead to damage of vital organs.”
Nakhla recommends getting a blood test to determine if you’re vitamin-deficient before supplementing, or at least discussing your vitamin choices and possible risks with your pharmacist, as no product is without side effects. You should also let your doctor and health care providers know what supplements you’re taking, even if they’re just vitamins.
“All of these over-the-counter medications as well as natural health products, which include vitamins and minerals, are viewed by individuals as relatively benign but we as pharmacists know that to not be the case,” she said.
“There’s many potential adverse effects that can occur if somebody takes too much of something or takes it for too long.”
Auguste said that people shouldn’t panic and stop taking vitamin D altogether. “Just don’t overdo it.”
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