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Vitamin D would have many benefits. However, a recent case study indicates that excessive use of vitamin D can cause kidney damage in people without vitamin deficiency.
The article was published online on April 8 in the Journal of the Canadian Medical Association.
"The purpose of this case study is to inform a wider audience than vitamin D in high doses [10,000 IU daily] patients with normal serum vitamin D levels may cause toxicity, "said Bourne Auguste, MD, University of Toronto, Ontario, Canada. Medscape Medical News.
"The public needs to know that taking more vitamin D than is recommended does not necessarily lead to additional benefit, but it can actually increase the damage, especially kidney failure," he added. .
The Osteoporosis Canada guidelines for 2010 recommend 400 to 1,000 IU of vitamin D daily for most adults and 800 to 2,000 IU daily for the elderly and those at increased risk of osteoporosis. In the United States, the recommended daily intake of vitamin D for men and women aged 1 to 70 is 600 IU daily and 800 IU for those over 70 years of age.
Since vitamin D has a wide therapeutic range, toxicity is rare, note Auguste and colleagues. However, as a fat-soluble vitamin, high doses of this substance for long periods can cause weight accumulation.
"Many patients think that vitamin D is a simple supplement with no harmful effects and perhaps historically overestimated," Auguste said. "Since it is so readily available in various over-the-counter formulations and that it is felt that it has many benefits without prejudice, the other patients [besides the one in this case study] may be at risk for vitamin D toxicity and potentially renal failure. "
The toxicity of vitamin D presents a wide range of symptoms that can delay the diagnosis. These symptoms include, among others, fatigue, high blood pressure, frequent urination, confusion and itching. Early recognition of vitamin D toxicity can prevent chronic kidney damage.
"The toxicity of vitamin D may not be recognized for a long time, because of the nonspecific symptoms that patients may present during the presentation.Patients could take over-the-counter supplements without full disclosure," Auguste explained. .
Management includes a thorough review of prescription and over-the-counter medications, a limitation of sun exposure, a decrease in dietary and supplemental vitamin D sources, and monitoring of vitamin D levels in asymptomatic patients. Because it is fat soluble, returning to normal can take several months. In addition, after stopping vitamin D supplements, calcium levels may continue to increase before being reversed.
"Clinicians should also consider adjunctive treatments beyond the cessation of vitamin D and calcium supplements, such as hydroxychloroquine, glucocorticoids, and ketoconazole in symptomatic patients." a decrease in the active form of vitamin D in the body, "advised Auguste.
Supplements and toxicity triggered by sunlight
The case reported concerns a 54-year-old man who had just returned from a trip to Southeast Asia, where he had spent long hours sunbathing (6 to 8 hours a day for 2 weeks) . Upon returning to Canada, a family doctor found that his creatinine level was elevated (132 μmol / L at an initial value of 100 μmol / L). Four weeks later, despite discontinuation of antihypertensive therapy and diuretics, which could have caused dehydration and increased creatinine, the patient's creatinine level was even higher (376 μmol / L); he was then referred to a kidney specialist.
Another interview revealed that the man had seen a naturopath who had prescribed high doses of vitamin D. Despite a known history of bone loss or vitamin D deficiency, he took 8,000 to 12,000 IU of vitamin D daily for two and a half years.
A report revealed hypercalcemia (ionized calcium, 1.48 mmol / L) and elevated levels of vitamin D (1,25-dihydroxyvitamin D3, 274 pmol / L, 25-hydroxyvitamin D3, 241 nmol / L). The results of the renal biopsy showed renal lesions (nephrosclerosis and microcalcifications without sarcoidosis or light chain deposition).
The nephrologist advised him to stop taking vitamin D supplements and eat calcium-rich foods. His diuretics remained on hold and the patient resumed antihypertensive treatment. At the second visit, doctors found that her levels of 1,25-dihydroxyvitamin D3 (the biologically active form of vitamin D) and calcium had continued to increase. The patient also described a recent skin itch, probably due to high calcium levels.
The patient refused to receive glucocorticoids because of concerns about weight gain. At the start of treatment with hydroxychloroquine at 400 mg per day, her calcium and vitamin D levels decreased. Near a year later, his calcium and vitamin D levels returned to normal, but he suffers from chronic stage 3B kidney failure.
The authors did not reveal any relevant financial relationship.
CMAJ. Posted online 8 April 2019. Full text
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