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More and more Americans are taking supplements, but consuming too many vitamins can cause negative health effects.
Take vitamin D: though many people are deficient in the nutrient, the rate of people exposed to vitamin D toxicity increased by 1,600% between 2005 and 2011, according to US Poison Control data.
The body can get vitamin D naturally from sunlight and foods like liver, but most people are deficient due to spending time indoors (and the fact that liver isn't a fan-favorite food), said Dr. Zhaoping Li, the director of the University of California, Los Angeles' Center for Human Nutrition.
"There are people taking really a lot," Li said, saying cancer patients have been swayed by a randomized clinical trial that people with cancer taking vitamin D supplements had a lower risk of dying compared to the placebo group. "We're talking about people taking 50,000 a day" — a dosage Li does not recommend.
Fortunately, Li said, overdosing on vitamin D is not as risky as vitamin A, which can swiftly cause liver toxicity and require an organ transplant. Too much vitamin D could, however, cause health problems like vomiting, constipation, and muscle cramps. One 54-year-old man experienced permanent kidney damage after overdosing on vitamin D supplements.