The number of Americans taking a vitamin D supplement has skyrocketed, with many taking more than the recommended daily amount, prompting concerns about risks associated with high doses.
In 2013-2014, 18.2% of American adults were taking at least 1,000 IU of vitamin D daily. In 1999-2000, that figure was just 0.3%, according to a research letter published in JAMA. Researchers also found that 3.2% of adults were taking 4,000 IU or more of vitamin D daily. That figure was just 0.3% 14 years earlier. The tolerable upper limit is 4,000 IU, and taking above that amount increases the risks for toxic effects.
The recommended daily allowance of vitamin D is 600 IU for adults up to 70 years old, according to the Institute of Medicine (IOM). Above that age, 700 IU may be taken.
The IOM has previously said that vitamin D supplementation is helpful in promoting bone health, but other benefits are inconclusive. They also cautioned that too much vitamin D can lead to hypercalcemia, which is characterized by nausea, vomiting, constipation and weakness. In addition, it can lead to a buildup of calcium in soft tissue, which can damage it.
A 2010 randomized, controlled trial, also published in JAMA, found that elderly women given an annual, ultra-high dose of vitamin D were more likely to experience falls than those who didn’t get the supplement. Another trial found that taking vitamin D and calcium supplements together may increase the risk for kidney stones.
Some people may legitimately need more than the IOM daily recommendation due to bone health issues, malabsorption or medications that interfere with the metabolism. For more on the pros and cons of vitamin D, check out this article from us.
Jonathan Block is MedShadow’s content editor. He has previously worked for Psychiatry Advisor, Modern Healthcare, Health Reform Week and The Pink Sheet.