While commonly known as the “sunshine vitamin,” vitamin D can have adverse effects if consumed in excess. Just as a deficiency in vitamin D poses health risks, so does an overdose.
For years, experts have cautioned that not everyone requires vitamin D supplements. In rare instances, high doses can be harmful, particularly for children and the elderly.
As the popularity of this supplement increases, it becomes crucial for patients and healthcare providers to understand the appropriate dosage and potential drawbacks. Although uncommon, the risks of overdosing are increasing, and in severe cases, can be life-threatening.
Excessive vitamin D enhances calcium absorption, potentially leading to hypercalcemia, where calcium accumulates in arteries or soft tissues. This condition can increase the likelihood of kidney stones, disturb bone metabolism, and cause symptoms such as nausea, vomiting, constipation, fatigue, muscle weakness, or bone pain, as detailed here.
Most individuals recover from vitamin D toxicity once supplements are halted, and they receive IV fluids or medication to reduce calcium levels. However, untreated vitamin D toxicity can, in rare cases, result in kidney failure necessitating dialysis, or even cause fatal intestinal bleeding.
Some research indicates that older individuals with elevated vitamin D levels in their blood might face a higher risk of falls.
A 2018 study by US researchers highlighted a “considerable complacency” regarding the toxic potential of vitamin D. The scientific community remains divided on what constitutes an excessive amount.
The review authors noted that interest in vitamin D has surged, partly due to popular books advocating high doses, leading to an increase in cases of vitamin D toxicity.
Vitamin D, often called the sunshine vitamin, is produced when the body is exposed to sunlight. This natural method usually provides about 90 percent of the vitamin D needed, with the remainder coming from foods like fatty fish or fortified dairy products.
Vitamin D is essential for calcium absorption, immune function, cell growth, metabolism, and neuromuscular activity. Prolonged vitamin D deficiency can increase the risk of neurological, autoimmune, bone, and cardiovascular diseases.
There is ongoing debate about the efficacy of vitamin D supplements. Some studies suggest they may slow aging, enhance cognition, or alleviate depressive symptoms, while other researchers question their benefits.
Nonetheless, vitamin D supplements carry risks. Many cases of toxicity arise from errors in addressing vitamin D deficiency.
A notable incident involved an 80-year-old man who mistakenly took a daily high-dose vitamin D tablet, intended as a weekly prescription from his naturopathic doctor. Fortunately, his condition improved once the error was identified, and the supplement was stopped.
It’s not only the elderly who must be cautious about dosage. In 2016, Denmark’s health authority recalled a supplement containing 75 times the recommended vitamin D level, affecting around 20 children with toxic reactions.
This issue is increasingly prevalent in the US as well.
Between 2000 and 2014, the US saw over 25,000 cases of vitamin D toxicity. From 2005 to 2011, these incidents surged by 1600 percent, often involving children or teens.
Fortunately, there were no deaths during this period, though five cases resulted in severe medical outcomes.
“Keep track of your levels,” advises a recent Harvard Medical School article, reviewed by journalist and physician Mallika Marshall.
“If you’re using a vitamin D supplement, you likely need no more than 15 mcg to 20 mcg (600 IU to 800 IU) daily. Unless advised by your medical team, avoid exceeding 100 mcg (4,000 IU) per day, which is the safe upper limit.”
Related: Can Vitamin D Slow Aging? A New Study Says Yes – But There’s a Catch
Harvard doctors recommend starting with vitamin D-fortified foods for those with a deficiency, as they are less likely to cause toxicity.
As always, consult a healthcare professional before beginning or stopping any medication or supplement.
