Here’s what we know today: Unless you’re taking mega, mega amounts of vitamin D, toxicity isn’t really a concern (which means it’s time for brands and consumers to catch up).
As one 2018 review recounts: “In statements released over the last decade, the Institute of Medicine (IOM) and the Endocrine Society have both concluded that acute vitamin D toxicity (VDT) is extremely rare in the literature, that serum 25(OH)D concentrations must exceed 150 ng/mL, and that other factors, such as calcium intake, may affect the risk of developing hypercalcemia and VDT.”
One key point here: that 150 ng/ml mention. That’s three times higher than the healthy range clinicians typically recommend (50 ng/ml) for vitamin D sufficiency.
Meanwhile, another 2014 study found that taking a whopping 20,000 IU of vitamin D3 daily successfully increased whole-body vitamin D levels without participants even coming close to levels associated with toxicity. So, successful, not scary.
Let’s also debunk the notion that fat-soluble vitamins are “dangerous,” simply because they can be stored in the body. According to Ferira, this is simply untrue. “Just because vitamin D is fat-soluble by design doesn’t mean it’s toxic at clinically useful doses, like 5,000 IU,” she says. “In reality, true reports of frank vitamin D toxicity with clinical evidence have occurred at 200,000 to 300,000 IU per day—yes, you read that correctly—in vulnerable populations like infants or folks with medical issues.”
Sweeping statements about fat-soluble nutrients and toxicity simply aren’t useful. Ferira continues, “That kind of fear-mongering totally lacks nuance and is an antiquated concept. Let’s use another fat-soluble as an example: vitamin A. Yes, you can get hypervitaminosis A (aka, too much vitamin A in the body) and turn orange if you eat a massive amount of carrot smoothies every day for many weeks. The same is true of any massive input that’s not the norm, and is well above the levels required to achieve sufficiency.”
The bottom line here: Getting too much vitamin D is very, very difficult—especially in a population where almost half are clinically insufficient (and almost one-third are deficient) and 93% of U.S. adults can’t even manage to get 400 IU of vitamin D from our diet.