That, folks, is where supplements come into play: Trusted nutrition and medical experts recommend 5,000 I.U. of vitamin D3 (the body’s preferred form) per day to help you get to—and stay!—above that 50 ng/mL threshold. But here’s the thing: That’s old-school science. While vitamin D toxicity is possible, it’s much more challenging to reach than you might think—so there’s really no excuse for brands not to up the ante. The risk of toxicity is not even relevant at useful, science-backed supplement doses, Ferira says. A little confused? Allow us to explain. At very high vitamin D doses (we explain what that entails below), “this helpful vitamin D/calcium relationship can tip from normal to not-so-normal, and too much calcium can contribute to kidney stones and blood vessel issues,” Ferira explains. So why the conservative messaging? “Public health guidance, such as that coming from the Institute of Medicine (IOM), needs to be conservative to balance the risk of toxicity in a population,” adds Gallo. “A number of other factors affect vitamin D status, including endogenous production (i.e., through sun exposure), adiposity, age, latitude, age, etc., which makes one recommendation for all individuals difficult.” A fair reason, but lo and behold, you are an individual and the research is evolving—and we are seeing a slight shift in perspective. Because of this widespread guidance, though, some supplement brands still tend to err on the lower side of the spectrum and assume the consumer will take more based on their needs. The issue, though, is that this makes people assume that 1,000 I.U. is cutting it (here’s why it’s not) and that they’re going overboard at clinically useful doses (like 5,000 I.U.), Ferira says. So, yes, while you technically can get too much vitamin D, we’re about to explain why it’s so incredibly unlikely. As one 2018 review recounts2: “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 study3 found that taking a whopping 20,000 I.U. 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 I.U.,” she says. “In reality, true reports of frank vitamin D toxicity with clinical evidence2 have occurred at 200,000 to 300,000 I.U. 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 supplement 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 deficient4) and 93% of U.S. adults5 can’t even manage to get 400 I.U. of vitamin D from our diet. To be clear, the U.L. is not the toxic level. Instead, the U.L. is the highest amount of a nutrient the general population can take that likely doesn’t have a risk of adverse health effects. “That’s an important call-out: general population,” Ferira continues. “We’re individuals, and the collective science plus your health care provider may determine you personally need less or more than the ‘average’ person.” In fact, some people may even need more than 10,000 I.U. of vitamin D3 per day to reach the desired 50 ng/mL range.* Gallo seconds the advice: “In cases where an individual may be at risk for deficiency, higher intake may be warranted—and this decision should be made in consultation with a health care professional who can monitor for any signs or risks of toxicity,” she says. That being said, this information paves a hopeful road: With more emerging research to back up these claims, perhaps brands will begin to offer more clinically useful doses of vitamin D in high-quality formats, with more realistic apprehensions for toxicity. Want to see some options we do approve of? Here are our favorite vitamin D supplements on the market.
