With 41% of American adults meeting the criteria for clinical insufficiency1, and an alarming 93-plus% failing to consume just 400 IU of vitamin D per day2, it’s possible you may need more of the sunshine vitamin yourself.* You see, research suggests we need a minimum of 3,000 IU vitamin D33 (which is the body’s preferred form) per day to achieve a total serum of 25-hydroxyvitamin D—also known as 25(OH)D, the clinical biomarker measure of whole-body vitamin D status—of 30 ng/ml4. That’s a whole lot more than the 400 IU per day the average person gets! Given that, it’s no surprise that 29% of American adults are straight-up deficient in D. Mind you, that stat considers diet and sun, too. Even that 30 ng/ml benchmark is really the bare minimum (because it’s the cutoff for clinical vitamin D insufficiency), which is not ideal. “As an endocrinologist, I know that achieving optimal serum 25(OH)D levels in the 50+ ng/ml range is imperative for immune health, bone health, and more,” says board-certified endocrinologist Brittany Henderson, M.D. And in order to reach that 50+ ng/ml range, you actually need 5,000 IU of vitamin D per day. Here’s how mbg’s vice president of scientific affairs, Ashley Jordan Ferira, Ph.D., RDN breaks it down: “Pharmacokinetic research3 shows that it takes 100 IU of vitamin D to increase a normal-weight adult’s serum D levels by about 10 ng/ml. So, that means that in order to achieve 50 ng/ml, you need 5,000 IU of vitamin D per day.” (Read more about that here). Basically, we’re not in a good place with the sunshine vitamin—and don’t let the fact that vitamin D deficiency is so common it can fool you into thinking it’s not a really big deal. In fact, deficiency can cause quite a long list of annoying and serious issues. So, let’s break down everything you need to know about vitamin D deficiency, including the telltale signs to look out for, plus what you can do to get your levels back into a healthy place. According to functional nutrition dietitian Whitney Crouch, RDN, CLT, the following people face higher risk of vitamin D deficiency: The impact of vitamin D deficiency is holistic, putting the whole body at risk of health issues, affecting bone density and immune system resilience to cardiometabolic health, to name a few, explains Crouch. Sufficient vitamin D is also a requirement for proper calcium absorption in the body. “Without it, you need more dietary calcium—and most people do not meet their calcium requirements as it is,” says Connie Weaver, Ph.D., a professor in Purdue University’s Department of Nutrition Science. The following signs of vitamin D deficiency are among the most common: In fact, according to a 2021 review8, numerous studies have identified an apparent link, noting that there is a potential positive influence of vitamin D on mental health. While anything below 30 ng/ml4 is considered insufficient, anything below 20 ng/ml4 is flat-out deficient. Once you know your numbers, you have a couple of options for boosting your levels above that baseline of 30 ng/ml (i.e., to a minimum of 50 ng/ml, per Henderson’s earlier advice). While animal sources provide D3, plant sources only offer D2 (with the rare exception of algae, which contains D3), says Crouch. Vitamin D3 is the form we produce via the sun and is the body’s preferred form, which means it more effectively increases vitamin D levels in the blood, she explains. Given that, the most concentrated food sources of vitamin D (all of which provide D3) are cod liver oil, trout, and salmon, according to the National Institutes of Health5. However, since we ideally need 5,000 IU of vitamin D per day just to reach our optimal 50 ng/ml levels, we can’t rely on these foods alone. (A serving of cod liver oil5 offers just 1,360 IU—and who’s really downing cod liver oil on a daily basis?) But what about milk, you might ask? Well, it turns out that a glass of milk only provides 100 IU of vitamin D. While that’s not true for every nutrient, it truly is the case for vitamin D. Since optimal blood vitamin D levels are between 50 and 70 ng/ml, you’ll need to supplement with 5,000 IU of vitamin D3 per day to reach and maintain the ideal throughout life, Crouch says.* Beyond that, Crouch recommends making sure you pair your supplement with healthy fats (like extra-virgin olive oil) to best absorb it.* As you supplement, work with your health care provider to test your levels a couple of times per year to ensure your efforts are paying off. Symptoms like brain fog, low mood, and suboptimal bone density can tip you off to low vitamin D levels—and supplements are necessary if you want to get your levels up to a truly optimal place of 50 ng/ml or higher.*
