For a country that celebrates the outdoors—from tailgates and baseball games to beach vacations and sunny road trips—America has a surprising problem: vitamin D deficiency. You’d think with all the access to sunshine, especially in places like California, Florida, and Texas, Americans would be overflowing with the sunshine vitamin. But that’s far from the truth. In fact, studies show that nearly 42% of adults in the United States are deficient in vitamin D.
The real kicker? Many individuals don’t even realize that vitamin D is not just about strong bones. It’s a hormone-like nutrient that helps regulate immunity, mental health, blood pressure, and even insulin levels. So the stakes are much higher than most people think. And while you can certainly take supplements, nothing beats the natural route—sunlight—if you can get it right.
When it comes to vitamin D, timing really is everything
But here’s where things get tricky: the timing of your sun exposure matters more than most people realize. If you’re heading out for a walk before work at 7:30 a.m. or catching a sunset jog after dinner, you’re probably not making much vitamin D at all. That’s because the body can only produce vitamin D when it gets hit with UVB rays—and those rays are strongest during a very specific window: roughly between 10 a.m. and 1 p.m.
Early morning and late afternoon sunlight may feel gentle and healthy, but they mostly deliver UVA rays, which do very little for vitamin D synthesis. In contrast, UVB rays during late morning and early afternoon can help your skin produce vitamin D efficiently—as long as you don’t overdo it.
The fix isn’t complicated, but it does require intention. If you can build a habit of stepping outside during the late morning or early afternoon—without sunscreen for just a short while—you’ll be doing your health a huge favor. This could mean taking your coffee break outdoors, going for a walk during your lunch hour, or eating outside in a sunny spot. The exposure doesn’t need to be excessive. Even 10 minutes with your arms and legs exposed can make a meaningful difference over time, especially if your skin is fair.