The Warm Glow of Sunlight
Sitting by a sunny window feels amazing, doesn’t it? But while the warmth of sunlight streaming through glass can brighten your day, it’s unlikely to boost your vitamin D levels. Why? The secret lies in the type of ultraviolet (UV) rays your body needs to produce vitamin D—and how glass blocks them.
How Vitamin D Works
Your skin produces vitamin D when exposed to UVB rays, a type of ultraviolet radiation found in sunlight. This "sunshine vitamin" is essential for strong bones, a healthy immune system, and more. However, most window glass is designed to filter out UVB rays while letting in UVA rays, which don’t contribute to vitamin D production. So, that sunny spot on your couch won’t help you meet your daily vitamin D needs.
A Bit of History
Vitamin D was first identified in the early 20th century, when scientists realized its role in preventing rickets—a bone disease common in children at the time. With the rise of industrialization, many urban dwellers spent less time outdoors, leading to a vitamin D deficiency epidemic. This discovery paved the way for fortifying foods like milk with vitamin D, a practice still common today.
Fun Fact
Did you know that cod liver oil, an old-school remedy for rickets, is packed with vitamin D? In the early 1900s, it was considered a miracle supplement for its bone-strengthening properties—despite its less-than-pleasant taste!
Getting Your Daily Dose
If sunlight through glass won’t cut it, how can you get enough vitamin D? Spending 10–30 minutes in direct sunlight a few times a week can often do the trick, depending on your skin tone and location. Alternatively, vitamin D-rich foods like salmon, egg yolks, and fortified cereals can help. Supplements are another great option, especially in winter or for those with limited sun exposure.
Final Thoughts
While soaking up the sun through a window can be relaxing, it won’t help your body produce vitamin D. To keep your levels up, step outside or reach for vitamin D-rich foods and supplements. After all, your bones and immune system will thank you!