Human Photosynthesis: How Longer Days Help Replenish Your Vitamin D

Your winter blues likely had a physical cause.

If the new season has put a spring in your step, it might be because longer days naturally replenish your vitamin D. Your body needs this fat-soluble vitamin to function properly, as it affects many areas of your body, including your bones, brain, immune system, and muscles. But unlike many other vitamins, it’s easier to get your daily dose from an afternoon stroll than the foods you eat. Click through the slideshow to learn more about how vitamin D is one of the most important and fascinating nutrients you consume—and make!—on a daily basis.