Sunlight is one of the most important resources we have. It’s a source of light, a source of energy, and a source of vitamin D. When we’re exposed to the sun’s rays, our skin soaks up vitamin D. So if there’s not enough sunlight or if we’re not in the sun as much, our vitamin D levels are lower. In fact, vitamin D levels in the U.S. population are highest in August and lowest in February, according to Science Daily.
Since there tends to be more sunlight in the U.S. in the warmer months of August and September than there is in the colder months from December through February, our vitamin D levels vary seasonally. We don’t soak up as many rays in those cold, winter months.
An essential nutrient for healthy bones, vitamin D can also be found in milk, egg yolk, and fish. However, sunlight is our most important source of vitamin D. Vitamin D helps protect against osteoporosis as well as seasonal illnesses like the flu.