Winter is here! Does sunlight provide enough vitamin D during the winter months? The answer: probably not. By learning to optimize Vitamin D level year-round, it is possible to support numerous health-promoting processes in the body.

Background: The body makes previtamin D3 when our skin is exposed to ultraviolet-B (UVB) rays from the sun. Previtamin D3 is then converted in the liver to calcidiol (25 hydroxyvitamin D). Next, it heads to the kidneys for its final conversion to its most active form, calcitriol (1,25-dihydroxyvitamin D).

Sunlight is how our bodies were designed to get most of the necessary vitamin D. But, the plunging temperatures and the need to stay inside, combined with the lower position of the sun during the winter months, makes it hard to get enough UVB radiation for the body to produce sufficient Vitamin D. For most parts of the United States, Vitamin D made from sunlight exposure is minimal between November-February. Studies consistently show that Vitamin D levels tend to peak in September and are at the lowest in March.

By optimizing vitamin D production from the summertime UVB rays, the body can carry some of it into the winter, since it is stored in our fat. Unfortunately, many people spend summer days working indoors and aren't able to get outside when the UVB rays are at their peak.

Benefits of Vitamin D

Vitamin D influences over 2,000 genes (about 10% of the human genome)! Without sufficient vitamin D, gene function may become impaired. It also supports healthy immunity, bone formation, glucose metabolism, and keeps the heart and skin healthy. Without proper Vitamin D, the risk for many conditions increases, including; obesity, diabetes, hypertension, rheumatoid arthritis, fibromyalgia, chronic fatigue syndrome, osteoporosis, Alzheimer's disease, and some cancers.

Test your vitamin D levels

To maintain optimal levels year-round, it's a good idea to have your vitamin D levels tested in the spring and the fall. S 25(OH)D test, also called 25-hydroxyvitamin D can be performed by your Doctor. This is the primary circulating form of vitamin D and is widely used as a marker of a person's vitamin D status. Although health organizations have different goal ranges, ideally, the lower range (below 30 ng/mL) is of concern. The normal range is 30-100 ng/mL. Most experts recommend keeping your levels between 50-80 ng/mL.

Foods

Food options high in vitamin D are somewhat limited. Seafood is a primary source of dietary vitamin D, but unless a lot can be eaten, it's not likely to be enough to meet primary needs. Some of the best food sources of vitamin D are cod liver oil, sardines, salmon, mackerel, tuna, egg yolks, and mushrooms.