During winter months, residents of northern US cities are experiencing more snowstorms like the recent "historic" nor'easter Juno, and the lack of sunshine is causing vitamin D deficiency, a new study warns.

According to nutrition researcher Peter Horvath, in Buffalo, NY for example, nearly 50 percent of people have insufficient amounts of vitamin D and 25 percent may be considered deficient.

Unlike other vitamins, vitamin D is created naturally by the body when the skin absorbs ultraviolet sunlight. But with sleet, snow, freezing temperatures and gusting winds during the winter, people bundle up and spend less time outside in the sunlight. Plus, during this time direct sunlight is hard to come by due to the Earth's tilt away from the Sun.

"Every cell in the body is responsive to vitamin D," Horvath said in a statement. "If you're deficient, you won't see the health effects for years and it could take months to get your levels back up."

Vitamin D deficiency could cause lower bone density, a weakened immune system, increased risk for type 2 diabetes, cancer and cardiovascular disease, and cognitive impairment in older adults.

Those who are most at risk of vitamin D deficiency are the elderly, pregnant and nursing women, and people of color, whose skin acts as a natural sunscreen. Pregnant women and nursing mothers are of particular concern because it affects children at a time when their bones are still developing. This could result in rickets, or the softening of bone.

In order to get your daily dose, Horvath recommends vitamin D supplementation of between 1,000 and 2,000 international units a day. Also, eating foods rich in vitamin D such as salmon, breakfast cereals and enriched milk is helpful.

It's also possible for people exposed to northern winters to take precautions before the colder months and soak up as much summer sun as they can. This way, high vitamin D levels may help them make it through winter.

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