The winter months have shorter days, and at the moment, it’s a lot colder too.

Vitamin D, also called the “sunshine vitamin,” is deficient in many more people than we realize. If you are someone who doesn’t like to go outside much or who stays inside most of the time, you may struggle with vitamin D deficiency. Vitamin D is one of our four fat-soluble vitamins (A, D, E and K).

There are two forms of vitamin D. D2 comes from fortified foods, plants and supplements. D3 comes from the sun, fortified foods and animal foods, such as fatty fish and cod liver oil, eggs and in supplements. Due to the increased number of D deficiencies, guidelines set by the FDA for ages 4 and older are 20 mcg or 800 IU per day. For vitamin D-deficient babies up to 12 months, they need 1000 to 5000 IU/per day for about 2 to 3 months, after 12 months old 5000 IU/day. For adults with vitamin D deficiency, you need 6000 IU per day of vitamin D for eight weeks followed by maintenance therapy of 1500-2000 IU/day. Of course have your doctor check your levels first.

To get an accurate test to see where your levels are, your doctor will do a vitamin D test. It’s a 25-hydroxy vitamin D blood test, levels of 20 to 50 nanograms/milliliter in a healthy person is satisfactory. Less than 12 ng/ml is a vitamin D deficiency. There are many health benefits that come with the right levels of vitamin D. Vitamin D promotes a healthy skeleton. Calcium helps with strong bones and teeth, but vitamin D helps the absorption of calcium in the gut and helps to maintain our blood calcium levels. An adequate level of Vitamin D supports a healthy immune system, brain and nervous system, it helps the health in pregnancies and infants, and it helps to regulate insulin levels and helps with diabetes management. Vitamin D also supports lung function and aids in cardiovascular health. It has improved hip and knee pain in people who suffered with vitamin D deficiency and insufficient levels.

So why has the vitamin D deficiencies risen? Our increased use of sunscreen, covering most of the body and decreased outdoor activities and the scare for skin cancer (in many people) is limiting the skin to produce vitamin D via sun exposure. Recommended for a healthy skin, low risk for skin cancer and getting enough vitamin D through sunlight is to expose most of your skin (shorts and T-shirt is fine) at mid-day for 10 minutes most days of the week. Dark skin has natural “sun block” and the recommendation is 3 to 5 times longer than fair skin. Dark skin takes longer for the skin from absorbing the UVB (ultraviolet B — the important part from sunlight to get your vitamin D). If you are not sure if your levels are where they need to be, have your doctor run that blood test, it’s the most accurate way to see if your levels are acceptable. If you are like me, I make sure I get enough true sunlight which is not blocked by sunscreen. Since I can’t eat fatty fish (allergic to all seafood) I take a vitamin D supplement. So don’t be “scared” of the outdoors! Ten minutes midday of sunlight on your exposed skin can give you the right amount of Vitamin D you need, especially in these winter months.

Ester H. Marsh is health and fitness director of the JF Hurley Family YMCA.