In the heart of winter in Minnesota, I am keenly aware of the lack of vitamin D we are getting from the sun. Vitamin D is an important nutrient that isn’t found naturally in many foods. The body can synthesize vitamin D when exposed to sunlight, but in the winter months our exposure to the outdoors and sunlight decrease (depending on your climate). Supplementation with Vitamin D may be recommended for many whose diet is deficient and exposure to sunlight is minimal.

What are functions of vitamin D in the body?

Some of the important functions of vitamin D in the body include muscle, cardiovascular and respiratory function, promoting absorption of calcium and phosphorus for developing and strengthening bones, and supporting the immune system to help protect against infection and illness.

Vitamin D research is active and studies have suggested that vitamin D may be involved in the prevention and treatment of a variety of disease conditions including some types of cancer, heart disease, diabetes and multiple sclerosis. Studies have supported a link between vitamin D deficiency and cognitive decline1, modulation of the immune/inflammation system2, and susceptibility for Chron’s Disease3.

Considering the range of functions of Vitamin D in the body and the potential impact the vitamin may have on a variety of diseases, ensuring adequate intake and synthesis of Vitamin D throughout the year is worth attention.

How much vitamin D do we need?

Every person is different – diet, health status and environment in which they live. Vitamin D is a fat soluble vitamin and supplementing at a very high dose can result in toxicity. Though toxicity is rare, caution should be taken when supplementing with vitamin D.

Because of the importance of this vitamin, it is recommended that you have blood levels of vitamin D tested regularly (annually or even bi-annually) to ensure that your blood levels are optimal. This test can be ordered by your doctor or home test kits can be ordered as well. The recommendations range from 30-100 ng/ml for optimal blood vitamin D. According to the Vitamin D Council, a nonprofit organization created to educate the public on vitamin D and health, 40-80 ng/ml is considered optimal.

Sun Exposure for Vitamin D synthesis

There isn’t a simple rule for how much time you should spend exposed to sunlight for adequate vitamin D synthesis. Many factors impact this including your geographic location, season of the year and skin type. The risks of damage to your skin with excess sun exposure, of course, must be considered as well. Some recommendations say 15-30 minutes of exposure to your arms, legs and face a few times per week may be appropriate for adequate vitamin D synthesis. Again, testing blood levels of vitamin D is the only way to know for sure how your diet and environment is affecting your levels.

Dietary Options

The best sources of vitamin D in the diet include the following:

    • Fatty fish (salmon, tuna, mackerel)
    • Canned fish (with bones)
    • Fortified dairy and dairy alternatives
    • Fortified orange juice
    • Egg yolks
    • Fortified cereals


If your vitamin D levels remain low, supplementation may be a good option to consider. Dosage again depends on your current levels. General recommendations range from 400 IU/day to 10,000 IU/day. Even as high as 50,000 IU/day may be recommended under a doctor’s supervision.

Vitamin D has many important functions in the human body. Learn your vitamin D status, evaluate your environment, diet and supplements and consider if you could be doing more to promote optimal health.

To learn more about healthy choices you can make every day for healthy living click here to join me for my FREE 30-minute monthly webinar – Health Break – Quick Steps to Looking and Feeling Fantastic.