Doctor’s Orders: Don’t Become Vitamin D Deficient This Winter

Catching some rays in the middle of the day for your vitamin D dose can become impossible once the temperature drops.

When it’s too cold to go outside, one can’t rely entirely on the suns rays as the source of Vitamin D. Matthew Landers/Unsplash


Vitamin D, nicknamed the “sunshine vitamin,” is essential to maintaining our health and immune system. As you might have guessed, the main source of this vital little vitamin comes from the sun. But as our weather transitions from warm to cold, so too must we adjust our sources of vitamin D, since catching some rays in the middle of the day can become impossible depending on where you live.

That vitamin D has a natural non-food source makes it unique among vitamins—sunlight actually allows it to be synthesized, or made, within our bodies. If you live in a cold climate, it’s normal for your vitamin D stores to dip in fall or winter—you’re simply not getting enough ultraviolet B (UVB) rays, which trigger the skin to produce vitamin D.

These rays are stronger near the equator and weaker at higher latitudes. And when you live in the northern circle of latitude that is 37 degrees above of the Earth’s equator, the rays simply do not hit your location at the right angle to get UVB light to the earth during fall or winter, so producing vitamin D from the sun becomes impossible. Draw a line across the country from San Francisco to Philadelphia—anyone living above this demarcation must look for alternative sources for Vitamin D from November through March. But even if you live in Los Angles or Orlando, and can get sun (and UVB rays) all year round, it’s still worth diversifying your sources.

Why does vitamin D matter?

Sufficient levels of vitamin D are necessary to absorb calcium, which helps prevent the brittle bone disease of osteoporosis. It has also been shown to play a role in preventing heart disease, cancer, Alzheimer’s disease, depression, strokes, high blood pressure, diabetes, multiple sclerosis and may slow the aging process. Worldwide, it is estimated 1 billion people have inadequate levels of vitamin D in their blood and deficiencies can be found in all ethnicities and age groups.

How do you get vitamin D from sunlight?

Your body produces large amounts of vitamin D3 (cholecalciferol) when the skin is exposed to the sun. Exposure time depends on the skin tone of each individual. People with very fair skin may only need about 10 minutes of time in the sun for their body to produce vitamin D. Those who have very dark skin may require up to at least 30 minutes of being in the sun or longer in order to make vitamin D. For the average person, 15-20 minutes at least three times a week where at least their face, arms and or legs are exposed is sufficient for their body to obtain enough vitamin D. However, the more skin that is exposed, the more vitamin D you will make. A person does not need to tan or burn to get the vitamin D they need.

Another factor affecting the amount of vitamin D skin will make is the time of day. The best time of day to be out in the sun in order for skin to produce the most vitamin D is midday, when your shadow is the shortest.

How do you get enough vitamin D in colder months?

It is very difficult to get enough vitamin D from food sources alone, as there are only a few that contain it naturally—the flesh of fatty fish such as salmon, tuna, and mackerel or fish liver oils are the best food sources. Other natural food sources include beef liver, egg yolks and cheese. Otherwise, foods such as milk and yogurt have been fortified with vitamin D but are not natural sources.

Here are the best suggestions on getting through the long winter months without becoming “D-ficient:”

  • If you live below the 37th degree latitude, you should be able to make vitamin D most of the year. Try to get outdoor several times a week, if not daily, for a 15 minute walk in the sun at midday.
  • Include good food sources of vitamin D daily—salmon, tuna, mackerel, mushrooms, eggs, cheese and vitamin D fortified foods such as milk (cow, almond, soy, and coconut milk are all usually fortified), yogurt, and some orange juices. A 4-ounce serving of salmon provides 265 percent of the daily amount recommended of vitamin D.
  • Take a supplement of vitamin D3 year round. Check with your physician on their recommendation of what amount to take. Generally, for people with adequate status, they can still take between 1,000 to 2,000 International Units (IU) of vitamin D each day to help maintain levels.
  • Have your blood levels checked at your doctor’s office. Studies suggest it’s best to have your levels above 30 nanograms/millilitre. Anyone who has levels below this may require a higher intake of supplements, but only with the advice from a doctor.


Dr. Samadi is a board-certified urologic oncologist trained in open and traditional and laparoscopic surgery and is an expert in robotic prostate surgery. He is chairman of urology, chief of robotic surgery at Lenox Hill Hospital. He is a medical contributor for the Fox News Channel’s Medical A-Team.  Follow Dr. Samadi on Twitter, Instagram, Pintrest,, davidsamadibio  and Facebook


Doctor’s Orders: Don’t Become Vitamin D Deficient This Winter