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Vitamin D for Dark Winter Months

Vitamin D for Dark Winter MonthsAs the days turns darker and we head into fall and winter, be aware that vitamin D deficiency is a real issue without natural exposure to sunlight on bare skin. Some studies have indicated that in the fall and winter months, skin generates little to no vitamin D above 37 degrees north. For reference, that’s over half the United States including the area south of San Francisco, St. Louis and Richmond, VA. Read on to learn how to get enough Vitamin D for Dark Winter Months.

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Factors such as geographic latitude, cloud cover, sun block, time spent indoors, clothing cover and skin pigmentation can lessen the absorption of vitamin D through the skin even in areas where rays are more direct. The Institute of Medicine now recommends a dietary intake of 600 IU daily (or 800 IU if over the age of 70). There are limited dietary sources of vitamin D and many people end up supplementing. Keep in mind that many will still experience low blood levels even when supplementing, so it is important to talk to your doctor about getting tested, continual monitoring, and the proper food sources, sun exposure and supplementation for your unique needs.

Aside from its role regarding calcium absorption in the gut, vitamin D is known for preventing both rickets and osteomalacia, helping to prevent osteoporosis. It also modulates cell growth and plays vital roles in immune function, reducing inflammation and gene coding. Vitamin D is now recognized as playing a role in cancer and auto-immune protection.

indexRead labels and consider specific processing carefully to be sure you really are getting a true vitamin D source in your food. For example, not all mushrooms contain vitamin D; they must be grown with ultra-violet light and will be marked as such to ensure they are a vitamin D source. Not all non-dairy milks or orange juice are fortified so be sure to read labels. Talk to your doctor to see if you should get your levels tested, monitored and possibly supplement this vitamin for optimal health.

Foods that contain vitamin D

Depending on the variety, studies show that salmon (especially wild varieties) contributes ~450-950 IU vitamin D per 3 ounce serving.

Canned tuna
Tuna varieties contain differing amounts of vitamin D, but the most convenient and affordable option is tuna canned in water. A 4 oz can contributes ~150 IU vitamin D.

Cod liver oil
More often used as a dietary supplement than a food commonly consumed, if cod liver oil is medically indicated, a small portion of one Tablespoon contributes a large portion of vitamin D at ~1300 IU.

Whole eggs
Don’t ditch that yolk! Fat soluble vitamins are contained in the yolk of an egg which contributes a small amount of dietary vitamin D at ~40 IU each. However, at such a low level of the vitamin, it is not indicated to eat enough eggs daily to get all of your vitamin D from this source.

Some mushrooms grown in ultra-violet light contribute vitamin D2 or ergocalciferol. Brands containing vitamin D will be marked as such since many types of mushrooms are grown in the dark and therefore will not be considered a vitamin D source.  Find a brand grown in light for ~400 IU vitamin D in 3 ounces of diced mushrooms.

Fortified milks (dairy and non-dairy)
Dairy milk and yogurts have been fortified with 100 IU per 8-ounces since the 1930’s. Many, but not all non-dairy or plant-based milks are also fortified so read labels carefully on any type of milk to be sure you are getting a fortified product.

Fortified orange juice
Many, but not all, packaged orange juices are fortified with vitamin D in levels similar to fortified milks (8-ounces contribute ~100 IU). They are also fortified with calcium. Keep in mind that freshly squeezed juices do not contribute vitamin D to the diet so read the labels of any juice package to verify that it is a fortified product.


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Ginger Hultin,MS, RD, CSO

An award-winning, nationally recognized nutrition expert and media spokesperson.

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