Vitamin D body functions and foods
Many body functions need vitamin D to occur, important functions like calcium and phosphorus absorption for strong teeth and bones, insulin production for blood glucose regulation, as well as the modulation of immune cells that keep us healthy (1).
Consuming this vital nutrient can be tricky, as there are few food sources of vitamin D.
Vitamin D is primarily made in the body when the skin is exposed to sunlight, which is why this essential nutrient is referred to as the “sunshine vitamin”.
But, consuming foods like rainbow trout, salmon, tuna, herring, canned sardines, dairy products, egg yolks, beef liver, and mushrooms can help to boost your vitamin D levels (2) (3).
Winter months mean lower vitamin D levels
Staying indoors and wearing more clothing means that during the winter most of us do not get enough sunlight on our skin to produce the levels of vitamin D that the body requires for proper function (1).
Additionally, during the winter the angle of the sun blocks the UVB rays, which the body uses to begin vitamin D production, so if you live above the 37th parallel (U.S. regions north of San Fransico, Denver, St. Louis, Atlanta, and Richmond) you are at greater risk for vitamin D deficiency and the disease states that are associated (4).
How much vitamin D do we need?
Blood levels of vitamin D are measured in the storage form of 25(OH)D, and the U.S. National Institutes of Health specifies that 50 nmol/l and above in adults is adequate to prevent health issues related to vitamin D deficiencies (5). Further, the Recommended Dietary Allowance (RDA) for adults is about 600 IUs daily (5).
The Endocrine Society states the preferred range for vitamin D as 100-150 nmol/l, recommending a daily intake of 1500-2000 IUs for adults to maintain this level (1).
Boosting vitamin D levels with food
Consuming foods that contain vitamin D is especially important during the winter months when we are not exposed to enough sunlight to produce vitamin D in sufficient amounts.
You can use this chart to help you build your weekly meal plan and include foods that contain vitamin D during the winter months.
Rainbow trout 3 ounces 645 IUs
Salmon 3 ounces 383-570
Tuna (canned) 3 ounces 231
Herring 3 ounces 182
Sardine (can) 3 ounces 164
Milk 1 cup 117
Yogurt 8 ounces 116
Kefir 1 cup 100
Cheese 1 ½ ounce 85
Egg 1 medium 36.1
Beef liver 4 ounces 55.4
Mushrooms 1 cup 6.72
Signs that you may have a vitamin D deficiency
Frequent illness or infections can be an indicator that your vitamin D levels need a boost. Vitamin D has been found to play a role in almost all immune cells in the body, which means that if this nutrient is not present at sufficient levels the immune system can fail us (9).
Slow wound healing can also indicate low vitamin D levels, as vitamin D plays a role in the formation of new skin (10) (11).
Hair loss, or alopecia, and premature whitening of the hair have been linked to low vitamin D levels (12) (13). You can read more about vitamin D deficiency and hair loss here.
Other manifestations of vitamin D deficiency can include muscle pain, anxiety, bone loss, and depression.
If you suspect a vitamin D insufficiency, you can see your healthcare provider for a simple low-cost 25 (OH) D test to be sure.