Vitamin D plays a large role in immune, bone, muscle and overall health. Whether you’re a growing teenager or retired adult, it’s important to be conscious of Vitamin D intake, especially during these winter months.

Vitamin D is a fat-soluble vitamin most commonly found in fortified foods, fatty fish and mushrooms. The body can also create Vitamin D when sunlight hits our skin. However, the key to synthesizing Vitamin D through our skin is to first have casual exposure. Winter days are short and it’s not uncommon to leave for school or work in the morning dark and come home in the evening dark with very little opportunity for causal sun exposure in between. It’s depressing and Vitamin D insufficient. In this instance, consider increasing dietary Vitamin D and/or taking a multivitamin that contains both Vitamin D and calcium.

A key component of Vitamin D is its somewhat romantic relationship with calcium. The body can’t properly absorb and use calcium to build strong bones without enough Vitamin D. In the instance of a Vitamin D shortage, calcium from food cannot be efficiently absorbed and utilized, so the body begins to leech calcium from bones to compensate. Leeched calcium is the first step towards brittle bones, a concern for women and the older population especially. Studies have also found that adequate vitamin D intake is needed to keep muscles strong and intact, whereas deficiency leads to weakness and muscle atrophy.

Less commonly known is the important role Vitamin D plays in immune health. Tis’ the season for flu shots and spikes in tissue sales, but you can give your immune system an advantage and decrease the risk of infection and illness through Vitamin D containing foods. Vitamin D helps promote the expression of immune cells, ultimately increasing immune strength while decreasing inflammation and risk of illness. Conversely, research has shown that Vitamin D deficiency is associated with increased risk of infection and illness. Nothing is more annoying than a weeklong bout with the flu or a head cold that just won’t go away.

The Endocrine Society recommends 1,500–2,000 IU of Vitamin D per day for adults (18 years and older).

Common food sources of Vitamin D include:

  • Fortified milks (cow, soy or rice based; check the food label)
  • Fortified cereal, yogurt, margarine and orange juice
  • Fatty fish including halibut, salmon, herring and tuna
  • Egg yolks, Swiss cheese, mushrooms, sunflower seeds
  • Liver and cod liver oil

Liver and cod liver oil are exceptionally high in Vitamin D because it is stored within the liver. When liver or liver oil is eaten all of that stored Vitamin D comes with it. It’s like winning the Vitamin D lottery!

Fortified foods are an easy and convenient way to consume Vitamin D daily. Orange juice and various milk products will often have a label touting its Vitamin D fortification. Consider eating fatty fish, such as salmon, tuna, herring and/or halibut, on a regular basis because they contain omega fatty acids in addition to Vitamin D; a prime combination for an immunity boost.

Three things to know about acquiring Vitamin D from sunlight:

  1. The intensity of the sun depends on your geographical location. The closer to the equator you live, the stronger the Vitamin D producing UVB rays. Typically, summer months are the best time to receive sun-given Vitamin D in the United States. During the winter the sun’s rays are less intense due to the rotation of the earth’s axis. For example, individuals living in Boston receive very little Vitamin D November through February as a result of their geography on the earth (not to mention being layered head to toe to in winter clothes to keep out the cold).
  2. The particular UVB light that produces Vitamin D does not pass through windows. This creates a great excuse to spend some time outside!
  3. While sun exposure is the best natural way to synthesize Vitamin D, current research indicates that one should always wear sunscreen to decrease risk of skin cancer and supplement Vitamin D as needed.

In short, Vitamin D is crucial for innate immunity, bone density, reduction of muscle wasting and inflammation as well as overall health. Vitamin D level is not monitored in routine blood tests, so it’s not a bad idea to have your level checked by a primary care physician.



Grace Hatfield is a Sodexo Dietetic Intern based in Christiansburg, Virginia. She has a Bachelor’s in Science in Nutrition & Dietetics from Arizona State and will be sitting for her certification exam to be a Registered Dietitian later this spring! Grace’s favorite food is cake, which she would eat for breakfast, lunch and dinner if possible.