Vitamin D and Dreary Winter

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.

Nutrition & Immune Health

Salmon SaladWith the arrival of colder temperatures in the winter months also arrives cold and flu season. While it may seem like getting sick at some point is inevitable, there are many nutritional strategies that can be applied (year round, really!) to boost the strength of your immune system and decrease your chances. As a sports dietitian, I am often counseling athletes on the importance of a healthy diet in maintaining a strong immune system to ensure consistent training year round. Today, I am here to share a few top nutritional strategies that have been shown to boost immune health:

  1. Consume a diet that is adequate in overall calories, balanced among the all three macronutrients, and rich in nutrient dense foods. Chronic calorie deficit over time, whether through failure to meet needs or intentional dieting for weight loss, can lead to impaired immune health in that it decreases the energy available to support normal bodily functions. Calorie deficit without careful consideration of diet quality can also lead to insufficient intake of vitamins and minerals related to immune health, including vitamins C, E, B6, A and D, Folate, Iron, Selenium and Zinc. Aim to include not only fruits and vegetables with each meal, but also quality lean proteins and whole grains too. A few high antioxidant foods to consider in boosting immune health include grapes, blueberries, raspberries and strawberries, nuts and seeds, any dark leafy greens, sweet potatoes and other orange vegetables, beans, fish and whole grains!
  2. Swap unhealthy (saturated) fats in your diet for healthy (unsaturated) fats, which are both anti-inflammatory and immune boosting. Instead of aiming for low-fat foods, aim to replace sources of saturated fat in your diet for healthy fats, especially omega-3 fatty acids, which support hormone production and help fight inflammation in order to keep our immune system strong. More specifically, essential fatty acids (omega-3’s and Omega-6’s) play a role in the production of eicosanoids, a class of chemical messengers involved in your body’s immune and inflammatory response. These healthy fats can be found in avocadoes, nuts (especially walnuts!), sunflower, sesame and pumpkin seeds, olives, flaxseed and wheat germ, chia seeds and fatty fish varieties.
  3. Ensure adequate Vitamin D intake for optimal immune strength. While we are able to naturally synthesize Vitamin D through sun exposure, it’s not uncommon for Vitamin D levels to drop off in the winter when colder whether forces us inside more. Low Vitamin D levels have a direct effect not only on bone health, but immune health as well, and it’s never a bad idea to have your levels checked by your primary care physician. To ensure you’re getting enough Vitamin D through diet, aim to consume a few of these foods daily: Cod Liver Oil, oily fish (trout, salmon, swordfish, mackeral, tuna and sardines), mushrooms, fortified cereals, tofu, dairy products, pork and eggs.
  4. Consume foods with naturally occurring probiotics to improve gut health. Gut health has a direct impact on both the health of our brain and our immune system. By incorporating foods with natural probiotics, including yogurts and cheeses, kefir, sauerkraut, miso, sour pickles and kombucha, you are feeding the healthy bacteria in your gut that in turn can lend to a stronger immune system.
  5. Flavor your foods with healthy herbs & spices. Many of the herbs and spices that we use to flavor our foods also have potent anti-microbial, anti-inflammatory and immune boosting properties. Garlic, onion, turmeric, ginger and cinnamon are a few herbs and spices that top the list.
  • Garlic is not only known for it’s unique and pungent flavor contribution to many dishes, but also it’s role as a potent anti-inflammatory, anti-viral and cancer preventative food. Garlic’s numerous beneficial immune benefits are due to sulfur compounds and being a quality source of vitamin C, vitamin B6, selenium and manganese.
  • Onions are not only a quality source of Vitamin C, but also one of the richest sources of flavonoids, especially quercetin, which has been shown to inhibit inflammation. Onions also contain the trace mineral selenium, which helps to initiate the body’s immune response.
  • Curcumin is a component of the spice turmeric and helps give it its distinct orange-yellow color. Turmeric is commonly found in curry spices and dishes. Curcumin is traditionally known for its anti-inflammatory effects but in recent decades has also been shown to be a potent immune-modulating agent.
  • Ginger, more commonly known for its anti-nausea benefits, also boosts anti-inflammatory and antioxidant activity within the body. Ginger is best consumed uncooked in it’s natural form, so aim to buy ginger whole and use a grater to include it in your dishes where possible.
  • Cinnamon is another spice that is not only rich in antioxidants, but also a quality source of manganese, calcium, fiber and iron. The essential oils found within cinnamon have also been shown to boost the immune system since they have antiviral, antibacterial and antifungal properties.

Wintertime doesn’t have to inevitably spell out cold and flu season. To boost your immune system and decrease your chances of getting sick aim to follow some of the tips above, and don’t forget to get plenty of sleep at night too!!


Kristen Chang
Kristen Chang

Kristen Chang is the current Co-Chair of Professional Education for VAND. She is an adjunct instructor for Virginia Tech and Radford University and the owner of the nutrition private practice, Real Food For Fuel, LLC.