What is vitamin D?
Vitamin D is an essential nutrient known for its role in bone health. It’s also a unique nutrient because it’s both a fat-soluble vitamin found in your food and a hormone your body can make when your skin is exposed to sunlight. There are 2 primary forms of vitamin D: D2 and D3. Vitamin D2 (ergocalciferol) is found primarily in plants and fortified food products. Vitamin D3 (cholecalciferol) is found mostly in animals and is the form found in your skin. In addition to being essential for bone health, vitamin D plays several other roles in your body that could be important for military performance and mission availability.
Why is vitamin D important for Service Members?
Your vitamin D levels could affect your physical and psychological health, performance, and mission availability in several ways:
- Vitamin D can play a role in physical performance. Higher vitamin D levels may lead to better performance on the Army Combat Fitness Test and improvement in other measures of physical fitness, such as power, strength, and aerobic endurance.
- Vitamin D is important for musculoskeletal health. Research indicates that vitamin D deficiency may be a risk factor for some overuse injuries, such as stress fractures that most commonly occur during basic training.
- Vitamin D supports your immunity. Service Members with adequate vitamin D levels may be at lower risk of illness, such as colds and respiratory infections.
- Vitamin D is important for brain function. Active-duty Service Members diagnosed with vitamin D deficiency may be at greater risk for diagnosis of depression than those with normal vitamin D levels. This doesn’t mean that vitamin D deficiency causes depression, but they may be linked.
How do I get vitamin D?
You can get vitamin D through sun exposure or foods that contain vitamin D. When you’re in the sun, ultraviolet B (UVB) radiation converts a molecule in your skin into vitamin D3. But getting enough sun exposure to activate this process may not be possible.
Foods with naturally-occurring vitamin D include fatty fish, fish oils, egg yolks, butter, and liver. You can also get vitamin D from “fortified foods,” which is where vitamins or minerals are added to foods during processing to increase their nutritional value. Milk, fruit juices, some breads and cereals, are often fortified and can help you reach or maintain your vitamin D needs.
Am I at risk for vitamin D deficiency?
Understanding your risk factors and taking action if necessary could help optimize your health and performance. Risk factors for vitamin D deficiency include any factors that interfere with skin synthesis of vitamin D and limited intake of foods rich in vitamin D. Here are some of the risk factors for vitamin D deficiency:
- Having dark skin pigmentation can decrease the skin’s ability to make vitamin D from sun exposure. People with darker skin need to get more sun exposure than people with fair skin to produce enough vitamin D.
- Having excess body fat can decrease concentrations of vitamin D in the blood because vitamin D is a fat-soluble vitamin and can be absorbed and held within fatty tissue. As your body mass index (BMI) goes up, vitamin D levels typically go down.
- Where you live can affect your risk for vitamin D deficiency. Living at high latitudes, further from the equator, limits your exposure to UV rays, and therefore, vitamin D production in your skin. In the United States, that line is at approximately 35 degrees north (along the same lines as Fayetteville, NC, or Albuquerque, NM). If you live above that line, sun exposure will contribute very little to your vitamin D levels during the cooler months. Also, if you live somewhere air pollution is regularly high enough to block sunlight and reduce UV exposure, that can also increase your risk for vitamin D deficiency.
- Limited exposure to the sun. Your risk for having low vitamin D levels can increase if you regularly use sunscreen or protective clothing, spend most of your day inside, or work at night.
- Aging decreases your skin’s ability to produce vitamin D from sun exposure. Service Members over age 30 have higher odds of vitamin D deficiency compared to younger Service Members. But it’s not clear whether this is due to the natural aging process, the frequent transition to supervisory roles (which are often indoors) through a Service Member’s career, or other factors.
- Having certain health conditions that affect the liver, kidneys, or gut can reduce vitamin D absorption and metabolism. So if you have an underlying medical condition that affects these organs, you could be at greater risk for vitamin D deficiency.
- Limited access to or intake of foods rich in vitamin D. Whether you live in a “food desert” where there aren’t many grocery stores, you’re deployed with less access to food variety, or you have a food allergy that keeps you from eating foods rich in vitamin D, you could be at greater risk for vitamin D deficiency.
Vitamin D deficiency risk assessment for military populations
Military life includes unique circumstances that put Service Members at risk for nutrient deficiencies. Check the graphic here to find out which risks for vitamin D deficiency might apply to you.
You can also download the Vitamin D Risk Assessment [PDF]
What can I do if I’m at risk for vitamin D deficiency?
Here are a few ways you can get more vitamin D:
- Eat fatty fish twice a week. Fish high in fat, such as trout and salmon, tend to have higher levels of naturally occurring vitamin D per 3-ounce serving compared to other types of fish.
- Choose milk or fruit juice, and cereal that’s fortified with vitamin D. Fortified foods are a great way to increase your intake of vitamin D. Various milk options are fortified with vitamin D, including plant milks, so be sure to check the labels.
- Eat the egg yolks. Some people toss their egg yolks because of the high calorie count. But egg yolks are loaded with various nutrients that are important for health, including vitamin D.
- Practice safe sun exposure. During the summer months in the continental United States (CONUS), as little as 15 minutes of sun exposure between the hours of 1000 and 1500 on your arms, legs, and face can be enough to meet your vitamin D needs.
- Talk to your healthcare provider. If you’re concerned about low vitamin D levels, talk to your healthcare provider about having your vitamin D levels checked. In some cases, a vitamin D supplement may be useful when you’re not able to get enough vitamin D from other sources. Be sure to look for a dietary supplement that is third-party certified.
Understanding your risk factors for vitamin D deficiency can motivate you to take action. Having sufficient vitamin D levels can improve your physical performance, reduce your risk of fractures, and contribute to your overall physical and mental health—making you mission- and duty ready. To learn more about vitamin D, see the NIH Office of Dietary Supplements Vitamin D Fact Sheet.