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Vitamin D: maybe you’ve heard of it? In recent years, the “sunshine vitamin” has been much-discussed for its possible role in preventing serious diseases like cancer and various unpleasant physical conditions. One of those is fatigue.
If you’re experiencing fatigue, can popping a daily supplement or increasing your consumption of vitamin D restore your energy levels? Here’s what the latest science says.
What is vitamin D?
Vitamin D is actually a prohormone, not a vitamin. That means it’s something the body makes and converts to a hormone. As you learned around age 13, hormones stimulate certain systems of the body into action. To oversimplify it: A surge of hormones gets things moving, while a dearth or imbalance of hormones can cause processes to slow or stop.
Vitamin D is called “the sunshine vitamin” because the body generates it when the skin is exposed to the sun. Technically, the liver and kidneys also play a role in converting vitamin D to its active form in the body.
Vitamin D’s also found in a variety of foods, including fatty fish (such as salmon and tuna), fish oil, vitamin D-fortified milk, eggs, and fortified breakfast cereals.
But most of us get most of our vitamin D from the sun, and our largely indoor lives have made that problematic. A large percentage of the population may be vitamin D deficient—up to 40% of Americans and 1 billion people worldwide (Parva, 2018).
Benefits of vitamin D
Here are five ways vitamin D helps our bodies.
Vitamin D’s primary role is to help the body maintain the right levels of calcium and phosphorus.
It affects how calcium is absorbed from food and how the body builds and reabsorbs bone (a process called bone remodeling, which the body is constantly doing). Studies suggest vitamin D could help prevent fractures and osteoporosis.
A lack of vitamin D has been associated with a higher chance of infection and an increased risk of autoimmune diseases. Vitamin D seems to help the immune system destroy bacteria and other invading microbes (Aranow, 2011).
Protection from certain cancers
Some studies have found that Vitamin D might have a protective effect against a number of cancers, particularly colorectal and breast (Meeker, 2016).
That could be because vitamin D regulates the genes that control cell differentiation, division, and death. Vitamin D also bolsters the immune system and reduces inflammation. All those processes can affect the development of cancer.
Can you get enough vitamin D from the sun?
Reduces risk of diabetes
Regular doses of vitamin D early in life have been found to reduce the risk of type 1 diabetes, and taking vitamin D later in life seems to reduce the risk of type 2 diabetes. Vitamin D seems to help the body process insulin, thus controlling blood sugar levels.
Promotes heart health
One study found that vitamin D deficiency is associated with major risk factors for cardiovascular disease—including high blood pressure, coronary artery disease, cardiomyopathy (enlargement of the heart muscle), and diabetes—and that vitamin D supplementation was associated with better survival (Vacek, 2012). However, other studies haven’t found those benefits.
Can vitamin D give you more energy?
Low energy or fatigue is a common symptom of vitamin D deficiency. That’s because vitamin D seems to help mitochondria—the part of a cell that generates energy—use oxygen and power various parts of the body, including muscles. The thinking, then, is that a lack of vitamin D may impact mitochondrial function, causing fatigue (Dzik, 2019).
In a 2016 study, researchers gave 120 fatigued (but otherwise healthy) people either a single megadose of vitamin D (100,000 IU) or a placebo. The researchers reported that the people who took vitamin D experienced “significantly improved” fatigue (Nowak, 2016).
Studies have found that supplementing with vitamin D has improved energy levels in people who have recently had a kidney transplant. One study of pro soccer players found that vitamin D levels were associated with better athletic performance (Koundourakis, 2014; Han, 2017).
Another study found that women who were deficient in vitamin D were more likely to report “weakness, fatigue, and non-specific pain” (Ecemis, 2013).
But the jury is still out. Large studies on otherwise healthy people taking a daily vitamin D supplement are lacking. A low vitamin D level might be the cause of your fatigue, or it might not.
If you’re experiencing fatigue, talk with your healthcare provider about your concerns. They can test your vitamin D level with a simple blood test to determine if you’re deficient.
How to get more vitamin D
You can get more vitamin D by eating D-rich foods, including fatty fish (such as salmon and tuna), fish oil, fortified milk, egg yolks, and fortified breakfast cereals.
You could also take a vitamin D supplement. The Office of Dietary Supplements recommends a daily intake of vitamin D of 600 IU for adults up to age 69 and 800 IU for adults 70 and older. The tolerable upper daily limit is 4,000 IU (100 mcg). Be careful when taking vitamin D supplements—vitamin D toxicity is possible (NIH, n.d.).
It is possible to get enough vitamin D from the sun, but only at certain times of the year. Some researchers believe that about five to 30 minutes of sun exposure between 10 a.m. and 3 p.m., at least twice a week to your face, arms, legs, or back (without sunscreen) can produce sufficient vitamin D.
However, there are no actual recommendations regarding the amount of time to spend in the sun since sun exposure also increases your risk of developing skin cancer. During the winter in the Northern Hemisphere, it can be impossible to get enough vitamin D via the sun. Vitamin D supplementation can be helpful in maintaining normal levels.
- Aranow C. (2011). Vitamin D and the immune system. Journal of investigative medicine : the official publication of the American Federation for Clinical Research, 59(6), 881–886. https://doi.org/10.2310/JIM.0b013e31821b8755
- Dzik, K. P., & Kaczor, J. J. (2019). Mechanisms of vitamin D on skeletal muscle function: oxidative stress, energy metabolism and anabolic state. European journal of applied physiology, 119(4), 825–839. https://doi.org/10.1007/s00421-019-04104-x
- Ecemis, G. C., & Atmaca, A. (2013). Quality of life is impaired not only in vitamin D deficient but also in vitamin D-insufficient pre-menopausal women. Journal of endocrinological investigation, 36(8), 622–627. https://doi.org/10.3275/8898
- Han, B., Wu, X., & Guo, Y. (2017). Improvement of fatigue after vitamin D supplementation in kidney transplant recipients. Medicine, 96(21), e6918. https://doi.org/10.1097/MD.0000000000006918
- Koundourakis, N. E., Androulakis, N. E., Malliaraki, N., & Margioris, A. N. (2014). Vitamin D and exercise performance in professional soccer players. PloS one, 9(7), e101659. https://doi.org/10.1371/journal.pone.0101659
- Meeker, S., Seamons, A., Maggio-Price, L., & Paik, J. (2016). Protective links between vitamin D, inflammatory bowel disease and colon cancer. World journal of gastroenterology, 22(3), 933–948. https://doi.org/10.3748/wjg.v22.i3.933
- National Institutes of Health, Office of Dietary Supplements – Vitamin D. (n.d.). Retrieved June 05, 2020, from https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional
- Parva, N. R., Tadepalli, S., Singh, P., Qian, A., Joshi, R., Kandala, H., Nookala, V. K., & Cheriyath, P. (2018). Prevalence of Vitamin D Deficiency and Associated Risk Factors in the US Population (2011-2012). Cureus, 10(6), e2741. https://doi.org/10.7759/cureus.2741
- Vacek, J. L., Vanga, S. R., Good, M., Lai, S. M., Lakkireddy, D., & Howard, P. A. (2012). Vitamin D deficiency and supplementation and relation to cardiovascular health. The American journal of cardiology, 109(3), 359–363. https://doi.org/10.1016/j.amjcard.2011.09.020
Dr. Mike is a licensed physician and the Director, Medical Content & Education at Ro.