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Vitamin D Under Review

Vitamin D is a hormone made in the skin and transformed into the active form in the kidneys and liver that allows the calcium and phosphorus in our diet to be absorbed and used by the bones, heart, and immune system.

Vitamin D can also be consumed in foods and supplements. Some foods that are high in Vitamin D are salmon, eggs, mushrooms, and fortified foods (cereal, tofu, dairy, and orange juice). Remember that vitamin D is fat soluble and will need to be consumed with fat for best absorption. For this reason, supplements will usually come as an oil-based capsule, just in case a person isn’t consuming fat when taking the supplement.

A recently published article in the New England Journal of Medicine may cause us to reconsider our common practice of recommending vitamin D supplementation for prevention of bone fracture in adults older than 50-55. The research found that when taking a vitamin D dose of 2,000 IU daily, there is no observed additional protection against fracture compared to placebo1. [There is some evidence that anthocyanins, particularly cherries, can decrease bone resorption in post-menopausal women. This is important research to watch as more studies look at dosing and strength of cherry compounds2.]

What does this mean in terms of ordering a vitamin D level or prescribing supplemental vitamin D in these individuals? What other reasons are there to supplement a clinical or subclinical low vitamin D level? Addressing fatigue and decreasing inflammation are two other conditions that may be addressed with vitamin D supplementation if it’s found to be insufficient in the body.

Fatigue can cause a significant loss of quality of life. Whether it comes from a secondary diagnosis such as depression3, fibromyalgia4, or multiple sclerosis5 or it seems to be idiopathic6, fatigue can cause health decline7. Vitamin D has been studied in relation to fatigue related to multiple sclerosis, fibromyalgia, and even generalized malaise.

Vitamin D helps to decrease inflammation. Research has looked at inflammation in specialized cells throughout the body. One study shows that vitamin D inhibits inflammation in the cells of the respiratory tract8. This means that respiratory disease that is caused by inflammation, including pulmonary infection, asthma, fibrosis, and acute injury can be affected by vitamin D supplementation when there is vitamin D deficiency. One mechanism of action seems to be that vitamin D interrupts signaling pathways that cause oxidative stress to produce fibrosis in COPD8. When vitamin D is supplemented, forced expiratory volume (FEV 1) is improved in COPD. Vitamin D also decreases cytokine production and inflammation in patients with asthma. 

For a closer look at vitamin D, review the fact sheets available through the National Institutes of Health. There are versions tailored to health professionals as well as consumers (in English and Spanish).


  1. LeBoff, M. S., et al. (2022). Supplemental vitamin D and incident fractures in midlife and older adults. New England Journal of Medicine
  2. Dodier, T., et al. (2021). U.S. Montmorency Tart Cherry Juice Decreases Bone Resorption in Women Aged 65-80 Years. Nutrients, 13(2), 544. 
  3. Manzanos, I., et al. (2022). Vitamin D: Between the brightness of the sun and the darkness of depression. Revista Colombiana de psiquiatria (English ed.)
  4. Lombardo, M., et al. (2022). The Efficacy of Vitamin D Supplementation in the Treatment of Fibromyalgia Syndrome and Chronic Musculoskeletal Pain. Nutrients, 14(15), 3010. 
  5. Bahmani, E., et al. (2022). The Effect of Home-Based Aerobic Training and Vitamin D Supplementation on Fatigue and Quality of Life in Patients with Multiple Sclerosis During COVID-19 Outbreak. Science & sports
  6. Nowak, A., et al. (2016). Effect of vitamin D3 on self-perceived fatigue: A double-blind randomized placebo-controlled trial. Medicine, 95(52).
  7. Knoop, V., et al. (2021). Fatigue and the prediction of negative health outcomes: A systematic review with meta-analysis. Ageing research reviews, 67, 101261. 
  8. Ahmad, S., et al. (2021). Vitamin D and its therapeutic relevance in pulmonary diseases. The Journal of nutritional biochemistry, 90, 108571.

This article was part of the August 2022 e-news FRESH Rx. Subscribe for similar content delivered to your inbox monthly.