Vitamin D, sometimes referred to as the “sunshine vitamin”, plays an important role in bone health, but unfortunately, Vitamin D deficiency is extremely common. Research suggests that up to 40 percent of adults in the US have insufficient levels, while 6 percent are considered deficient. Worldwide, vitamin D deficiency affects around 1 billion people.

In the throes of the COVID-19 pandemic, Vitamin D gained renewed attention for its important role in enhancing immunity. Recent research has stressed the importance of this critical vitamin not just for good bone health, but also for brain and heart health, obesity, mood, and potentially preventing chronic disease.

Why Vitamin D?

Vitamin D plays a critical role in the absorption of minerals like phosphorus and calcium, both of which are essential for strong bones and muscles. People with very low vitamin D blood levels are more likely to experience muscle cramps and bone or joint pain. In the elderly, vitamin D insufficiency is a major cause of metabolic bone disease and can exacerbate osteoporosis. Studies find that vitamin D deficiency is associated with increased risk of hip fracture, with one study revealing that up to 40 percent of patients suffering an acute hip fracture were vitamin D deficient. Additionally, studies reveal that an increase in calcium, along with daily supplementation of vitamin D decreases the risk of vertebral and nonvertebral fractures and increases bone mineral density.

Where to get it

The best source of vitamin D is casual exposure to sunlight, so get outside! It is estimated that 80 to 90 percent of the body’s requirement for vitamin D comes from the sun. Exposure to sunlight causes the photoproduction of vitamin D3 in the skin. Once formed, vitamin D3 is metabolized sequentially in the liver and kidneys.

Unfortunately, not many foods naturally contain Vitamin D. It is found in substantial levels only in certain fatty fish, some eggs, and in fortified foods like milk and cereal. So, to help meet the recommended daily requirement, it is generally accepted that a calcium intake to 1000-1500 mg/d along with an adequate source of vitamin D of at least 400 IU/d is important for maintaining good bone health.

Authored by Zach Meeker, Research Assistant for Midwest Orthopaedics at Rush University Medical Center


Sizar O, Khare S, Goyal A, et al. Vitamin D Deficiency. [Updated 2021 Jul 21]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from:

Nair, R. and Maseeh, A. (2012). Vitamin D: The “sunshine” vitamin. Journal of Pharmacology, Apr-Jun 2012, 118-126.

Holick, MF. Vitamin D and bone health. Journal of Nutrition. 1996 Apr;126(4 Suppl):1159S-64S.

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