Vitamin D

Vitamin D, a fat soluble vitamin, has the noteworthy distinction as the only vitamin that the human body manufactures both efficiently and abundantly if given the right environment. And what is that environment? Sun, plenty of sun.

Mother Nature, borrowing from her photosynthesis playbook, has co-opted the Sun, specifically Ultra-Violet B (UVB) radiation, to optimize vitamin D production.

In the top layer of skin, referred to as the epidermis, UVB triggers the synthesis of vitamin D from a substance that is a derivative of cholesterol. However, vitamin D in this form is biologically inactive and must undergo two additional modifications, one in the liver (25 OH Vitamin D) and one in the kidney (1,25OH Vitamin D), before it is considered functional.

Vitamin D’s notoriety in the popular press usually stems from its role in bone health, specifically osteoporosis. However, vitamin D is a versatile vitamin materially contributing to a broad scope of physiologic and biologic processes. Some research estimates vitamin D influence close to 1250 genes. That’s huge!

3 Musculoskeletal Health Benefits

1. Vitamin D Promotes Joint Health

Chronic unhealthy inflammation drives degenerative joint disease. Research demonstrates that vitamin D has a positive influence on the immune systems response to chronic injury. Vitamin D mitigates uncontrolled inflammation by blocking the production of key proteins that magnify the inflammatory response.

Additionally, scientific investigation implies that vitamin D enhances the production of cartilage extracellular proteoglycans; thus, boosting the joint’s shock absorbing properties.

Moreover, vitamin D has been shown to curb the  synthesis of matrix metalloproteinases, the tissue destroying enzymes responsible for considerable cartilage damage.

Finally, vitamin D promotes the ideal calcium mineralization and density of subchondral bone. Subchondral bone, as its name implies, is the area of bone just below cartilage. The sub chondral bone provides cartilage with the strong structural support needed to counteract daily wear and tear.


Boston researchers found that individuals with similar characteristics who were deficient in vitamin D and who were assessed radiographically for osteoarthritis had an increased risk for osteoarthritis of the knee. (Zhang FF, Driban JB, Lo GH, et al. Vitamin D deficiency is associated with progression of knee osteoarthritis. J Nutr. 2014;144: 2002-2008)


Population studies have shown people with insufficient Vitamin D levels are at increased risk for both developing osteoarthritis and for osteoarthritis progression. Some data indicates a 3-fold increase in both incidence and progression of in the setting of inadequate vitamin D. (McAlindon et al. Ann Intern Med. 1996;125:353-359.)

2.  Vitamin D Boost Bone health

Calcium is stored in bones. Optimal amounts of calcium make bones strong. If bone has insufficient calcium than it is weaker and at risk for breaking. Vitamin D stimulates calcium absorption from the gut. If vitamin D levels are sub optimal than less calcium is absorbed and there is less calcium in bones. Calcium deficiency makes osteoporosis and fracture more likely.

Additionally, vitamin D has been shown to promote a healthy immune response to injury and to constrain excessive inflammation; underscoring another mechanism in which vitamin D supports bone health. Chronic inflammation and free radical damage stimulates the activity of cells, called osteoclasts, that actively resorb bone. Increased bone resorption further decrease the strength and density of bone.


Boston researchers demonstrated epidemiological evidence that higher serum vitamin D levels are associated with a greater bone mineral density  in both young and old populations (Bischoff-Ferrari HA, Dietrich T, Orav EJ,et al. Positive association between 25-hydroxy vitamin D levels and bone mineral density: a population-based study of younger and older adults. Am J Med 2004; 116: 634–639.)

3.  Vitamin D Supports Muscle Health

As individuals age they are at risk for a muscle condition called sarcopenia. Sarcopenia manifests as loss of muscle mass, weakness, decreased function, and infiltration of fat into muscle. Unhealthy inflammation is thought to contribute to sarcopenia. Research implies that vitamin D discourages a disproportionate immune response to muscle injury.

Additionally, muscle cells have receptors that are sensitive to vitamin D stimulation. Scientific investigation has demonstrated an association between healthy Vitamin D levels and healthy amounts of type II muscle fiber. Type II muscle fibers are important for strength, muscle mass, and power.


Dutch researchers showed that older adults that had low serum vitamin D concentrations were twice as likely to have sarcopenia over a 3-year follow-up period, when compared with participants who had higher vitamin D concentrations (Visser M, Deeg DJH, Lips P. Low vitamin D and high parathyroid hormone levels as determinants of loss of muscle strength and muscle mass (sarcopenia): the longitudinal aging study Amsterdam. J Clin Endocrinol Metab 2003;88:5766e72.

Other Health Benefits

There are other conditions that vitamin D may assist, although more research is needed and for some conditions results to date have been mixed. Those include:

  • Vitamin D deficiency has been associated with colon cancer, prostate cancer, breast cancer
  • Optimal vitamin D levels promote brain and nerve health
  • Vitamin D supports healthy blood sugar
  • Vitamin D boosts heart function

Rich Sources of Vitamin D

Fortified foods provide the majority of the vitamin D in the American diet. The flesh of fatty fish (such as salmon, tuna, and mackerel) are among top sources.

Recommended daily allowance (RDA)

The Food and Nutrition Board has developed a table of recommended daily allowances (RDAs) of vitamin D, based on age and gender. The values are:








Infants 0–12 months*

400 IU
(10 mcg)



400 IU
(10 mcg)



Toddlers 1–13 years

600 IU
(15 mcg)



600 IU
(15 mcg)



Teens 14–18 years

600 IU
(15 mcg)



600 IU
(15 mcg)

600 IU
(15 mcg)

 600 IU
 (15 mcg)

Adults 19–50 years

600 IU
(15 mcg)



600 IU
(15 mcg)

600 IU
(15 mcg)

 600 IU
 (15 mcg)

Elderly 51–70 years

600 IU
(15 mcg)



600 IU
(15 mcg)



>70 years

800 IU
(20 mcg)



800 IU
(20 mcg)



* Adequate Intake (AI)


Vitamin D from natural foods is generally well tolerated. RDA amounts can be obtained from a balanced, healthful diet and moderate sun exposure. 

The National Institutes for Science has published an upper limit value of 100 mcg or 4000 IU /day. 

Excessive intake of vitamin D may cause blood calcium to reach levels that are dangerous. This high blood calcium level is known as hypercalcemia. The excess calcium is deposited in blood vessels, the heart, and the kidneys. Potentially increasing risk of cardiovascular disease and kidney stones.

Any consideration a supplementation should be discussed with a qualified health professional familiar with your unique medical history.


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 Lucas J. Bader MD

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