Vitamin D is Essential for Bone Health

By: Michael (Mike) Shaw, PA-C, ABAAHP

Vitamin D is often referred to as the “sunshine vitamin” because the body produces it when the skin is exposed to UVB rays from sunlight. It triggers the synthesis of vitamin D3 in the body. UVB rays convert a steroid in the skin called 7-dehydrocholesterol into vitamin D3.1 Vitamin D2 is a vitamin we eat while D3 is a hormone produced by our bodies. Vitamin D is one of four fat-soluble vitamins the body needs. A fat-soluble vitamin can be dissolved in fats and oils, absorbed with fats in the diet, and stored in fat tissue in the body. 2

Vitamin D3 helps control how much calcium and phosphate you absorb from food. Calcium is essential for bone health. Phosphate is needed for healthy bones, teeth, muscles, nerves, and basic bodily functions. 3 Vitamin D comes in two forms: Vitamin D2 (Ergocalciferol), which is naturally found in some plants, and Vitamin D3 (Cholecalciferol) in animals and fish. 4 D3 is the preferred supplement form. 5 

There are only a few foods naturally rich in D3. The best sources of vitamin D3 are fatty fish and fish liver oils. Small amounts of D3 can also be found in cheese, beef liver, and egg yolks. 6 In addition, the Food and Drug Administration (FDA) recommends dairy products and cereals to be fortified with vitamin D. 6 Examples of foods high in D3 are salmon, swordfish, tuna, sardines, and cod liver oil. 6 (graphic/element)

Vitamin D Has Been Shown To

Virtually every organ system of the body has receptor sites for the utilization of D3. 7 (graphic/element)

  • Reduce inflammation.
  • Strengthen bones and builds stronger muscles. 
  • Boost immunity and helps the immune system fight viral invasion and bacterial infections.
  • Support autoimmune conditions such as rheumatoid arthritis, psoriasis, and Hashimoto’s thyroiditis. 
  • Improve heart function by strengthening the heart muscle and keeping arteries flexible and relaxed. 
  • Improve mood by lessening depressive feelings.

Two medical conditions resulting from prolonged vitamin D deficiency are rickets and osteomalacia. Rickets is a condition in infants and children of soft bones and skeletal deformities caused by the failure of bone tissue to harden. Osteomalacia is a condition in adults of weak and softened bones that can be reversed with D3 supplementation. 8

The FDA’s Recommended Dietary Allowance of vitamin D3 for adults 19 years and older is 600 IU daily for men and women and adults over 70, 800 IU daily. 9 The FDA Tolerable Upper Intake Level of D3 for children ages 9+ and adults is 4,000 IU. 9 

The reference range for 25 HydroxyD3 at Quest10 and LabCorp,11 the two largest labs in the country, is 30 to 100 ng/ml. Riordan Clinic Bio-Center Laboratory reference range is 40 to 80 ng/ml. Achieving a level of 70 or above is considered optimal. 

Most new patients at Riordan Clinic have low reference range levels or are deficient in D3 unless they are on supplementation. Patients with a D3 level in the low to mid reference range are recommended to start 5,000 IU D3/K2 daily. For overtly deficient patients, the recommendation is 10,000 IU D3/K2 daily. After three months, a recheck of the blood level is recommended to achieve the target goal.

Vitamin D3 is one of five nutrients comprising my top five supplements supporting health and longevity. It is easy to achieve a functional vitamin D level through well-tolerated supplementation. It should be a part of everyone’s supplement program. The payback is significant, and the cost and effort is minimal. If you are not currently taking D3, start today!


  1. Wacker M, Holick MF. Sunlight and Vitamin D: A Global Perspective for Health. Dermatoendocrinol. 2013;5(1):51-108. doi:10.4161/derm.24494
  2. National Research Council (US) Committee on Diet and Health. Diet and Health: Implications for Reducing Chronic Disease Risk. Washington (DC): National Academies Press (US); 1989. 11, Fat-Soluble Vitamins. Available from:
  3. “Vitamin D.” The Nutrition Source, Harvard School of Public Health, Jan. 2022,
  4. Arnarson, A. (2018, March 4). Vitamin D2 vs. D3: What’s the Difference? Healthline. Retrieved May 18, 2022, from 
  5. Gonzalez, C. (2010, October 20). Vitamin D Supplementation: An update. U.S. Pharmacist – The Leading Journal in Pharmacy. Retrieved May 18, 2022, from,blood%20concentration%20of%20vitamin%20D
  6. Harvard School of Public Health. (2022, May 17). Vitamin D. The Nutrition Source. Retrieved May 18, 2022, from,%2C%20cheese%2C%20and%20beef%20liver
  7. Di Rosa, M., Malaguarnera, M., Nicoletti, F., & Malaguarnera, L. (2011). Vitamin D3: A Helpful Immuno-modulator. Immunology, 134(2), 123–139.
  8. “Vitamin D.” The Nutrition Source, Harvard School of Public Health, 17 May 2022,,%2C%20cheese%2C%20and%20beef%20liver
  9. Vitamin D Fact Sheet for Health Professionals. National Institutes of Health. August 17, 2021.  
  10. “QuestAssureD™ 25-Hydroxyvitamin D (D2, D3).” Quest Diagnostics: Test Directory,
  11. “Vitamin D Testing: Assessing Vitamin D Sufficiency in Your Patients.”,