The sunshine vitamin health benefits go way beyond bone health

About 35% of Americans are deficient in vitamin D, which can lead to symptoms like fatigue, and cognitive issues beyond bone fragility. However, this statistic is based on a vitamin D level of 30 nmol/L as an adequate level for health. True health benefits are really seen at a much higher level.

Vitamin D is technically a steroid hormone rather than a traditional vitamin. It regulates various cellular processes by binding to the vitamin D receptor (VDR) and modulating gene expression.⁽²⁾

3 Ways to Get Your “D”

Goats, Sunlight, Vitamin D, and Rickets

Back in 1916, Professor Harry Steenbock at the University of Wisconsin had been working with goats and discovered that goats kept outside in the sun maintained a positive calcium balance; conversely, during the winter, when they were kept inside, they displayed a negative calcium balance. He led a series of experiments on other small animals using UV light to determine calcium/phosphorus balance (one of Vitamin D’s main jobs is to facilitate calcium/phosphorous in the small intestine). This led to the discovery that sunlight triggers synthesis of vitamin D in the skin through a positive calcium/phosphorous balance, thereby preventing rickets.⁽³⁾

Foods Rich in Vitamin D

Elmer McCollum identified the dietary component in cod liver oil that cured rickets, naming it vitamin D.⁽³⁾ Foods high in vitamin D are fatty fish, egg yolks, and fortified products, but these often fail to meet daily needs.⁽⁴⁾

Vitamin D Supplements

Vitamin D supplements (especially over-the-counter D3) are effective in raising blood levels and are comparable to sunlight-derived vitamin D.⁽⁵⁾

Activation Process

In order for vitamin D to be bioavailable, it needs to go through a complex process called activation:

• Liver Conversion: Vitamin D is hydroxylated in the liver to form 25-hydroxyvitamin D [25(OH)D], the main circulating form measured in blood tests.
• Kidney Activation: The kidneys convert 25(OH)D into calcitriol (1,25-dihydroxyvitamin D), which binds to VDR to regulate calcium absorption and immune function.⁽⁶⁾

Vitamin D Plays an Important Role In:

• Immune System Modulation: Enhances immune responses and reduces inflammation. May lower risks of autoimmune diseases like rheumatoid arthritis and type 1 diabetes.⁽⁷⁾
• Bone Health: Ensures adequate bone mineralization, preventing rickets, osteomalacia, and osteoporosis.⁽³⁾
• Cardiovascular Health: VDRs in the heart help regulate cardiovascular function, reducing risks of heart attacks and strokes.⁽⁸⁾
• Respiratory Health: Adequate levels may mitigate infections like influenza, tuberculosis and asthma symptoms.⁽⁹⁾
• Glucose Metabolism: Improves insulin sensitivity and supports pancreatic beta-cell function, reducing type 2 diabetes risks.⁽¹⁰⁾
• Cancer Prevention: Higher levels are linked to reduced colorectal cancer risk via inhibition of cancer cell growth and tumor angiogenesis.⁽¹¹⁾ Optimal blood levels for cancer prevention and immune support are 75–100 nmol/L (30–40 ng/mL). Regular monitoring is advised.⁽¹²⁾

Risk Groups for Deficiency

Populations at risk include individuals with limited sun exposure, darker skin tones, older adults, those who are obese (as vitamin D stores in fat and isn’t effectively converted/activated), and those with malabsorption conditions such as kidney disease, celiac disease, or Crohn's disease.⁽¹³⁾

Citations

1. Sizar O, Khare S, Goyal A, et al. Vitamin D Deficiency. (StatPearls)
2. Demer LL, Hsu JJ, Tintut Y. Steroid Hormone Vitamin D: Implications for Cardiovascular Disease. Circ Res. 2018.
3. Deluca HF. History of the discovery of vitamin D and its active metabolites. Bonekey Rep. 2014.
4. Healthline. 7 healthy foods high in vitamin D.
5. Tangpricha V. Vitamin D in food and supplements. Am J Clin Nutr. 2012.
6. Nykjaer A, et al. Renal Uptake and Activation of Vitamin D3. Cell. 1999.
7. Aranow C. Vitamin D and the immune system. J Investig Med. 2011.
8. Judd SE, Tangpricha V. Vitamin D deficiency and risk for cardiovascular disease. Am J Med Sci. 2009.
9. Hughes DA, Norton R. Vitamin D and respiratory health. Clin Exp Immunol. 2009.
10. Angellotti E, Pittas AG. The Role of Vitamin D in Prevention of Type 2 Diabetes. Endocrinology. 2017.
11. Na SY, Kim KB, et al. Vitamin D and Colorectal Cancer. J Cancer Prev. 2022.
12. Balvers MG, et al. Recommended intakes of vitamin D. J Nutr Sci. 2015.
13. Nair R, Maseeh A. Vitamin D: The "sunshine" vitamin. J Pharmacol Pharmacother. 2012.

Written By: Brooke Lounsbury