The sunshine gives me an overall feeling of well-being. I can feel it in my bones, heart and mind. The common denominator is vitamin D. Vitamin D exposure has an influential role in osteoporosis and may have a role in preventing heart failure and enhancing mood. The sources of vitamin D are sunlight, diet, prescription and supplements.
Sun exposure for vitamin D production in the body has many variables that must be considered. There are vitamin D receptors in the skin cells, and vitamin D production starts with cholesterol conversion to vitamin D3 in the skin when exposed to ultraviolet B (UVB) light from the sun. Vitamin D is then stored in fat cells and used by the body when needed. This form of vitamin D is called calcitriol. The question is how much skin exposure to the sun will give us enough vitamin D for a healthy life. Vitamin D deficiency is seen in the elderly who are homebound, people living north of the 34th latitude, seasonal differences (more exposure from spring to early fall), time of the day, clothing covering the arms and legs and the use of sunblock (Holick MF, Am J Clin Nutr. 2004 Dec; 80 (6 Suppl):1678-88S). A study was conducted primarily to analyze the prevalence of vitamin D deficiency in the United States based on the latest published data collected by NHANES 2011-2012. Of the 4,962 participants surveyed and examined, 1,981 (39.92%) were found to be vitamin D deficient.
Dietary intake can play a role in increasing our vitamin D levels. Our dietary choices are vitamin D–rich foods and foods enriched with vitamin D. The highest amounts of vitamin D are seen in fatty fish, which includes herring, salmon, halibut, channel catfish and tuna. Lower amounts of vitamin D are seen in foods such as yogurt and vitamin D–enriched milk and cereals.
The supplemental vitamin D choices are cholecalciferol (vitamin D3) and ergocalciferol (vitamin D2). Dosing ranges of vitamin D3 are 600–4,000 international units (IU) daily. Doses of vitamin D2 range from 50,000–200,000 IU daily. The most used form of vitamin D is cholecalciferol, and it is the same form produced in the human body. Cholecalciferol is 1.7–3 times more potent and has a longer effect than ergocalciferol in the ability to increase the serum 25-hydroxyvitamin D levels in the body.
The Office of Dietary Supplements of NIH recommendation for vitamin D intake for adults 19–70 years of age is 600 IU daily, 71 years of age and greater 800 IU daily, pregnant and breastfeeding teens and adults 600 IU per day. Vitamin D levels (25-hydroxy-vitamin D) are ordered to assess if a patient is vitamin D deficient. High-risk patient populations for vitamin D deficiency include osteoporosis, black and Hispanic people, obesity (BMI > 30 kg/m2), chronic kidney disease, anorexia nervosa, gastric bypass surgery, malabsorption syndromes and people who wear total skin coverage.
Osteoporosis patients were my first exposure to vitamin D supplementation. Calcium salts and vitamin D combination products have been and are being utilized to increase bone density and a decrease in fractures. Vitamin D helps regulate calcium absorption in the intestine, which leads to increased bone absorption of calcium. Vitamin D deficiency causes the osteoclasts in the bone to break down the bone matrix, leading to bone loss. A meta-analysis of randomized, controlled fracture prevention trials with vitamin D reported that oral vitamin D supplementation between 700 and 800 units per day appeared to reduce the risk of hip and any nonvertebral fractures in ambulatory or institutionalized elderly persons. A vitamin D dose of 700 to 800 units per day reduced the relative risk of hip fracture by 26% and any nonvertebral fracture by 23% (JAMA 2005, May 11;293(18):2257-64).
Vitamin D supplementation has been studied in heart failure in addition to the evidence-based medications that are prescribed. Patients with heart failure, especially if they have a poorly pumping left ventricle, will have a thickened left ventricle. To compensate for a poorly functioning left ventricle the heart muscle will stretch and get fibrosed (thicker), a condition called ventricular remodeling. Seven randomized controlled trials, with a total of 465 patients, including 235 cases in the vitamin D group and 230 cases in the control group, were included in a study. The primary and secondary endpoints were the size of the left ventricle (left ventricular end diastolic dimension), how the ventricle pumped, called left ventricular ejection fraction, and adverse reactions. High-dose vitamin D (>4000 IU/day) was more effective at reducing the left ventricular dimension than low-dose vitamin D (<4000 IU/day). Vitamin D supplementation increased the pumping action of the heart in patients with reduced ejection fraction. Vitamin D supplementation was found to inhibit the remodeling of the left ventricle and improve its function (BMJ Open. 2018 Aug 30;8(8):e020545). At this time vitamin D does not seem to change the risk of death in heart failure. More studies are needed to validate if vitamin D has a role in heart failure therapy.
Those of us who live north of the 34th latitude have a higher risk of vitamin D deficiency in the winter months. We also have a higher risk of seasonal affective disorder (SAD). One of the treatments for this disorder is UV light. One of my co-workers would do a session of UV light each day during their lunch hour. They felt less depression during the winter months when using the UV light therapy. A study of 15 participants with SAD were randomized to either 100,000 IU of vitamin D (one time dose) (n = 8) or phototherapy (n = 7). They reported that depression (assessed with the Hamilton Depression Scale) decreased in persons who received vitamin D (from 10.9 to 6.2, p = .040) as compared to those who received phototherapy (from 12.6 to 11.3, p = ns). There were no untoward side effects from the dose of vitamin D. The limitation of this study was the vitamin D dose was given once and not a daily dose. More studies need to be done to see how vitamin D may affect mood.
Vitamin D is a fat-soluble vitamin and is not without toxicities. A few of the side effects seen with toxicity are accumulation of calcium in the blood (hypercalcemia), nausea and vomiting, weakness, and frequent urination. Vitamin D toxicity might progress to bone pain and kidney problems, such as the formation of calcium stones.
The role of vitamin D is food for thought. We have been cooped up in our homes during the pandemic and these past winter months. Hopefully we are all getting out for some sun exposure and exercise. Please consult your physician if you are concerned you may be vitamin D deficient. Your healthcare giver will be more than happy to discuss and evaluate if you may be vitamin D deficient. Be well and safe.