Vitamin D rich foods – Image credit – Wiki Health

By Gunda Siska, PharmD – Pharmacy Times

Sept. 20, 2019 – Vitamin D helps our immune systems stay balanced during the cold and flu season, and serve as a pharmacy resource.

There are Vitamin D receptors and activating enzymes on the surfaces of all white blood cells.The role that vitamin D plays in keeping the immune system healthy is very complex because the immune system has to be perfectly balanced. If there is too much stimulation, autoimmune diseases can set in. If there is not enough immune system activity, frequent infections can occur.Low levels of vitamin D have been linked with both extremes, and low levels of vitamin D have been associated with worsening autoimmune diseases.Low levels of vitamin D are not the underlying cause of the autoimmune disease, but low levels of vitamin D can make autoimmune disease states worse.
Low levels of vitamin D have also been associated with frequent infections. In 2009, the National Institute of Health warned that low vitamin D levels are associated with frequent colds and influenza.And so it appears that vitamin D helps keep the immune system balanced much like a gymnast walking on a balance beam. Since the NIH announcement, there have been many studies to determine the best regimen of vitamin D supplementation and to better understand this association.

In 2017, a large analyses of prospective clinical trials showed that taking vitamin D reduces the odds of developing a respiratory infection by approximately 42 percent in people with low baseline levels of 25-hydroxyvitamin D; below 25 mg/mL. The analysis suggests that taking vitamin D daily or weekly was more effective than larger doses taken in single or monthly boluses. The most common daily dose used was vitamin D3 300-4,000 IU. In a recent study, researchers found monthly high-dose vitamin D supplementation does not prevent acute respiratory infections in older adults with low levels of vitamin D. They performed a randomized, double-blinded, placebo-controlled trial of 5110 adults. Participants were given 200,000 IU vitamin D3 followed by 100,000 IU monthly (n=2,558) or placebo (n=2,552) for a median follow-up 1.6 years.
Study participants reported upper and lower acute respiratory infections on monthly questionnaires. A slightly higher majority (74.1%) of vitamin D users reported at least 1 respiratory infection, whereas 73.7 percent of the placebo group reported at least 1 respiratory infection. The hazard ratio for vitamin D compared to placebo was 1.01 (95%CI, 0.94, 1.07).

During the flu season, it is important for pharmacists to convey that daily and weekly vitamin D supplementation helps keep the immune system balanced during the cold and flu season. 



Here below is a summary of information on Vitamin D: 

Vitamin D is a group of fat-soluble secosteroids known as the “sunshine vitamin”, vitamin D is available in two major forms: vitamin D2 AKA Ergocalciferol and vitamin D3 AKA Cholecalciferol.

Vitamin D, if not referred to otherwise, is in the form or either vitamin D2, D3 or both forms. Vitamin D3 is created in the skin of vertebrates after exposure to UVB light from the sun and is also available in foods or in supplemental form.

Health Benefits

There are various health benefits offered with vitamin D including to but not limited to boosting the immune system, fight off viral infections, limit inflammation in the body, strengthens bones, protects against various forms of cancer, prevents and treats both Type I & II diabeteshypertension, glucose intolerance, multiple sclerosis, various autoimmune diseases, schizophrenia, and other medical conditions.

Vitamin D supplements provide various benefits in people with tuberculosis. The vitamin may also help prolong life, assist with breathing ability in asthma sufferers and helps form and maintain bones.

Beauty Benefits

There are many beauty benefits associated with consuming vitamin D such as the treatment of psoriasis, plays a large role in skin cell metabolism and maintenance, treatment of itchy, flaky skin, acts as a powerful antioxidant which protects against free radical damage, prevents premature aging and damage to skin, and has been shown to help reduce dark circles around the eyes.

Food Sources

Vitamin D exists naturally in human absorption of the sunlight, but is also available in a variety of food sources including but not limited to:

  • Catfish
  • Salmon
  • Mackerel
  • Sardines
  • Tuna
  • Eel
  • Fortified Milk
  • Eggs
  • Shrimp
  • Cod Liver Oil
  • Mushrooms

Daily Dose Recommendations

  • Infants & Children: Up to 13 Years 5 Mcg/ Day, 14-18 Years 5 Mcg/Day
  • Adults: 19-50 Years 5 Mcg/Day, 51-70 Years 10 Mcg/Day, 71+ Years 15 Mcg/Day


Side Effects

Toxicity of vitamin D can occur from over intake of vitamin D2 which is available from plants or vitamin D3 which is available from animal sources. Symptoms include nausea, vomiting, high blood pressure, loss of appetite, kidney malfunction, depression, and illness.


The most common deficiency is caused by lack of exposure to sunlight and can be remedied by increasing your time in the sun, ingesting foods with vitamin D or taking a vitamin D supplement.