How the “Sunshine Vitamin” Supports Immunity

By: Patience Lister

It’s easy to take the “sunshine vitamin” for granted during the summer months. All that time spent outdoors exposed to the sun’s ultraviolet rays helps fuel our bodies’ production of vitamin D. But as the weather cools and we settle into the short, darker days of autumn and winter, we become more reliant on our diets to provide adequate levels of vitamin D. Because of its role in immune function, keeping your vitamin D intake up is especially critical this time of year as cold and flu viruses become more prevalent.

Vitamin D 101

Vitamin D is a fat-soluble vitamin found in oily fish such as salmon, mackerel, and herring, as well as egg yolks, organ meats, and some mushrooms. It’s also made naturally in the skin from exposure to the sun’s ultraviolet rays, hence the name “sunshine vitamin”.[1]

Vitamin D exists as either vitamin D2 or D3. The D3 cholecalciferol form, produced by the body and found in animal products, is recognized as the more biologically active form. Its receptors are found throughout the body and it has many important functions, such as assisting with calcium and phosphate absorption to support healthy bones and teeth, helping muscle function and proper nerve transmission, gene regulation, insulin production, and supporting cognitive well-being.[2]

Vitamin D supports immune function

Vitamin D is one of the key vitamins required for healthy immune function, and has been used therapeutically for infections since the mid-1800s in the form of cod liver oil.[3] All you need to do is tally up the wide scope of vitamin D receptors found throughout the immune system to confirm its importance in supporting both the innate and adaptive aspects of immunity.[4]

The impact that inadequate vitamin D intake has on immunity begins early in life and continues through old age. Babies with low blood levels of vitamin D are more susceptible to respiratory tract infections during their first six months of life.[5] Additionally, elderly people deficient in vitamin D are more prone to complications from influenza infections.

Vitamin D deficiency is also a risk factor for some chronic health problems, including autoimmune disorders and heart conditions.1,[6]

How much vitamin D do we need?

Despite its importance for many aspects of health, some Canadians do not get enough vitamin D through their diet or sun exposure. More than one in four Canadians age three to 79 do not have adequate vitamin D levels. This is especially noteworthy in youth and young adults age 12–35, where 38% of people are not getting enough vitamin D.[7]

The recommended daily intake of vitamin D is:[8]

  • 400 IU for infants aged 0 to 12 months
  • 600 IU for children over 1 year and adults
  • 800 IU for adults over 70 years
  • 600 IU during pregnancy and lactation

Elderly people are at a greater risk of not getting enough vitamin D because the body is less able to make vitamin D as we age. Additionally, people with lactose intolerance, breastfed infants, and individuals with darkly pigmented skin are more likely to need additional vitamin D in their diets.

A daily dose of SunVitamin

Although vitamin D can be obtained from the diet, there are a limited number of foods found in nature that contain sufficient levels. Similarly, sun exposure is not a reliable way to maintain adequate levels, especially with regular use of sunscreen that blocks UVB rays, for people living at northern latitudes, people with dark skin, and pregnant women.1,[9]

Taking a daily vitamin D3 supplement, such as SunVitamin D3, is a convenient and reliable way to meet your body’s requirements for maintaining overall health. SunVitamin D3 provides the natural cholecalciferol (D3) form of vitamin D to support healthy immune system function. Each liquid softgel contains 1000 IU of vitamin D3 in a base of organic flaxseed oil for enhanced absorption and contains no GMOs. It is also a vegetarian-friendly choice.

If you’re concerned about your exposure to cold and flu viruses and you want to keep your immune system working at its best, then vitamin D should be near the top of your list of nutrients to consider. Your diet and the amount of time you spend out in the sun are good indicators of whether you’re getting enough. If you’re not, a daily vitamin D supplement is a simple way to fulfill your body’s requirements and support a healthy, well-functioning immune system.


[1] Nair R, Maseeh A. Vitamin D: The “sunshine” vitamin. J Pharmacol Pharmacother. 2012; 3:118-26.

[2] Bikle DD. Vitamin D metabolism, mechanism of action, and clinical applications. Chem Biol. 2014; 21:319-29.

[3] Kamen DL, Tangpricha V. Vitamin D and molecular actions on the immune system: modulation of innate and autoimmunity. J Mol Med (Berl), 2010; 88:441-50

[4] Prietl B, Treiber G, Pieber TR, et al. Vitamin D and immune function. Nutrients. 2013; 5:2502-21.

[5] Hong M, Xiong T, Huang J, et al. Association of vitamin D supplementation with respiratory tract infection in infants. Maternal & Child Nutrition. 2020; 16 :e12987.

[6] Fletcher J, Cooper SC, Ghosh S, et al. The role of vitamin D in inflammatory bowel disease: Mechanism to management. Nutrients. 2019; 11:1-16.

[7] Statistics Canada. Canadian Health Measures Survey: Non-environmental laboratory and medication data, 2016 and 2017 [Internet]. Statcan.gc.ca 2019 [cited 18 September 2020]. Available from: https://www150.statcan.gc.ca/n1/daily-quotidien/190206/dq190206c-eng.htm

[8] Government of Canada. Vitamin D and Calcium: Updated Dietary Reference Intakes [Internet]. Camada.ca 2020 [cited 10 September 2020]. Available from: https://www.canada.ca/en/health-canada/services/food-nutrition/healthy-eating/vitamins-minerals/vitamin-calcium-updated-dietary-reference-intakes-nutrition.html#a10

[9] Farrar MD, Mughal MZ, Adams JE, et al. Sun exposure behavior, seasonal vitamin D deficiency, and relationship to bone health in adolescents. J Clin Endocrinol Metab. 2016; 101:3105-13.

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