Vitamin D

Research Library

This scientific research is for informational use only. The results reported may not necessarily occur in all individuals. Care/of provides this information as a service. This information should not be read to recommend or endorse any specific products.

Vitamin D3 is essential for bone health and many of us simply don’t get enough of it.* The best source of Vitamin D3 is from direct sunlight; however, many people don’t get enough exposure to direct light as they would need to meet their vitamin D needs. Additionally, as we age, the capacity of our skin to synthesize Vitamin D3 decreases. Vitamin D3 is not highly prevalent in many foods, although many milk products on the market are fortified with Vitamin D. People who are lactose intolerant and those who don’t get enough sunlight may be at risk of deficiency.


Vitamin D is found in our diet, but we also produce it through exposure to sunlight. However, a number of factors impact the ability for people to get necessary levels of vitamin D through sun exposure.

Regional factors that prevent people from getting sun exposure include cloud cover patterns, smog, and the angle with which the sun hits the earth. In cities north of 37 degrees latitude (imagine a line drawn between San Francisco and Richmond, VA), it’s hard for people to produce enough vitamin D from sun exposure, especially between the months of November and March.

The ability for skin to absorb light also impacts how well people can produce vitamin D, as does the use of sunscreen and the number of hours per day spent inside. It should be noted that UVB rays necessary to produce vitamin D do not penetrate glass, so sitting near a window indoors won’t help you produce sufficient vitamin D.

  1. Vitamin D - Fact Sheet for Health Professionals

    National Institute of Health - Office of Dietary Supplements, National Institute of Health - Office of Dietary Supplements, 2016

Supports immune system

Using a randomized, placebo-controlled, double-blind design, researchers studied the effects of vitamin D supplementation in pregnant women and found that there was an effect on regulatory immunity. Supplementation of 2,000 IU vitamin D produced a significant increase in the concentration of IL-10+ CD4+ cells in the peripheral blood. Women that took 2,000 IU daily saw an increase of 27% from baseline to their third visit (1)

Vitamin D3 has been shown to act at the first stage of the body’s immune response. Researchers studied the effects of vitamin D3 on dendritic (immune) cell differentiation, maturation, and function and concluded that vitamin D3 inhibits a full differentiation of monocytes into dendritic cells and does not promote their differentiation into macrophages. Cellular differentiation is the process during which young, immature cells take on individual characteristics and reach their mature form and function (2).

Authoritative bodies outside the United States have recognized the relationship Vitamin D plays with the immune system. The European Food Safety Authority Panel on Dietetic Products, Nutrition and Allergies (NDA) concluded that a cause and effect relationship has been established between the dietary intake of vitamin D and contribution to the normal function of the immune system and healthy inflammatory response (3). Additionally, Health Canada corroborates that vitamin D helps to maintain/support immune function (4).

  1. Daily cholecalciferol supplementation during pregnancy alters markers of regulatory immunity, inflammation, and clinical outcomes in a randomized, controlled trial

    Zerofsky MS, Jacoby BN, Pedersen TL, Stephensen CB, JN, 2016

  2. Vitamin D3 affects differentiation, maturation, and function of human monocyte-derived dendritic cells

    Piemonti L, Monti P, Sironi M, Fraticelli P et al, J Immunol, 2000

  3. Scientific Opinion on the substantiation of health claims related to vitamin D and normal function of the immune system and inflammatory response (ID 154, 159), maintenance of normal muscle function (ID 155) and maintenance of normal cardiovascular function (ID 159) pursuant to Article 13(1) of Regulation (EC) No 1924/2006

    EFSA 2010: European Food Safety Authority (EFSA), EFSA Journal, 2010

  4. Multi-Vitamin/Mineral Supplements Monograph

    Health Canada, 2018, 2018