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,