Low energy, low mood, and a general under-the-weather feeling in winter’s cold, dark months could be a symptom of anything from a mood disorder to the flu, but it could also be a vitamin D deficiency. A simple blood test from your doctor can help you determine if that’s the case.

How should I get my D?

The most natural way to get the amount of vitamin D your body needs to thrive is by standing outside in the sunlight. Human skin has the ability to make vitamin D3, or cholecalciferol, from a reaction with ultraviolet B (UVB) rays. The more skin you expose, the more vitamin D you will make. This does not mean that laying out until you are crisp with sunburn is good for you, but spending half the amount of time it takes for a burn is a good rule-of-thumb for vitamin D production, according to the Vitamin D Council [1]. We all burn at different rates though, right? Yes. The skin pigment that proportionally makes our skin darker, melanin, blocks UV rays and protects skin from burning, but it also prevents some vitamin D production. This means paler skin needs less exposure time to build up vitamin D than darker skin. This also means, people with darker skin are at greater risk of becoming vitamin D deficient when they live in certain parts of the world, or live a particular lifestyle, where extended bare-skin sun exposure is inconvenient, unlikely, or impossible.

What are contributing factors to deficiency of D?

The reason many people are at risk for vitamin D deficiency is that during winter months there are fewer hours of sunlight every day, so there are fewer opportunities to spend time in the sun (of course, the distance between your home and the equator affects the magnitude of this effect). If you live in an area where winter is cold, many people generally stay indoors, or bundle up. This means less skin is exposed, even if you get outside during the day. Let’s not forget that many people work indoors during sunlight hours and do not have the option for exposure. Glass windows block UVB rays, so sitting indoors in a sunny spot is still not effective. Others work nights and must sleep during sunlight hours. Air pollution can block UVB rays from skin if you live in a smoggy area, and clouds can block UVB rays if you live in a foggy area. Just to add insult to injury, aging also contributes to vitamin D deficiency. Our skin slows down its vitamin D production as we age. It’s nearly impossible to get enough sunlight in this day and age to maximize natural vitamin D production. And unfortunately, foods containing vitamin D just can’t balance out this loss of sunlight [1].

Add on top of all this what we know about skin cancer. Skin cancer is potentially life threatening. Because of this fact, more and more people are choosing to stay out of the sun completely, or slather skin with sunblock or sunscreen before any exposure. These SPF creams and lotions block skin from UVB needed for vitamin D production and could actually be the cause of vitamin D deficiency in some people while simultaneously saving skin from cancer.

Why do we need vitamin D?

Vitamin D is unique, not only because we make it in response to sunlight, but also because it acts as a hormone once it is absorbed [2]. You may have thought vitamin D was just for healthy bones, but the liver converts it into a hormone/secosteroid whose receptors are located throughout the brain. You need vitamin D for healthy brain development, maintenance, and functions from mood, to learning, to memory [3]. This why feeling blue, foggy, or low in the wintertime can sometimes be attributed to vitamin D deficiency.

Vitamin D must be present in adequate levels for the gut to absorb calcium and phosphorus, minerals that are critical for building and maintaining strong bones. Because of this relationship, vitamin D deficiency can play a major role is children developing rickets, adults developing osteomalacia, and elderly adults developing osteoporosis [4]. Aside from brain and bone health, vitamin D great influence over the function of the immune system, has anti-inflammatory properties, and modulates cell growth [4]. 

The vitamin D receptor has been found all over the body in various tissues and cell types. Of particular interest to many scientists is the role vitamin D plays in the cardiovascular system. Cross-sectional studies have shown that vitamin D deficiency is associated with increased risk of cardiovascular diseases, including hypertension, heart failure, and ischemic heart disease [5]. Although the mechanisms mediating these associations have yet to be elucidated, there are several strong hypotheses. It is clear, however, that vitamin D is linked to cardiovascular health.

I’m not a sun worshiper, how can I get more D?

Make a vitamin D supplement part of your regular health regimen. The Vitamin D Council states that sun exposure and supplements are the only effective ways to get enough vitamin D. You just can’t get enough vitamin D from diet alone. There are competing recommendations on the amount of vitamin D each person should be taking, so as always, please consult your physician before committing to a dose. Metabolic Maintenance offers vitamin D-3 (a more potent and natural form of vitamin D than D-2) in doses of 2000 IU, 5000 IU, 10,000 IU, or 25,000 IU so you can easily choose the most appropriate dose to supplement your sun exposure.


  1. Vitamin D Council: “About Vitamin D: ‘How do I get the vitamin D my body needs?’” Accessed Jan. 29, 2019. https://www.vitamindcouncil.org/about-vitamin-d/how-do-i-get-the-vitamin-d-my-body-needs/
  2. Vitamin D and Health: Vitamin D Sources and Function. Harvard T.H. Chan School of Public Health. Accessed Jan. 29, 2019. https://www.hsph.harvard.edu/nutritionsource/vitamin-d/#vitamin-d-sources-and-function
  3. Rowe, Keith. “How to Boost Your Mood With Vitamin D.” Brain MD. Feb 2018. https://www.brainmdhealth.com/blog/how-to-boost-your-mood-with-vitamin-d/ 
  4. Vitamin D Fact Sheet for Health Professionals. National Institutes of Health Office of Dietary Supplements. February 11, 2016.
  5. Judd, Suzanne E., and Vin Tangpricha. “Vitamin D deficiency and risk for cardiovascular disease.” The American journal of the medical sciences 338.1 (2009): 40-44.