Vitamin D, also known as the sunshine vitamin, is an incredibly key nutrient for most all of our bodies’ functions, cell growth, and maintenance. This important vitamin has been shown to prevent cancer and osteoporosis, increase immune health, support mood and depression, and studies have shown that it can even help in the prevention of type I diabetes.

There is a lot of talk nowadays about vitamin D deficiency and supplementation, and this is not a topic to be taken lightly! Vitamin D deficiency is shockingly common for various reasons (which we’ll look at in a moment), and symptoms can be serious. However, it is of utmost importance that we do our research and understand which crucial functions this vitamin carries out in the body, consider if we might be deficient (and perhaps invest in testing), and know how to safely and effectively supplement.

First and foremost, let’s begin by looking at several of the key roles vitamin D plays. Interestingly, unlike most other vitamins, vitamin D is actually a steroidal hormone that is most effectively produced by the body with adequate sun exposure. Vitamin D has been shown to provide the following:

•Bone strengthening, prevention of osteoporosis, and bone fractures

•Increased immune health

•Increased mood and support for depression

•Prevention of cancer

•Prevention of Type I diabetes

In addition, the body cannot properly absorb calcium without appropriate vitamin D levels. Remember that vitamins and minerals do not work in isolation, but rather compliment each other and work in conjunction.

Now, let’s dive into how vitamin D is processed by the body and its’ various forms. Similarly to vitamins A, E and K, vitamin D is a fat-soluble vitamin, meaning it absorbed in the presence of fat and stored in our body for extended periods of time. In fact, if we expose ourselves to adequate levels of direct sunlight for a period of time, we might be okay going for a stretch of weeks or even months with acceptable vitamin D levels in periods of no or little sunshine. The two main forms of vitamin D are vitamin D2 (ergocalciferol) and D3 (cholecalciferol). Vitamin D3 is the more biochemically active and readily absorbed form, which makes it more valuable when choosing a supplement than its’ D2 counterpart.

When Vitamin D enters the body, it is first broken down and converted by the liver to its’ storage form, calcidiol. Next, it passes through the kidneys where it is converted to its biologically active form, calcitriol. Now it is ready to be escorted throughout the body to all of our cells’ VDRs (vitamin D receptors), where it actually has been shown to affect gene expression (turning on and off certain genes, such as those linked to cardiovascular disease and cancer).

How do I know if I am vitamin D deficient?

First of all, it is important to understand that vitamin D deficiency is quite common. A 2011 study, 42% of the U.S. population is deficient, and more specifically 82% of African Americans and 70% of Hispanics. Deficiency could manifest with the following symptoms:

•Depression and mood disorders

•Increased risk of cardiovascular disease


•Muscle weakness

•Bone pain

•Getting sick often and slow recovery time

•Rickets, a bone disease common in children living in developing countries.

Those living in colder climates are more susceptible to vitamin D deficiency, although many tropical cultures often go to great lengths to stay out of the sun, even though sunlight is readily available. It is absolutely important to avoid burning; however, exposing as much skin as possible to direct sunlight most days of the week can boost our vitamin D to appropriate levels. The amount of exposure an individual needs really varies on factors such as skin color, geographic location (how strong the sun is), and time of day. Once the skin turns just slightly pink (without burning), this is typically the appropriate time to either leave the sun or apply sunscreen.

The RDA (recommended daily allowance put forth by the Institute of Medicine) for vitamin D is as follows:

• 400 IU (10 mcg): Infants, 0-12 months.

• 600 IU (15 mcg): Children and adults, 1-70 years of age.

• 800 IU (20 mcg): Elderly and pregnant or lactating women.

Many professionals see these levels as quite low, and would say that most people can safely supplement with between 1,000-4,000 IU per day, as opposed to the 400-600 IU RDA.

The good news for vitamin D deficiency is that testing is widely available and relatively inexpensive. Your doctor or healthcare professional should be able to provide a test that looks at 25-hydroxy D levels in the blood, or you can even purchase an at-home testing kit such as this option created by the Vitamin D council. However, it is certainly best to interpret your results with a doctor or trusted practitioner, in order to determine appropriate supplement dosing.

Are there food sources of vitamin D?

The short answer to this question is yes, there are foods that contain vitamin D. However, one of the primary reasons vitamin D deficiency is so common is that it is quite difficult to obtain enough from food sources alone. If you have eaten a whole foods diet rich in vitamin D containing foods your entire life, you might be able to sustain good levels between diet and sun exposure. However, if you have a history of eating a diet high in processed/packaged foods and live in a colder climate, supplementation is likely necessary. Here are the foods highest in vitamin D, in this order:

•Salmon (3 oz.=75% of the RDA)


•Beef liver

•1 whole egg (yolk and whites)

•1 can of sardines

•1 tbsp. cod liver oil (over 200% of the RDA)

So, unless you can commit to eating salmon just about every day, reaching optimal vitamin D levels can be tough. Here is a high quality fermented cod liver oil supplement to consider by GreenPasture, which is a safe and effective food-based method of supplementing.

Vitamin D is a fascinating nutrient that serves many important functions. Considering the above-mentioned factors that potentially put you at risk for deficiency, you can make an educated decision about the next best step. Beginning with vitamin D testing is never a bad idea, and from there determining if supplementation is right for you. And while it isn’t easy to reach optimal levels from food sources alone, remember that eating a varied diet rich in real, whole foods is important for so many reasons, vitamin D levels just being one.



*Disclaimer: This info is not intended to be a substitute for the medical advice of a licensed physician. Please consult with your doctor in any matters relating to your health.

Rachel Fiske, NC, CPT-NASM Rachel Fiske is a Holistic Nutrition Consultant and graduated from Bauman College of Holistic Nutrition in Berkeley, California, and a Certified Personal Trainer through the National Academy of Sports Medicine. Rachel works with clients individually via skype, focusing on issues of weight management, GI problems, hormonal imbalances, fatigue and more via a whole foods diet and lifestyle changes. Consultations include diet journal analysis, individualized menu planning, and herbal/supplementation protocols.