The Essential Guide to Vitamin D

Vitamin D is a nutrient for overall well being. It is often referred to as the “sunshine vitamin” because our skin produces it when exposed to sunlight. Having sufficient levels of vitamin D is linked to bones improved function, better mood and potentially lower risks of serious ailments such as osteoporosis, cancer, diabetes and autoimmune diseases. Surprisingly deficiency in this vitamin is quite widespread with an estimated 30-50% of adults not getting enough. Continue

reading to learn why our bodies require vitamin D discover the food sources identify those at risk of having levels and explore science backed strategies for optimizing your vitamin D status.

What is Vitamin D and Why Do We Need It?

Vitamin D stands out among other vitamins as it acts more like a hormone, in our bodies. There are two forms of vitamin D;


  1. 1. Vitamin D2 (ergocalciferol): Found in plant based foods and supplements. However its not absorbed effectively as the form.

  2. 2. Vitamin D3 (cholecalciferol): This form occurs naturally in our skin when exposed to sunlight. It can also be obtained from animal based foods and supplements. This particular form is preferred for supplementation purposes.

When we obtain vitamin D from sunlight exposure, food or supplements it undergoes two conversion processes, within our bodies. First in the liver vitamin D is transformed into 25 hydroxyvitamin D, which's the form circulating in our system and used to determine our vitamin D levels. Then in the kidneys 25 hydroxyvitamin D is converted into its form known as 1,25 dihydroxyvitamin D.


Vitamin D interacts with receptors present throughout our body and influences the expression of numerous genes. Vitamin D plays roles in:

  1. 1. Bone health: Active vitamin D facilitates the absorption of calcium from food and its deposition into bones. It works together with calcium to promote bone growth and strengthen them.

  2. 2. System regulation: Vitamin D affects the functioning of cells by reducing excessive inflammation. This helps maintain an response while preventing autoimmune disorders.

  3. 3. Cell growth: Active vitamin D regulates cell growth and differentiation processes within our body. This may contribute to safeguarding against types of cancers.

  4. 4. Muscle functionality: Vitamin D receptors are found in muscles and insufficient levels of this nutrient have been associated with fatigue and weakness.

Considering these ranging functions of vitamin D it becomes evident that maintaining levels is essential for overall health.

What leads to a deficiency in Vitamin D?

Given the functions that vitamin D carries out one might assume that vitamin D deficiency is uncommon. However, that is not the case.


  • Older adults: As we get older our skin becomes less efficient at producing vitamin D from sunlight and our kidneys convert less of it into its active form.

  • People with dark skin tones: Greater melanin reduces vitamin D production from sun exposure.

  • Those who are overweight or obese: Excess body fat traps vitamin D so less is available to enter circulation.

But arguably, one of the most common reasons for vitamin D deficiency is inadequate sun exposure. Indoor lifestyles coupled with concerns about skin cancer have led many people to limit direct sun exposure. Additionally, those living farther from the equator during winter months won’t get enough UVB rays required for vitamin D synthesis.


Lets delve deeper into why relying solely on sun exposure often falls short when it comes to maintaining optimal levels of vitamin D.

Why Sun Exposure Isn’t Enough

When our skin is exposed to UVB rays, from the sun our bodies produce vitamin D3. However there are factors that influence the amount of vitamin D produced:

  • Time of Day and Season: The sun must be high enough in the sky for UVB rays to penetrate the atmosphere. This only occurs for a portion of the day and varies by latitude and season.
  • Geography/Climate: Proximity to the equator and cloud cover influence UVB exposure and vitamin D production. Increased pollution also absorbs UVB rays.
  • Skin Pigmentation: Pale skin is more efficient at generating vitamin D from sunlight compared to darker skin tones due to melanin competing with vitamin D synthesis.
  • Sunscreen Use: Using sunscreen with a sun protection factor (SPF) can hinder vitamin D production through the skin. Both chemical filters and mineral blockers found in sunscreens are effective in blocking UVB rays.
  • Age: As we age our skins ability to convert UVB rays into vitamin D decreases due to the loss of key precursors in the skin.
  • Body Composition: Higher levels of body fat and higher body mass indexes (BMIs) have been associated with levels of vitamin D. Fat cells tend to store circulating vitamin D making it less available for use by our bodies. Given all the variables that affect vitamin D production from sunlight, experts recommend sensible sun exposure of 10-30 minutes a few times per week along with oral vitamin D intake.

Relying solely on the sun is an unreliable means of meeting needs.

In Part 2 of our Vitamin D blog, we will explore how much Vitamin D is needed on a daily basis and the best Food Sources. 

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