Ultimate Guide to Vitamin D Deficiency

The Ultimate Guide to Vitamin D Deficiency

Vitamin D deficiency is common in the US. Get to know it better by causes, signs, and symptoms and what to do to ensure you're getting enough.

Published March 5, 2019 - 10 Min Read

“You are my sunshine, my only sunshine.  You make me happy when skies are grey.  You'll never know dear, how much I love you.  Please don't take my sunshine away”

Do these lyrics from the popular children's song, "You Are My Sunshine" sound familiar? 

They should serve as a reminder of how important it is to get our daily dose of vitamin D - the sunshine vitamin.  Not only does vitamin D promote a positive mood, but it also plays a vital role in numerous bodily functions.  With vitamin D deficiency   on the rise, it's important to know what you can do to prevent a vitamin D deficiency from arising and what to do if your levels are inadequate.

So, what exactly is vitamin D? 

For quite some time, our understanding of the role of vitamin D3 was limited.  We understood the importance of vitamin D for the regulation of calcium for bone health, but this changed with more research.  We now understand that nearly every cell within our body contains vitamin D receptors. Vitamin D modulates more than 2000 genes within our cells. The relationship of vitamin D to the supply of numerous substances affects just about every area of wellness. 

Compared to other nutrients, vitamin D is a fat-soluble vitamin that functions more like a hormone in the body rather than a micronutrient. Vitamin D is essential for many facets of health, for example, absorption of calcium and phosphorus from food, which is crucial for healthy bones. Vitamin D is a hormone which has an impact on a lot of tissues in our entire body, and the thyroid gland is among them.  

While it is possible to get too much vitamin D, it isn't the case for most people today. The majority of us aren't getting enough.  

Here are a few of the primary roles of vitamin D:

  • Vitamin D improves the immune system.
  • It protects our body in any seasonal illnesses like cold, cough, and flu.  
  • Vitamin D, based on research, is capable of controlling blood pressure. 
  • If vitamin D in the body is low, the higher the risk of high blood pressure. 
  • Vitamin D reduces the risk of Alzheimer’s disease and other cognitive related impairments. 
  • Vitamin D possesses a range of anti-inflammatory properties known to keep our lungs healthy.
  • Vitamin D is a perfect partner to calcium making it beneficial to our bones, muscles, and balance. 

Vitamin D might appear to be a simple nutrient. However, Vitamin D deficiency causes serious health problems. And to treat it properly, we need to enlighten ourselves with the factors that cause it. 

Why Vitamin D from the Sun May Not be Enough

According to health professionals, Vitamin D is an essential nutrient to our body that we must get from external sources. Vitamin D is the only vitamin which individuals don't have to consume through food but has the potential to be produced via the sun. This capability to synthesize vitamin D makes sunlight an important human"food source" which is as crucial to your quality of life as food and fluids.

Notably, this relevance of sunlight is often overlooked. Under the proper conditions, humans can synthesize the UV-B rays from the sun into usable vitamin D for the body. Evolutionarily, humans have adapted to a great deal of sun exposure. And while indigenous peoples were exposed to the sun almost all day, in today's culture, we aren't getting enough sunlight due to various lifestyle factors. Due to limited sun exposure, sunscreen, and other reasons, very few of us get enough sun exposure to meet our vitamin D requirements.

Additionally, our ability to turn the sunlight's rays into usable vitamin D is more complicated than you think. For synthesis to occur, the following five conditions must be met:

  • Direct sunlight contact
    Clouds, glass windows, clothing and sunscreen all get in the way of synthesis
  • Adequate exposure of bare skin
    A minimum of 25 percent of the exposed surface must be in direct contact with the sun
  • Sufficient intensity of sunlight
    Depending on geography, only certain months during the year are adequate for vitamin D synthesis from the sun.  For North America, this is typically the summer months.
  • Long enough period of tanning
    Varies depending on skin type

As you can see, getting vitamin D from the sun is no easy feat.  For this reason, it's important to consider vitamin D supplementation as a way to get a healthy supply of vitamin D.

Vitamin D Deficiency Causes 

Scientific research conducted in the U.S found that a growing number of Americans require Vitamin D deficiency treatment. The study concluded that seventy-five percent of the US population needs vitamin D therapy treatment.  

With so many people showing signs of deficiency, the questions to address are what causes it, and what you can do to correct it. 


  • Limited sunlight exposure – As we pointed out earlier, getting enough vitamin D from the sun is less common today than it was for our ancestors.
  • Obesity or Overweight – It decreases blood levels of vitamin D. 
  • Dark Skin – People with darker skin tones are more prone to deficiency.  The reason for this is because the pigment melanin decreases the ability of the skin to absorb sunlight as a source of vitamin D. 
  • Kidney Problems – The kidneys play a vital role in the conversion of vitamin D to active body properties. Thus, if the kidneys fail to work correctly, vitamin D is also at risk.
  • Digestive Disorders – This factor affects the ability to absorb vitamin D from food. 

Vitamin D deficiency isn't limited to these factors.  Additional factors can contribute to one's ability to get enough vitamin D and increase the risk of inadequacy.  Studies have shown that the smog in many cities protects portions of sunlight and affects the UV-B range has to reach the epidermis.

Now that we know the potential causes, how do we determine if an individual is suffering from such? 

Vitamin D Deficiency Symptoms

It is important to catch a deficiency as early as possible and take corrective action to address it.  Knowing that a deficit exists and what to do about it will undoubtedly help people reduce the risk of converting minor problems to serious ones. 

The following is a list of the most common Vitamin D symptoms:

  • Increased risk of illnesses or infections
  • Excessive tiredness and exhaustion
  • Back pain and Bone pain
  • Slow healing process of wounds
  • Hair loss
  • Muscle Pain
  • Depression and other mental health issues
  • Increased risk of urinary incontinence in women

Vitamin D Deficiency – its Link to CANCER

New studies indicate that vitamin D may play a role in the prevention and treatment of cancer.  This research is controversial, but it's important to point out the connections.  Vitamin D is one of the most significant issues of cancer research. The amount of studies with this topic has grown exponentially in the past several decades, resulting in a better comprehension of connections and the mechanisms at play.  The research around this topic began with observational studies that found a correlation with lower incidence of cancer rates with populations in sun-rich environments closer to the equator.  Based on these observations it was guessed that vitamin D deficiency could be a significant risk factor for cancer.

In the study of vitamin D linkage to cancer, here are some of the key findings:

  • Vitamin D has anti-tumor properties
  • The prevalence of disease decreases with increasing solar radiation
  • The incidence of several cancers decreases with increasing vitamin D levels
  • Vitamin D controls many fundamental mechanisms that play a well-known role in the evolution and spread of cancer
  • Vitamin D inhibits the growth of cancer cells in cell cultures
  • Vitamin D inhibits the development of cancerous tumors in animal experiments
  • Vitamin D inhibits the metastasis of cancer in animal experiments
  • High vitamin D levels in humans correlate with higher odds of survival in cancer.

All these findings strongly support a central purpose of vitamin D in cancer, and yet the issue remains contentious. The data is presently difficult to interpret due to the relationship between vitamin D with many factors that require additional investigation in long-term research studies. The preceding research continues to be too fragmentary to draw authoritative conclusions.

Recognizing the root causes and knowing the associated symptoms of vitamin D deficiency are the first step.  Putting a plan in place that ensures you get enough is the second step. Regular bloodwork is a critical factor in staying on top of your health.  Through consistent check-ups and monitoring, you can usually catch a deficiency before it develops into more severe health risks.  

How to Test for Vitamin D Deficiency

The easiest way to test your vitamin D levels is through a blood test that measures circulating vitamin D.  This test is known as 25-OH-vitamin-D.  While the levels of 25-OH-vitamin-D that indicate a deficiency are clearly defined, it is more unclear when we consider what is optimal.  

As a fat-soluble vitamin, vitamin D gets stored in fat tissue and cells.  Vitamin D is absorbed into fat and muscle cells and stored for later use.  When these cells reach capacity, vitamin D is released back into the bloodstream over time, thereby contributing to vitamin D distribution. The better the body stores are satisfied, the higher circulating vitamin D levels will be, which provides the assessment of vitamin D levels in bloodwork.

Although 25-OHD isn't the active form of vitamin D that our body uses, it is a good indication of supply.  The vitamin D hormone calcitriol is the usable form of vitamin D.  The body converts vitamin D to calcitriol as needed.  This can be highly variable which is why 25-OHD provides a better measurement for vitamin D.  Another important factor to pay attention to with testing is the units used.  Currently, two different units of measurement are used: ng/ml and nmol / l.  This frequently leads to confusion because a reading of "90" could indicate very different results.  For the sake of this article, we will refer to ng/ml as the measurement.

So what is the optimal level of vitamin D?  

The challenge with many of the RDIs (Recommended Daily Intake) as they exist today are they fail to address optimal levels for nutrients.  Instead, RDIs are set at levels known to prevent disease.  Determining a standardized optimal level is difficult, especially when considering all the variables like age, skin pigmentation, geography, and lifestyle to name a few.  Based on the most current research, a general rule of thumb is to aim for levels in the range of 40-60 ng/ml.  A study that looked at hunter-gatherer populations indicates that this is the range maintained by our ancestors. Most Americans fall well beneath these levels, especially during the winter months. 

How to Increase Vitamin D Levels

Only a small number of foods comprise vitamin D, making it difficult to get enough of this vital nutrient from the diet.  Contrary to what you may have heard about milk, it's not a great way to increase vitamin D or calcium.  The acidic nature of dairy leeches calcium from bones.  So much for doing a body good!

One of our favorite vitamin D containing foods is mushrooms!  Similar to how we synthesize vitamin D from sunlight, mushrooms do the same.  This makes them a powerhouse for vitamin D and a perfect choice for plant-based diets.  Avocados and chlorella are also good sources of vitamin D2 and can be included in the diet to maintain healthy levels, but getting all the vitamin D from whole foods alone is inadequate if you're already low.  This is why we need the sun, or in most cases, supplementation.

How to Supplement with Vitamin D

Due to the complex nature of vitamin D, just increasing your vitamin D intake may not be enough. Other issues that could be limiting your ability to synthesize and use vitamin D may exist.  Magnesium and vitamin K2 both play a critical role in our body's ability to convert and use vitamin D.  It just so happens that both these nutrients are also in short supply in modern lifestyles.  

Like most minerals or nutrients, when you're unable to get yourself a level that is healthy, that's where supplements can prove to be beneficial!  Depending on your vitamin D levels, you may need anywhere between 2,000 and 5,000 IU of vitamin D daily to attain and maintain an optimal supply.  When considering a vitamin D supplement be sure to look for natural forms of vitamin D and the inclusion of vitamin K2 as all-trans MK-7. 

Vitamin K2 is most common in fermented foods and grass-fed animal products.  This makes K2 challenging to get through the diet. The standard American diet doesn't include these choices, and vegan diets restrict meat consumption.  If you're looking for a product that satisfies your vitamin D + K2 criteria that is soy-free and vegan-friendly, check out our All-in-One Essentials shake.  We formulated it to provide 1000 IU of vegan vitamin D3 with optimal levels of K2 from fermented chickpeas.  Additionally, you'll get a bump in magnesium to complete the trio of essential vitamins and minerals needed for optimal vitamin D intake and usage.  

So there you have it.  The ultimate guide to vitamin D deficiency and a few tips about what you can do to ensure you're getting enough for optimal health.  Now it's time to hit the beach...sun's out - bums out!


Jimmie Davis, Andrew Williams, Randi Soyland. Sunshine Lyrics | AZLyrics.com. https://www.azlyrics.com/lyrics/low/sunshine.html. Accessed March 03, 2019.

David Rotter. Vitamin D Deficiency. https://www.vitamind.net/mangel/. Accessed March 04, 2019.





All information, content, and material of this article and website is for informational purposes only and is not intended to serve as a substitute for the consultation, diagnosis, and/or medical treatment of a qualified physician or healthcare provider.

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Chris Manderino

Written by Chris Manderino

Co-Founder of LYFE FUEL in Newport Beach, CA. Chris was an NFL fullback for the Cincinnati Bengals and Kansas City Chiefs before embarking on a journey to pursue his passion for health & nutrition. Chris is a graduate of the University of California, Berkeley and earned a completion certificate from the T. Colin Campbell Course in Plant-Based Nutrition. 

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