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Fun Facts About D3 Deficiency


Sorry. The headline is click bait. There are no fun facts in the data showing that more than half of the U.S. population is D3 deficient. And the health consequences of having deficient levels of D3 can be significant, pervasive, and even deadly. This is especially true for at risk populations, many of whom were hardest hit by the pandemic. Low D3 may also play a role in 20+ cancers, dementias, diabetes and many more significant health problems.


Scope and Severity  

A February 2022 peer-reviewed PLOS ONE study indicated D3 deficient COVID-19 patients can be 14 times more likely to have a severe or critical case, and potentially 10 times more likely to die. One study author added this:

“We checked a range of timeframes and found that wherever you look over the two years before infection, the correlation between vitamin D and disease severity is extremely strong.” 

Dr. Amiel Dror

If you are D3 deficient you are significantly more likely to get infections, and significantly more likely to have symptoms that are more severe and persist longer. And evidence continues to show other possible impacts from low D3.

    1. Bone problems/skeletal metabolism – rickets in children & osteoporosis and fractures in adults
    2. Cancers – correlations to breast, colorectal, kidney, lung, pancreatic*
    3. Cardiovascular disease
    4. Diabetes
    5. Compromised immune response
    6. Autoimmune diseases – rheumatoid arthritis
    7. Inflammation, inflammatory diseases – allergies & asthma
    8. Parkinson’s
    9. Dementia & Alzheimer’s
    10. Depression, anxiety
    11. Reduced cognitive ability

* About 20 different cancers have incidence rates inversely related to solar UV-B doses and serum vitamin D concentration. Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5802611/

Vitamin D3 is produced in the skin in response to ultraviolet B radiation from sunlight or can be obtained from the diet (ie, animal sources such as deep sea fatty fish, egg yolks, or liver) or from supplements. Additionally, D2 plays a vital role in calcium homeostasis.


Probably the biggest change in the last fifty years has been a dramatic shift in how American’s feel about spending time in the sun. Getting too much sun is dangerous. This author lost his sister to malignant melanoma. But the best answer, at least for many, may not to turn off the sun completely. Get sun intelligently.

As a nation we went from laying on tin foil on the garage roof basting ourselves in coconut oil for hours on end to SPF 50+, broad brim hats, and staying inside. Did we over-correct? Getting a moderate amount of sun in small doses is not just OK, but part of how our bodies function optimally.

Dietary sources of vitamin d3
Dietary sources of vitamin d3

Dietary sources were never the primary way for humans to manufacture D3, but we’ve changed the script there, too. Decades of dairy bashing, demonizing egg yolks, and removing liver and onions from American menus further contributed to the D3 dilemma. Then we fortified milk and followed up with “Do less dairy.” Although, many plant-based diary are supplementing their products with D3 as milk does.  

Most Milleniels and Gen-Xers don’t even know liver and onions was ever an entrée option. We hated it. I remember walking in the house after hockey practice to the wafting stench of liver and onions thinking, “What did I do now. Why am I being punished?” But did our mom’s, and aunts, and grandmas know something?

The other primary dietary sources of D3 are fatty fish, but salmon and trout are expensive and not always readily accessible, especially by at risk populations. 

But even eating foods that are rich in D3 for every meal in ridiculous portions will still leave most of us D3 deficient. Even getting enough sun isn’t a universal solution. In fact, a study of professional surfers in Maui showed 1 in 3 to be ‘Low-D’. Another shows 1/3 of the adult population in Hawaii to be D3 deficient. 

Athletes Effected Too

In 2016 researchers found that 70% of athletes were deficient – but 80% of that population was moved to adequate D3 levels after 1-year at 2,200 IUs per day)

Athletes who train indoors, or in higher latitudes (north of Atlanta), or in winter months, or who use sunscreen, sunglasses, or other methods to shield the skin can have suboptimal vitamin D levels.

In fact, it is estimated that only 5% of collegiate athletes meet the recommended intake of vitamin D.

The Risks of Being Vitamin D Deficient as an Athlete

By Joel Totoro, RD, 11/08/18, 7:00AM MST

The Hockey USA article also references studies that link D3 supplementation to gains in muscle recovery and athletic performance, and a Navy study that reduced stress fractures among female recruits by 20%. 

So, how do we change our “D” grade in D3? 

So far, we’ve learned that you can lie in the sun on a beach in Hawaii eating egg, salmon, and liver sandwiches for a year and still not be getting enough D3. As humans our lifestyles have changed faster than evolution could dial in the adjustment

Vitamin D3 written in hand on chalkboard

Next week we will focus on what to do: 

  • Measuring D3: The Futility of Guessing
  • The Calcium Connection
  • At Risk Populations and D3
  • D3 Masquerading as a Hormone?
  • New Delivery Technology
  • Understanding What’s in the Best Supplements

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