Vitamin D, also known as “calciferol,” is one of the most studied nutrients to date. Yet, global health leaders claim that Vitamin D deficiency is a worldwide health epidemic. With 1 billion people across the globe being Vitamin D deficient or insufficient, how do you avoid becoming part of that statistic? Let’s start with a better understanding of Vitamin D so you know what to look out for.


What is Vitamin D Anyway?

The essential role that Vitamin D plays in health is well known. Yet, the unique characteristics of Vitamin D can lead to confusion because it is not actually a vitamin at all, but a prohormone produced phytochemically in the skin of yeast and animals. Because this prohormone can be obtained through the diet after we eat said yeast and animals, it may look and act like a vitamin at times. But we can also produce it ourselves.

There are several different forms of Vitamin D so let’s break it down:

  • Vitamin D2, also known as “ergocalciferol,” is produced naturally in yeast in the presence of ultraviolet-B (UVB) light. D2 is also the form more commonly found in fortified food products. The slight difference in chemical structure compared to D3 results in a lower affinity for the binding protein used to transport Vitamin D through the blood, leading to faster clearance from the circulation.
  • Vitamin D3, also known as “cholecalciferol,” is produced naturally in animals (including humans) in the presence of UVB light. D3 can be found in dietary sources such as fish, beef liver, egg yolk, and some fortified food products. Because D3 has a higher affinity for its carrier protein, research shows that D3 increases blood concentrations of the vitamin more than D2.
  • Both Vitamin D2 and D3 are required to be “activated” through several hydroxylation steps that take place in the liver and the kidney before it can be biologically active as 1,25-dihydroxycholecalciferol (1,25(OH)2D), also known as “calcitriol.” This form exerts effects on the body and influences health in several ways.


What Happens If You Don’t Get Enough Vitamin D? 

Many people are surprised to learn they aren’t getting enough Vitamin D. But data show that up to 94% of people don’t even consume the Estimated Average Requirement (EAR) of 400 International Units (IU) per day. Adequate Vitamin D status is important because Vitamin D receptors are distributed nearly everywhere in the body, suggesting it plays a role in numerous aspects of health. Let’s go over just a few ways Vitamin D deficiency can affect health:

Musculoskeletal weakness: Vitamin D deficiency may lead to proximal muscle weakness, increased risk of falls, and global bone discomfort. This can be significant for people over the age of 65, in which falls are the leading cause of injury and bone fractures.

Bone health: A deficiency in Vitamin D results in decreased intestinal absorption of dietary calcium and phosphorus. As a result, normal bone metabolism is altered and the skeleton then becomes the body’s primary source of calcium leading to bone demineralization, fragility, rickets in children, and osteoporosis in adults.

Autoimmune disease: Vitamin D has been associated with several autoimmune diseases and studies have found that taking just 400 IU of Vitamin D daily reduces the risk of developing multiple sclerosis and rheumatoid arthritis. Vitamin D has been found to relieve symptoms of psoriasis as well.

Cardiovascular disease: Literature suggests a relationship between suboptimal Vitamin D levels and increased risk of cardiovascular disease. One study found that Vitamin D levels were inversely related to cardiovascular risk factors: high blood pressure, high blood glucose levels, and increased body mass index (BMI).

Several types of cancer: It is well documented that the risk of developing and dying of colon, prostate, breast, ovarian, and non-Hodgkin’s lymphoma cancers are related to living at higher latitudes and being more at risk of Vitamin D deficiency.

Neurocognitive dysfunction and mental illness: Vitamin D has been found to bind to receptors and activate neurons in brain regions implicated in behavior and protect the brain by bolstering antioxidant and anti-inflammatory defenses. Deficiency has been linked to depression, decreased cognitive function, dementia, and Alzheimer’s disease.

INFOGRAPHIC – Global Vitamin D Levels



But There’s Some Controversy…

There is some dispute among experts about the definition of deficiency, optimum levels, and dietary recommendations of Vitamin D. In 2010 the Institute of Medicine (IOM) issued a report suggesting that Vitamin D levels (measured as blood levels of calcidiol) should not fall below 20ng/mL.

However, in 2011 the Endocrine Society Clinical Practice Guidelines defined Vitamin D deficiency as levels <30ng/mL, suggesting that anything less could increase risk of disease. And that’s not all.

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An article published in 2016, written by some of the scientists who were part of the original IOM report, stated that 20ng/mL was meant to be a referenced “acceptable” level, not a number used to define deficiency. They are currently advocating for a much lower cut-off point to define deficiency. To add to the confusion, you can easily find other articles and statements that support each of these recommendations.

Even though work still needs to be done to find a definition of deficiency and adequacy that everyone agrees on, there are some definitions and recommendations that are widely accepted and likely very helpful. The IOMs Recommended Dietary Allowance (RDA) of 600 IUs per day for adult males and females and 800 IUs for males and females over the age of 70 years old seems to be a good place to start. The National Institute of Health has also created a great Vitamin D Fact Sheet that shares up-to-date information if you would like to see more.


Who Is At Risk of Being Deficient?

Some signs you may experience if deficient in Vitamin D include mood changes, weak bones, muscle cramps or muscle weakness, bone and joint pain, and fatigue. Vitamin D deficiency can occur if you are not obtaining enough Vitamin D from your diet and through UVB sunlight exposure. Those people at greatest risk of Vitamin D deficiency include:

  • Those who use sunscreen regularly or clothes that cover the skin. Humans typically obtain 90% of Vitamin D from sunlight, so blocking the skin from UVB rays can negatively affect Vitamin D levels.
  • Those who have natural factors that reduce the skin’s production of Vitamin D, such as increased skin pigmentation and aging. People with darker skin tones have natural sun protection that requires more time in the sun to make the same amount of Vitamin D. Older populations are at higher risk due to reduced efficiency of Vitamin D synthesis by the skin, reduced appetite and nutrient intake, and reduced exposure to outdoors in general.
  • Those who live in geographic locations that impact UVB exposure or spend limited time outdoors. The latitude at which you live, the season of the year, and the time of day can all affect the sunlight required to synthesize Vitamin D.
  • Those who have medical conditions that lead to altered intestinal absorption or increased needs are also at risk. Medical conditions such as Chron’s disease, cystic fibrosis, celiac disease, irritable bowel syndrome, or those who have had gastric bypass surgery will have altered Vitamin D absorption and utilization.
  • Those who take medications, such as anticonvulsants or glucocorticoids, which can increase metabolism and destroy Vitamin D.
  • Those who are pregnant or lactating are also at risk for deficiency simply due to increased needs.
  • Those who are overweight/obese are at greater risk due to increased body fat sequestration of Vitamin D, a fat-soluble vitamin, making it less bioavailable.
  • Those who do not obtain adequate Vitamin D from their diets due to dietary choice (strict vegetarian or vegan diets) or intolerance (dairy allergies) are at high risk.


More Is Not Always Better

Since Vitamin D is a fat-soluble vitamin and can be stored, excess amounts may become toxic. Widespread fortification of food and drink back in the 1950s led to several reported cases of toxicity. While rare nowadays, Vitamin D toxicity can lead to hypercalcemia with symptoms that include nausea, metallic taste, pancreatitis, increased thirst and urination, constipation, weakness, confusion, and ataxia.

Toxicity is not likely to occur from sunlight and food intake alone, but inappropriate supplementation may increase risk. The National Academy of Sciences has set the Tolerable Upper Intake Level (UL) of 4,000 IUs per day in adults and children ages 9+ suggesting that intake below this level is unlikely to have adverse health effects.

BLOG: Many People Believe They Are Deficient in Key Nutrients

Hypovitaminosis D may be classified as vitamin D deficiency or vitamin D insufficiency. In adults, vitamin D deficiency is defined as a serum calcidiol (25-hydroxy-vitamin D) level of less than 20 ng/mL (50 nmol/L). Vitamin D insufficiency is defined as a serum calcidiol level of 20 to 30 ng/mL (50 to 75 nmol/L).2

Hypovitaminosis D may be classified as vitamin D deficiency or vitamin D insufficiency. In adults, vitamin D deficiency is defined as a serum calcidiol (25-hydroxy-vitamin D) level of less than 20 ng/mL (50 nmol/L). Vitamin D insufficiency is defined as a serum calcidiol level of 20 to 30 ng/mL (50 to 75 nmol/L).2


How Can You Make Sure You Get What You Need?

First, it would be wise to test your levels before making any significant lifestyle changes. You may already be obtaining adequate amounts of Vitamin D, especially if you commonly eat foods that contain this prohormone and are active outside in the sunshine often. However, you never know unless you test.

BLOG: Vitamin D: Are You Getting Enough?

Furthermore, if you fall anywhere on the list of “people at risk” provided above, knowing your number may be even more important. Testing is easy nowadays and can even be done in the comfort of your home with a single finger prick. You can learn more about home Vitamin D testing here: Then, depending on your current Vitamin D status, you can alter your food, supplement, or sunshine consumption appropriately.

These statements have not been evaluated by the Food and Drug Administration. This test is not intended to diagnose, treat, cure, prevent or mitigate any disease. This site does not offer medical advice, and nothing contained herein is intended to establish a doctor/patient relationship. OmegaQuant, LLC is regulated under the Clinical Laboratory improvement Amendments of 1988 (CLIA) and is qualified to perform high complexity clinical testing. The performance characteristics of this test were determined by OmegaQuant, LLC. It has not been cleared or approved by the U.S. Food and Drug Administration.

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