The growing awareness of the beneficial health effects of vitamin D supplementation and the over-the-counter availability of vitamin D supplements has resulted in a giant interest in vitamin D supplementation, often used as weekly high or mega doses. However, is vitamin D over-supplementing in people with healthy blood levels
helpful and safe?
In this series of four articles you will find the answer to many important questions about vitamin D.
What is vitamin D?
Vitamin D is an essential prohormone or precursor of a hormone (the active form of vitamin D, called calcitriol is a hormone)that is needed for optimal health and well-being in all stages of life, from birth to old ages.
It is also called the sunshine vitamin because it can be produced in the human skin upon exposure to ultraviolet rays. Besides sun exposures, vitamin D also can be obtained from foods in our diet or through supplements.
Vitamin D is pretty well-known for its critical role in maintaining strong bones, as it helps our body absorb calcium. But, in fact, vitamin D assists our body in a variety of functions. (1)
Why do we need vitamin D?
Vitamin D is crucial for health, and has a wide range of biological functions such as:
. Regulates the immune function, cell growth and neuromuscular function
. Supports brain and nervous system health
. Promotes calcium absorption in the intestine
. Maintains adequate blood levels of calcium and phosphate
. It works synergistically with the vitamins A and K to protect soft tissues from calcification
. Protects bone health against osteoporosis, rickets, and bone fractures
. Influences the expression of more than 200 genes
. Stimulation of insulin production
. Supports cardiovascular health
. Supports lung function
. It works as a potent hormone in many types of tissues and cells in the body, etc. (2, 3)
What is the best way to know if an individual is deficient in vitamin D?
Measuring the blood levels of 25(OH)D or 25 hydroxyvitamin D, is the best way to determine vitamin D status, and usually is measured in nanograms per milliliter. Other marker commonly used to measure vitamin D blood levels is 1,25(OH)2D or the biologically active form. However, it provides no information about vitamin D status because it is often normal or even elevated in children and adults who are vitamin D deficient. (4,)
What is the definition of vitamin D deficiency?
Vitamin D deficiency occurs when we do not have appropriate levels of vitamin D in our blood.
The U.S. Laboratories reference range for adequate vitamin D levels
The U.S. lab reference range for adequate vitamin D is between 30-74 ng/mL. However, data strongly suggests that the ideal vitamin D levels might be lower than the numbers above. And, there is no scientific evidence that support benefits or provide additional protection in vitamin D levels above 60 ng/mL. On the other hand, there is evidence suggesting that vitamin D above these levels can cause damage to our health and toxicity. (5, 6)
What is considered a healthy vitamin D level?
In fact, if we look at the most influential vitamin D guidelines, we realize that determining a healthy vitamin D level can be tricky. And in order to understand what I am saying please, take a look below:
In 2011, the Institute of Medicine (IOM) report, based on a long-term examination data, showed that blood levels of 25(OH)D of 20 ng/mL or below, as deficiency. And levels of 20 ng/mL or higher, as adequate vitamin D levels for good bone health in at least 97.5% of the population. (7)
In 2014, the respected American Endocrine Society report, suggested a higher adequate minimum of 25(OH)D of 30 ng/mL or higher for children and adults, as they classified levels from 21 to 29 ng/mL as insufficient, and levels of 20 ng/mL and below as deficiency. Besides, they recommended levels between 40 to 60 ng/mL as ideal for both children and adults. (8)
In 2016,adifferent opinion about a healthy vitamin D target was presented by the New England Journal, in an article titled: Vitamin D Deficiency, Is There Really A Pandemic. In this study, was examined a massive amount of data from the National Health and Nutrition Examination Survey (NHANES) for 2007 through 2010 and reveals that only 13 percent of Americans 1 to 70 years of age are at risk for vitamin D deficiency. (9)
Also, this study found that 6 percent of Americans had 25(OH)D of 12.5 ng/mL or less. And as a result, they suggested 12.5 ng/mL as a minimum vitamin D level, saying that at this level, would most certainly be eliminated the called “pandemic” of vitamin D deficiency around the U.S.
Complicated, isn't it? As the controversy around a healthy level of vitamin D continues in many new studies, articles and all around the health community, it is imperative to have personalized interventions in order to avoid both, deficiencies and also overprescribing of vitamin D supplements.
What vitamin D deficiency can cause?
As vitamin D deficiency is recognized as a public health problem, low vitamin D levels has been extensively studied and shown to be associated with various negative health outcomes, such as: (10,11)
. Defects in bone mineralization
. Fracture risk
. Muscle weakness
. Autoimmune diseases
. Cardiovascular diseases
. Metabolic syndrome
. Cognitive decline
. Allergies and asthma
. Cancer, etc.
As you could see, acute vitamin D deficiency can lead to a multitude of preventable diseases, and, without a doubt, it is essential to treat vitamin D according to the severity of the deficiency of each individual.
However, even more crucial is the need to address the major risk factor for vitamin D deficiency: our modern indoor lifestyle and lack of sun exposure. And you are going to see it and more in the next article.
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