Why Vitamin D?

Most people have a vague idea that, if a nutrient was named after one of the first letters of the alphabet, it must be important, which is a fair assumption. We need vitamin D for bone health, muscle function, and an effective immune system, followed by a lot of “maybes.” In other words, the jury is still out on vitamin D as a cancer preventer, or a treatment for diabetes or multiple sclerosis.

Where does it come from? This sounds crazy, but when ultraviolet light from the sun hits our skin, it somehow causes the body to produce a “group of fat-soluble secosteroids.” We can also consume our vitamin D in a more conventional way, through eating food. Certain fish and their derivatives (e.g. cod liver oil) are replete with it. Beef liver, eggs, and Swiss cheese have a lot of it, too. Orange juice, milk, margarine, and yogurt tend to come fortified with vitamin D as an additive. It is of course available in capsules as a supplement.

Are obesity and vitamin D in a relationship? The question has been around for years, in a form that describes many medical mysteries: Which came first, the chicken or the egg? People have wondered whether vitamin D deficiency contributes to obesity, or is somehow caused by it. Catherine Peterson, Ph.D., wrote,

Data accumulated over the last decade have lead researchers to speculate that the vitamin D deficiency epidemic may be a major contributor to many obesity-associated complications such as the metabolic syndrome and diabetes.

The lack of vitamin D had been linked to respiratory tract infections, autoimmune diseases, and unhealthy bones. By 2018, it was suspected that having enough of it might protect humans against heart failure, cancer, and diabetes.

In Denmark, research by Copenhagen University Hospital and the Novo Nordisk Foundation revealed vitamin D deficiency to be common among obese children and adolescents.

Using data from the Netherlands Epidemiology of Obesity study on thousands of men and women aged 45–65, researchers looked specifically at where fat tends to settle. The four possibilities are total fat; belly fat (a.k.a. abdominal subcutaneous adipose tissue); fat that encases the internal organs (visceral adipose tissue); and hepatic fat, which collects inside the liver. According to the study results,

They discovered that in women, both total and abdominal fat were associated with lower vitamin D levels, but that abdominal fat had the greatest impact. In men, however, lower vitamin D levels were significantly linked with fat in the liver and abdomen.

And yet, the question remained unanswered: “Does a deficiency in vitamin D cause fat to be stored in the abdominal region, or does belly fat decrease the organism’s levels of vitamin D?”

Greek researchers determined that when overweight and obese children were given vitamin D supplements for a year, they had “significantly lower body mass index, body fat and improved cholesterol levels,” implying the promotion of weight loss and the reduction of risk factors related to heart disease and metabolic disease.

By 2018, it had been confirmed that the blood and most of the body’s organs contain receptors for vitamin D. It helps the body retain some minerals and prevents over-absorption of signaling chemicals. The question seemed to be settled:

Unfortunately, people who are obese also have a greater risk of developing a vitamin-D deficiency. Inversely, research now suggests that consuming up to 4,000 IU of vitamin D can benefit weight loss.

Your responses and feedback are welcome!

Source: “Vitamin D & Vitamin D Deficiency,” ClevelandClinic.org, undated
Source: “Vitamin D Deficiency & Childhood Obesity: A Tale of Two Epidemics,” NIH.gov, February 2014
Source: “Obesity is associated with vitamin D deficiency in Danish children and adolescents,” NIH.gov, 01/26/18
Source: “Belly fat linked to vitamin D deficiency,” MedicalNewsToday.com, 05/21/18
Source: “Vitamin D supplements may promote weight loss in obese children,” EurekAlert.org, 09/27/18
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OVERWEIGHT: What Kids Say explores the obesity problem from the often-overlooked perspective of children struggling with being overweight.

About Dr. Robert A. Pretlow

Dr. Robert A. Pretlow is a pediatrician and childhood obesity specialist. He has been researching and spreading awareness on the childhood obesity epidemic in the US for more than a decade.
You can contact Dr. Pretlow at:


Dr. Pretlow’s invited presentation at the American Society of Animal Science 2020 Conference
What’s Causing Obesity in Companion Animals and What Can We Do About It

Dr. Pretlow’s invited presentation at the World Obesity Federation 2019 Conference:
Food/Eating Addiction and the Displacement Mechanism

Dr. Pretlow’s Multi-Center Clinical Trial Kick-off Speech 2018:
Obesity: Tackling the Root Cause

Dr. Pretlow’s 2017 Workshop on
Treatment of Obesity Using the Addiction Model

Dr. Pretlow’s invited presentation for
TEC and UNC 2016

Dr. Pretlow’s invited presentation at the 2015 Obesity Summit in London, UK.

Dr. Pretlow’s invited keynote at the 2014 European Childhood Obesity Group Congress in Salzburg, Austria.

Dr. Pretlow’s presentation at the 2013 European Congress on Obesity in Liverpool, UK.

Dr. Pretlow’s presentation at the 2011 International Conference on Childhood Obesity in Lisbon, Portugal.

Dr. Pretlow’s presentation at the 2010 Uniting Against Childhood Obesity Conference in Houston, TX.

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