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Overweight people have difficulty with utilizing vitamin D – and that may lead to complications

Overweight people have difficulty with utilizing vitamin D – and that may lead to complicationsVitamin D is important for our bones, cardiovascular system, immune defense, and for preventing cancer. Still, vitamin D supplements are less effective if you are overweight and that may lead to a variety of problems, according to a new study that is published in Journal of Bone and Mineral Research. In other words, being overweight means that you have an increased need for vitamin D. Other studies even show that overweight individuals have an increased need for magnesium, which activates vitamin D in the liver and kidneys with help from different enzymes.

All our cells need vitamin D, which is viewed as a hormone and needs to be activated before it can benefit our cells. The sun during the summer period is our main source of vitamin D. To begin with, a prohormone called cholecalciferol is synthesized from cholesterol in our skin. Vitamin D supplements also contain cholecalciferol, which is not yet biologically active. The activation happens when the liver converts cholecalciferol into 25-hydroxyvitamin D3 with help from enzymes. This is the form of vitamin D that is measured in blood tests. When vitamin D is needed, the kidneys convert 25-hydroxyvitamin D3 into the most active form using other enzymes. Put differently vitamin D from sunlight or from supplements is not of any use to the body’s cells, unless it has been activated.

Overweight and lack of vitamin D – it is a vicious cycle

The new study showed that levels of the enzyme that converts cholecalciferol into 25-hydroxyvitamin D3 was much lower in the livers of overweight mice. The researchers therefore believe that it is much more effective to treat vitamin D deficiencies in overweight people if you give them 25-hydroxyvitamin D3 instead of using other forms of vitamin D
One of the scientists behind the new study, Dr. Jeffrey Roizen from Children’s Hospital of Philadelphia, says that overweight and obesity reduce the liver’s ability to convert cholecalciferol into 25-hydroxyvitamin D3. It also appears that obesity’s impact on the liver may have clinical consequences for the bones, cardiovascular system, immune system, cancer prevention, and a number of other functions, simply because vitamin D remains inactive.
While earlier studies have shown that low vitamin D levels increase the risk of overweight and obesity, the new study demonstrates that overweight and obesity in itself can increase the risk of becoming vitamin D-deficient. This can easily turn into a vicious cycle that contributes to the many types of disease that follow in the wake of overweight, including diabetes.

The active form of vitamin D is found in certain foods

It turns out that the active form of vitamin D (25-hydroxyvitamin D3) is found in animal food sources such as egg yolk and oily fish. It is assumed that this form of vitamin D has a biologically activity that is five times greater than what you see with cholecalciferol from sun or from supplements. There are also studies suggesting that diabetics have difficulty with converting cholecalciferol into 25-hydroxyvitamin D3, which is why a group of researchers have chosen to feed diabetic rats with eggs.
The study results were significant. The rats’ blood sugar levels dropped by nearly 50 percent compared to the rats that got a standard diet. In addition, levels of triglycerides, which is a cardiovascular risk factor, had dropped by 52 percent.
The science team now wants to investigate why vitamin D from egg is utilized better. They assume that it is not just because egg contains 25-hydroxyvitamin D3 but also other nutrients.
The next step is to find the lowest number of eggs needed to improve blood sugar levels in people with diabetes. Even if egg yolk is a rich source of active vitamin D, one egg a day does not cover the actual need for the nutrient. Therefore, it is necessary to look closer at the enzymes that activate vitamin D from sunlight and from supplements.

Magnesium activates vitamin D

Magnesium is involved in over 350 enzyme processes, including the liver enzymes that convert cholecalciferol into 25-hydroxyvitamin D3. Magnesium also regulates blood levels of vitamin D by raising them when they are low and lowering them when levels are too high.
Because deficiency is quite widespread and it is an overlooked problem, many people have difficulty with regulating their blood levels of vitamin D. They also risk that vitamin D is unable to effectively prevent many diseases. It is therefore vital for your health to get plenty of magnesium and vitamin D and to have the two nutrients in the right balance. The official recommendations for vitamin D intake seem to be too low for overweight and obese people.

  • Vitamin D and magnesium work closely together
  • This is highly important for preventing osteoporosis, infections, cancer, and a number of other diseases
  • There is evidence that overweight people and diabetics have an increased need for vitamin D and magnesium


Vitamin D3 source Name for vitamin D3 and enzyme activity
Supplements Cholecalciferol
Skin Cholecalciferol
Synthesized from a form of cholesterol called 7-dihydroxycholesterol and UVB rays from sunlight
Egg yolk
Oily fish
25-hydrocholecalciferol D3
Synthesized with help from the enzyme 25-hydroxylase
(requires magnesium)
Kidneys 1,25-dihydroxycholecalciferol D3
Synthesized with help from the enzyme 1-alpha-hydroxylase.
(requires magnesium)


Kate Anderton. Vitamin D supplementation less effective in presence of obesity shows study. News Medical Life Sciences. Feb. 2019

Eleanor Dunlop et al. Vitamin D3 and 25-hydroxivitamin D3 Content of Retail White Fish and Eggs in Australia. Nutrients. 2017

Iowa State University: New promise for diabetics with vitamin D-deficiency. ScienceDaily. 2016

Qi Dai et al. Magnesium status and supplementation influence vitamin D status and metabolism; results from a randomized trial. The American Journal of Clinical Nutrition 2018

Anne Marie Uwitonze, Mohammed S Razzaque. Role of magnesium in Vitamin D Activation and Function. The Journal of the American Osteopathic Association. 2018

American Osteopathic Association. Low magnesium levels make D-vitamin ineffective. ScienceDaily. 2018


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