The Relationship Between Vitamin D Deficiency and Type 1 Diabetes

 Type 1 diabetes develops due to malfunctioning of the immune system. Mounting scientific evidence indicates that vitamin D plays a vital role in the normal functioning of the immune system and vitamin D deficiency can lead to the malfunctioning of the immune system.  Consequently, your own immune system starts to attack and kill your own insulin producing cells in the pancreas, reacting as if they are invading viruses that must be destroyed. Once you are unable to produce insulin, you develop Type 1 diabetes.


Evidence for the Link Between Vitamin D Deficiency and Type 1 Diabetes.  

Researchers have investigated the level of vitamin D in patients with Type 1 diabetes and found it to be low in the vast majority of these patients.

In a recently published study in the Journal of Pediatrics, researchers from the Joslin Diabetes Center noted that the vast majority of their Type 1 diabetic patients were low in vitamin D. The study was done in children and teenagers.  

 In my clinical practice, I check vitamin D level in all of my Type 1 diabetic patients and find it to be low in virtually all of them.  


Evidence that Vitamin D can Prevent Type 1 Diabetes.  

Scientific evidence now exists to show that proper vitamin D supplementation can prevent Type 1 diabetes.   One such study comes from Finland. This study  began in 1966 when a total of 10,821 children born in 1966 in northern Finland were enrolled in the study. Frequency of vitamin D supplementation was recorded during the first year of life.

At that time, the recommended dose of vitamin D for infants in Finland was 2000 I.U. per day.  These children were then followed for 31 years for the development of Type 1 diabetes.

Researchers made the amazing discovery that those children who received the daily recommended dose of 2000 I.U. of Vitamin D during the first year of their life, had an almost 80% reduction in the risk for the development of Type 1 diabetes compared to those children who received less vitamin D.  

This is a ground breaking study! If some drug achieved this kind of results, it would hit the headlines and become the standard of care at once. Sadly, even many diabetes experts are not aware of this astounding study even though the study was published in 2001 in the prestigious British medical journal called Lancet.   Investigators in the U.S. continue to spend millions of dollars in their pursuit of a “drug” to prevent Type 1 diabetes. So far, this kind of research has produced disappointing results. Amazingly, they have largely ignored the strong evidence that shows the outstanding role of vitamin D in preventing Type 1 diabetes. Vitamin D is not a drug. There is no glory or huge profits in simply telling people to take enough vitamin D.  

It is interesting to note that the recommended allowance of vitamin D for infants in Finland was reduced from 2000 I.U.  to 1000 I.U. per day in 1975 and then further reduced to 400 I.U. per day in 1992. (For comparison, in the U.S. it has been 200 I.U. a day).  This reduction in the daily allowance had no scientific basis except the observation that this amount of vitamin D is present in a teaspoonful of cod-liver oil which has long been considered safe and effective in preventing rickets.   In the last decades, the incidence of Type 1 diabetes in Finland has been climbing which is most likely related to the decrease in the daily recommended allowance of vitamin D.

As of 1999, Finland has the highest reported incidence of Type 1 diabetes in the world . In Finland, the yearly sunshine and therefore vitamin D skin synthesis is much lower compared to more southern areas. Therefore, the population in Finland is at even higher risk for vitamin D deficiency.    

Not only in Finland, but in other countries as well, scientists have discovered the amazing power of vitamin D supplementation in preventing Type 1 diabetes.  In one such study called EURODIAB, researchers found vitamin D supplementation during infancy can significantly reduce the risk for developing Type 1 diabetes. This study was carried out in seven centers in different countries across a variety of populations in Europe.  


The Relationship Between Vitamin D Deficiency and Type 2 Diabetes.  

Is there a relationship between vitamin D deficiency and development of Type 2 diabetes? The answer is yes. Life-style factors that are well known to cause Type 2 diabetes include obesity, old age and physical inactivity. It’s interesting to note that all of these factors also cause vitamin D deficiency.  

Vitamin D is important for normal glucose metabolism. It acts through several mechanisms on glucose metabolism:  

1.     Vitamin D directly acts on insulin producing cells in the pancreas to produce more insulin.

2.     Vitamin D directly acts on the muscle and fat cells to improve insulin action by reducing insulin resistance.

3.     Vitamin D reduces inflammation which is commonly present in patients with Insulin Resistance Syndrome and Type 2 diabetes.

4.     Vitamin D indirectly improves insulin production and it’s action by improving the level of calcium inside the cells.  

Now you can understand the important role vitamin D plays in keeping blood glucose normal. Intuitively, vitamin D deficiency can lead to diabetes.


Evidence that Links Vitamin D Deficiency to Type 2 Diabetes  

Is there any scientific evidence to link vitamin D deficiency to Type 2 diabetes? The answer is yes. 

Numerous scientific studies have found vitamin D to be low in patients with Type 2 diabetes.   One such remarkable study looked at the level of vitamin D, prevalence of insulin resistance and risk for Type 2 diabetes in the U.S. population. In this study, researchers concluded that people with a low level of vitamin D were at high risk for the development of insulin resistance and Type 2 diabetes.    

Evidence that Vitamin D can Prevent Type 2 Diabetes  

Is there evidence to show that vitamin D can prevent the development of Type 2 diabetes? The answer is yes. 

In a study from Finland, researchers collected health data in men and women from the ages of 40 to 74. None of these individual had Type 2 diabetes at the start of the study. They followed these individuals for 22 years to see the pattern of development of Type 2 diabetes. These researchers found that people who had higher level of vitamin D were less likely to develop Type 2 diabetes. Thus vitamin D appears to have a protective effect against the development of Type 2 diabetes.  

In another study from the U.S., researchers found that vitamin D and calcium supplementation were able to reduce progression from pre-diabetes to diabetes. This protective effect of vitamin D was similar in magnitude to other measures which have been shown to reduce the progression from pre-diabetes to diabetes, such as a weight reducing diet, intense exercise and use of the drug, metformin.  

In summary, vitamin D has the potential to prevent Type 1 as well as Type 2 diabetes. It can also prevent the devastating complications of diabetes such as heart attacks and kidney failure. Unfortunately, most diabetics continue to be low in vitamin D. Many diabetics are on a long list of expensive medications, but unfortunately, all too often, vitamin D is not included. Sadly, most physicians don’t pay attention to the important relationship between vitamin D and the health of a diabetic patient. Isn’t it time that proper vitamin D supplementation become an integral part of diabetes management?  

For an in depth, complete discussion of insulin resistance and diabetes, please refer to  “Take Charge of Your Diabetes.”  and You Tube videos about Insulin Resistance.


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This article was written by Sarfraz Zaidi, MD, FACE. Dr. Zaidi specializes in Diabetes, photoEndocrinology and Metabolism.

Dr. Zaidi is a former assistant Clinical Professor of Medicine at UCLA and Director of the Jamila Diabetes and Endocrine Medical Center in Thousand Oaks, California.

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