Vitamin D and Type II Diabetes

Type II Diabetes

Type II diabetes is a condition in which the body has a hard time managing sugar the right way. Usually you develop type II diabetes in adulthood, past the age of 40, but you can develop it earlier, too. Once you get type II diabetes, it lasts for the rest of your life. If your diabetes isn’t managed, you can develop diabetes symptoms, including eyesight issues, skin conditions, circulation problems, and high blood pressure. Type II diabetes (T2D) usually occurs gradually, meaning that the condition is mild to start but gets worse and worse as time goes by. Most people with the disease are overweight when they are diagnosed. Treatments for T2D require lifelong monitoring of sugar levels in your blood, healthy eating, regular exercising, and possibly diabetes medication. Some people with T2D can manage their condition with diet and exercise alone, but many need additional help with medications. Researchers are interested in whether vitamin D helps your body manage sugar in your blood. Additionally, they’re interested in vitamin D’s role in regulating calcium, which also helps manage sugar in your blood.

There is some research showing that young people who have higher vitamin D levels decreased their chances of developing T2D later in life compared to people who had lower vitamin D levels. Studies have also shown that vitamin D supplements can help some symptoms of T2D. At this time, the research is conflicting on whether supplementing people at high risk of developing diabetes is helpful in reducing the risk of T2D. If you are at risk of T2D and want to take vitamin D, it is unlikely to harm you or make your symptoms worse. However, it may not prevent diabetes. There is some evidence that vitamin D will improve symptoms associated with T2D, if you have T2D. You should not take vitamin D in the place of other medications for your condition. Talk to your doctor about taking vitamin D or any other supplement.

What is Type II diabetes?

Type II diabetes is a condition in which the body has a hard time managing sugar the right way. Usually you develop type II diabetes in adulthood, past the age of 40, but you can develop it earlier, too. Once you get type II diabetes, it lasts for the rest of your life. Beta cells in your pancreas make a hormone called insulin. Insulin helps to shuttle the glucose that enters your bloodstream after a meal into your liver and muscle tissues. Insulin ensures your body either uses or stores this glucose, helping your body to manage glucose the right way. People with type II diabetes (T2D) either:

• don’t make enough insulin to help manage all the glucose, or
• their body “ignores” the insulin they do make, making it hard to manage all the glucose.¹

When glucose starts to build up in the blood stream instead of being used or stored, it can cause diabetes complications. Complications include eyesight issues, skin conditions, and high blood pressure.² T2D usually occurs gradually, meaning that the condition is mild to start but gets worse and worse as time goes by. Most people with the disease are overweight when they are diagnosed. An excess of fat makes it difficult for your body to use insulin correctly. Treatments for T2D require lifelong monitoring of sugar levels in your blood, healthy eating, regular exercising, and possibly diabetes medication. Some people with T2D can manage their condition with diet and exercise alone, but many need additional help with medications.

How common is type II diabetes?

T2D has become a common condition in recent years. Currently 8.3% of the US population has T2D. The percentage of people with T2D is increasing worldwide, and more than one million people are newly diagnosed in the United States annually.³

What does type II diabetes feel like?

Symptoms of T2D often occur slowly. You can have T2D for years and not know it. Here are some symptoms you might have if you have T2D:⁴

• Increased thirst and frequent urination. Excess sugar in your blood causes your body to release fluid.
• Increased hunger. Without insulin to move sugars into the right places, your muscles and organs become tired, triggering strong hunger.
• Weight loss. Without the ability to metabolize glucose for energy, your body uses other fuel stored in muscle and fat, causing you to lose weight.
• Fatigue. When your cells aren’t able to get the sugar they need because of poor insulin function, you become lethargic and even short-tempered.
• Vision problems. If your sugar in your blood is too high, fluid may be pulled from the lenses of your eyes, causing blurred vision.
• Slow healing or frequent infections. T2D affects your ability to heal and fight off infection.
• Patches of dark skin. Occasionally people with T2D have areas of dark skin in the folds and creases of their bodies – like your armpits or neck – which can be a sign that your body is “resistant” to insulin.

If you have some of these symptoms or you are concerned that you might have T2D, setup an appointment with your doctor.

What causes type II diabetes?

T2D occurs when the body stops producing enough insulin or the body becomes “resistant” to insulin. What we mean by resistant to insulin is that for reasons researchers don’t fully understand, the body doesn’t use insulin as much as it should. Exactly why this happens is not fully clear, although being overweight and lack of physical activity seem to play a role. Beta cells in the pancreas make a hormone called insulin. The pancreas releases insulin after you eat to allow glucose from your food to enter your liver and muscle tissue.  T2D occurs when:

• The pancreas doesn’t produce enough insulin, or
• The cells in your body are not open to insulin, which is often called insulin resistance.

Without enough insulin being used, your body doesn’t break down sugar into glucose. Then your body’s cells don’t get the glucose they need. When your cells aren’t getting enough glucose, they don’t function the right way and sugar builds up in the blood stream and can cause damage to multiple areas of the body, including damage to your nerves and kidneys. Some people are more likely to get T2D than others. Certain factors increase your chances of getting T2D, though it’s not fully understood why some of these factors increase your chances. Factors include:⁵

• Being overweight. The more fat tissue you have, the harder it is for your body to use insulin.
• Weight distribution. If your body stores fat in your mid section, your risk is greater than if your extra fat is stored elsewhere.
• Lifestyle. The less exercise you get, the greater your risk. Physical activity helps control your weight, helps you use glucose well, and helps your body use insulin better.
• Family history. Your risk increases if you have a family member who has T2D.
• Race. People of certain races – including African Americans, Hispanics, American Indians and Asian-Americans – are more likely to develop T2D than Caucasian Americans.
• Age. The risk of T2D increases as you age, especially after age 45.
• Prediabetes. Prediabetes is a condition in which your blood sugar levels are higher than normal, but not high enough to be diagnosed as diabetes. If you have prediabetes, you are at very high risk of getting T2D.
• Gestational diabetes. If you have developed gestational diabetes during pregnancy, you are at an increased risk of T2D later in life.

What is the link between vitamin D and type II diabetes?

Vitamin D is most known for its role in bone health, but researchers are beginning to uncover its role in many other areas of your health. Doctors believe there is a link between vitamin D and T2D because studies have shown that people who have the lowest vitamin D levels in their blood are at an increased risk of developing T2D later in life. They also notice that people newly diagnosed with T2D often have lower vitamin D levels than people without diabetes. Doctors and scientists think that vitamin D may have a hand in T2D by playing a role in your pancreatic beta-cell function, insulin action, and inflammation. Let us explain a little more:

Pancreatic beta cell function

If you have T2D, sometimes the beta cells in your pancreas that produce insulin don’t work the right way. Researchers are interested in vitamin D because there are specific receptors in pancreatic beta cells that only start “turning-on” if they get enough vitamin D. Researchers think that getting enough vitamin D can help your pancreatic beta cells function properly. They have done studies on animals where they removed these vitamin D receptors, and these animals couldn’t produce as much insulin as they should.⁶

How our body uses insulin

Insulin sensitivity occurs when your body is “sensitive” to insulin. If you are sensitive to insulin, you don’t need very much insulin to help your body turn sugar into glucose, your body’s main source of energy, because your body uses insulin well. On the other hand, people with T2D are often “resistant” to insulin, where their bodies don’t use insulin very well at all. People with T2D lack sensitivity to insulin and have resistance to insulin. Researchers are interested in the role vitamin D plays in improving insulin sensitivity and increasing insulin secretion. Studies have reported a link between low vitamin D and decreased insulin sensitivity.^7, 8 Furthermore, vitamin D plays an important part in the regulation of calcium. Calcium helps to control the release of insulin, so alterations in calcium can have a negative effect on beta cell function, which may hinder normal insulin release. Some scientists and doctors believe that if vitamin D helps proper insulin function, some of its effects might be because of calcium.

Can vitamin D prevent type II diabetes?

Several studies have looked at how much vitamin D people get and if they develop T2D later in life. There have been three recent reviews, where researchers looked at all the studies out there on vitamin D and T2D, combined them, and determined if there was a connection between vitamin D and T2D.

• A 2011 review looked at studies where they either examined how much vitamin D people were getting by measuring their vitamin D blood level or by administering a vitamin D supplement and then followed participants to see if they got T2D later in life. They found that people with higher vitamin D blood levels (>25 ng/ml) had a decreased chance of getting T2D later in life compared to those with the lowest levels (<14 ng/ml).⁹
• In a 2012 review, researchers looked at studies examining how much vitamin D people were getting by measuring their vitamin D blood level. The researchers then followed participants to see if they got T2D later in life. People with the highest vitamin D blood levels had a 19% decreased chance of developing T2D compared to those with the lowest levels.¹⁰
• In a 2013 review, researchers combined studies where they examined how much vitamin D people were getting by measuring their vitamin D blood level and then followed participants to see if they got T2D later in life. Participants with the highest vitamin D levels had a decreased risk of diabetes compared to those with the lowest vitamin D levels. Every 4 ng/ml increase in vitamin D was associated with a 4% lower risk of getting T2D later in life.¹¹

However, these reviews mainly looked at studies that were observational, meaning we don’t know if low vitamin D caused T2D later in life or if low vitamin D was associated with some other unknown risk factor which caused T2D to develop later in life. A recent trial in 2011 gave 2000 adults at high risk of T2D either 2000 IU of vitamin D per day or 400 mg calcium. They wanted to see if vitamin D helped improve symptoms associated with T2D compared to participants who didn’t get vitamin D. They found that vitamin D supplementation improved pancreatic B cell function – important for making insulin – and helped control the rise of blood sugar.¹² However on the other hand, another very recent trial found that vitamin D supplementation in people with pre-diabetes (higher than normal blood sugar levels) had no effect in reducing people’s chances of getting diabetes later. Furthermore, people who supplemented with vitamin D didn’t produce more insulin and they weren’t any more sensitive to insulin than those taking a dummy pill. They were also just as likely to get diabetes later in life as people taking the dummy pill.¹³

Can vitamin D improve certain aspects of type II diabetes?

Researchers are interested in vitamin D for improving certain aspects of T2D. They want to know if getting enough vitamin D can help:

• Reduce insulin resistance and improve sensitivity.
• For people with T2D that don’t make enough insulin, if vitamin D can help you produce more insulin.

There have been a few trials that have looked if vitamin D can help in these aspects. Three trials report:

• Among obese adolescents without diabetes, vitamin D supplementation of 4,000 IU/day improved how sensitive the participants were to insulin.¹⁴
• People with T2D who were eating yogurt fortified with vitamin D (1000 IU/day) and calcium (600 mg/day) had significantly lower blood sugar levels, less inflammation, and increased glucose regulation – ensuring their body used the glucose as energy – compared to T2D participants eating yogurt without vitamin D.¹⁵
• Researchers in New Zealand found that vitamin D supplementation improved insulin resistance and insulin sensitivity, but only if the dose was large enough and administered over a sufficient period of time.¹⁶

On the other hand, there are three small trials which found that vitamin D supplementation in patients with T2D didn’t significantly decrease blood sugar levels, regulate glucose management, and decrease insulin resistance. However, these trials were fairly small and had relatively short study lengths, making it hard to get a good picture if vitamin D had any effect (2-6 months).⁹

Key points from the research

• People newly diagnosed with T2D tend to have lower vitamin D levels than people without T2D.¹⁷
• A review of the research found that people with higher vitamin D levels have a decreased risk of developing T2D later in life compared to people with the lower levels.¹⁰
• However, one randomized controlled trial found that vitamin D supplementation in people with pre-diabetes (higher than normal blood sugar levels) had no effect on insulin secretion, insulin sensitivity, or the development of diabetes when compared to a group of participants taking a dummy pill.⁹
• We need more research before we can definitively say if vitamin D can help prevent T2D or not.
• For people already with T2D, there is some evidence that vitamin D may help improve resistance to insulin, increase sensitivity to insulin, and more effectively control blood sugar levels. Still more research is needed to say definitively.

What does this mean for me?

There is currently some evidence that getting enough vitamin D may reduce your risk of developing T2D, although what are called large scale intervention studies are needed before we can say for sure. There is intriguing research suggesting that supplementing with vitamin D may help improve some of the aspects associated with T2D. Studies have shown that vitamin D supplementation improves insulin sensitivity and decreased blood sugar levels. However, not all people with T2D see improvement in symptoms. If you or someone you know has T2D, it’s unlikely that taking vitamin D will make your symptoms worse or cause any harm if you take 10,000 IU or less daily, although you may not see improvement in your T2D either. If you have T2D, it’s important to talk to your doctor about taking vitamin D or any other supplements. Don’t take vitamin D in place of any medications you are currently prescribed.

References

1. American Diabetes Association. Diabetes Basics. Retrieved from https://diabetes.org/living-with-diabetes/type-2 on 06/02/13.
2. Mayo Clinic. Complications. Retrieved from https://www.mayoclinic.org/diseases-conditions/type-2-diabetes/symptoms-causes/syc-20351193 on 06/02/13.
3. American Diabetes Association. Diabetes Statistics. Retrieved from https://diabetes.org/about-diabetes/statistics/about-diabetes on 06/02/13.
4. Mayo Clinic. Type 2. Retrieved from https://www.mayoclinic.org/diseases-conditions/type-2-diabetes/symptoms-causes/syc-20351193 on 05/29/13.
5. Mayo Clinic. Risk Factors. Retrieved from https://www.mayoclinic.org/diseases-conditions/type-2-diabetes/symptoms-causes/syc-20351193 on 05/29/13.
6. Zeitz U, Weber K, Soegiarto DW, et al. Impaired insulin secretory capacity in mice lacking functional vitamin D receptor. Faseb Journal, 2003.
7. Scragg R, et al. Serum 25OHD, diabetes, and ethnicity in the Third National Health and Nutrition Examination Survey. Diabetes Care, 2004.
8. Chiu KC, et al. Hypovitaminosis D is associated with inulin resistance and beta cell dysfunction. Am J Clin Nutr, 2004.
9. Mitri J, Muraru MD, Pittas Ag. Vitamin D and type 2 diabetes: a systematic review. European Journal of Clinical Nutrition, 2011.
10. Khan H, et al. Vitamin D, type 2 diabetes and other metabolic outcomes: a systematic review and meta-analysis of prospective studies. Proceedings of the Nutrition Society, 2012.
11. Song Y, et al. Blood 25 hydroxyvitamin D levels and incident type 2 diabetes. Diabetes Care, May 2013.
12. Mitri J, et al. Effects of vitamin D and calcium supplementation on pancreatic B cell function, insulin sensitivity, and glycemia in adults at high risk of diabetes: the calcium and vitamin D for diabetes mellitus randomized controlled trial, 2011.
13. Davidson MB, et al. High-Dose Vitamin D Supplementation in People with Prediabetes and Hypovitaminosis D. Diabets Care, 2012.
14. Belenchia AM, et al. Correcting vitamin D insufficiency improves insulin sensitivity in obese adolescents; a randomized controlled trial. Am J Clin Nutr, 2013.
15. Shab Bidar S, et al. Regular consumption of vitamin D-fortified yogurt drink (Doogh) improved endothelial biomarkers in subjects with type 2 diabetes: a randomized double-blind clinical trial.
16. von Hurst PR, Stonehouse W, Coad J. Vitamin D supplementation reduces insulin resistance in South Asian women living in New Zealand who are insulin resistant and vitamin D deficient – a randomised, placebo- controlled trial. Br J Nutr, 2010.
17. Pittas Ag, Chung M, Trikalinos T, et al. Systematic review: Vitamin D and cardiometabolic outcomes. Ann Int Med, 2010.