Type 2 diabetes is quickly becoming one of America’s most pressing public health concerns. Diabetes is the sixth leading cause of death in the United States; it is the leading cause of blindness, non-traumatic limb amputations, and kidney failure, and it costs the country more than $170 billion annually.
If current trends continue, 1 in every 3 Americans will be diabetic within the next four decades. Any single factor or combination of factors that could reverse this trend would be welcome news.
A study published in the August 2011 issue of The American Journal of Clinical Nutrition suggests that higher doses of vitamin D might be just such a boon.
Vitamin D – More like a Hormone than a Vitamin
Since the mid-twentieth century, scientists have recognized vitamin D’s importance in calcium metabolism. By increasing the absorption of calcium from your intestine and kidneys and enhancing the activity of cells that remodel your bones, vitamin D promotes skeletal health and helps maintain an electrochemical environment that permits normal nerve, heart, and muscle function.
During the past decade or so, scientists have learned that nearly every cell in your body possesses vitamin D receptors, or VDRs, that regulate a wide array of physiologic activities. Unlike other vitamins, which typically act as cofactors for metabolic enzymes or provide antioxidant protection, vitamin D circulates through your bloodstream, exerting hormone-like effects upon cellular VDRs in a wide range of tissues and organs.
One particular area that has drawn the interest of researchers is how vitamin D affects your immune system. Vitamin D is a vital participant in normal immune activity, and deficiencies of this essential nutrient have been linked to a variety of diseases, such as type 1 diabetes, multiple sclerosis, and rheumatoid arthritis.
Diabetes Is Characterized by Disordered Glucose Metabolism
Whenever you eat a meal, a hormone called insulin is released from specialized cells – beta cells – in your pancreas. Insulin’s primary function is to stimulate the cells of your liver, muscles and adipose tissue to absorb glucose from your bloodstream. Thus, insulin serves to remove glucose from your bloodstream, where it can be toxic, and enables the intracellular oxidation of glucose, which produces energy for all of your bodily functions.
If you have diabetes, you do not metabolize glucose normally. In type 1 diabetes, your pancreas does not produce enough insulin to remove glucose from your bloodstream. In type 2 diabetes, your cells are resistant to insulin’s effects, so glucose only moves into your cells slowly. In either type of diabetes, your blood glucose levels are elevated unless you take extra insulin and/or medications to improve insulin sensitivity.
People who are at risk for type 2 diabetes can often be identified by the presence of certain physical and physiologic traits. The constellation of abdominal obesity, high blood pressure, abnormal lipid levels (high triglycerides or low HDL cholesterol), and insulin resistance are all risk factors for type 2 diabetes. If you possess any three of these four traits, you have a condition called metabolic syndrome, which is quickly becoming the most important risk factor for diabetes and heart disease in the United States.
Vitamin D Improves Beta-Cell Function and Enhances Insulin Sensitivity
During a 16-week study involving 92 people who were at risk for type 2 diabetes, researchers at Tufts Medical Center in Boston, Massachusetts, demonstrated that taking 2,000 IU of vitamin D daily improved beta cell function – thereby enhancing insulin secretion – and blunted the rise in serum glucose among the study’s subjects.
Currently, the Institute of Medicine’s Food and Nutrition Board recommends that adults take 600 to 800 IU of vitamin D daily, depending on their age, with an upper limit of 2,000 IU. Some experts, such as Dr. Reinhold Vieth at Toronto’s Mount Sinai Hospital, believe that current recommendations for vitamin D intake are too low; these scientists contend that the current upper limit should represent the recommended daily dose, and the upper limit should be increased to at least 10,000 IU.
Whether long-term vitamin D “treatment” of at-risk individuals will reduce the impact of type 2 diabetes remains to be seen. However, given the role diabetes will play in the health of upcoming generations of Americans, a little of the “sunshine vitamin” seems like inexpensive insurance.
Sources
- Centers for Disease Control and Prevention: Number of Americans with Diabetes Projected to Double or Triple by 2050
- J Mitri, et al. Effects of Vitamin D and Calcium Supplementation on Pancreatic β Cell Function, Insulin Sensitivity, and Glycemia in Adults at High Risk of Diabetes: The Calcium and Vitamin D for Diabetes Mellitus (CaDDM) Randomized Controlled Trial. Am J Clin Nutr. 2011;94(2):486-94
- R Vieth. Critique of the Considerations for Establishing the Tolerable Upper Intake Level for Vitamin D: Critical Need for Revision Upwards. J Nutr. 2006;136(4):1117-1122
Stephen Allen Christensen - Dr. Steve Christensen's writing has appeared in magazines, professional journals, poetry anthologies, and children's books since 1976.
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