Checking Out Vitamin D's Role in Type 2 Diabetes
Some studies suggest that maintaining high vitamin D status may be important for protection from type 2 diabetes. Type 2 diabetes is 20 times more common than type 1 diabetes, and the incidence is rising at an alarming rate as the population becomes heavier and more sedentary.
Even in a person who seems destined to develop type 2 diabetes because of family history, it’s possible to hold off or prevent the disease by maintaining a normal weight, eating properly, and doing plenty of physical exercise.
Type 2 diabetes develops in response to three factors:
As body weight increases, your body becomes insensitive to your own insulin and the pancreas puts out high levels of insulin in order to keep the blood sugar normal.
Over time, the pancreas begins to fail so that it can no longer make the large amounts of insulin levels needed by the insulin resistance.
The intestines make less of other hormones (called incretins) that normally boost insulin release, slow stomach emptying, and increase the feeling of fullness so that you eat less. With low levels of incretins, people developing type 2 diabetes eat more and gain more weight.
Describing type 2 diabetes
In the early stages of type 2 diabetes, the pancreas compensates for insulin resistance by pumping out more insulin. Later on, the pancreas begins to fail, meaning that it can’t make enough insulin to maintain normal blood glucose any longer, and the blood glucose rises above the levels that define diabetes: 126 mg/dl (7 mmol/L) or greater after an overnight fast, or 200 mg/dl (11.1 mmol/L) or greater after eating.
When high levels of glucose in the blood are maintained for ten or more years, the following damage may result:
Changes in the eye that can lead to the formation of cataracts (clouding of the eye lens) and glaucoma (a disease involving high fluid pressure within the eye that can cause blindness).
Changes in the back of the eye (retinopathy) that involve leaks forming in the existing blood vessels as well as new blood vessel formation (neovascularization). These changes can lead to blindness and retinal detachment.
Changes in the kidneys may lead to kidney failure.
Changes in the nerves of the body may lead to a variety of abnormalities of sensation or movement, the most common of which is tingling and numbness, as well as loss of sensation in the feet.
Changes in the heart and blood vessels may lead to heart attack, stroke, or decreased or absent blood flow to the legs and feet.
The combination of nerve damage and peripheral vascular disease leads to ulcers and infections in the feet that do not heal. These infections can progress to gangrene and may require amputation.
Type 2 diabetes used to be known as adult-onset diabetes or non-insulin-dependent diabetes. The last name is a little misleading — type 2 diabetes is still a problem with insulin, and many people end up being treated with it. The name derived because it’s not immediately life-threatening to go without insulin treatment in type 2 diabetes.
Type 2 diabetes: treatment and prognosis
Because the pancreas is intact but failing in type 2 diabetes, treatments range from making the body more sensitive to its own insulin, to boosting insulin production even further, to suppressing glucagon production, to slowing carbohydrate absorption in meals.
A major way to accomplish this at the start is lifestyle change. The patient must lose weight and begin a lifelong habit of daily exercise. By doing this a person can delay or prevent all the blood glucose abnormalities and the complications of diabetes. The problem is that many people cannot sustain the lifestyle changes necessary to slow type 2 diabetes.
All treatment in type 2 diabetes begins with weight loss, consuming a nutritional diet, and exercise. If diet and exercise aren’t completely successful, options include numerous classes of pills and injections, up to and including insulin, to bring blood glucose under control.
If you bring diabetes under control with diet and exercise, you generally bring high blood pressure and high cholesterol under control as well. It’s like killing three birds with one stone.
Vitamin D's role in type 2 diabetes
Type 2 diabetes is a lifestyle disease linked closely to overweight and obesity. Because obesity leads to lower serum 25-hydroxyvitamin D levels, it becomes harder to link vitamin D status directly to type 2 diabetes risk. However, some studies do suggest that maintaining high vitamin D status may be important for protection from type 2 diabetes.
Type 2 diabetes results from insulin insensitivity and a relative lack of insulin:
Calcitriol (active vitamin D) increases insulin production in cultured pancreatic beta cells and increases insulin sensitivity in cultured muscle cells.
African Americans, who have the lowest levels of vitamin D because of their skin pigmentation, have the highest levels of type 2 diabetes. However, they also have a higher prevalence of overweight and obesity — two well-established risk factors for the disease.
High vitamin D status is associated with a lower risk of developing type 2 diabetes.
Normal levels of vitamin D are associated with control of many things that cause complications in diabetes: higher levels of HDL-C, lower levels of LDL-C, better blood pressure control, and reduced hemoglobin A1c levels.
The impact of vitamin D supplements is just starting to be explored in small clinical trials.