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In this article:
Key Points
- Diabetes is a disease in which glucose builds up in the bloodstream and is eventually cleared from the body through the kidneys, rather than entering cells and providing energy to the body.
- About 18.2 million Americans – 6.3% of the total US population – have diabetes. Of these, 5.2 million who have diabetes aren’t even aware of it.
- People with diabetes are two to six times more likely to have atherosclerosis than people without diabetes, putting them at greater risk of heart attack and stroke.
- The better a person controls blood sugar, the less likely that long-term complications may develop or worsen.
The foods that we eat are broken down by the digestive tract into smaller substances that enter the bloodstream, providing all the nutrients our bodies need to function properly and stay healthy. Minerals, such as sodium, potassium, and calcium, are important for keeping the body’s systems running and are used for strong bones and teeth. Fats are used for energy and to help build cell walls. Glucose, a type of sugar, enters cells throughout the body – including the heart – and also provides energy.
There are several different types of sugars and almost all foods provide the body with some form. A key player for the body’s use of sugar in the form of glucose is insulin. Insulin is a hormone that is released from the pancreas when we eat meals and helps glucose transfer from the blood into cells. Therefore, insulin levels are typically high after a meal, and are lower again in a few hours, after the meal has been digested and sugar levels in the blood are decreased.
Diabetes defined
Diabetes is a disease in which glucose builds up in the bloodstream and is eventually cleared from the body through the kidneys, rather than entering cells and providing energy to the body. This can happen because the pancreas either produces little or no insulin, or, there may be enough insulin being released after a meal but the cells in the body don’t respond to it, making them unable to let the glucose in. In either case, your blood sugar levels become too high while your cells remain short of glucose. The result: diabetes symptoms that may include frequent urination, excessive thirst and hunger, weight loss, blurred vision, nausea, fatigue, and drowsiness.
There are two major forms of diabetes:1
Type 1 Diabetes: With this form, almost all of the insulin-producing cells in the pancreas have been destroyed by the body’s own immune system. The trigger for this destruction may be related to environmental or genetic causes. Type 1 diabetes usually develops in people under 30 years of age. In fact, it used to be called juvenile-onset diabetes or insulin-dependent diabetes mellitus (IDDM). Approximately 5% to 10% of all cases of diabetes account for the Type 1 form.
Type 2 Diabetes. About 90% to 95% of people with diabetes have this form. The pancreas still produces insulin but the cells of the body have become resistant to its effects. Over time, the pancreas may stop making insulin altogether. Formerly called adult-onset diabetes, or noninsulin-dependent diabetes (NIDDM), the main risk factors associated with Type 2 diabetes include older age (though children and adolescents are also beginning to acquire the Type 2 form at an alarming rate), obesity, physical inactivity, and a family history of the disease.
Doctors diagnose diabetes with a blood test, usually measured after at least two overnight fasts. Another blood test is the glycated hemoglobin – or HbA1c – test that measures overall sugar control during the previous two or three months. Doctors may also use a glucose tolerance test, in which you drink a very concentrated sugar solution after an overnight fast. Your blood sugar level is then measured hourly for three hours. This is a very common test for women who may be at risk for experiencing diabetes during their pregnancy.
According to the American Diabetes Association (ADA) and the Centers for Disease Control and Prevention (CDC), about 18.2 million Americans – 6.3% of the total US population – have diabetes. Of these, 5.2 million who have diabetes aren’t even aware of it. What’s more, approximately 1.3 million new cases are diagnosed in the United States each year in people 20 years of age and older.1 By the year 2030, the number of cases of diabetes is expected to rise to more than 30 million Americans, including both diagnosed and undiagnosed people.2
Some racial and ethnic groups are more prone to Type 2 diabetes. For example, African Americans and Hispanic Americans have about twice the risk as white people. About 17% of Japanese-American men 71 to 93 years of age have recognized diabetes and 19% have undiagnosed diabetes. The number of Native Americans between the ages of 45 and 74 years who have diabetes is startling: 43.5% of men and 52.4% of women.3
For people who have not been diagnosed with diabetes, having blood sugar levels tested is important because it is possible to have diabetes without knowing it. Testing may reveal "pre-diabetes", in which blood glucose levels are higher than normal but fall short of the diabetes range.
People with pre-diabetes may have no symptoms, but the condition is a strong warning sign that should not be ignored. According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), most people with pre-diabetes will develop Type 2 diabetes within 10 years, unless they lose weight through diet and exercise.4
Diabetes may increase your risk of heart disease
Diabetes is a serious disease that can affect many parts of the body, including the heart and brain. When sugar levels are high, levels of fatty substances in the blood tend to rise, which may lead to
atherosclerosis (narrowing or clogging of the
arteries). People with diabetes are two to six times more likely to have atherosclerosis than people without diabetes, putting them at greater risk of heart attack and stroke.5
Diabetes can pose many long-term complications, such as damage to the nerves, eyes, kidneys, legs, and skin. If diabetes damages heart nerves, a person may not feel the chest pain or discomfort called angina, an important warning sign of heart disease.6 This means that even though diabetes increases the risk of heart disease, some people may be less likely to notice that they have heart disease symptoms.
Unfortunately, diabetes also increases your risk of coronary artery disease (CAD). The leading cause of death in people with diabetes is heart disease. A survey by the ADA indicated that 68% – a full two-thirds – of the 2000 participants did not know their risk of cardiovascular disease and its relation to diabetes.7 See Coronary Artery Disease for more information.
The higher risk makes it crucial for people with diabetes to take aggressive steps to prevent or delay heart disease. This includes having regular medical checkups and working closely with one’s doctor to manage diabetes and control risk factors for heart disease, such as smoking, high blood pressure, and high cholesterol.
Diabetes management
Controlling blood sugar levels is central to diabetes treatment. The better a person controls blood sugar, the less likely that long-term complications may develop or worsen. To treat diabetes, doctors often prescribe dietary changes, increased physical activity, weight control, and medications.
People with Type 1 diabetes must inject insulin several times daily to mimic how the body would naturally release insulin in response to meals, if it were able to do so. Some patients opt to wear a pump that delivers very small amounts of insulin continuously throughout the day and night through a needle or catheter inserted in the skin. Extra doses of insulin can be pumped in close to mealtimes to manage the expected increased level of glucose in the blood. Though blood glucose must still be monitored daily, people who use the pump prefer it over injections because it helps them lead a more normal lifestyle.
People with Type 2 diabetes may not need medication to control blood sugar if they can keep their levels in check by eating a proper diet, exercising, and maintaining a healthy body weight. Because extra fat interferes with the body’s ability to use insulin, exercise and weight loss can make the body respond better to insulin. This goes a long way in providing patients who have full-blown disease a chance to prevent or delay diabetic complications, and gives patients with pre-diabetes a chance to prevent or delay the onset of Type 2 diabetes. You can learn more in Nutrition Matters and Exercise for Heart Health.
If blood sugar levels can’t be managed through diet and exercise, a medication, such as oral anti-diabetic drugs (taken by mouth) and/or insulin injections may be needed. Oral anti-diabetic drugs can reduce blood sugar levels in Type 2 diabetes, but they do not work for Type 1. Furthermore, patients with diabetes may also need drugs to control high cholesterol and high blood pressure, all of which may help cut the risk of heart attack and stroke.
Several different types of medications are available to help control Type 2 diabetes. Your doctor will select which one may be best for you. People with diabetes may sometimes need to take more than one type. All anti-diabetic drugs are used to help support the positive results of diet and exercise. Some common types are:8
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Alpha-glucosidase inhibitors work in the digestive tract. When sugars are eaten, these drugs help slow down the rate the body takes up sugars from the digestive tract and cause a smaller rise in blood sugar levels after meals. Over time, this results in lower HbA1c levels and better blood sugar control.
Biguanides help keep blood sugar levels in check both between and after meals. They do this by decreasing the amount of glucose made in the liver for the body, decreasing the amount of sugar that is passed into the body from the digestive tract after meals, and increasing the amount of insulin the body’s cells are able to take up and use. Meglitinides work by helping the pancreas release more insulin to the body, keeping blood sugar levels lower after meals. Sulfonylureas help the pancreas release more insulin to the body so that sugar can be changed into energy. These drugs also help the cells of the body take up insulin from the blood so that blood sugar levels are better controlled. - Thiazolidinediones help cells of the body better respond to the action of insulin so that more blood sugar can be taken up and used for energy.
Metabolic syndrome
Metabolic syndrome, also known as insulin-resistance syndrome, isn’t an actual disease but a cluster of heart disease risk factors. Genes may play a role in determining who develops the syndrome. Doctors may diagnose metabolic syndrome when a person has at least three of the five following conditions:8
Excess weight around the waist (measuring more than 40 inches for men and 35 inches for women) High levels of triglycerides [150 milligrams per deciliter (mg/dL) or higher] Low levels of HDL (good) cholesterol (below 40 mg/dL for men, below 50 mg/dL for women) High blood pressure [130/85 millimeters of mercury (mm Hg) or higher] High fasting blood glucose levels (110 mg/dL or higher)
Research suggests that people with metabolic syndrome may also face an increased risk of developing Type 2 diabetes or heart disease. In one study, researchers found that men with metabolic syndrome had 1.7 times the risk of CAD and 3.5 times the risk of developing diabetes after five years of follow-up. The greater the number of factors, the higher the risk: the same study found that men with four or five features of metabolic syndrome had a 3.7-fold increase in heart disease risk and a 24.5-fold increase for diabetes.9
The earlier doctors are able to identify people who may be prone to diabetes, the sooner lifestyle changes can be prescribed to prevent or delay the disease.
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Sources
1. Centers for Disease Control and Prevention. National diabetes fact
sheet: general information and national estimates on diabetes in the United States, 2002. Atlanta, GA: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, 2003. http://www.diabetes.org/diabetes-statistics/national-diabetes
-fact-sheet.jsp. Accessed June 8, 2004.
2. Wild S, Roglic G, et al. Global prevalence of diabetes: Estimates for the year 2000 and projections for 2030. Diabetes Care, 2004; 27:1047-53.
PubMed
3. Statistical Fact Sheet – Risk Factors: Diabetes Mellitus Statistics. American Heart Association, 2004. http://www.americanheart.org/downloadable/heart/
1077868087937FS12DIAB4.pdf. Accessed June 8, 2004.
4. Insulin Resistance and Pre-diabetes. National Diabetes Information Clearinghouse (NDIC), National Institute of Diabetes and Digestive and Kidney Diseases, NIH Publication No. 03-4893, May 2004. http://diabetes.niddk.nih.gov/dm/pubs/insulinresistance/ . Accessed June 8, 2004.
5. Diabetes Mellitus. The Merck manual of Medical Information, 2nd ed. Ed. M.H. Beers et al. New Jersey: Merck & Co., Inc., 2003. p.962
6. Prevent Diabetes Problems: Keep Your Heart and Blood Vessels Healthy. National Diabetes Information Clearinghouse (NDIC), National Institute of Diabetes and Digestive and Kidney Diseases, NIH Publication No. 03-4283, September 2003. http://diabetes.niddk.nih.gov/dm/pubs/complications_heart/ . Accessed June 8, 2004.
7. Results of Diabetes-Heart Disease Link Survey Released. Diabetes Dateline, Winter 2002-2003, National Diabetes Information Clearinghouse, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health. http://diabetes.niddk.nih.gov/about/dateline/wint03/9.htm. Accessed June 8, 2004.
8. Drug Facts and Comparisons 2004, 58th ed. Ed. Cada DJ et al. St. Louis, MO: Wolters Kluwer Health, 2003. p. 363-386.
9. Redefining diabetes control. Diabetes and Cardiovascular Disease Review, 2002, Issue 1, p. 1-3. http://www.diabetes.org/uedocuments/DCVDissue1.pdf. Accessed June 8, 2004.
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