Diabetes mellitus can be controlled by diet, exercise, and medications, as needed. When it is not well controlled, it affects many parts of the body, particularly the heart, eyes, kidneys, and nerves. In addition, birth complications occur more often in infants born to women with poorly controlled diabetes.
Prevention of complications depends on control of blood sugar and managing the major risk factors for heart disease, such as smoking, blood pressure, and high cholesterol. Diet plays an important role, along with exercise and appropriate medications.
Cardiovascular disease is the leading cause of death in individuals with diabetes. Control of cardiac risk factors is therefore essential.
- Regular check-ups, including a physical examination and blood testing, are recommended for all individuals with diabetes. Further, an EKG or cardiac stress testing may be appropriate for some patients.
- Blood pressure control is particularly important. The goal blood pressure should be less than 130/80 millimeters of mercury (mmHg), and further lowering may be beneficial.
- The goals for blood cholesterol levels are somewhat different for people with diabetes than for the general population. Low density lipoprotein (also called LDL, or "bad" cholesterol) should be less than 100 milligrams per deciliter (mg/dl), or 2.6 millimoles per liter (mmol/L), in the measuring system used outside the U.S. In certain patients (especially those with known heart disease), the goal may be less than 70 mg/dl (1.8 mmol/L). Triglycerides (particles of fat in the bloodstream) should be less than 150 mg/dl, and high density lipoproteins (HDL or "good" cholesterol) should be greater than 45 mg/dl (1.2 mmol/L) for men and greater than 55 mg/dl (1.4 mmol/L) for women.
Dietary and behavioral modifications, including smoking cessation and loss of excess weight, are important for the prevention and management of cardiac complications. When further therapy is needed, specific medicines may be helpful.
- An aspirin a day is recommended for most persons older than 30, particularly in those who have additional cardiovascular risk factors. Potential side effects must be considered, including ulcers and bleeding.
- Hypertension in diabetes patients should be treated with an angiotensin-converting enzyme (ACE) inhibitor (e.g., lisinopril) or angiotensin receptor blocker (e.g., losartan). Further drugs to lower blood pressure may be required, including diuretics, beta blockers, and calcium channel blockers
- Cholesterol-lowering medications, such as statins, are likely to be effective in reducing cardiovascular risk.
To reduce the risk of cardiac complications, the appropriate dietary changes are those that improve cholesterol levels, reduce blood pressure, and control blood sugar. These steps are discussed in detail in the chapters on coronary heart disease, hyperlipidemia, hypertension, and diabetes. Here are two important nutritional considerations:
- A substantial body of evidence suggests that a combination of a vegetarian diet, regular exercise, smoking cessation, and stress management yields greater improvements in cardiovascular disease, compared with other regimens.
The Multicenter Lifestyle Demonstration Project, which included 440 patients with coronary artery disease, of whom 91 also had diabetes, showed that such a regimen benefits those with diabetes about the same as it benefits those without diabetes. In a randomized, controlled trial of individuals with type 2 diabetes, a low-fat vegan diet reduced LDL cholesterol by 21 percent and reduced triglycerides by 16 percent among participants. These changes were particularly remarkable in that many of the study participants were already receiving cholesterol-lowering medications, yet the diet led to substantial further improvements.
The type of carbohydrate in the diet may be important. Diets high in refined carbohydrates and "simple" sugars may increase triglyceride levels for some individuals, but high-carbohydrate diets that are drawn from high-fiber and complex carbohydrate foods - beans, starchy vegetables, and whole grains - appear to have the opposite result.
- A randomized controlled clinical trial of alpha-lipoic acid supplementation, administered at 800 mg/day for four months, showed improvements in heart and nerve function. However, further study with a larger number of individuals is required to assess whether these initial findings bear out.
Complications of Diabetes Mellitus: Eye Complications
Changes in the retina pose a major long-term threat to vision. This is due to damage to the blood vessels and nerves of the eye, which is primarily caused by poor control of blood sugar. Improved control of blood sugar has been shown to reduce the risk of eye damage in many studies. Blood pressure control is also important; it reduces the risk of eye damage.
- Poor blood sugar control
- Longer duration of diabetes
Eye damage can be diagnosed during a routine ophthalmologic examination.
- The best approach is prevention by use of appropriate diet, exercise, and medications to control blood sugar and blood pressure .
- In some advanced cases, laser surgery may be used.
Nutritional interventions that improve blood sugar, blood pressure, and cholesterol levels may help prevent or slow eye damage. A specific diet therapy to prevent eye damage has not yet been established. However, evidence from the Diabetes Complications and Control Trial suggested that diets high in fat and low in fiber may increase the risk for eye damage.
Complications of Diabetes Mellitus: Kidney Disease
Diabetic kidney disease, if uncontrolled, can result in kidney failure and the need for dialysis or kidney transplantation. Persistently elevated blood pressure increases the risk, as do high blood sugar, cholesterol, and triglyceride levels.
All individuals with diabetes are at risk for kidney disease. Pima Indians with type 2 diabetes have a particularly high risk of kidney disease and African-Americans with type 2 diabetes appear to have more than four times the risk of kidney failure, compared with Caucasians. This may also be true for Native Americans and Mexican-Americans.
Risk factors include:
- Family history of diabetic kidney disease
- Poor blood sugar control
- Dietary factors (see Nutritional Considerations below)
Other possible risk factors include obesity, increasing age, duration of diabetes, and smoking.
- The first steps are a medical history and a physical examination.
- Blood and urine testing will be performed.
- Control of blood sugar is essential for preventing further kidney damage.
- If blood pressure is not controlled through diet and lifestyle changes (to below 130/80), treatment with ACE inhibitors (e.g., lisinopril) or/and angiotensin receptor blockers (e.g., losartan) helps prevent worsening of kidney damage. Calcium channel blockers or diuretics may be appropriate substitutes.
- Control of cholesterol and triglyceride levels is important.
- Weight loss is helpful, perhaps because of its beneficial effects on blood sugar, blood pressure, and cholesterol.
Reducing saturated fat, cholesterol, and animal protein intake may reduce the risk for kidney damage. Excessive intake of total protein and animal (not vegetable) protein has been shown to be a risk factor for abnormal kidney function. In short-term studies, vegetarian diets and diets deriving protein primarily from soy and other plant sources have improved kidney function. These diets also improve blood pressure control, which further helps reduce the risk for kidney damage. In addition, dietary sodium restriction is recommended.
Complications of Diabetes Mellitus: Nerve Damage
Nerve damage is a particularly common diabetes complication that affects approximately half of all diabetes patients. Symptoms may include loss of sensation, tingling, or pain in the extremities. If severe, nerve damage may lead to joint deformities and infections that ultimately require amputation.
- Poor blood sugar control
- Long duration of diabetes
A medical history and a physical examination are used to diagnose nerve damage. A diagnosis can be made by simple tests that measure whether the patient can sense vibration, hot or cold objects, or pain in the extremities.
- Diabetic nerve damage is best addressed through prevention, which requires good control of blood sugar. In cases of existing nerve damage, symptoms may improve with diet and lifestyle changes, as noted below.
- In addition to good control of blood sugar, appropriate foot care is essential. Properly fitted shoes, foot hygiene, daily foot inspection for areas of irritation (special mirrors can help), regular nail care, and immediate consultation with a health care provider whenever an abnormality occurs are all important.
- Medications also may help alleviate painful symptoms of nerve damage. These include antidepressants, anticonvulsants (e.g., carbamazepine and gabapentin), and capsaicin cream.
The following nutritional considerations may help decrease symptoms:
- A combination of a vegetarian diet and exercise may have particular value in treating diabetic nerve damage. One study tested the effects of a vegan diet and regular walking on 21 individuals with pain due to nerve damage; symptoms completely disappeared in 17 study participants and improved in the remainder. Evidence suggests that in addition to the effect of vegetarian diets on blood sugar control, their effect on body weight, blood pressure, and cholesterol are important. Future clinical trials are needed to determine the value of dietary modifications for this condition.
- In addition to the benefits of a diet and exercise regimen, some nutritional supplements have shown potential benefit. Alpha-lipoic acid appears to be safe and effective for improving symptoms of diabetic nerve damage in long-term and short-term clinical trials. Other supplements under investigation include gamma-linolenic acid, carnitine, and magnesium.
- Complications of Diabetes Mellitus: Complications for the Newborn
Women with diabetes should take special care during pregnancy. A particular concern is unusually large birth weights in their newborns. Some women develop diabetes mellitus during pregnancy, a condition that disappears after delivery; this is called gestational diabetes. Although gestational diabetes is not associated with an increase in birth defects, it can cause other difficulties, such as increased birth weight, birth trauma, and an increased risk of cesarean section.
Avoiding complications requires good blood sugar control before pregnancy. Women with diabetes can be counseled to plan their pregnancies so that good control can be started early. In particular, control of blood sugar has been shown to prevent increased birth weight, which increases the risk of many complications of delivery