The rates of diabetes vary dramatically throughout the world. In some areas, this disease is nearly non-existant. In others, nearly half the population has it. A large percentage of the people with diabetes live in the United States where between 5 and 10 percent of the population is believed to have diabetes.

Diabetes Defined

Diabetes is actually two different diseases. In insulin dependent diabetes mellitus (IDDM), which used to be called juvenile onset diabetes, people produce inadequate amounts of the hormone insulin (or in some cases, none of it). Insulin is needed to transport blood sugar, or glucose, into cells. So without insulin, glucose builds up in the bloodstream. These people must have insulin injections to live.

In non-insulin dependent diabetes mellitus (NIDDM), which used to be called adult onset diabetes, the production of insulin varies. In many cases the cells are not responsive so that, again, glucose can't move into cells. NIDDM may or may not require insulin injections. In most cases this disease can be treated by diet and exercise. most people with diabetes in this country have NIDDM.

Insulin is actually involved in many processes in the body. High levels of blood glucose can be damaging to many organs and tissues. People with diabetes are more likely to have high levels of blood cholosterol and are at very high risk for atherosclerosis. Uncontrolled diabetes can lead to heart disease and can also cause damage to nerves, kidneys, reproductive organs, eyes and limbs. Controlling diabetes is very important.

Soyfoods and Diabetes

The best diet for most people with diabetes is one that is low in fat, high in complex carbohydrates (starch and fiber) and moderate in protein. No one food essential and no one diet will meet the needs of all people with diabetes. But soyfoods may have an interesting role to play in diabetes in two different ways:

• Soyfoods may slow the absorption of glucose into the bloodstream.
• Soy protein may help to prevent or control some of the complications of diabetes such as atherosclerosis (blockage of the arteries) and kidney disease.

Glycemic Index

The glycemic index is a measure of how much blood glucose rises when a particular food is consumed. Foods with a low glycemic index produce smaller rises in blood glucose which is helpful in the control of diabetes. Soybeans have a low glycemic index. This may be because soybeans are high in compounds called phytates and tannins, which slow the digestion and absorption of the starch in soybeans. All beans have a low glycemic index, but soybeans are even lower than other beans.

Soluble Fiber

Foods contain two types of fiber. Insoluble fiber is generally found in whole grains and vegetables. It is imoportant for the health of the intestines and may help to reduce the risk of colon cancer. Soluble fiber is found in beans, oats, fruits and some vegetables. It helps to delay the absorption of nutrients into the bloodstream and may help to control blood glucose levels. Soybeans and some soyfoods (such as tempeh, textured soy protein and soy flour) are rich in soluble fiber. The effects of soluble fiber are fairly small, but they can contribute to the control of blood glucose.

Soy Protein and Cholesterol

Since people with diabetes are at high risk for developing heart disease, they need to make a special effort to keep blood cholesterol levels low. The best way to do this is to eat a diet that is low in fat, especially saturated fat, and low in cholesterol. But the type of protein in the diet may help, too. Adding soy protein to the diet, or replacing animal protein with soy, has been shown to reduce blood cholesterol levels. The effect is best in people who have very high cholesterol levels to begin with. It also takes about 25 grams of soy protein - the amount in two to three servings of soyfoods - to have an effect. But including soyfoods in a low-fat diet can be one approach to reducing blood cholesterol levels for some people.

Soy Protein and Kidney Disease

People with diabetes are at high risk for developing kidney disease. Often, people with kidney disease need to reduce their protein intake since high protein diets may worsen kidney function. But there is some evidence that the type of protein people eat may be just as important as the amount. Replacing animal protein in the diet with soy protein has been shown, in some cases, to improve kidney function in patients.

Soyfoods and Fat

Most people with NIDDM are overweight. Weight loss is an important approach to controlling this disease and reducing fat intake helps with weight loss. Many soyfoods are high in fat. People who are watching their fat intake can choose some of the lower-fat or fat-free soyfoods which include textured soy protein, reduced fat tofu and reduced or nonfat soy milk.

The Diabetic Exchange List

To control blood sugar, many find it easiest to plan menus using Exchange Lists for Meal Planning, published by the American Dietetic Association. Soyfoods can be included in this menu planning approach using the following exchanges:

• 1/2 cup soybeans - 1 protein exchange
• 1/2 cup tofu - 1 protein exchange
• 1 tofu hot dog - 1 protein exchange
• 1/4 cup tempeh - 1 protein exchange
• 1/4 cup roasted soynuts - 1 protein exchange
• 1/4 cup prepared textured soy protein - 1 protein exchange
• 1 ounce soy cheese - 1 protein exchange plus 1 fat exchange
• 1 cup low-fat soy milk - 1 milk exchange
• 1 cup regular soy milk - 1 milk exchange plus one fat exchange

Soyfoods and Kidney Health

The kidneys are clusters of mini filters that sift unwanted chemicals out of the bloodstream and excrete them in urine. Diet can have an effect on both healthy and diseased kidneys. For example, diets high in protein cause healthy kidneys to filter blood at a much faster rate - a sign that the kidneys are working harder. In people who are susceptible to kidney disease, this extra work may be damaging over time.

While a slower filtration rate is a good sign in healthy kidneys, in kidney disease it is a sign of progressively worsening kidney funcion. In people with kidney disease, high protein intake may cause the kidneys to work more slowly and, over time, kidney function may deteriorate.

Diet for Kidney Disease

People ith kidney disease are often advised to eat a lower protein diet. These patients need to eat a diet that contains only about 50 grams of protein, which is close to the recommended daily allowance for protein. For comparison, many Americans eat over 100 grams of protein per day. Decreasing protein intake has an added benefit in kidney disease. It helps to limit the amount of phosphorus in the diet. Phosphorus is a nutrient that can make kidney disease worse, and it is found primarily in foods rich in protein.

In addition, patients with kidney diesease need to eat a diet that helps lower blood cholesterol levels. High blood cholesterol levels can cause damage to the kidneys and make kidney disease worse.

Soyfoods Can Help Kidney Disease Patients

Soybeans and the foods made from them have a role to play in treating kidney disease. First, there is evidence that the type of protein in soyfoods doesn't affect the kidneys in the same way that animal proteins do. In some studies, when patients replaced animal protein in their diet with soy protein, kidney funcion improved or was favorably affected. For this reason, some nutrition researchers suggest that kidney disease patients consume more of their protein in the form of soy.

This could be good news for people with kidney disease. Reducing the amount of protein in the diet can be a challenge to many people since it can require considerable dietary modification. Since so many soyfoods mimic other high protein foods in the diet, replacing some protein sources with soy protein can be a plesant way to change your diet.

Nutritionists need to do much more research on the relationship of soy protein to kidney disease. But unil more information is available, there is no disadvantage to using protein in the diets of people with kidney disease - and there may be some benefits.

Soyfoods may help people with kidney disease in one other way. The protein in soy helps lower blood cholesterol levels. It does take high levels of soy protein to do this, and the effects are best in people with high blood cholesterol levels.

Soyfoods and Kidney Stones

Although kidney stones are not life-threatening, they can be a very painful condition. Many of these stones contain calcium, and high amounts of calcium in the urine can cause kidney stone formation. Since high intake of animal protein increases calcium loss in the urine, people who tend to form kidney stones are often advised to reduce their intake of animal protein. One large study showed that the more animal protein men ate, the more likely they were to form kidney stones. Replacing some animal protein in the diet with soy protein may reduce kidney stone formation since soy protein does not raise the level of calcium in the urine as much as animal protein.

This information was prepared by Mark Messina, PhD, and Virginia Messina, MPH, RD, authors of The Simple Soybean and Your Health.