People with type 1 diabetes must receive injections of insulin to manage their blood glucose levels. An insulin pill isn’t yet on the horizon—as a protein, insulin would be digested if it passed through the GI tract. People with type 1 diabetes either give themselves injections several times per day, or have a medical device known as an insulin pump that delivers insulin as needed, particularly following a meal or snack. Regular monitoring of blood glucose levels with a glucose meter gives people with diabetes a way to track the impact of their food choices and activity level, so that they can adjust insulin injections accordingly to maintain desirable blood glucose levels. Type 2 diabetes, however, generally does not require insulin injections and can often be managed, and even prevented or reversed, by lifestyle modifications (including diet and physical activity) that promote insulin sensitivity and a healthy body weight.

109

Different foods have different effects on blood glucose, even when they contain the same amount of starch and sugars. Specifically, how the body processes particular carbohydrates dictates how much and at what rate glucose will be released into the bloodstream and therefore how much insulin is released. For example, starches in foods can be partially “trapped” within the physical structure of grains or in the internal portion of larger food particles. These physical structures can make it difficult for digestive enzymes to gain access to the starch, slowing digestion and the subsequent appearance of glucose in blood. Such starches, that remain undigested and enter the large intestine, are called resistant starches. Diets high in resistant starch may improve insulin sensitivity and make people feel full for longer periods. Examples of foods high in resistant starches include beans, under-ripe bananas, whole grain kernels, and pasta.

110

At the other extreme, starches in some foods—such as boiled potatoes and many breakfast cereals—are digested so quickly that blood glucose rises nearly as rapidly as what is seen after consuming an equal amount of pure glucose.

Surprisingly, sucrose, lactose, and fructose and foods that contain these sugars (such as candies, dairy foods, or fruit) often produce a less dramatic rise in blood glucose than starchy foods. This is because fructose and galactose (a monosaccharide in lactose) have no immediate impact on blood glucose levels, until they are converted to glucose in the liver. Diets high in fiber, especially soluble fiber, also seem to help control blood glucose levels. One study found that people who consumed 50 grams of fiber per day with at least half as soluble fiber were able to control their blood glucose better than those who ate less fiber.

Since food sources of carbohydrates have different effects on blood glucose levels, Laffel tells children and their families to pay attention to a measure known as glycemic index (GI) which ranks foods by how quickly and to what degree they raise blood glucose levels. The amount of available carbohydrate (starch and sugars) present in the food is compared with the equivalent amount of glucose, which has a GI of 100. Foods with a high GI raise blood glucose quickly and cause considerable spikes in blood glucose levels, while foods with a low GI cause a smaller and more gradual increase. Low GI diets help individuals with diabetes better control blood glucose levels and are associated with reduced risk of developing type 2 diabetes.

Although glycemic index can be a helpful measure to consider, it has some limitations. For example, we rarely eat carbohydrate containing foods in consistently the same amounts (smaller or larger amounts would alter the GI) or eat these foods by themselves. And even carbs with high GIs have less effect on blood glucose when consumed with protein, fat, or fiber, which all delay gastric emptying. Even factors such as the ripeness of a fruit or how a carbohydrate is processed can alter its GI. (INFOGRAPHIC 5.7)

111

Question 5.7

The GI of a food, however, often does not reflect the amount of carbohydrates contained in the servings of food that we typically consume. Foods with a low to moderate GI can still cause a dramatic rise in blood glucose levels if consumed in large amounts. So consumers can also consult the glycemic load (GL), which calculates the effect of the actual serving size of food on blood glucose (by multiplying the GI by a food’s grams of carbohydrates, divided by 100). The GL is a more useful assessment of a food’s effect on blood glucose.

Some research suggests that diets emphasizing low-GI and low-GL foods in the overall diet may help manage diabetes, control body weight, and improve other health conditions. In addition, low-GI foods are often rich in fiber and other nutrients, which have clear benefits for health.

Registered dietitians and other health care providers may also teach their patients with diabetes about carbohydrate counting, or “carb counting,” a meal-planning technique that can help manage blood glucose levels. If part of the person’s diabetes management is to keep blood glucose levels in a desirable range, they can determine the total amount of carbohydrates (in grams) to include each day according to their energy needs and activity level. By portioning out that total among the day’s meals and snacks, they are better able to align their diet and medication. But those with diabetes have to do more than just watch their carbohydrate intake. Individuals with diabetes have a much higher risk of death from heart disease than those without diabetes; therefore, they also have to keep track of their fat intake, limiting saturated fat to less than 7% of their total calories, and eating as little trans fat as possible. Some fats are heart healthy, though, and doctors will often tell people with diabetes to eat two or more weekly servings of fish, which provide omega-3 polyunsaturated fatty acids.

112

Physical activity also helps improve insulin sensitivity, lower blood glucose levels, and keep weight off over the long term. Exercise alone may not be enough—but that, plus weight control and a varied and balanced diet, provide the foundation for managing and preventing type 2 diabetes.

When those lifestyle changes aren’t enough, oral medications are available to lower blood glucose levels of individuals with type 2 diabetes, and some people may require insulin injections to get their glucose under control.

It is possible to overmedicate patients with diabetes; they can develop hypoglycemia, in which their blood glucose levels drop too low (diagnosed when < 70mg/100 ml blood), causing symptoms ranging from irritability, headache, hunger, weakness or fatigue, sweating, and rapid heartbeat.

There are different types of hypoglycemia— fasting hypoglycemia, for instance, occurs when people have not eaten, have drunk too much alcohol, or have underlying hormonal conditions or tumors, such as pancreatic tumors. People with reactive hypoglycemia, in contrast, experience symptoms when they eat large amounts of carbohydrates, causing a huge release of insulin and rapid drop in blood glucose. (In response, the adrenal glands release epinephrine—also known as adrenaline—which, like glucagon, functions to raise blood glucose by stimulating glucose synthesis in the liver.) The best way to manage or prevent hypoglycemia is to not eat too many carb-heavy meals or snacks, include some protein along with carbohydrates, and emphasize foods that contain fiber, particularly soluble fiber.

■ ■ ■

Today, millions of people take insulin and, along with appropriate diet and physical activity, are able to manage their diabetes and lead productive, healthy, and happy lives.

Although the work of Banting and his colleagues to develop insulin revolutionized diabetes therapy, scientists are continuing to investigate ways to treat diabetes without relying on cumbersome and unpleasant injections—and hopefully prevent and cure it altogether. “Insulin therapy is like the difference between automobiles between 1922 and 2013—we’ve got vastly better automobiles,” says Bliss. “But is there something better than the automobile? Is there something better than insulin that can effectively cure diabetes, and reverse the damage done? Scientists have kept trying and trying.” And in the past several decades, the development and widespread use of effective and safe synthetic human insulin has made the dependence on cow and pig pancreatic cells obsolete.

113

Research toward a cure for type 1 diabetes is ongoing and varied in approach. Efforts have been made to understand the immune system attack that causes type 1 diabetes, and to intervene in that process. Another important effort is to regenerate the cells that produce insulin through the use of embryonic or adult stem cells.

While the development of insulin therapy revolutionized diabetes treatment, today we face an increasing epidemic of type 2 diabetes and concern about the long-term consequences of living with diabetes. Scientists are therefore continuing to investigate better ways to treat all different types of diabetes with the hope of one day preventing and curing it altogether.