Diabetes and Heart Health: What is the link?

Over the past decades there has been a dramatic rise in the number of people with type II diabetes. Once a fairly rare disease, increasing rates of obesity have driven a climb in the number of cases globally. The number of adults with type II diabetes has more than doubled since 1980, rising from 153 million (1) to 415 million in 2015, and predictions are that it will affect 640 million people by 2040 (2). This has concerning consequences for worldwide heart health. Diabetes is one of the major risk factors for cardiovascular disease, and cardiovascular disease rates will rise in response to the diabetes epidemic (3). Measures taken to prevent or treat diabetes will improve heart health around the globe.

What is diabetes?

Diabetes is a disease where blood glucose levels are too high over a long period of time. Blood glucose is required for energy and is kept at a stable concentration by the action of insulin. Normally after a meal, glucose levels rise and this triggers a rise in insulin. Insulin tells the body to start to take up glucose from the blood and blood sugar falls again. Insulin keeps blood glucose levels from increasing too much. When people have diabetes, blood glucose can no longer be controlled effectively by the action of insulin.

Three types of diabetes

There are three types of diabetes: type I, type II and gestational diabetes. Type I diabetes normally starts in childhood when the cells in the pancreas that make insulin do not function properly. The exact cause is unknown however it is thought that the combination of genetics and an environmental trigger cause the body to destroy the insulin-making cells. This means that the body cannot make enough insulin to reduce blood glucose levels after a meal, and the body also cannot get the nutrients that it needs for normal growth and development. Insulin must be given as a treatment. The prevalence of type I diabetes has remained stable.

Type II diabetes tends to start later in life. For this type of diabetes, the cells in the body do not react to the insulin that is being produced. Cells do not take up glucose as they should, and blood glucose levels remain. Further along the course of the disease, the body’s ability to produce insulin is also reduced. Type II diabetes is far more likely to occur in obese, sedentary adults.

In gestational diabetes, the state of pregnancy means that the body’s cells are less able to take up glucose from the blood. It is thought that this helps the fetus to secure its own supply of glucose by preventing the mother from using it for herself. Gestational diabetes generally resolves after the mother has given birth, however women who have had gestational diabetes are at a higher risk of developing type II diabetes later in life (4).

How is diabetes linked to heart health?

The two pillars of heart health are healthy blood vessels and a healthy heart. High blood glucose levels can affect both. Firstly, high blood glucose gets in the way of the normal expansion of the blood vessels. Blood vessels can expand and contract to adjust for different blood flow. When blood glucose levels are high, blood vessels cannot expand properly to allow for blood flow changes. High blood pressure results. High blood pressure damages the small blood vessels in organs, and is the main cause of diabetic complications such as blindness and kidney failure. Secondly, high blood glucose makes changes to white blood cells so that they are more likely to form a plaque in arteries. This increases the risk of a heart attack. Thirdly, high blood glucose levels change blood platelets so that they are “spiky” and more likely to cause clots in arteries, thus contributing to the risk of stroke (5).

People with diabetes need to closely control their blood glucose to avoid very high and very low levels. Reducing elevated blood glucose levels is a key strategy to support heart health (5). People with type I diabetes cannot make enough insulin themselves, and it is provided as an injection or semi-continuous pump. They should also adopt a lifestyle that avoids extreme spikes and dips in their blood glucose through regular exercise and a healthy diet. Type II diabetes and gestational diabetes can often be managed in the early stages with diet and lifestyle changes alone. However, many people use medication to gain control over their blood glucose (5).

Key lifestyle approaches for diabetes and heart health (3)

Choose low glycemic index foods
Maintain a healthy weight
Exercise regularly
Eat more fruits and vegetables
Limit saturated fat
Reduce salt intake

Nutrition for Diabetes

Regardless of the type of diabetes, a healthy diet and lifestyle are important for managing the condition. For type II diabetes, modest weight loss of around 5 percent can help to manage blood sugar. Excess body fat contributes to insulin resistance (6). Tied in with weight loss, regular exercise helps muscle cells to be more responsive to insulin, thus providing better control of blood glucose (7). Healthy dietary advice promotes increasing the consumption of fruit and vegetables, and limiting intakes of fat and salt. These measures are proven to help reduce the risk of cardiovascular disease, and are also appropriate for diabetics (3).

Foods containing carbohydrates raise blood glucose levels. The ability of a food to raise blood glucose levels is called the “glycemic index”. Some foods, such as boiled potatoes or pasta made from refined grains, cause a sharp increase in blood glucose after they are consumed and are considered to have a high glycemic index. Foods with large amounts of fiber make blood glucose levels rise more slowly. Foods containing a lot of fruit sugars also give a much slower rise in blood glucose, because these fruit sugars must be converted to glucose by the liver, which is a slow process. Fruit and high fiber foods are considered to have a low glycemic index. It is better for diabetics to choose low glycemic index foods because blood glucose levels rise slowly, making them easier to control (8).

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