According to International Diabetes Federation’s (IDF) Diabetes Atlas 2015, 1 in every 52 adults aged 20 – 79 years in Ghana has diabetes and the numbers are expected to continue to rise as even greater numbers are un-diagnosed. There are three main types of diabetes; Type 1, Type 2 and Gestational diabetes. Type 2 diabetes is the commonest and accounts for at least 90% of all cases of diabetes. In this article, we give an overview of the science behind the dietary management of Type 2 Diabetes.
What is Type 2 Diabetes?
Type 2 diabetes is a chronic disease characterised by insulin resistance and or relative insulin deficiency leading to high blood glucose (blood sugar) levels. Insulin is a hormone, produced by the pancreas and is required to transport glucose from the bloodstream into the body’s fat and muscle cells for energy. In insulin-resistance, the body’s cells become less responsive to the action of insulin, therefore glucose accumulates in the bloodstream leading to higher than normal levels. Over time, the high level of high blood glucose damages many body organs and tissues such as heart, blood vessels, eyes, kidneys and nerves leading to complications of kidney failure, heart diseases, strokes, blindness and leg and foot amputations.
There are several risk factors for Type 2 diabetes, including family history, increasing age and ethnicity, however the most important modifiable risk factors are diet and lifestyle. Obesity, unhealthy diets and physical inactivity combine with genetic factors to influence the risk of developing Type 2 diabetes. The increasing prevalence of Type 2 diabetes has been attributed mainly to the unhealthy lifestyle behaviours that lead to overweight and obesity.
Diet and Treatment of Type 2 Diabetes
The aim of treatment of Type 2 diabetes is to (i) maintain a normal blood glucose level (ii) decrease excess body weight to improve insulin resistance (iii) prevent long term complications. There are a range of treatments to manage Type 2 diabetes, including oral medication, insulin injections and dietary and lifestyle changes. Dietary and lifestyle changes play a large and significant role in the treatment of Type 2 diabetes irrespective of other treatments.
Overweight and Obesity
Overweight and obesity are strongly linked to insulin resistance, therefore weight reduction is considered as one of the key strategies in the management of Type 2 diabetes. Many scientific studies have shown that weight reduction and an increase in physical activity decreases insulin resistance and improves blood glucose control. IDF guidelines recommend that overweight and obese individuals with Type 2 diabetes should reduce daily food calorie intake by 500 to 600 calories and when possible they should be referred to a dietitian who will help them to follow a low-calorie diet of 800 to 1200 calories per day.
Many guidelines also recommend that an initial modest weight loss of 6 kg – 10 kg, depending on degree of excess weight. This may provide benefits of improving blood glucose, blood pressure and blood cholesterol levels, especially in individuals with early stage Type 2 diabetes.
Physical activity or exercise has been found to significantly improve blood glucose control in Type 2 diabetes even if it does not result in weight loss. On the other hand, a sedentary lifestyle characterised by low levels of physical activity has been found to be a significant independent risk factor for type 2 diabetes. Regular exercise decreases body fat content and also improves the body’s sensitivity to insulin. Many guidelines recommend moderate intensity physical activity such as brisk walking for at least 150 minutes per week at intervals of no longer than 48 hours. This is equivalent to 30 minutes of brisk walking, 5 days a week. If weight loss is required, then 1 hour of moderate intensity physical may be required daily for 5 days per week.
Food consists of nutrients with the 3 major nutrients also known as macronutrients being carbohydrates, proteins and fats. Carbohydrates are found in many foods (1) starchy foods such as plantain, yam, cassava, corn, rice, wheat and wheat flour and their products (2) added sugars in sugary foods and drinks (3) naturally occurring sugars found in fruits.
Most carbohydrates are digested in the stomach and broken down to simple sugars or glucose. Normally, the glucose produced after digestion travels from the stomach through the small intestines into the bloodstream and then finally transported to the body muscle and fat cells to be used as energy for daily activities of living. However, glucose cannot be transported to the muscle and fat cells without the hormone insulin. Insulin acts like a key to the muscle and fat cells, allowing sugar to enter to be used for energy.
Type and portion of carbohydrates: Scientific research evidence informs us that both the type and quantity of carbohydrates eaten in a meal influences blood glucose levels. Different types of carbohydrates are digested and absorbed at different rates and this determines how quickly they raise blood glucose after eating. The Glycaemic index (GI) is a ranking of foods and how quickly they raise blood glucose; low GI foods give a slow rise in blood glucose levels after eating thus helps control blood glucose levels in people with Type 2 diabetes.
The total amount of carbohydrate eaten in a meal is an even more important determinant of the level of rise in blood glucose after eating. It is well established that high carbohydrate diets leads to high blood glucose levels in Type 2 diabetes. However, the evidence regarding the ideal amount of carbohydrates for people with Type 2 diabetes is inconclusive.
Therefore, it makes sense to take an individualised approach in collaboration with a dietitian to set goals and develop a suitable eating plan. Monitoring carbohydrate intake and its effect on an individual’s blood glucose level is a key strategy in achieving adequate blood glucose control.
Eating patterns: A range of eating patterns for reduced energy intake and weight loss where appropriate and tailored to the individual is recommended by many guidelines. A variety of eating patterns (combinations of different foods or food groups) are acceptable for the management of diabetes such as Low carbohydrate, Low Glycaemic index, Mediterranean diet and Low fat diets.
In a recent systematic review looking at the effect of various diets in the management of Type 2 diabetes, Low-Carbohydrate, Low-Glycaemic Index, Mediterranean, and High-protein diets all led to a greater improvement in blood glucose control. The largest effect was seen in the Mediterranean diet, which consists of mainly plant foods including fruits, vegetables, whole grains, nuts, and legumes (beans, peas, and lentils); fresh and minimally processed foods; moderate amounts of olive oil, moderate amounts of fish and poultry; low to moderate amounts of cheese and yogurt with meals; low to moderate amounts of alcohol with meals for those who drink and minimal amounts of red meat or sweets. Most guidelines recommend selecting from any of the above eating patterns taking into consideration the individual’s personal preferences. There is no standard meal plan or eating pattern that works universally for all people with Type 2 diabetes.
Dietary management of Type 2 diabetes is backed by robust scientific evidence on strategies that can help control blood glucose, reduce the risk of complications such as kidney disease and heart disease and improve overall health. Managing overweight and obesity, physical activity, control of carbohydrate portions, selection of low GI carbohydrates and range of specific healthy eating patterns have been proven effective in the management of Type 2 Diabetes. People with Type 2 diabetes should therefore have the opportunity to see a dietitian and discuss individualised goals dietary plans to manage their condition effectively.
Following this overview of the Science behind diet and Type 2 diabetes, we will examine over the next coming weeks, specific components of diets and practical ideas in managing Type 2 Diabetes.