Diabetes & Sugar
From 2000 to 2010, the prevalence of diabetes in Canada doubled from 1.3 million to 2.5 million people (1). Today, more than one in four Canadians — or over ten million people —lives with diabetes or prediabetes; if nothing is done, by 2020, it will be almost one in three. Diabetes will cost an estimated $14 billion in 2015. The Canadian economy and all Canadians are paying the cost of treating diabetes-related complications.
Diabetes is a condition characterized by an elevation in blood glucose (blood sugar) levels due to either a lack of insulin or a reduced effectiveness of one’s own insulin. People with diabetes need to manage their glucose level in an effort to achieve their target blood glucose. Diabetes is a leading cause of blindness, end-stage renal disease, heart disease, stroke, and non-traumatic amputation in Canadian adults.
There are three common types of diabetes. Type 1 diabetes occurs in people when their beta cells, located in the pancreas, no longer function. Consequently, very little or no insulin is released into the circulation. As a result, glucose builds up in the blood instead of entering the cells to be used as energy. About five to 10 per cent of people with diabetes have type 1 diabetes. Type 1 diabetes generally develops in childhood or adolescence but can develop in adulthood.
Type 2 diabetes occurs when the body cannot properly use the insulin that is released or does not make enough insulin. Glucose builds up in the blood instead of being used as energy. Over 90 per cent of people with diabetes have type 2 diabetes. Type 2 diabetes develops in adulthood most commonly, but children can be affected.
A third type of diabetes, gestational diabetes, is a temporary condition that occurs during pregnancy. It affects up to 18% cent of all pregnancies and increases the risk of developing type 2 diabetes for mother and child in the future.
Overweight and obesity are risk factors for the development of prediabetes, type 2 diabetes and gestational diabetes. Approximately 60% of adult Canadians (3) and one-third of children and youth aged 5 to 17 years are overweight or obese (4). Children who are obese are at increased risk of remaining overweight or obese as adults (5,6). Type 2 diabetes is being diagnosed earlier than ever before, and more frequently in children.
Behavior modification, including dietary management for people at-risk of type 2 diabetes, attempts to reduce the likelihood of progression to diabetes. Dietary management may target weight loss, but also promotes the consumption of healthy foods. For people diagnosed with diabetes, adhering to a healthy diet optimizes glycemic control and reduces the risk of developing complications.
World Health Organization sugars intake guideline
In 2015 the WHO released guidelines on the intake of free sugars for adults and children. These guidelines recommend:
- Reduced intake of free sugars throughout the life-course (strong recommendation)
- In both adults and children, intake of free sugars not exceed 10% of total energy (strong recommendation)
- Further reduction to below 5% of total energy (conditional recommendation)
The WHO states that the first two recommendations are based on the health risks of free sugars consumption in predisposing those who consume them to overweight and obesity, and dental caries. WHO’s third recommendation states that a further reduction of free sugars to below 5% (about 6 teaspoons) of total energy intake per day would provide additional benefits. The limits would apply to all sugars added to food, as well as sugars naturally present in honey, syrups, fruit juices and fruit concentrates.
Diabetes Canada supports these recommendations for Canadians and acknowledges the importance of the outcomes described by the WHO. Diabetes Canada recommends reducing free sugars consumption by the general population to promote dental health and decrease the risk overweight and obesity and subsequent illnesses. Furthermore, for people living with diabetes, limiting sucrose intake to 10% or less of total daily energy is recommended by the 2013 Clinical Practice Guidelines for the Prevention and Management of Diabetes in Canada. Intake of sucrose >10% of total daily energy may increase blood glucose and triglyceride concentrations in some individuals with type 2 diabetes.
Sugars in our food supply
Sugars are ubiquitous in our food supply and are consumed as a naturally-occurring component of many foods including milk, yogurt, fruits, and vegetables. It is also frequently added during food preparation, at the table and during food processing.
Sugars come in many forms. Glucose, fructose, and sucrose are commonly used sugars. Glucose occurs naturally in fruits and plant juices. Most ingested carbohydrates are converted into glucose during digestion and it is the form of sugar that is found in our blood. Fructose is found in fruits, some vegetables, cane sugar, and honey. It is one of the components of table sugar (fructose combined with glucose forms the disaccharide sucrose). It is also consumed as a high-fructose syrup. Sucrose is found in the stems of sugar cane and roots of sugar beet. It also occurs naturally with fructose and glucose in fruits and some roots vegetables such as squash. Maltose is found in certain grains (e.g. barley) and is less sweet than glucose, fructose or sucrose. Lactose is found in milk and other dairy products.
Free sugars are those sugars that are removed from their original source and added to foods as a sweetener or as a preservative. There are many different forms of ‘free sugars’ including cane juice, corn syrup, brown rice syrup, barley malt, agave nectar, and fruit juice concentrate.
The WHO defines ‘free sugars’ as sugars and syrups added to foods during processing or preparation. This definition is inclusive of all sugars added to foods during cooking (or processing), such as honey, syrups, fruit purees, and juices that are added to a food. This definition does not include sugars found naturally in white milk, vegetables, and fruit. These sugar-containing foods also contain vitamins, minerals, and fibre which provide health benefits. These naturally occurring forms of sugar are referred to as bound sugar and are considered part of a healthy diet (9). The body metabolizes naturally occurring and added sugars in the same way however, digestion and absorption of free sugars may be faster as they are not bound into the food matrix. Foods that have high amounts of free sugars tend to offer less nutritional value. Foods with no free sugars tend to be higher in beneficial nutrients than those high in free sugars. Many people consume sugars with no knowledge of its presence in the food that they consume.
It has been estimated that Canadians eat 110 grams of sugars per day (26 teaspoons or 21 per cent of total energy intake, based on a 2,000 calorie-a-day diet) (10). This included sugars from all sources including milk products, vegetables, and fruit as well as free sugars. This estimate varied across sub-groups. People with diabetes were estimated to consume 73 grams of sugar (18 teaspoons) per day. Teenage boys between 14 to 18 years consumed 172 grams daily (41 teaspoons). Almost half of the average daily sugar intake of children from 1 to 8 years old and adolescents from 9 to 18 years old came from beverages, specifically milk (20% and 14%, respectively) fruit juice (15% and 9% respectively), regular soft drinks (4% and 14% respectively), and fruit drinks (6% and 7% respectively). Milk was the primary source of sugar among children aged 1 to 8, but in those age 9 to 18, regular soft drinks ranked first. Beverages accounted for 35% of adults’ daily sugar intake. Notably these data are from 2004, and consumption may have changed since then.
What are the effects of consuming sugars on the risk of developing diabetes?
Numerous clinical trials, cohort studies, and meta-analyses have been performed to describe the impact of consumption of sugars on weight gain, as well as risk for and development of diabetes. Te Morenga et al. recently performed a systematic review and meta-analysis (2013) for the WHO and estimated that adults who reduced intake of dietary sugars decreased 0.80 kg body weight among randomized controlled trials. The same systematic review and meta-analysis, however, did not show a body weight decrease in the randomized controlled trials of children. Conversely, an increase intake of sugars was associated with an increase of 0.75 kg of body weight in both adults and children. A reduced intake of free sugars was associated with weight loss and increased intake of sugars was associated with weight gain in European adults in the EPIC-InterAct cohort study. Other researchers have performed systematic reviews and meta-analyses and calculated pooled estimates showing a statistically significant positive relationship between increased consumption of calories in the form of sugars and weight gain. In the absence of weight gain seen in calorie matched trial comparisons, the relationship between weight gain and consumption of sugars appear to be mediated through an increase in calorie consumption (28-30).
A meta-analysis by Sonestedt reviewed the evidence between the intake of total sugars, sucrose or fructose and type 2 diabetes. Nine studies were included, four of which evaluated the association between intake of total sugars, sucrose or fructose and type 2 diabetes. The data were inconclusive after adjusting for weight gain or BMI. Two of three studies found significant positive associations with total fructose intake. No studies found an association between sucrose or total sugars intake and diabetes and some researchers reported an inverse association. Sievenpiper et al. recently described the association between total sugars, total sucrose, and total fructose in an updated systematic review and meta-analysis of prospective cohort studies including more than 300,000 people. These authors failed to detect an independent risk for diabetes for all of these cases (32).
The link between intake of sugars and fasting plasma glucose, post-prandial glucose and insulin levels was reviewed by Kahn and Sievenpiper and Sonestedt et al. both groups determined that there is insufficient evidence to link sugars with these proxies of diabetes risk.
In summary, large amounts of free sugars are often found in highly processed, high energy, high calorie foods. Excessive calorie consumption often occurs with these high-free-sugars foods, leading to weight gain. Given the established relationship between type 2 diabetes and overweight and obesity, as well as the relationship between excess calories and weight gain, consumption of sugars must be duly considered by all people trying to manage their weight and their risk for diabetes.
Moderate amounts of sugars can safely be consumed by people with diabetes and those at risk.