Sugars are common components of modern-day diets. They are found in a wide range of foods and drinks, including fruits and fruit juices, honey, jams and marmalades, soft drinks, desserts and other sweet treats. In addition to providing sweetness and an attractive taste, sugars are a source of energy, and therefore sweet foods and drinks are best enjoyed in moderation. This article provides answers to some widespread questions on the subject of sugars and health, drawing on the latest scientific evidence.
What is sugar?
The building blocks of all carbohydrates are sugars. Sugars can be classified according to how many sugar units (saccharides) are combined in one molecule. Glucose, fructose and galactose are single unit sugars, also known as monosaccharides. Double unit sugars are called disaccharides. The most widely known are sucrose (table sugar) which contains one glucose molecule and one fructose molecule and lactose (milk sugar) which is made up of galactose and glucose. Sucrose is commonly referred to as ‘sugar’. Other uses of the term ‘sugar’ may more generally refer to all sugar compounds.1
Are naturally occurring sugars healthier than added sugars?
No, the sugars themselves are the same. Sugars are sometimes categorised as either “natural” or “added”. While these terms may be associated with being “more healthful” and “less healthful”, respectively, it is incorrect to label sugars in this way. This is because added sugars are in fact extracted or produced from naturally occurring sources; for example, glucose and fructose from honey, fruits, and some vegetables, lactose from milk and dairy products, and sucrose from fruits, sugar cane and sugar beet. Glucose-fructose syrups are derived from corn starch, and table sugar is produced by crystallising the syrups of either sugar cane or sugar beet. This means that each sugar (monosaccharide or disaccharide) — whether found naturally in a piece of fruit, or added to a cake or a biscuit — remains structurally the same.2
Added sugars may be associated with food products of low nutritional value. In contrast, when sugars are eaten as part of intact plant sources they are typically accompanied by other nutrients and fibres. Overall, it is a healthful diet that counts.
Can sugars cause overweight and obesity?
Yes, but only if you eat or drink more than you need so that the total amount of energy consumed exceeds the amount of energy burned over time. Because sweet foods and beverages are attractive, managing sweetness may require special vigilance. Paying attention to portion size and energy content of foods will ensure that daily calories are not in excess of energy requirements.
It is commonly believed that “liquid calories” from sugar-sweetened beverages are less likely to make us feel full than are calories from solid foods, but research remains inconclusive.3 The hypothesis is that liquid calories are not even perceived by the body. However, the mixed research results suggest that other factors, such as desire, availability and cost of foods or drinks, may override satiety and relate to intake. Consuming a caloric food or beverage, does not guarantee that the calorie content of the subsequent meal will be reduced by a corresponding amount. As always, eating or drinking more leads to higher energy intakes.
In 2010, both the European Food Safety Authority and a systematic review concluded there was insufficient evidence from randomised controlled trials of adequate size and duration to support a link between sugar-sweetened beverages and weight gain.4,5 Recent longer-term randomised controlled trials suggest that reducing intakes of sugar-sweetened beverages, or replacing them with non-caloric beverages, results in less weight gain.6,7 However, these studies essentially just show one of many possible approaches to reduce caloric intake and thus achieve better weight management.
Because overweight and obesity are complex conditions, it is unlikely that a single food or food group is a primary cause of obesity. A recent systematic review showed an association between the intake of sugars and increase in body weight, an effect totally accounted for by the difference in energy intake associated with sugar.8 Given that all digestible carbohydrates contain 4 kcal/g, substituting sugar (gram for gram) with starch would not lower energy intake.8 Energy from protein is also 4 kcal/g. Fat provides 9 kcal/g, and alcohol 7 kcal/g. As stated above, increasing dietary intake from any energy source above energy needs will eventually lead to weight gain, unless balanced by increasing physical activity. Moderating sugar intake so as to not exceed daily energy requirements may help reduce the risk for obesity.
Can sugar cause diabetes?
No. Type 2 diabetes is the main type of diabetes and affects around 90% of people with diabetes worldwide. Rates of diabetes are highest among older adults and are associated with excess body weight, particularly abdominal, a lack of physical activity and unhealthy diets.9
Total intake of sugars or a specific type of sugar has not been causally linked with type 2 diabetes.4 In some studies higher consumption of sugar-sweetened beverages coincided with higher rates of this disorder.10,11 This link may be related indirectly to lifestyle factors including greater body weight. Weight loss and lifestyle changes including diet and physical activity may prevent or delay the development of diabetes, and help reduce the risk of long-term complications. Dietary recommendations for people with diabetes are no different from those for the general population.
Does table sugar have a high glycaemic index?
No. Table sugar, or sucrose, has an intermediate glycaemic index (GI).1
The GI is a measure of the rise and fall of blood glucose levels after eating carbohydrate-containing foods relative to a standard food, usually white bread or glucose. Foods with a low GI are more slowly digested and absorbed, and result in less blood glucose response, compared to foods with a high GI. Diets containing more low GI foods are associated with reduced risk of metabolic diseases including diabetes. Glucose and maltose have a high GI. Table sugar consists of glucose and fructose, fructose is a (very) low GI carbohydrate, and therefore sucrose has an intermediate GI. Lactose has a low GI.1
The GI value of foods is also influenced by their content of dietary fibre, and other nutrients including fat and protein (which lower GI), and the cooking and processing methods used.1 Overall the blood glucose response is influenced by the combined GI value of different foods and the total amount of carbohydrate eaten.
Can sugar make children hyperactive?
No. Many parents believe that too much sugar can contribute to their children’s hyperactivity, but this relationship is not supported by the scientific evidence. This belief stems from case studies in the 1970s. However, earlier studies were methodologically flawed. The majority of controlled experimental studies do not support the notion that sugar intake leads to an increase in activity or hyperactivity.12 A link between sugar intake and activity may be the result of ‘reverse-causality’: more active children need more energy and therefore have higher sugar intakes.
The perceived association is also influenced by parental beliefs and expectations. In one study, the parents who were told their child was given a drink containing sugar rated their child’s behaviour as more hyperactive; even though all drinks were sugar-free.13
Can sugars damage your teeth?
Yes, sugar has the potential to cause tooth decay; the frequency, rather than the amount, of sugar consumed is the main issue. Frequent consumption of sugar-containing foods can increase the risk of tooth decay. Sugars and certain other carbohydrates (mainly starch) are fermented by bacteria in the mouth. This causes a decrease in pH that can lead to the demineralisation of tooth enamel and eventually over time tooth decay.3
Fluoride inhibits demineralisation and helps remineralisation, significantly reducing the risk of tooth decay. Hence, oral hygiene practices that involve the use of fluoridated toothpaste are related to lower levels of tooth decay.3
Is sugar addictive?
No. There is no evidence that sugar is addictive in humans. “Addiction” refers to physiological and psychological processes which cause dependence and withdrawal symptoms on cessation of intake, such that the person actively seeks the material to prevent withdrawal. Although research in rodents has shown that rats under specific conditions (e.g. food withdrawal alternating with bingeing on glucose or sucrose solutions develop an alleged “sugar dependence” over short periods of time), these observations have little relevance to the situation in human consumers.14
It is important to draw a distinction between individuals having a strong compulsion (who feel ‘addicted’ toward (over)eating), versus the idea that specific foods or nutrients are themselves ‘addictive’. While food addiction as a concept has been postulated as an explanation for increasing obesity levels, scientific research has found that overweight individuals do not show any convincing behavioural or neurobiological profiles that resemble addiction. It is likely that the food environment plays an important role for the majority of people who overeat.15,16 The availability of highly palatable food and drink, together with a strong culture of consumption, encourages overeating. This environment may be particularly challenging for individuals with a tendency towards binge eating, who show a strong ‘wanting’ (as well as a ‘liking’) for sweet, fatty foods.15
The World Health Organization suggests that ‘free’ sugars (all monosaccharides and disaccharides added to foods by the manufacturer, cook and consumer, plus sugars naturally present in honey, syrups and fruit juices) make up no more than 10% of a person’s daily energy intake.17 For an adult requiring 2000 kcal a day, this equates to no more than 200 kcal from free sugars, about 50 grams or 12 teaspoons of sugar. However, in the setting of Dietary Reference Values for carbohydrates and fibre in 2010, EFSA concluded that there is insufficient evidence to set an upper limit for intake of total or added sugars.4 Rather, dietary recommendations should take into account what is practically achievable for nutritionally adequate diets. Evidence of the relationships between dietary patterns (including sugar-containing foods) and health in specific populations should be considered when developing dietary goals and food-based dietary guidelines (FBDGs). FBDGs exemplify that sugar-containing foods form the smallest proportion of a healthful diet, at the top of a food pyramid.18
Taken together, current scientific evidence does not support direct causal links between sugars and obesity, diabetes, or hyperactivity. There is no evidence that sugars are ‘addictive’ in humans. With respect to dental health, the potential impact of sugars and other fermentable carbohydrates on tooth decay appears to be preventable with good oral hygiene and the use of fluoride. The importance of overall lifestyle habits such as physical activity should not be overlooked; ultimately, energy intake needs to be matched with energy expenditure to avoid weight gain.
Sugars are a common part of our diet and contribute energy, but also make our foods more attractive by adding sweetness. Consuming any nutrient in excess can have a negative impact on weight and health. When eaten in moderation, however, sugar can be enjoyed as part of a balanced diet and healthful lifestyle.
- EUFIC Basics (2012). Carbohydrates: http://www.eufic.org/article/en/page/BARCHIVE/expid/basics-carbohydrates/
- Hess J et al. (2012). The confusing world of dietary sugars: definitions, intakes, food sources and international dietary recommendations. Food Funct 3:477-86.
- Bellisle F et al. (2012). Sweetness, Satiation, and Satiety. J Nutr 142(6):1149S-54S. doi: 10.3945/jn.111.149583n. [Epub ahead of print]
- EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) (2010). Scientific Opinion on Dietary Reference Values for carbohydrates and dietary fibre. EFSA Journal 8(3):1462.
- Mattes RD et al. (2010). Nutritively sweetened beverage consumption and body weight: a systematic review and meta-analysis of randomized experiments. Obes Rev 12(5):346-65.
- Ebbeling CB et al. (2012). A randomized trial of sugar-sweetened beverages and adolescent body weight. N Engl J Med 367:1407-16.
- de Ruyter JC et al. (2012). A trial of sugar-free or sugar-sweetened beverages and body weight in children. N Engl J Med 367:1397-406.
- Te Morenga L et al. (2013). Dietary sugars and body weight: systematic review and meta-analyses of randomised controlled trials and cohort studies. BMJ 346:e7492
- World Health Organization website. Diabetes programme, about diabetes section: http://www.who.int/diabetes/action_online/basics/en/index.html Accessed on 17 October 2012.
- Montonen J et al. (2007). Consumption of sweetened beverages and intakes of fructose and glucose predict type 2 diabetes occurrence. J Nutr 137(6):1447-54.
- de Koning L et al. (2011). Sugar-sweetened and artificially sweetened beverage consumption and risk of type 2 diabetes in men. Am J Clin Nutr 93(6):1321-7.
- Bellisle F. (2004). Effects of diet on behaviour and cognition in children. Br J Nutr 92 Suppl 2: S227-32.
- Hoover DW et al. (1994). Effects of sugar ingestion expectancies on mother-child interactions. J Abnorm Child Psychol 22(4):501-15.
- Ziauddeen H et al. (2012). Obesity and the brain: how convincing is the addiction model? Nat Rev Neurosci 13(4):279-86.
- Blundell JE & Finlayson G. (2011). Food addiction not helpful: the hedonic component — implicit wanting — is important. Addiction 106(7): 1216-18.
- Gearhardt AN et al. (2011). Can food be addictive? Public Health and Policy Implications. Addiction 106(7): 1208-12.
- Mann J et al. (2007). FAO/WHO scientific update on carbohydrates in human nutrition: conclusions. Eur J Clin Nutr 61(1):S132-7.
- EUFIC Review (2009). Food-Based Dietary Guidelines in Europe: http://www.eufic.org/article/en/expid/food-based-dietary-guidelines-in-europe/