The truth about sugar

What are sugars?

Sugars are types of soluble carbohydrates that provide energy in our diet. Compared to other types of carbohydrates, they are quickly absorbed into our body and are less filling. They can be used to enhance the flavour of food and drink which makes them an attractive option for both consumers and the food and drink industry.

What types of sugar are there?

Sugars can be described as either intrinsic or extrinsic. Intrinsic sugars occur naturally within the cellular structure of food, while extrinsic sugars do not. Extrinsic sugars can occur naturally, such as in honey and lactose, but they can also be added to food and drink by the consumer, the manufacturer or the caterer. Extrinsic sugars can be sub-categorized into milk sugars and free sugars (Figure 1). Generally, intrinsic sugars are not thought to have an adverse effect on general health or dental health, whereas free sugars are thought to be detrimental to health and contribute to tooth decay and the obesity epidemic.4

Various terms can be used to describe the sugars in dietary recommendations (Table 1). Throughout this article, the term free sugars will be used.

Where are free sugars usually found?

Free sugars are commonly found in sugared soft drinks, confectionery, cakes and biscuits, sugared breakfast cereals and jam, preserves and honey. Free sugars are also found in foods and drinks considered ‘healthy’, including fruit juices, smoothies and dried fruit. Unexpectedly, free sugars can be added to and hidden in other foods and drinks, including baked beans, readymade sauces and yoghurts. Products that state they have ‘no added sugar’ may still contain fruit juice, fruit concentrate or other free sugars and will therefore still contain extrinsic sugars and be potentially detrimental to health if consumed in large quantities. It is important always to check food labels for sugar content.

How do you identify sugars found in food and drink?

Consumers spend between 4 to 10 seconds choosing food and drink products and clear food labelling is an important tool to allow people to make healthier food choices.5 However, it can still be difficult to identify sugars in food and drink owing to the wide variety of names available.4 A number of sugars have names which end with ‘ose’ but this rule does not apply to all sugars, making it difficult to reduce or eliminate them from the diet.

While nutrition information on food labels has improved in recent years, often a detailed breakdown of how much carbohydrate is made up of sugar is not given. The order of items in the ingredients list can provide further insight, with items being listed in descending order so that those present in higher quantities appear near the top of the list. If any term for sugar appears near the top of the list of items in the food or drink label, then it can be considered to be high in sugar.6

The Department of Health produced guidance on how to determine if a food or drink has low, medium or high levels of sugar in an understandable format (Table 2). This can be illustrated using a ‘traffic light’ system of green, amber and red or by stating the amount of total sugars per 100 g for food or per 100 ml for drink.7

What is the current guidance on sugar intake?

The World Health Organization (WHO) currently recommends that free sugars should make up less than 10% of total energy intake per day. However, the new guideline from the WHO proposes that reducing this to below 5% of total energy intake per day would have additional benefits.8 The Scientific Advisory Committee on Nutrition (SACN) has recently recommended that free sugars account for no more than 5% daily dietary energy intake.1 For an adult woman of normal BMI, with an intake of around 2,000 calories per day, 5% would equate to 100 calories. Sugar provides four calories per gram so this would mean that 5% was approximately 25 g of sugar (six teaspoons).9 For the average man, with an intake of around 2,500 calories per day, 5% would be nearer to eight teaspoons of sugar per day. Since children have a lower energy requirement, 5% will mean a lot less than this. Given a standard 330 ml can of cola contains 35 g of sugar (between 8 and 9 teaspoons), the challenge in reducing free sugars to this level can be highlighted.9

What happens when you over-consume sugars?

Over-consumption of sugars can lead to an increased risk of excess calorie intake, potentially leading to overweightness and obesity. This can also lead to an increased risk of developing high blood pressure, type 2 diabetes, cardiovascular disease and some cancers. A diet containing high levels of sugars can also increase the risk of developing dental plaque, caries, periodontal disease and halitosis.6 This article only deals with the effects of sugars on dental health and obesity.

Is fresh fruit good for your teeth?

It is recommended that at least five portions of fruit and vegetables are consumed daily (ie ‘5 A Day’). When consumed as part of a balanced diet, fresh fruit (containing intrinsic sugars) is good for your teeth. While it is recognized that acidic fresh fruits, such as citrus fruit and apples may cause dental erosion if eaten in large quantities, the individual and population health benefits of fruit consumption far outweigh any oral health detriments from these foods.4^,10

Is canned fruit good for your teeth?

Most canned fruit on the market are bathed in sugar-rich syrup which contains free sugars. Due to this added sugar, canned fruit can be harmful to your teeth. However, an alternative would be to choose canned fruits containing natural fruit juice instead, which contain lower amounts of free sugars and are less harmful to teeth.

Is fruit juice good for your teeth?

Fresh unsweetened fruit juice contains free sugars because the juicing process releases the fructose, sucrose and glucose from the whole fruit. The free sugars of unsweetened fruit juice may amount to as much as a standard soft drink, therefore it is potentially cariogenic.11 Frequent exposure to the sugars and acids present when fruit is juiced can lead to tooth decay and dental erosion.4^,10 Despite this, fruit and vegetable juice contains beneficial vitamins and minerals and current guidance recommends one glass (150 ml) of unsweetened fruit or vegetable juice per day as part of your ‘5 A Day’. However, juice only ever counts as a maximum of one portion a day, even if you drink more than one glass. This is mainly because it contains less fibre than whole fruits and vegetables. Therefore, it is a good idea to limit the amount of fruit juice you drink and consume at mealtimes only.

Pure or 100% fruit juice should not be confused with ‘fruit juice drinks’ which contain very little pure fruit juice, as well as water and added sugar. These are harmful to teeth without the added benefit of vitamins. ‘No added sugar’ fruit juice drinks are also available but these are still acidic and contain free sugars from the small amount of pure fruit juice they contain and could still be harmful if consumed in large quantities.

Are fruit smoothies good for your teeth?

Fruit smoothies contain free sugars as the blending process releases the fructose, sucrose and glucose from the whole fruit. Fruit smoothies are not recommended between meals owing to their free sugars' content and acidity. A smoothie can count as one of your ‘5 A Day’ due to the vitamins and minerals it provides. A smoothie can provide up to two of your five portions if it contains all of the fruit pulp from the whole fruit as well as juice.

Is dried fruit good for your teeth?

Dried fruit can be a very convenient, portable snack. However, dried fruit contains free sugars and is not good for your teeth (Figure 2). The sugar in dried fruit is super-concentrated. When fruit is dried, almost all the water is lost, but no sugar is lost. Also, dried fruit is very sticky and can easily get stuck in your teeth, giving it a prolonged oral retention time and compounding its cariogenicity. As consumption of dried fruit is low, there are no epidemiological data linking its consumption to dental caries.11 Small portions of dried fruit can contribute to the ‘5 A Day’ target; however, it should not be chosen as a between meals snack.4^,10

Is milk good for your teeth?

Milk is an important source of calcium and phosphorus, both of which contribute to the maintenance of healthy teeth. The most abundant protein in milk is casein and is protective as it forms a thin film on the enamel surface which prevents loss of calcium and phosphate from the enamel when the teeth are exposed to acids in the mouth.12

Cow's milk contains about 4.8 g lactose per 100 g milk. This amount could be sufficient to classify as cariogenic, but there is much evidence that lactose is the least cariogenic of the common dietary sugars. Milk may have a role in the control of dental erosion but evidence is, at present, limited.13

However, infants should not be put to bed with a feeding bottle as this can lead to early childhood caries. The frequency and duration of sugar from milk in the mouth increases the risk of development of tooth decay.4^,10

Is honey good for your teeth?

Honey is a naturally occurring free sugar. There has been much debate in the past about whether or not honey is harmful to the teeth, mostly as part of the debate about raw sugar versus refined sugar. Occasionally this debate has recognized that honey has antibacterial activity, but where the effect of this has been investigated the results have been equivocal. However, what has not been taken into account is that honey varies very markedly in the potency of its antibacterial activity.14

Recent research with honey selected to have a good level of antibacterial activity has shown that there is potential for protection of dental health if such honey were used in place of refined sugar in the manufacture of candy. It can be concluded that, although honey may be cariogenic because of its high content of fermentable sugars, with selected honeys that have higher levels of antibacterial activity there is the potential for harm to the teeth to be reduced by inhibition of the cariogenic bacteria. However, as with all sugars, honey should be consumed in limited amounts and at mealtimes only.14

Dummies should not be dipped into honey or sugary drinks. This introduction to sweetness at an early age can encourage a sweet tooth and the development of tooth decay.4

How does sugar intake affect obesity?

Obesity develops when energy intake (calories) from food and drink consumption is greater than the body's energy requirements over a prolonged period, resulting in the accumulation of excess body fat.1 A healthy, balanced diet and physical activity is recommended for healthy weight, in particular, a diet high in fruit, vegetables and complex carbohydrates and low in fat, saturated fat, salt and sugar.

A recent report by the Scientific Advisory Committee on Nutrition (SACN) found that diets higher in free sugars resulted in higher energy intake; leading to weight gain over time. However, there was a lack of evidence to draw conclusions on the direct impact of sugar on body weight in adults.1

In other studies of adults with ad libitum diets (ie no strict control of food intake), reduced sugar intake was associated with a significant decrease in body weight (0.80 kg). Moreover, increased sugar intake was associated with a comparable significant weight increase of 0.75 kg (trials were of at least two weeks duration and cohort studies at least one year). Equal exchange of dietary sugars with other carbohydrates had no impact on body weight.15

How does consumption of sugar-sweetened beverages affect obesity?

Evidence shows that the intake of sugar-sweetened beverages (SSB) is a determinant of body weight in those consuming an ad libitum diet, mediated by changes to energy intake and therefore distorting energy balance. Energy in liquid form, such as SSB, may be less satiating than energy from solid foods, resulting in increased consumption and subsequently energy intake, particularly in children. Advice relating to sugar intake should form a key component of strategies to reduce the risk of overweightness and obesity.15

How does consumption of high fructose corn syrup affect obesity?

Recently, there has been a lot of attention given to the impact of fructose and, specifically, high fructose corn syrup (HFCS), on levels of obesity. SACN found few studies on the impact of individual sugars such as glucose, fructose or sucrose on obesity. No studies were identified meeting the SACN review criteria that investigated the effects of HFCS; however, some have argued that the use of HFCS is linked to increased obesity rates.1

A systematic review and meta-analysis found that most trials investigating the effect of fructose on body weight had methodological limitations and were of poor quality. They concluded that fructose did not cause weight gain in isocaloric diets, ie when substituted for other carbohydrates providing similar calories. Unsurprisingly, high doses of fructose providing excess calories was found to lead to increased body weight, likely due to the extra calories rather than the effect of fructose itself.16 These findings were reinforced by a review in overweight and obese subjects, concluding that there was no evidence to suggest that fructose consumed in normal amounts was associated with an increase in food intake or body weight.17

Would the introduction of a sugar tax reduce levels of obesity?

It has been suggested that a tax on sugar, in particular SSB, would have a positive impact on obesity levels. A literature review and meta-analysis was undertaken to examine the potential impact of a SSB tax on consumption levels, overweightness, obesity and BMI (although no UK studies were included). All studies showed that a tax on SSB resulted in lower demand for the product and an increased demand for fruit juice and milk. The higher the price increase, the greater the reduction in consumption. Some studies suggested that higher prices of SSB may lead to modest reductions in weight.18

There is some suggestion that, relative to income, an SSB tax would affect those on a low income more than those on a high income. However, low income groups are likely to reap greater benefit given that they are more price sensitive and therefore more likely to reduce consumption of SSB.18 In contrast, Briggs et al found no significant differences between income groups when modelling the effect of a 20% SSB tax in the UK on the prevalence of overweight and obesity.19 This study estimated that the 20% tax would reduce consumption of SSB by around 15% and reduce the number of obese adults in the UK by 1.3% (n = 180,000) and the number who are overweight by 0.9% (n = 285,000). The greatest effects were likely to occur in those under 30 years (the major consumers of SSB) with no significant differences between income groups. The modelling was based on a sales tax and not an excise tax (which is preferred by health bodies as it results in a uniform price increase per unit volume, removing the incentive to switch to larger portion sizes that would represent better value for money).19

In a recent position statement, the UK Faculty of Public Health advocated for the introduction of a 20p per litre excise duty on SSB as part of a multi-faceted approach to reducing obesity.20

What other strategies are in place?

The UK Health Forum provides an excellent review on options for actions to support reduction of sugar consumption, ranging from producing/importing less, using less (through reformulation and substitution), selling less, marketing less, recommending less, and finally eating less.21 Public Health England has outlined the steps to help people reduce their sugar intake. This includes a full scale Change4Life social marketing campaign in January 2015 focused on sugar reduction.22

Sometimes, we need novel ways to ‘sell’ the sugar message. In August 2014, the Wellgate Shopping Centre in Dundee city centre saw an interesting two-day pop-up ‘Know Sugar Shop’. This initiative was organized by the co-founder of Snook, Lauren Currie and her team, who took a fresh approach to engaging the public with sugar issues. The team asked Dundee citizens for feedback on creative approaches to facilitating dietary change, such as the open kitchen, grab tag and challenge cards. They certainly broke the traditional mode in health promotion and over 700 people came to listen and learn about sugar sources and innovative ways to break old habits.23