Sugar in the diet has enjoyed a high level of publicity in recent years, with some experts blaming our sugar intake and, in particular, our consumption of sugary drinks for the increase in obesity which has occurred in most developed and many less developed countries in the past 50 years. What are the facts behind these headlines? The most familiar form of sugar is table sugar or sucrose. Sucrose is classed as a disaccharide, as it’s made of two molecules of simple sugars, one of glucose and one of fructose. Sugars are highly soluble in water, so they’re good for making syrups and sweetening liquids. They’re also important in fermentation processes used in baking, brewing, and other industries.
We are all born with a strong taste preference for sugar, but in early human societies the only sources of sugar were wild or cultivated fruit or honey. In the 18th century cultivation of sugar cane in the plantations in the West Indies began on a large scale. This was made possible by the slave trade, which saw West Africans shipped to work on the plantations, mostly under terrible conditions. Raw cane sugar was shipped to the UK and refined into table sugar by removal of molasses and other impurities. Initially table sugar was a luxury commodity, but it soon became cheaper and formed a large part of the diet of working families in the newly industrialised cities.
Most of the sugar was used to sweeten tea or in home-produced jams, cakes, biscuits, and puddings. Sugar consumption in the UK continued to rise during the 20th century, apart from the years of the two world wars. In the food rationing at the end of the Second World War, sugar was rationed to 8 ounces per adult per week. When rationing was lifted, sugar consumption rose again and by the 1960s, Britons were eating about 50 kilogrammes per person per year, or one large 1 kilogramme bag per week. In the last few decades, there has been a gradual decrease in the amount of sugar we eat but a major change in the way we eat it.
Much less is bought as table sugar, while much more is consumed in soft drinks and processed foods such as biscuits, cakes, confectionery, and even savoury foods such as sauces. There has also been a change in the plants we use to produce our sugar. Sugar beet production has increased in the UK and other EU countries under the Common Agricultural Policy. At present around half the sugar in the UK comes from sugar cane and half from sugar beet. In North America, cornstarch is used to make corn syrup with high levels of glucose and fructose, known as high fructose corn syrup, and this is widely used in manufacturing of food and drinks.
Most people obtain some sugars from food such as milk, fruits, and vegetables, which contain vitamins, minerals, and / or plant fibre, which can be lacking in our diet. As a result, health experts now separate sugars in these foods from free sugars, a term which covers all the other sugars in the diet. Table sugar, sugar in drinks, confectionery and bakery goods, syrups, honey, fruit purees, and dried fruit. Importantly, the term free sugars also includes the sugars in fruit juice. Although these are no different from the sugars in the whole fruit, they are consumed more quickly and without the accompanying plant fibre so can cause more rapid surges in blood sugar.
This is why health advice is now to have whole fruit when possible and limit fruit juice to one small glass per day. So do we really need all of this sugar in our diet? In the body, glucose is used by all cells to provide energy, and blood glucose or blood sugar is kept under control by hormones such as insulin and glucagon. The glucose in the blood can, however, be derived from starchy foods in the diet or from breakdown of body fat stores. No sugar is needed in the diet except in a few unusual situations such as insulin overdose in diabetics or after extreme physical exercise.
Too much sugar, particularly if taken in small but frequent amounts between meals, undoubtedly leads to tooth decay. In recent years sugar, in particular sugary drinks and high fructose corn syrup, have been blamed for rising obesity levels. However, in the UK sugar consumption peaked before obesity levels began to rise. Also we have high levels of obesity now despite having very little high fructose corn syrup in our foods and drinks, which suggests that sugars cannot be entirely to blame for the obesity epidemic. We will discuss some of these issues in much more detail in the weeks to come.
However, the fact that processed foods with added sugars have become cheaper and are heavily marketed by manufacturers and retailers is thought by many to play an important part in over consumption of calories. High sugar intake may have a more direct link with the dramatic rise in the number of people with type 2 diabetes and is likely to be a factor in the recent rise in nonalcoholic fatty liver disease. How much sugar should we have? Until 2014 the recommendation in the UK was that 11% of our calories should come from free sugars. There are many adults and the majority of children, particularly adolescents, are still consuming quite a lot more than this.
The average figure for adults and preschool children are around 12% but in 4 to 10-year-olds, the figures reach 14%, and in adolescents the average is about 15%, with highest value in boys. Most of this comes from soft drinks, biscuits, and confectionery. The latest assessment by international experts is that even 11% is too high and that no more than 10%– and ideally only 5%– of our calories should come from free sugars. For an average adult not doing much exercise, this would be equivalent to about 6 teaspoons or cubes of added sugar per day, which is less than the amount in one can of regular soft drinks. Is it easy to work out how much free sugars are in our food?
Not very, since manufacturer’s labels and even our standard food composition tables give values for total sugars, because only total sugars can be measured chemically. Foods which contain vegetables which have naturally occurring sugars such as tomato or root vegetable soup show the sugar on the labels, but this is probably not free sugars. By contrast, foods which contain milk and/or whole fruit but also contain fruit puree or other sweeteners, including low-fat yoghurts and prepared baby foods, can have high levels of free sugars even if they are marketed as healthy foods. So to sum up, sugar was once a luxury food item, but now it’s widely used to sweeten many processed foods and drinks.
In the UK our intake of free sugars, that is all sugars apart from those in milk, whole fruit, and vegetables, is about double the amount now recommended by health experts. However, the health consequences of this high consumption is hotly debated among the scientific world. We will explore some of these controversial issues later in the course.
Dietary sugar is an integral part of our western diets. In its natural form it can be found in most fruit and vegetables but it can also be added to number of processed food and drinks.
In this video, Geraldine McNeil of the University of Aberdeen explains the different types of sugars available in the diet, and gives a brief overview of how sugar consumption has changed over the last century. She explains terms such as ‘free sugars’ and discusses the hype surrounding our current sugar consumption levels and health. She gives examples on how much sugar is contained in a number of commonly consumed foods, and tells us how much we should consume for optimal health.
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