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Sugars: Types, Health Effects, Sources and Food Labeling

Sugars are simple carbohydrates that either occur in foods naturally or are added to foods and beverages during processing to give them a sweet taste or other properties. Along with starches (another form of sugar, but with a larger molecule), they provide the main source of energy to the body.

In most people’s minds, sugars are synonymous with sweets, although some varieties do not taste sweet. Those that have a sweet taste often serve to sweeten foods and beverages, thereby making them more appealing. In addition to serving as sweeteners, sugars play many other important roles in foods. They add aroma, color, bulk, flavour, tenderness and texture to food and also act as a preservative.

Experts recommend that people get their sugars primarily from fruits and vegetables, as well as nutrient-dense foods such as wholegrain breads, cereals, rice and legumes. Sugary foods like candy or sweets that provide few nutrients should be consumed in moderation.

Types of Sugars

Sugars are made up of a combination of carbon, hydrogen and oxygen and belong to the category of foods known as simple carbohydrates or complex carbohydrates. Simple carbohydrates are made up of either a single chemical unit (monosaccharide) or two units (disaccharide) of sugar. The following are the three monosaccharides found in foods:

  • Glucose. Also known as grape sugar, this type of monosaccharide has a mildly sweet flavor. Glucose is in medicine referred to as “blood sugar” because it is the main form of sugar found in the bloodstream.
  • Fructose. The sweetest of all sugars, fructose, as its name suggests, occurs naturally in fruits and honey. It is also the main constituent of high-fructose corn syrup largely used to sweeten soft drinks in the US.
  • Galactose. Barely tastes sweet and is found in sugar beets, dairy products and gums.

When two molecules of monosaccharide join together, they become disaccharides. There are three types of disaccharides found in foods:

  • Sucrose (glucose + fructose). Commonly referred to as table sugar, sucrose is found naturally in sugar beets, sugarcane, honey, maple syrup and many fruits and vegetables.
  • Lactose (glucose + galactose). Also known as milk sugar, lactose naturally occurs in milk and dairy products.
  • Maltose (glucose + glucose). Also referred to as malt sugar, maltose is the least common disaccharide in nature but it commonly occurs in foods when glucose is caramelized.

Complex carbohydrates are sugars composed of at least three glucose units (monosaccharides). Some are strung together in long chains known as polysaccharides. Complex carbohydrates do not taste sweet because their molecule is too large to fit on the sweet receptors of the taste buds. They are found in legumes, whole-grain breads and cereals and starchy vegetables. When consumed, their long molecules are broken down in the body into a simple sugar (monosaccharide).

Health Impact of Sugars

Sugars are the body’s major source of energy, providing four calories of energy for each gram. Monosaccharides and disaccharides are digested and absorbed very quickly. The body just needs to break down disaccharides into simple sugars, which are then immediately absorbed. Once inside the bloodstream, the single sugars (glucose) move into the body’s cells where they are converted to energy.

The body only uses as much glucose as needed to fuel its activity at any given time. Excess levels of glucose are stored in the liver and muscles in the form of glycogen (polysaccharide of glucose). When carbohydrate intake produces more glucose than the body can use and store in the liver and muscles, the excess glucose is turned into body fat.

The sugars present in foods such as fruit, vegetable and dairy products are also important sources of valuable nutrients, vitamins and minerals. However, although necessary for good health, too much sugar can contribute to negative health impacts. Consuming excessive amounts of sugary foods and beverages results in ingesting too many calories, which ultimately leads to weight gain. However, calories obtained from sugar are no more likely to cause weight gain than those obtained from fats or proteins.

Eating sugars and carbohydrates in any form, whether the source of the sugar is hard candy, pasta, milk, fruits or any other food that contains sugars, causes acids to form on the teeth, which can lead to tooth decay. In fact, the factors that determine the risk of tooth decay are how often a person eats foods with sugars and how long the food stays on the teeth. Therefore, certain foods that are considered relatively healthy (e.g., raisins), but stick to the teeth, promote decay for longer periods of time and pose a greater risk of tooth decay than sugary candies, which are easily washed away by saliva or water.

In addition, recent studies suggest that children who consume fewer sugary drinks during childhood may cut their risk of heart disease and diabetes later in life. Moreover, excessive consumption of sugary foods and beverages was found to increase the incidence of pancreatic cancer.

Contrary to general belief, sugar consumption does not cause diabetes or hypoglycaemia in people who do not have diabetes. Also, there is no convincing scientific evidence to support theories linking the intake of sugar with attention deficit-hyperactivity disorder (ADHD) or behavior problems in children.

Sources of Sugars

Sugars occur naturally in foods and beverages or are added to them during processing. Sugars that occur naturally in plants are the result of photosynthesis. In this process, plants use the sun’s energy to create carbohydrates (glucose) that serve as food for the plant’s growth. The best examples of plant foods with naturally occurring sugars are fruits and vegetables. However, plants can change carbohydrates from starches to sugars or vice-versa to suit their own needs. These changes are the reason why fruits get sweeter as they ripen or why younger vegetables taste sweeter before they mature.

Another example of naturally occurring sugar is lactose that can be found in milk. This type of sugar is much less sweet than sugars from plants such as fructose or sucrose.

Many plants supply sugars that are used not only to sweeten foods and beverages but also add color, volume, soften texture and enhance the food’s flavor. For instance, sugarcane and sugar beets are major sources of sucrose. The starch of maize is the source of corn syrup that is converted into high-fructose corn syrup (HFCS). Many sweet soft drinks and processed foods in the US are sweetened with HFCS. Other examples of naturally occurring sugars that are added to foods during preparation and processing include honey, maple syrup, molasses and sorghum molasses.

Moderating Intake: How to Spot Sugar on Food Labels

Sugary soft drinks, candy, cakes and sweets are foods that provide few or no nutrients, while containing lots of added sugar that has been refined. They are often called “empty calorie foods”. An excess intake of refined sugars can lead to undesired weight gain and related health problems. Therefore, dieticians encourage people to get moderate levels of sugar as part of a well-balanced diet.

Food labels offer the best information about a food’s sugar content. The nutrition facts label on processed food packaging reveals information such as the amount of sugars, total carbohydrates, fats and calories per serving. However, keep in mind that certain words are synonyms for sugar. These include:

  • Any word that ends in “ose” (e.g., maltose)
  • Brown sugar
  • Corn syrup
  • Corn sweetener
  • Crystalline fructose
  • Dextrin
  • Dextrose
  • Fructose
  • Fruit juice concentrate
  • Glucose
  • High fructose corn syrup
  • Honey
  • Invert sugar
  • Lactose
  • Maple syrup
  • Malt syrup
  • Maltose
  • Molasses
  • Raw sugar
  • Sucrose
  • Turbinado sugar

The higher sugar appears on the ingredient list, the more likely it is that it is present in significant amounts. However, if a sugar occurs naturally in a product, it will not be listed with other ingredients.

Some people who are trying to cut back on their sugar intake may consider using sugar substitutes. Sugar substitutes sweeten foods and beverages without adding excessive calories to a person’s diet. Nonetheless, they still should be consumed in moderation.