Sugars are simple carbohydrates that provide the main source of energy to the body. They occur naturally in foods or are added to them during preparation and processing. Most types of sugars taste sweet, although some do not.

Sugars are found in nutritious foods such as fruits, vegetables and milk products. They also are found in processed foods with few nutrients, including candy, soda and other sweets. Sugars are commonly thought of as the white, granular substance known as table sugar. However, there are many different types of natural sugars, including glucose, fructose, galactose, sucrose, lactose and maltose. 

In addition to providing the body with energy, sugars serve as a food sweetener and preservative. However, sugars also can have negative health impacts. Consuming too much sugar can contribute to both weight gain and tooth decay.

Sugars are simple carbohydrates that occur naturally in foods or that are added to them during preparation and processing. Along with starches (another form of sugar), they are the main dietary source of energy for the body. Sugars are formed by carbon, hydrogen and oxygen molecules. Different types of sugars have specific chemical structures.

Many plants supply sugars found in people’s diets. Sugarcane and sugar beets are major sources of such sugars. Sugarcane grows in the subtropics, while sugar beets grow in more temperate areas. Sucrose is derived from both of these plants. Other sugars can be derived from other plant products, such as corn syrup. Many sweet soft drinks and processed foods in the United States are sweetened with high fructose corn syrup.

Sugars usually taste sweet, although some do not. They are found in fruits, vegetables, milk products, candy, soda and other sweets. Sugars themselves are not unhealthy. In fact, they often serve to sweeten nutritious foods, thereby making them more appealing. The sugars found in foods such as fruit, vegetable and milk products are also important sources of valuable nutrients, vitamins and minerals.

However, sugary foods do not boost a person’s health. Candy, soda and sweets provide few or no nutrients and contain sugar that has been refined, or processed. Although these carbohydrates help provide fuel for energy, they are “empty calories” with little or no nutritional value. An excess intake of refined sugars can lead to undesired weight gain.

Sugars play many other roles in foods in addition to serving as sweeteners. In many foods, they add aroma, color, body, flavor and texture to food. For example, sugars provide the energy for yeast in baking, which allows dough to rise. Sugars also contribute bulk, tenderness, smooth-crumb texture and a lightly browned surface to cakes. Other foods that benefit from sugar include:

• Canned jams, jellies and preserves. Sugars act as a preservative by tying up water that otherwise might be used by molds and yeast to grow.
  
  
• Cookies. When sugars and shortening are creamed together, they bring air into the dough. They also provide a light-brown color and crisp texture to cookies.

Experts recommend that people follow the recommendations of the U.S. Department of Agriculture’s (USDA) Food Guide Pyramid in establishing a diet that is well-balanced and that provides the nutrients necessary for maintaining good health. People are urged to get their sugars from fruits and vegetables, as well as nutrient-dense foods such as pasta, rice, bread and legumes. Sugary foods that provide few nutrients can still be enjoyed, but should be consumed only in moderation.

Example of types of sugar and their calorie content are as follows:

Sugars are commonly thought of as the white, granular substance known as table sugar. However, there are many different types of sugars. As with all carbohydrates, sugars are made up of a combination of carbon, hydrogen and oxygen. Sugars can either 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. There are three types of monosaccharides:

• Glucose. Also known as dextrose, it has a mildly sweet flavor. Glucose is the main form of sugar that circulates in the bloodstream and is often referred to as "blood sugar."
  
  
• Fructose. The sweetest of the sugars, it occurs naturally in fruits and honey. It is also found in high-fructose corn syrup (in soft drinks) and is a major source of sugar in the diet of Americans.
  
  
• Galactose. Hardly tastes sweet, found in gums, dairy products and sugar beets.

When two monosaccharides join together, they become disaccharides. The following are the three disaccharides found in foods:

• Sucrose (glucose + fructose). Commonly called table sugar and also found naturally in sugarcane, sugar beets, honey and many fruits and vegetables.
  
  
• Lactose (glucose + galactose). Naturally occurs in milk and dairy products.
  
  
• Maltose (glucose + glucose). Also known as malt sugar, it is the least common disaccharide in nature.

Complex carbohydrates are sugars that are made up of longer chains of sugar units. However, they do not taste sweet because the size of their molecules is too large to fit on the sweet receptors of the taste buds. They are found in whole-grain breads and cereals, legumes and starchy vegetables that provide nutrition in the form of vitamins, minerals and fiber.

Complex carbohydrates are composed of at least three glucose units. In some cases, they may be composed of many monosaccharides strung together in compounds known as polysaccharides. When a person consumes a complex carbohydrate, it is broken down in the body into a simple sugar.

Sugars are also classified according to their source. Intrinsic or naturally occurring sugar refers to the sugar found naturally in foods such as fruits, vegetables and milk products. Extrinsic or added sugar refers to the sugar added while processing foods, such as the sugar added to soft drinks, fruit beverages, ice cream, snacks and other processed foods or beverages. Naturally occurring sugars are no healthier for a person than extrinsic sugars. All sugars provide energy for the body in the same way.

Refined sugar is a term that describes sugar separated either from the stalk of sugarcane or from the beet root of sugar beet. Juice in the plant that contains the sugar is extracted and processed into dried sugar crystals. It is then sold as granulated or white sugar. Sugarcane or sugar beet that has been processed into table sugar leaves behind thick syrup known as molasses. Brown sugar is refined sugar combined with molasses for color and flavor. Raw sugar (also called turbinado, demerara, or muscavado sugar) is derived from processed sugarcane that has undergone a specific refining process.

Sugars are the body’s major source of energy. Both sugars and carbohydrates provide the body with 4 calories of energy for each gram. Simple carbohydrates are digested very quickly. When a person consumes a food containing sugars, digestive enzymes either break down disaccharides into their simplest elements (glucose, galactose and fructose) or immediately absorb the sugars if they already are in the form of monosaccharides. Once inside the bloodstream, the single sugars (known as blood sugar, or glucose) move into the body’s cells and are converted to energy. Fiber is the only carbohydrate substance that does not follow this rule. Fiber is a polysaccharide and contains cellulose and hemicelluloses that are not digested by the body, and as a result do not contribute energy.

The body only uses as much glucose as is needed to carry out activity at any given time. The levels of glucose in the blood are regulated by insulin, a hormone produced in the pancreas.  Excess levels of glucose are stored in the liver and muscles in the form of glycogen. If the body’s glucose levels drop, a hormone in the body called glucagon triggers the conversion of glycogen into glucose, which provides more energy for the cells.

When the body’s total capacity of glucose and glycogen is combined, it equals about 1,800 calories of energy. When carbohydrate intake produces more glucose than the body can use and store, the excess glucose is turned into body fat.

While sugars are essential for good health, they also can contribute to negative health impacts. Eating excessive levels of sugar results in ingesting too many calories, which in turn leads to weight gain. However, it is important to note that the calories obtained from sugar are no more likely to cause weight gain than calories from other sources, such as fats or proteins.

In addition, eating sugars and carbohydrates causes acids to form on the teeth, which can lead to tooth decay. This is true whether the source of the sugar is hard candy, milk, pasta or any other food that contains sugars. Generally, the factors that determine the risk of decay are how often a person eats foods with sugars and how long the food remains on the teeth.

Somewhat surprisingly, some foods that are considered relatively healthy (such as raisins or granola) may cause an even greater risk of tooth decay than sugary candies such as chocolate or hard candy. This is because chewy foods that stick to the teeth promote decay for longer periods of time than foods that are easily washed away by saliva or water.

Recent research has also found links to other negative health consequences associated with sugar consumption. For example, one recent study found that children who consume fewer sugary drinks during childhood may cut their risk of illnesses such as heart disease and diabetes later in life. Another study found a link between excessive consumption of sugary foods and drinks and increased incidence of pancreatic cancer.

Despite these findings, many trends indicate that people continue to consume increasing levels of sugar. For example, one study found children consume sodas and other sugary drinks more than any other beverages while at school.

However, many long-held beliefs about negative health effects attributed to sugars have been debunked in recent years. In the past, sugars have been blamed for causing behavioral problems and aggravating attention deficit-hyperactivity disorder (ADHD). However, there is no scientific evidence to support any link between the intake of sugars and hyperactivity or behavior problems. The cause of the behavior problems and ADHD is poorly understood.

For more than a quarter century, scientists have understood that sugar consumption does not cause diabetes. However, this myth still persists among many people. Diabetes results from the body’s inability to use insulin normally. While diet can have a major impact on the health of a person with diabetes, diet itself cannot cause the disease. Moderate amounts of sugar can be part of a well-balanced diet for people with diabetes, according to the American Diabetes Association.

Sugars either occur in foods naturally or are added during processing. Sugars that occur naturally in plants are the result of photosynthesis, in which plants use the sun’s energy to create carbohydrates that serve as food for the plant’s growth. Fruits and vegetables are examples of plant foods with naturally occurring (intrinsic) sugars.

Plants also can change carbohydrates to suit their own needs. For example, a fruit changes a carbohydrate from a starch to a sugar as it matures. This is why ripened fruits taste sweet. In contrast, vegetables tend to change their carbohydrates from sugars to starches, which is why younger vegetables taste sweeter before they mature.

Lactose is another sugar that occurs naturally in foods. It is found in milk, but is much less sweet than sugars such as sucrose.

Sugars also can be added to foods during preparation and processing. Many home-cooked meals include added sugar. Baked foods may have added sugar or honey, homemade jellies and jams may have added sugar and homemade baked beans may include molasses and sorghum molasses. Sugars such as sucrose and fructose also are added to many foods during processing.

Foods that get their flavor and in some cases, texture and bulk, from sugars include:

• Breads
• Candies
• Fruits
• Ketchup and other condiments
• Milk
• Salad dressings
• Soft drinks
• Vegetables

Foods that are the most common sources of added sugars in the American diet include:

• Cakes, cookies and pies
• Candy
• Dairy desserts (e.g., ice cream)
• Drinks such as fruit punch and lemonade
• Regular soft drinks (not diet or sugar-free)

Experts 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 that is present on processed food packaging reveals information such as the amount of sugars, calories and carbohydrates per serving. It is important to remember that certain words are synonyms for “sugar.” These include “corn syrup,” “dextrin,” “molasses” and any word that ends in “ose” (e.g., maltose).

According to the U.S. Department of Agriculture (USDA), consumption of various sweeteners in the United States has increased from an estimated 113 pounds (51.2 kilograms) per person in 1966 to 147 pounds (66.7 kilograms) in 2001. Other sugars commonly appear on food labels as the following:

• High fructose corn syrup
• Fruit juice concentrate
• Malt syrup
• Crystalline fructose
• Maple syrup
• Brown sugar
• Corn sweetener
• Dextrose
• Fructose
• Glucose
• Honey
• Invert sugar
• Lactose
• Maltose
• Raw sugar or turbinado sugar
• Sucrose

The higher sugar appears on the ingredient list, the more likely it is that sugar is present in significant amounts. If a sugar occurs naturally in a product, it will not be listed with other ingredients. People who are trying to cut back on their sugar intake are encouraged to look for phrases such as “sugar-free” or “no sugar added.”

Terms that commonly appear on labels include:

• Calorie-free (less than 5 calories)
  
  
• Sugar-free (less than 0.5 calories per serving)
  
  
• Reduced sugar or less sugar (at least 25 percent less sugar per serving than standard food)
  
  
• No added sugars, without added sugar, no sugar (no sugars added during processing or packing)

Other tips for reducing sugar intake include:

• Do not overindulge in foods that are mostly sugars. Foods that contain a lot of sugar but few other nutrients include candy, cake, cookies, jam, jelly, soft drinks and syrup.
  
  
• Moderate the use of table sugar. Use minimal amounts of table sugar to sweeten coffee or tea, cereal or French toast. Cinnamon can serve as a good substitute for sugar when sweetening certain foods. 
  
  
• Use sugar substitutes. These products sweeten foods and drinks without adding excessive calories to a person’s diet. Sugar substitutes often are used by people concerned about weight gain, or who have medical conditions such as diabetes. However, sugar substitutes still should be consumed in moderation. Like sugar, they do not provide any nutrients.

Preparing questions in advance can help patients have more meaningful discussions with health professionals regarding their conditions. Patients may wish to ask their doctor or registered dietitian the following questions related to sugars:

1. How much sugar should I include in my diet?
   
   
2. How can I tell if my sugar intake is too high?
   
   
3. Who can help me create a meal plan that includes moderate levels of sugar?
   
   
4. What are some foods that contain sugar, but are also rich in other nutrients?
   
   
5. What are the dangers of a high-sugar diet?
   
   
6. Is it possible to harm your health by eating too little sugar?
   
   
7. Can you suggest some sugar alternatives that can help me sweeten foods?
   
   
8. What are some cooking tips for decreasing levels of sugars in meals and baking?
   
   
9. What are some tips for encouraging my child to eat low-sugar foods?
   
   
10. I have diabetes. Should I alter my sugar intake?