What is fructose?
Fructose is a monosaccharide, or single sugar, that has the same chemical formula as glucose but a different molecular structure. Sometimes called fruit sugar, fructose is found in fruit, some vegetables, honey, and other plants. Fructose and other sugars are carbohydrates, an important source of energy for the body.
What other types of sugars are there?
The food supply contains a variety of sugars called monosaccharides (single sugar units like fructose and glucose) and disaccharides (two monosaccharides linked together). Glucose is the main source of energy for the body because most complex sugars and carbohydrates break down into glucose during digestion. Starches contain many single sugar units linked together. The various sugars perform different functions in the body, but they all can provide energy.
Sucrose is a disaccharide that contains equal parts of glucose and fructose. Known as table or white sugar, sucrose is found naturally in sugar cane and sugar beets. Other sugars in foods and beverages include:
|Lactose||Disaccharide containing glucose and galactose||Naturally occurring in milk|
|Maltose||Disaccharide containing two glucoses||Crystallized from starch|
|Dextrose||Another name for glucose||Crystallized from sugar cane, sugar beets and starches|
|Corn Syrup||Primarily single glucose units||Produced from corn starch|
|High Fructose Corn Syrup||Primarily a mixture of glucose and fructose single units||
Produced from corn starch
Is fructose safe?
High fructose corn syrup and all other sugars are “generally recognized as safe” by the Food and Drug Administration (FDA).
The Surgeon General’s Report on Nutrition and Health, the National Academy of Sciences report Diet and Health, and Healthy People 2000: National Health Promotion and Disease Prevention Objectives by the U.S. Department of Health and Human Services support this conclusion.
In a 2002 scientific statement on sugar and cardiovascular disease, the American Heart Association concluded that, for most individuals, consuming fructose either pure or in the form of sucrose has neither beneficial nor adverse effects.
What are the differences in the way glucose and fructose are metabolized by the body?
Even though commonly consumed sugars provide basically the same number of calories, they are metabolized and used by the body in different ways. For instance, glucose from dietary sources is digested, absorbed, transported to the liver, and released into the general blood stream. Many tissues take up glucose from the blood to use for energy; this process requires insulin. Fructose is predominantly metabolized in the liver, but unlike glucose it does not require insulin to be used by the body.
Does fructose cause diabetes?
Diabetes is a disorder affecting the way the body produces and uses insulin and how it handles blood glucose. Insulin is essential for aiding glucose transport into cells. People with type I diabetes do not produce insulin, whereas those with type II diabetes either do not produce enough insulin or cannot efficiently use the insulin their bodies make. Factors such as overweight and obesity, lack of physical activity, and genetic predisposition all increase the risk for type II diabetes.
People with diabetes must pay attention to the amount of all carbohydrates—sugars and starches—they consume.
Because fructose does not increase blood glucose and does not require insulin, individuals with diabetes can often tolerate it better than other sugars. In fact, studies show that small amounts of oral fructose may actually improve glycemic control in people with diabetes.
Does fructose cause obesity?
Excess body fat results when people do not balance their energy (caloric) input with energy output. Extra calories may come from any caloric nutrient—proteins, fats, alcohol and carbohydrates including starches and sugars such as fructose. Lack of physical activity plays a significant role in promoting body fat accumulation and development of obesity.
Some researchers have speculated that fructose may not be as satiating (produce feeling of fullness) as other carbohydrates because it does not stimulate insulin and leptin secretion nor suppress ghrelin production—all hormones that help to regulate hunger and food intake. However, it is important to note that this speculation is based on preliminary research that tested fructose levels at least three to four times higher than the average amount consumed by Americans. Further, very few Americans ever consume fructose in isolation, but rather in combination with glucose.
What about increased use of HFCS during the last 20 years and rising rates of obesity; is it cause and effect?
There is no scientific proof of cause and effect with respect to the consumption of HFCS rather than other sugars, such as sucrose, regarding obesity rates. Some studies suggest we are consuming more calories, but the imbalance of calories consumed and expended is what has caused the weight increase—we consume more calories than we need.
Hypotheses that suggest rise of obesity began at the same time as increased use of HFCS in foods and beverages are correlations—taking two simultaneously occurring events and asking if there may be cause and effect. This may seem to be a likely chain of events but doesn’t necessarily show cause and effect; other events that have not been considered may be equally important to consider. Many factors have changed since the 1970s, including activity levels.
Is there a difference between drinking calories and eating calories?
There continues to be debate about whether there is a difference between the way the body handles liquid and solid calories. The studies that have looked at this question do not replicate each other. Some studies show that there is the same level of satiety when subjects consume calories in liquid form as when consumed in solid form. Other studies show that there is a difference of satiety depending on the source (beverage or food) of the calories. Additional research is needed to answer this question.
Does fructose cause insulin resistance syndrome?
Insulin resistance is a condition in which the body does not effectively use the insulin it produces. The body compensates by producing greater amounts of insulin in order to maintain normal blood glucose levels. Insulin resistance—along with obesity, hypertension, and blood lipid disorders—is part of the metabolic syndrome. Insulin resistance sometimes leads to type II diabetes and heart disease.
Although experimental animals fed very large quantities of fructose have developed insulin resistance, feeding studies in humans have never demonstrated this effect. Excess body fat, lack of physical activity and a genetic predisposition are thought to be the primary drivers for developing insulin resistance, not fructose consumption.
What effect does fructose have on triglycerides in the body?
Triglyceride is a technical term for fat that occurs in food and in the body. Both dietary fat and carbohydrates contribute to the formation of triglycerides in the body but in different ways. Excess consumption of calories from fats, proteins, or carbohydrates—including starches and sugars—promotes accumulation of body fat.
Research in humans has shown inconsistent effects of sucrose and fructose on triglycerides in the bloodstream. The variable effects may be related to factors such as the amount of fructose consumed; body weight status; and baseline blood triglyceride, insulin and glucose levels. An elevation in blood triglycerides has been seen mostly in sedentary overweight and obese subjects and with test diets that are high in both fructose and total carbohydrate and low in dietary fiber and fat. Some research suggests that chronic elevation of triglycerides in the bloodstream may increase the risk for insulin resistance and coronary heart disease.
Which foods and beverages contain fructose?
Natural sources of fructose include fruits, some vegetables, honey, sugar cane and sugar beets. Because it is a component of sweeteners such as sucrose and high fructose corn syrup, fructose is present in variable amounts in a wide range of sweetened foods and beverages.
What is high fructose corn syrup?
High fructose corn syrup (HFCS) is a liquid sweetener used in the manufacture of foods and beverages. In the late 1960s scientists developed an enzymatic process that transforms dextrose (glucose) from corn starch into a mixture of fructose and glucose. The most common form (70% in food supply) is HFCS-55, which contains 55% fructose and 45% glucose. By comparison, sucrose contains 50% fructose and 50% glucose. HFCS-55 and sucrose have similar sweetness intensity.
Which foods and beverages contain high fructose corn syrup?
HFCS is present in numerous products including soft drinks, fruit drinks, sports drinks, baked goods, candies, jams, yogurts, condiments, canned and packaged foods, and other sweetened foods.
Why is high fructose corn syrup in so many products?
HFCS is a useful ingredient because of its sweetness and ability to blend with other food and beverage ingredients. When methods for producing HFCS improved, food and beverage companies replaced other sweeteners with HFCS.
USDA’s Economic Research Service has tracked the amount of caloric sweeteners in the food supply, measured in per capita deliveries, since 1966. Refined sugar (sucrose) is the predominately used sweetener, but a portion of its use has been replaced over time by HFCS. United States per capita deliveries in 1966 were 97.3 pounds for refined sugar and zero for HFCS. In 2010, per capita deliveries totaled 66.0 pounds for refined sugar and 48.9 pounds for HFCS.1 Total deliveries of all caloric sweeteners increased 17% from 1966 to 2010. However, between 1999 and 2010, total deliveries of all caloric sweeteners decreased by 13%. Per capita deliveries of sweeteners by U.S. processors and refiners and direct-consumption imports to food manufacturers, retailers, and other end users represent the per capita supply of caloric sweeteners. Actual human intake of caloric sweeteners is lower because of uneaten food, spoilage, and other losses.
How much fructose should I consume in a day?
There are no specific dietary requirements or recommendations for fructose. The National Academy of Sciences’ Institute of Medicine (IOM) recommends total carbohydrate intakes should comprise 45 to 65% of calorie intake. Most of the carbohydrates should come from fruits and fruit juices, vegetables, whole grains, legumes, and dairy products or other rich sources of calcium.
The IOM also found that diets with more than 25% of caloric intake from added sugars were associated with significantly decreased levels of essential nutrients (e.g., calcium, magnesium, and zinc) in some population groups. Added sugars are sugars and syrups added to foods during processing or preparation. The IOM did not recommend an ideal level of added sugars consumption.
The 2010 Dietary Guidelines for Americans recommend reducing intake of calories from added sugars. Because fructose is a component of most added sugars, moderating the amount of added sugars in the diet will automatically moderate fructose intake. Added sugars do not include the fructose found naturally in fruits and vegetables, which is covered under the consumption levels recommended by the Dietary Guidelines, which vary depending on age, gender, and level of physical activity. For more information on recommended intakes of fruits and vegetables, click here.
All sugars, including fructose, can be included in a health promoting diet if eaten in moderation.
1Economic Research Service, USDA. The Economics of Food, Farming, Natural resources, and Rural America. Table 50: U.S. per capita caloric sweeteners deliveries for domestic food and beverage use, by calendar year. 7/25/2011.