Fructose is a natural simple sugar found in fruits, honey, and vegetables. In its pure form, fructose has been used as a sweetener since the mid 1850s and has advantages for certain groups, including people with diabetes and those trying to control their weight. Of course, fructose has been consumed for centuries in foods we still eat. It is known as a simple sugar because it is a single sweetening molecule. Fructose is also known as a monosaccharide.
High fructose corn syrup (HFCS) is also a sweetener and is used to sweeten foods and beverages. However, HFCS is not the same as fructose. HFCS is a mixture of fructose and glucose, made by an enzymatic process from glucose syrup from corn. The most common forms are HFCS-42 and HFCS-55, which contain 42% fructose (and 58% glucose) or 55% (and 45% glucose). Table sugar (sucrose) has 50% fructose (and 50% glucose) and so is very similar to HFCS.
Misinformation about fructose recently appeared in the media. This misinformation alleges obesity and negative health consequences from the consumption of HFCS and fructose. Many incorrectly use the terms “fructose” and “HFCS” interchangeably, confusing the public as well as health and nutrition professionals. It is important to be aware of the differences between these sweeteners.
Fructose is one of the main types of sugars found in fruits such as apples, in fruit juices, and in honey. It is also a component of sucrose (table sugar) in equal quantity to glucose to which it is linked. As with table sugar, fructose can be bought at the supermarket; both can be used in the same ways in home cooking and processing. Hence fructose is found also in processed foods such as desserts, dairy products, and preserves.
An important difference is that fructose is up to twice as sweet as sucrose, and sweeter than HFCS. This means less fructose can be used to achieve the same level of sweetness. Consequently fewer calories are consumed from foods of similar sweetness where fructose replaces sucrose or HFCS.
Unlike table sugar or HFCS, fructose does not cause a rapid rise and subsequent large fall in blood glucose levels, which means it has a low glycemic load or glycemic index (GI). Glycemic index (glycemic load per gram carbohydrate) is a measure of how carbohydrates affect blood glucose concentrations. As expected, glucose itself has a high value because it is rapidly absorbed into the blood stream; its GI or glycemic load per gram is 100. In contrast, the glycemic load per gram fructose is only 19, while that of table sugar is 65 – midway between its component parts glucose and fructose. HFCS has a similar GI value to table sugar, though its precise value depends on the fructose content of the HFCS that is used.
When foods high in sugar are eaten, blood sugar rises rapidly to a peak. The higher the rise the greater the fall, which then quickly results in a dip below normal blood sugar levels, and may arouse appetite. Some researchers believe that carbohydrate foods with a low glycemic effect have health benefits, which remains controversial. The World Health Organization concludes that low GI foods may help to prevent obesity, weight gain and type II diabetes. The U.S. Institute of Medicine made no recommendations on GI due to a lack of sufficient evidence of benefit long term against the economic costs of change towards low glycemic carbohydrate diets.
Low glycemic carbohydrate foods may be of benefit to people with diabetes, as they can help to prevent surges in blood glucose. While the American Diabetes Association recognizes that fructose produces a lower blood glucose response when used in foods in place of sucrose or starch, it does not believe GI to be sufficiently important at this time to merit changes to its existing advice on carbohydrate exchanges.
The name “high fructose corn syrup” is used because HFCS has a higher content of fructose compared to “regular” corn syrup, yet it contains a substantial amount of glucose and may be more glucose than fructose. HFCS and table sugar (sucrose) usually contain similar amounts of glucose and fructose.
HFCS is obtainable mainly in two forms:
Although high fructose corn syrup (HFCS) and fructose are often confused as being the same, they are not interchangeable as the two sweeteners are quite distinct. There is also a difference between table sugar and HFCS, though this appears to be of little consequence. It is that the glucose and fructose in table sugar are linked chemically and so table sugar needs digesting before absorption can occur. This digestive process occurs very rapidly for sucrose and so there is no significant difference in the overall rate of absorption. Because both table sugar and HFCS are absorbed into the blood stream as glucose and fructose, their subsequent metabolism is identical.
Some have suggested that a rise in the use of HFCS in the United States (US) over the past 30 years could explain the rise in obesity and type II diabetes, and that this is due to increased fructose consumption. However, there is no scientific support for this suggestion.
In the US, table sugar accounted for 83% of all sweeteners used in 1970, and for only 43% in 1997. During the same period, use of HFCS increased from 16% to 56%. However as table sugar and HFCS contain similar quantities of fructose, the overall level of fructose in the US diet has stayed unchanged.
As in the US, Europe has experienced a dramatic rise in the prevalence of obesity and type II diabetes. Unlike the US, the production of HFCS is controlled in the European Union (EU). This means that far less HFCS is consumed in Europe than in the US. As a result, the increased rates of obesity and type II diabetes in the EU cannot be explained by increased consumption of either fructose or HFCS.
The ultimate cause of obesity is consuming more calories than are expended during rest and physical activity. In view of the wide choice of foods now available and of the sedentary lifestyles in the US, a specific food or ingredient cannot be blamed for increased incidence of obesity and diabetes in the US or Europe. Physical activity or the lack thereof is an important factor along with the amount of calories consumed.
A group of experts convened during 2004 by Virginia Tech’s Center for Food and Nutrition Policy and the University of Maryland’s Joint Institute for Food Safety and Applied Nutrition has concluded, “Currently, there is no convincing evidence to support a link between HFCS consumption and overweight/obesity. There is also no evidence to suggest that humans absorb or metabolize HFCS any differently than sucrose.”
Appetite and the amount of food consumed are influenced by a range of complex factors. External influences can override the body’s own control, for example eating with friends for social benefits or experiencing a wide variety of foods or just eating for pleasure.
Though it has been claimed that fructose does not suppress appetite in the same way as other sugars, fructose does not cause rapid surges and dips in blood glucose levels, which is one factor thought to stimulate eating.
Recent news stories have focused on the potential effect of fructose on triglyceride levels in blood. Differences in the observations make it easy for individuals to fall into the trap of justifying a belief rather than scrutinizing and refuting a hypothesis. Consequently, stories arise that overemphasize a few studies which claim effects for high levels of fructose while largely ignoring others that find no effect or even an opposite effect, both in the morning before eating (fasted state) and after a meal (post-prandial state). These stories fail to account for the high variability in circulatory triglyceride responses to diet and there is over-interpretation and extrapolation from studies in animals with a different metabolism to humans.
All carbohydrates, even rapidly digestible sucrose, cause abdominal discomfort when consumed to excess. Some individuals may exceed their capacity for fructose absorption if large amounts are eaten. Under such circumstances, fructose may be associated with abdominal complaints, such as bloating and flatulence.