The prevalence of obesity has increased in epidemic proportions in the last 30 years (1). The World Heath Organization estimates that there are at least 1.6 billion overweight adults globally, of which 400 million are obese (2). An overweight adult is roughly defined as one who exceeds the maximum desired weight for his/her height for normal physiological functions. Obesity is when the individual weighs 20% or more above this desired weight (3). Being overweight can negatively affect an individual’s energy and mood, and more dreadfully, make the individual more prone to various diseases such as cardiovascular complications, kidney and liver failure and diabetes (2). Though the detrimental effect of being overweight is indisputable, the exact causes of the rapid increase in incidents remain uncertain. More studies are now beginning to investigate the effects of the various new dietary components introduced in the last three decades in light of advances in biotechnology. One of these is the high-fructose corn syrup (HFCS).
Table sugar vs. high fructose corn syrup
Table sugar was the most common food sweetener used both domestically and industrially due to its sweetness and functional properties, which include adding structure and preservation to the food product. It is generally extracted from sugar canes or sugar beets. The human body cannot readily use table sugar for energy and it must first be digested and broken down into simple sugars. One molecule of table sugar can be broken down into 1 glucose molecule and 1 fructose molecule. Glucose and fructose are both simple sugars that can be absorbed by the human body and converted to energy for usage or storage. Since the introduction of HFCS in the 1970’s to the food industry, manufacturers have switched to preferentially use HFCS over table sugar as the main sweetening agent in processed food products (4). This is because HFCS are cheaper to transport and produce, easier to store and mix into food and actually taste sweeter (4). Food products sweetened with HFCS can therefore be made with lower cost and sold at a lower price. This is especially exemplified in fast food industries in their ability to sell cheap meals or enlarge the size of a meal at little extra cost. This sounds beneficial from both a manufacturer’s and a consumer’s point of view. However, it is no coincidence that the emergence of HFCS usage in food is shadowed by the increase in obesity worldwide.
Typically, HFCS is made from genetically modified corn or maize such that the sugar contents of the plant are enriched. Extracted corn starch contain mainly of the simple sugar, glucose (4). Conversion to the sweeter simple sugar, fructose, is then done using enzymes that are also genetically enhanced to work more efficiently (4). Therefore, the use of HFCS in common food products has raised concerns in people on strict organic diets. Depending on the sugar conversion process, HFCS can be made to have varying fructose content. The HFCS-55 (55% fructose content) is now used extensively in soft drinks, baked goods, candies, canned fruits, jams and various dairy products (4). Unlike table sugar, HFCS contains simple sugars that do not require further digestion to be absorbed by the human body. This contributes to the higher sweetness factor of HFCS. Furthermore, HFCS-55 contains a higher fructose to glucose ratio than table sugar (1). These characteristics show that substituting table sugar with HFCS results in an overall increased absorption and consumption of fructose. In fact, fructose consumption has increased drastically by 26% in the last three decades (4).
Glucose vs. fructose
Whether or not the increased consumption of fructose is contributing to the increased prevalence of overweight and obesity can only be assessed after investigating the differences in the human body breakdown of fructose and the more common simple sugar, glucose. Glucose is arguably the most important sugar in the human body since it is usable by virtually all tissues and organs (5). Furthermore, it is the preferred energy source for the brain (5). Conversely, fructose must be converted in the liver to energy, fat or glucose before it can be used by other organs (1). Therefore, excess fructose consumption may overwork the liver causing an increased risk of liver diseases and liver failure (6). Glucose and fructose breakdown in the liver both result in energy and fat production among other products. However, the glucose breakdown pathway is turned off when there is an accumulation of energy and fat, thereby preventing excess production. Fructose breakdown does not have this feedback mechanism and energy and fat production depends solely on the presence of fructose (1). Therefore, a massive ingestion of fructose would result in an overwhelming production of energy and fat.
Appetite regulation can be simplified to the relay of messages between the gut and the brain. The gut as well as other body organs will send out hunger and satiety signals depending on the presence or absence of nutrients. One of such nutrients is glucose. After a meal, the elevation in blood glucose level will shut off the hunger signal and send a satiety signal to the brain. As a result, the individual would feel satiated. Conversely, fructose is less capable at regulating these signals (7). Therefore, while a high glucose meal will make an individual satisfied, an equal caloric high fructose meal would leave the individual still feeling hungry. Thanks to HFCS usage, associated food products can be sold at much larger portions with a relatively small increase in price. This makes it very tempting for consumers to purchase and eat more food than they actually need in order to satisfy their hunger. This contributes to increased weight-gain in individuals that consume high fructose meals.
Fructose and diabetes
Adequate amount of circulating glucose in the blood is essential for healthy body functions. However, a chronic elevation in blood glucose level can lead to diabetes. Fortunately, in the presence of high blood glucose, the hormone insulin is released to promote glucose storage into cells thereby decreasing blood glucose level. Diabetes results when there is inadequate insulin activity in the presence of high blood glucose. Inadequate insulin activity could be either due to a lack of insulin production or secretion, or due to a lack of insulin sensitivity due to insulin resistance on body cells. Insulin resistance often results from a chronically elevated blood insulin level, a trademark of early stage diabetes. Fructose does not stimulate insulin release and it does not directly increase blood glucose levels. As such, a high fructose diet would result in lower elevation of blood glucose as well as less insulin release (7). Therefore, it was once believed that a high fructose diet might benefit diabetic and pre-diabetic individuals and alleviate the associated symptoms (4,8). On the contrary, long term high fructose diet actually makes the individual less sugar-tolerant and more insulin-resistant (9). In the end, they become even more diabetic than individuals undergoing a normal diet (9).
Not only can a high fructose diet worsen the symptoms in diabetic patients, it can actually increase the risk of developing diabetes in healthy individuals. There are more than 171 million people in the world with diabetes and at least 50% of all people with diabetes are unaware of their condition (10). Even with treatment, it is impossible to regulate blood glucose level in diabetic patients as tightly as in healthy individuals. The chronically elevated blood glucose becomes toxic to the body and can add stress to the liver and kidneys increasing the risk of organ failures (10). Glucose in blood along with the increased fat production after a fructose diet may accumulate and lead to formation of plaques that can complicate the cardiovascular system leading to heart failures or limb amputations. Build up of these plaques in the eyes make diabetes the leading cause of blindness in developed countries (10). Currently, around 3.2 million deaths per year worldwide are attributable to complications of diabetes and this equates to around six deaths every minute (10).
The most common cause of diabetes seen in developed countries is due to a build up in body fat, which can lead to insulin resistance and ultimately diabetes. As stated earlier, a high fructose diet induces an uncontrolled production of energy and fat as well as an overall increased appetite, resulting in increased caloric intake. Together, these health consequences associated with a high fructose diet suggest a strong link between the worldwide increase in fructose consumption with the increased incidences of obesity and diabetes.
HFCS in our lives
Fructose exists naturally in small amounts in honey, root plants and various fruits. When taken at this low amount in a regular diet, fructose has beneficial effects on health (8). However, the detrimental effects of a high fructose diet, as a result of eating HFCS sweetened foods, are becoming more and more evident. HFCS are now used to sweeten the majority of processed food products found on the kitchen shelves of everyday homes as well as being extensively used in fast food restaurants. Most of these food products target the young adolescents; therefore, it is no surprise that the younger generations are facing greater issues with becoming overweight and obese. Currently HFCS are not used to enrich baby formulas for reasons we should all be concerned about. It is important to educate the general public on the possible long term effects of a high fructose diet as well as make global efforts on significantly decreasing and hopefully eliminating the use of HFCS in food. At this rate, it is estimated that number of people with diabetes worldwide will increase more than two fold to 366 million by 2030 (10). It is unquestionably necessary to take actions now or we will be facing a very supersized future.
1. Elliott SS, Keim NL, Stern JS, Teff K, Havel PJ. 2002. Fructose, weight gain, and the insulin resistance syndrome. Am. J. clin. Nutr. 76:911-922
2. World Health Organization: obesity and overweight [article online], 2006. Available here. Accessed 15 February 2007
3. Starky S (Ed.): The obesity epidemic in Canada. Economic division, Library of Parliament [article online], 2005. Available here. Accessed 15 February 2007
4. Bray GA, Nielsen SJ, Popkin BM. 2004. Consumption of high-fructose corn syrup in beverages may play a role in the epidemic of obesity. Am. J. Clin. Nutr. 79:537-543
5. Dienel GA, Hertz L. 2001. Glucose and lactate metabolism during brain activation. J. Neurosci. Res. 66:824-838
6. Kelley GL, Allan G, Azhar S. 2004. High dietary fructose induces a hepatic stress response resulting in cholesterol and lipid dysregulation. Endocrinology 145(2):548-555
7. Teff KL, Elliott SS, Tschöp M, Kieffer TJ, Rader D, Heiman M, Townsend RR, Keim NL, D’alessio D, Havel PJ. 2004. Dietary fructose reduces circulating insulin and leptin, attenuates postprandial suppression of ghrelin, and increases triglycerides in women. J. Clin. Endocrinol. Metab. 89(6):2963-2972
8. Vaisman N, Niv E, Izkhakov Y. 2006. Catalytic amounts of fructose may improve glucose tolerance in subjects with uncontrolled non-insulin-dependent diabetes. Clin. Nutr. 25:617-621
9. Jürgens H, Haass W, Castañeda TR, Schürmann A, Koebnick C, Dombrowski F, Otto B, Nawrocki AR, Scherer PE, Spranger J, Ristow M, Joost H, Havel PJ, Tschöp MH. 2005. Consuming fructose-sweetened beverages increases body adiposity in mice. Obes. Res. 13:1146-1156
10. World Health Organization: diabetes [article online], 2006. Available here. Accessed 15 February 2007