The startling rise in the levels of obesity around the world has been blamed on many factors – sedentary lifestyles, more eating out of home, bigger portion sizes. One hypothesis that surfaced in the USA was that the rise in overweight was due to an increase in the intake of high fructose corn syrup (HFCS) a sweetener commonly added to beverages and foods in the USA in place of sucrose (table sugar). But the science doesn’t support this theory.

What is High Fructose Corn Syrup (HFCS)?

HFCS was first introduced to the food supply in the 1970s. It’s made from corn starch which is broken down and enzymatically-treated to produce fructose. The fructose is then blended with glucose to achieve the desired ratio of the two sugars.  

HFCS is composed of either 42 per cent or 55 percent fructose (depending on the type of HFCS and the degree of sweetness required).The name HFCS confuses a lot of people who think that HFCS is high in fructose. In fact, the amount of fructose in HFCS is similar to that in sucrose which is made up of 50 per cent fructose and 50 per cent glucose. (See table below). Both sucrose and HFCS supply 16 kilojoules (or 4 calories) per gram. 

Sucrose and HFCS differ in their bonding. Sucrose is a disaccharide in which glucose and fructose and joined by a chemical bond whereas the glucose and fructose in HFCS is not bound. Once digested, the two sweeteners appear to be mtetabolised similarly.  

HFCS was classified as GRAS (Generally Recognised As Safe), by the US Food and Drug Administration in 1983. The FDA reaffirmed this classification in 1996. The sweetener is used in many different foods and beverages in the USA because of its unique properties. While it sweetens foods (the sweetness level is similar to table sugar), it also reduces water activity to inhibit microbial spoilage and helps to extend the shelf life of a product. HFCS helps baked foods brown better and improves the texture of these products. A whole range of food products in the USA, from tomato ketchup to soft drink, from cookies to breads, have HFCS added. It also helps keep the cost of food production down as it is cheaper than sucrose, the sugar it usually replaces in foods and beverages. 

Comparison of Sugars in Various Sweeteners

(From Hein et al 2005) 

Pure Fructose and HFCS are not the same

A lot of the misunderstanding in this area appears to stem from the confusion between studies using pure fructose and those using HFCS. Fructose is found naturally in fruits, honey, some vegetables, sugar cane and beets.  

Fructose appears to affect appetite and fullness in a different way to other sugars and it was hypothesized that this effect may increase the risk of obesity. 

Studies using very high doses of pure fructose (not HFCS) show that fructose appears to lower the levels of the hormones insulin and leptin, (both of which are associated with satiety) and increase the level of ghrelin, a hormone that seems to affect our perception of hunger, when compared to glucose. This led to theories that HFCS could affect normal food intakes leading to increased deposition of fat. However studies on HFCS and sucrose show no differences in the effects of these sweeteners on insulin, leptin or ghrelin even when they are taken at doses much higher than the average intake. 

Studies using very high doses of fructose have reported that fructose may raise blood triglyceride levels. However the levels used in the study far exceeded those found in the average diet and no studies have been conducted with HFCS. As HFCS has a similar composition to sucrose, it would be expected to have similar metabolic effects. Sucrose has not been shown to raise triglyvceride levels when taken in amounts found in a typical diet. 

No Direct Link between HFCS and Obesity

The theory about the possible link between HFCS intakes and the rising incidence of obesity surfaced because over the past 25 years there has been a significant increase in the use of HFCS in foods in the US. And the ever increasing girths of the American population seemed to mirror this rise. Yet this association doesn’t prove cause and effect. Many other factors have changed in the USA over the last 25 years – people are less active, serving sizes have increased and more people are eating out more frequently. 

Another important point to note in this debate is that the growth in the incidence of overweight and obesity is not confined to the US even though HFCS is not commonly used in other parts of the world.  

A report from the Center for Food, Nutrition and Agriculture Policy Workshop in 2005 stated, “there is currently no convincing evidence to support a link between HFCS consumption and overweight/obesity”. 

There have been two recent reviews on HFCS and obesity. The findings of the first of these was released in April 2007 (”High Fructose Corn Syrup – Everything you wanted to know and were afraid to ask”, Experimental Biology Annual Conference). A second review undertaken by the University of Maryland Center for Food, Nutrition and Agriculture Policy (CFNAP) was published in August 2007. The conclusion reached by both of the reviews is that HFCS and sucrose are chemically similar and that they are metabolized by the body in a similar manner. 

The reviews looked at the increase in HFCS use in the US food supply. As it was used to replace sucrose, the intake of sucrose fell at the same time. While the combined intake of sucrose and HFCS increased, so too did available energy from fats, oils and grain products. The overall contribution of calorie-contributing sweeteners (sucrose, fructose, honey etc) to total calorie intake in the US has not changed significantly over the last few decades. What has happened is that the total number of calories consumed in the USA has risen while the levels of physical activity have declined. This imbalance in energy intake versus energy expenditure is what is thought to have caused the obesity epidemic. And the excess calories have come from multiple sources - not just HFCS. 

Liquids versus Solids

Because a significant percentage of the increase in HFCS in the US was in the form of sweetened beverages, studies have also looked at the effects of calories taken in liquid form versus those taken as solids on satiety. The evidence is conflicting, probably because satiety is quite a complex area. It depends on many factors including calorie content, energy density (the calories per gram or ml) and how the food or beverage is taken (as a snack or as part of a meal).  

Some studies have shown that calories taken as solids are more satisfying than those taken in liquid form but other studies have contradicted these findings. Looking specifically at the effect of HFCS on energy intake, a recent study has shown that beverages containing the same number of calories have similar effects on appetite levels. 

The study (Perrigue et al 2006) compared various beverages of equivalent caloric content and reported that there were no differences in energy intake levels or appetite-related hormone levels between beverages sweetened by HFCS, those sweetened by sucrose or milk when they were taken as part of a meal. The researchers concluded that; "Energy balance consequences of HFCS-sweetened soft drinks are not different from those of other iso-energetic drinks, e.g., a sucrose-drink or milk.”

Summing It Up

While more studies are needed, there is currently no scientific evidence to suggest that HFCS or other sugar sources have a unique effect (other than contributing calories) on obesity. Too many calories from any source can lead to weight gain.

That doesn’t mean that you should consume unlimited amounts of HFCS or sugar. Just as with most messages on healthy eating – you should enjoy them in moderation as part of a healthy diet 

References:

·         Hein GL, Storey ML, White JS, Lineback DR. (2005). Highs and lows of high fructose corn syrup: a report from the Center for Food and Nutrition Policy and its Ceres[R] Workshop. Nutrition Today 40 (6):253-256  

·        Anderson GH. (2007)  “Much ado about HFCS in Beverages: the meat of the matter” AJCN, 86(6); 1577-1578

·         Forshee et al. (2007). "A critical examination of the evidence relating high fructose corn syrup and weight gain". Critical Reviews in Food Science and Nutrition 47: 561-582.

·         Perrigue M et al (2006). Hunger and satiety profiles and energy intakes following the ingestion of soft drinks sweetened with sucrose or high fructose corn syrup (HFCS). Proc. Exper. Biol. 2006. Abstract #LB433

·         Schorin MD (2006). High Fructose Corn Syrups Part 2: Health Effects. Nutr Today 41(2):70-77

·      Melanson et al. (2007). "Effects of high-fructose corn syrup and sucrose consumption on circulating glucose, insulin, leptin, and ghrelin and on appetite in normal-weight women". Nutrition 23: 103-12.

·         Monsivais et al. (2007). "Sugars and satiety: does the type of sweetener make a difference?” American Journal of Clinical Nutrition 86: 116-123.