by Meghan Johnson
The correlation between the rise in consumption of high fructose corn syrup (HFCS) and the rise in obesity rates in the United States has often been misinterpreted to mean that high fructose corn syrup is uniquely causing obesity. While it’s tempting to want to blame America’s weight problem on a single ingredient (especially when it has no real nutritional value), we must look to science before we can make such accusations.
What is high fructose corn syrup?
HFCS is a chemically altered sweetener that has become increasingly popular in the US over the past 40 years. The sweetener is used in place of other sugars due to its ability to make high fiber foods more palatable, inhibit microbial spoilage by reducing water activity, and extend shelf life through moisture control. Its manufacturers claim foods taste fresher because HFCS protects the firm texture of canned fruits and reduces freezer burn in frozen fruits. Because of its preservation characteristics, HFCS is commonly found in processed foods such as bread, cereal, granola bars, lunchmeat, yogurt, and condiments as well as soda.
Does HFCS encourage weight gain more than other added sugars?
The main case against the sweetener is that its sugar composition affects the body differently than natural sugars from cane, beets or honey. Compositionally, HFCS is nearly identical to table sugar (sucrose), which is made up of equal parts fructose and glucose molecules. Glucose is one of the simplest forms of sugar and is a component of all dietary sugars. Fructose is also a simple sugar, found in fruits and honey.
Advocates for HFCS argue that both sugar and HFCS are metabolized the same way in the body, and therefore one is no more harmful than the other. Those on the other side of the argument insist that HFCS is metabolically different than sugar and causes excess fat storage, leading to obesity.
What does Science say?
There is some scientific evidence supporting the idea that glucose and fructose (especially the kind found in HFCS) are metabolized differently . However, the studies were conducted on lab animals and can’t be generalized to humans.
Most notably, Princeton scientist Bart Hoebel’s study found differences in the uptake pathways (the way the fructose molecules are absorbed.) Without glucose regulation, the fructose molecule can be absorbed into the body’s cells and cause unlimited energy production. Excess energy, or calories, is stored as adipose tissue, or fat. Another difference was identified in the sugars’ stopping molecules. In glucose metabolism, stopping molecules halt further energy production when enough energy has been made. Hoebel’s work suggests that the stopping molecules are not activated for the fructose molecule found in HFCS. Once again, these results were only seen in rats.
The other side of Science
Dr. John White is a leading researcher cited on the Corn Refiner’s Association website (the main agency advocating for the continued use of HFCS and makers of the “Sweet Surprise” commercials). Dr. White finds three main problems with the current studies trying to link HFCS to obesity in humans. They include:
1. The studies were conducted using rats. Rats are not humans and you cannot draw conclusions from findings that have not been proven to hold true with humans. Our metabolic pathways are fundamentally different.
2. The level of fructose given to the rats far exceeds what any typical human would consume. When fructose is given without glucose, it behaves differently and humans never consume those quantities of straight fructose. Hoebel allowed his rats unlimited consumption of the sweetener so that the rats were getting about 3,000 calories per day of straight fructose (when translated to humans).
3. Sucrose was only used as a control in some of the study’s arms. The study’s findings are not valid if the same controls were not used across all arms of the study.
Lastly, the case for HFCS’s link to obesity violates one of the foundational concepts of science; that correlation does not equal causation. Just because two things are moving together, increasing or decreasing at the same rate over time, we cannot make assumptions that one thing is causing the change in the other.
There is little evidence to show that high-fructose corn syrup is, uniquely, causing Americans to become fat. Metabolically, HFCS does not really appear to be very different from other added sugars. According to Dr. White, “All of these caloric sweeteners contain fructose in about a 1:1 ratio, and what would surprise people is that once these sweeteners reach the blood stream, they are all equivalent. If you substitute one for another, you get metabolic equivalence. They deliver the same sugars to the blood streams in the same concentrations.”
What does this mean for me?
The important take-away is that eating any sugar or nutrient in excess will lead to weight gain. Dr. White said, “The only link between HFCS and obesity is that if you overeat HFCS, just like any nutritional component, you stand the chance of gaining weight. Added sugars will contribute to obesity if they’re over consumed.” The connection between HFCS and weight gain is simply that Americans are eating more across all categories, including added sugars, and that more and more products are popping up with added sugars in them to lengthen shelf life or enhance taste.
To avoid consuming HFCS until more conclusive evidence is found, consume minimally or unprocessed foods such as fresh fruits and vegetables, whole grains (watch out for breads!), and plenty of lean protein such as legumes, eggs or lean animal protein. HFCS has already been removed from many products to meet consumer demand but if you’re unsure if what you’re eating contains the sweetener, just flip over the box and check the ingredient label.
Meghan Johnson is a first-year FPAN student with a specialization in Health & Nutrition Communication. She relocated to Boston from Washington DC and is doing her best to acclimate to the lingo, the bitter winds, and clam chowder.