A Word on High Fructose Corn Syrup
All the food-label-reading-consumers out there know that High Fructose Corn Syrup (HFCS) is found in many processed foods. Manufacturers love the stuff for four reasons:
1) Unlike sucrose (regular table sugar) it is stable in acidic food and beverages, meaning it doesn’t go bad on the shelf.
2) It is cheap to make because it is derived from plain corn.
3) It comes in a syrup form which is quick and easy to dissolve into food products.
4) It is intensely sweet, so less can be used for the same degree of sweetness as sucrose—more bang for the buck!
Chemical Structure of High Fructose Corn Syrup
Structurally, both sucrose and HFCS are made up of the same two sugar molecules, or monosaccharaides, called glucose and fructose. The difference between them is HFCS is made up of un-bonded monosaccharides at a ratio of 45% glucose and 55% fructose. That’s why it is called “high” fructose. On the other hand, sucrose is a disaccharide made up of one glucose and one fructose molecule each, bound tightly together by an oxygen atom. Just an extra 10% fructose and free, un-bonded monosaccharides is all that differentiates HFCS and sucrose. So, why are so many food products getting hyped up lately, marketing that they no longer contain HFCS? Why does it have such a bad rap?
I was first introduced to the properties of HFCS in a biochemistry class I took in 2008. My professor suggested that HFCS blocks a receptor in our brain which signals satiety. I thought she called it the PABA receptor, but I can’t find the research to back that up, so don’t quote me. However, if that suggestion is true, it could help explain why it is possible to eat a whole sleeve of Oreos without feeling full until much later.
Digestion of High Fructose Corn Syrup
First of all, the only form of sugar which the body can use is glucose—it recognizes no other sugar as acceptable “food.” Thus, our bodies are equipped with special enzymes that help break down and convert various sugars, ingested in the form of carbohydrate starches, into glucose. When sucrose is ingested, enzymes in our mouth and stomach must break it down into glucose and fructose in order for the liver to absorb the sugar. High fructose corn syrup is already made up of the un-bonded monosaccharides, so no extra digestion is needed in this first step. Glucose is quickly absorbed into to the liver where it is then transported to the tissues of the body. Some is stored in the liver and muscles as glycogen, but most is used as immediate fuel for the brain and other tissues. Fructose, on the other hand, is slowly absorbed, requiring extra help from various enzymes to convert it to usable energy or compounds for storage in the liver.
Photo cred. www.wikipedia.org
To drive this concept home, here’s what happens in carbohydrate digestion when we eat a piece of whole-wheat bread. Chewing in the mouth combined with salivary amylase helps break the complex starch into glycogen. Down it slides to the stomach where hydrochloric acid breaks it into disaccharides, or sucrose molecules. In the small intestine the enzyme, sucrase, breaks the molecules into the monosaccharides glucose and fructose. Digestion will be slowed here because of the digestion-resisting fibers contained in the whole-wheat bread. This is a good thing, because it prevents blood sugar spikes. Glucose enters the liver where it is then dispersed to the brain and tissues for food. Some is stored in the liver and muscles for later. Fructose enters the liver where it hangs out for a while, waiting to be converted into one of three different compounds: glycogen for energy storage, triglycerides for fat storage, or free glucose for immediate energy. Most converted fructose is used for glycogen storage.
Fructose conversion to Glycogen-https://en.wikipedia.org/wiki/Fructolysis
Fructose conversion to Triglyceride-https://en.wikipedia.org/wiki/Fructolysis
Fructose conversion to glucose-http://www.medbio.info/Horn/Time%201-2/carbohydrate_metabolism%20March%202007a.htm
What is the big deal with eating too much fructose?
It must be clarified here that fructose alone, is a naturally-occurring sugar molecule found in fruits, vegetables, and honey. The unnatural characteristic of HFCS is simply that fructose exists in a higher concentration than what is found in whole foods. There are two major differences in the digestion of foods containing HFCS versus those that do not. First of all, they cause a quick spike in blood sugar since there is no digestion needed for the liver to absorb the glucose and fructose. Second, most foods containing HFCS are not high in fiber, so there’s nothing to slow the digestion in the small intestine. Third, the liver gets overwhelmed with the high ratio of fructose needing to be converted to usable energy compounds. Following, I will explain how science is finding that consuming too much fructose can possibly be harmful.
First of all, biology teaches us that if large amounts of fructose are consumed, it can spill into the colon, unabsorbed, and result in intestinal gas and loose stools. Nobody wants to experience that kind of trouble, right?
Many studies are being conducted to find the connection between HFCS and obesity. Back to my professors suggestion about HFCS blocking our normal satiety cues. Studies like this one from the Journal of the American Medical Association are backing her suggestion. Researchers are finding that fructose could block blood flow to the areas of the brain which regulate hunger, allowing for overeating.
The issues with eating too much fructose don’t stop at just the effects it can have on the brain. Remember that glucose is the only form of sugar the body recognizes as suitable for fuel? If too much fructose is consumed and the enzymes can’t convert it all to glucose, where does the surplus go? It is often stored as fat. In the American Journal of Clinical Nutrition, I found many studies showing various other potential health consequences from too much HFCS consumption–everything from insulin resistance, high cholesterol, and cardiovascular disease to a possible link in liver failure.
As with any controversial food items, there are just as many arguments for why HFCS is NOT bad for the human body. I found one here. Ironically, the author of this study is associated with the Corn Refiners Association and works as a consultant to a food and beverage industry. So, as valid as the research may be, it is difficult to accept this work as fact when such a conflict of interest exists. Of course the researcher won’t say that HFCS is bad for us—the Corn Refiners would oust the poor soul! 😉
One thing was common among most studies trying to prove or disprove the adverse health effects of HFCS, and that was its connection to increased calorie consumption. Because it is a preservative, it’s mostly found in processed “junk food.” You might ask, does the HFCS cause over consumption of calories, or does it just happen to be a sweetener used in already high-calorie snacks? Maybe HFCS has nothing to do with consuming too many calories—or maybe it does. If my biochemistry professor was correct, then foods containing HFCS may just shut down our satiety cues, making it easier to overeat. So, knowing what I do about HFCS, what foods do I limit in our home?
HFCS is added to many products shelved on the inner aisles of the grocery store like processed breads, snacks, candies, cakes, cereals, yogurts, sodas, sauces, and condiments. Does this mean we NEVER eat candy or drink soda at the Andersen house? No. However, we try to save such things for rare occasions and we don’t eat them on a regular basis. That DOES mean that you will most likely not find products containing HFCS in our cupboards. Products that we eat every day like peanut butter, crackers, bread, and yogurt are carefully selected to ensure they do not contain HFCS, or most other additives and chemicals for that matter.
In the end, whole foods grown and harvested from the good earth do not contain HFCS. There’s no HFCS injected into our fresh produce, and surely it can’t be found in my precious tomatoes growing in the garden out back. Thus, if you choose to drink water over soda and cook from scratch with the whole foods that God put on this earth to nourish the bodies He gave us, you will significantly decrease your consumption of HFCS. And you will probably have a better chance at not over eating. Simple as that.