2012 has been the year of High Fructose Corn Syrup. As the debate rages on, you may be tempted to persuade your family & friends not to eat the stuff (especially considering UCLA’s recent study). If this is the case, you need to have a convincing argument. Not just alarmist rhetoric, but cold hard facts. This is why I have written HFCS 101. It presents the most basic biology behind why the sweetener presents health risks. With this knowledge, you’ll finally be able to convince your mom to put the ice cream down while she is getting her nightly fix of America’s Next Top Model.
Before I begin, please note that I am NOT advocating the use of other sweeteners over HFCS. While it is true that HFCS has some uniquely unenviable biological consequences, consumption of ‘added sugar’ in general presents little by way of health benefits (understand what is considered an ‘added sugar’).
I’ll start this ‘lesson’ with the absolute basic principle – HFCS has more fructose than normal table sugar. Most often, it contains 55% fructose & 45% glucose (compared to 50/50 in table sugar). However, it can sometimes be composed of up to 90% fructose. In these sections, I talk about the differences in the way fructose is digested compared to glucose in the body. These effects are amplified when HFCS is consumed.
Now to the biology (yes!) -
1. Fructose is digested into fat much easier than glucose.
When HFCS/sugar are consumed, the fructose and glucose molecules are absorbed at the intestines. From there, the body processes these molecules in different pathways.
Glucose: Glucose is processed in an intensely regulated pathway, with insulin being the main regulator. Insulin is a hormone released by the pancreas into our blood, and it is in charge of regulating the amount of glucose in our blood. When we consume glucose, insulin is released. The hormone sends the message to our cells to absorb glucose from the blood through a cell surface transporter called Glut-4. Once glucose has entered the cells, a complex interaction of hormones controls the amount of and the rate at which glucose is converted into fat.
Fructose: Fructose is processed in a pathway independent of insulin. Instead of being absorbed into the cells through the Glut-4 transporter, it is actually absorbed through a transporter called Glut-5 (I know, what a stark difference). This transporter is not controlled by insulin, so once fructose is in the blood, it is absorbed into the cells with little regulation. Once in the cells, fructose is quickly cut in half by an enzyme, turning it into two molecules that are the direct precursors of fat molecules. These molecules are quickly turned to fat, and voila, our blood suddenly has significantly elevated fat levels (much more so than what could be achieved by glucose.)
So what is the issue with fat in the blood?
Well, this may seem relatively intuitive. More fat in the blood means obesity, clogged arteries, heart disease etc. But what you may not have known is that this condition is also correlated with a higher risk of insulin resistance, which means that your cells stop responding to insulin’s messages about glucose absorption. When insulin resistance becomes serious, it is called Type 2 Diabetes.
2. Fructose does NOT signal to the body that we are nourished, while glucose does.
When we consume any from of carbohydrate (sugar molecules), it makes sense that our bodies should realize that they have received nourishment. That’s where HFCS bucks the trend.
Glucose: As I mentioned earlier, when glucose is consumed, insulin hormone is released. Along with telling cells to absorb glucose, insulin directly regulates another hormone, leptin. Leptin is in charge of regulating hunger. When insulin concentrations in our blood increase, so do leptin concentrations. This spike in leptin signals to the body that it has been nourished, and it does not need to eat more. Furthermore, the brain can absorb glucose because the brain’s cells have that infamous Glut-4 transporter. When glucose is absorbed, the brain realizes we have consumed nutrients, and it reduces our hunger.
Fructose: Fructose is the anti-glucose in this comparison. When fructose is consumed, insulin is not released (because insulin cannot regulate fructose absorption). Since insulin is not released, leptin is also not released. The lack of leptin means that when fructose is consumed, the body does not get the message that it has been satiated, so we will just keep on eating (and we know what that leads to). Furthermore, the brain CANNOT absorb fructose molecules because it lacks the Glut-5 transporter. Thus, when fructose is consumed, the brain does not send out signals to the body to stop eating!
So what is the issue with over-eating?
I am not really sure if I need to answer this question. But for your assurance, I will provide you with this fact. Studies have shown that people whose bodies cannot create the hormone leptin are extremely obese. Thus, consuming excessive amounts of fructose, a molecule that does not induce leptin secretion, cannot be good for our health.
High Fructose Corn Syrup has consistently associated with a higher risk of metabolic syndrome. Metabolic syndrome is a general term for a cluster of health issues, including obesity, excessive insulin in the blood, elevated fat in the blood, and elevated blood pressure. To learn more about HFCS’s impacts on health, check out FoundHealth’s articles on HFCS & Hypertension/ Heart Disease/ Diabetes/ Autism.
If you would like to learn more/see references, click on any of my HFCS & Heath Challenge articles above. References are included there.
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