Is high fructose corn syrup worse for you than other sugars?
The simplest and shortest answer: if you are concerned or want to optimize your health it’s a good idea to keep your daily intake of added sugar, regardless of the type, to a minimum.
Well, too much sugar in general, not just high-fructose corn syrup, can lead to excess calories which is linked to particular health problems, such as type 2 diabetes, weight gain, high triglyceride levels and metabolic syndromes. All of these health complications can increase your risk for heart disease. According to the American Heart Association recommendations, women should not consume more than 100 calories a day from added sugar from any source, and no more than 150 calories a day from added sugar for men. This corresponds to about 9 teaspoons of excess sugar for men and about 6 teaspoons of added sugar for women.
So what is high fructose corn syrup?
First let’s discuss sugars in general. There are about 20 naturally occurring simple sugars, called monosaccharides, which are naturally found on the planet. Glucose, fructose, galactose, and ribose have a significant role in human nutrition meaning that these are only four sugars that can be absorbed by the gut and metabolically processed in the human body.
Some sugars in our diet come in the form of a disaccharide meaning that two simple sugars are chemically linked together by a covalent bond. The table sugar you add to your coffee every morning is sucrose. Sucrose is a disaccharide containing one molecule of glucose covalently bound to one molecule of fructose (see image below). When you eat sucrose, it gets broken down into one molecule of fructose and one molecule of glucose.
In terms of chemical identity and how the sugar is processed, there isn’t anything special about getting fructose from high corn syrup compared to ingesting it from fruits and berries.
The most common forms of high fructose corn syrup contain either 42% or 55% fructose. In contrast sucrose (sugar), the most well-known sweetener made by crystallizing sugar cane or beet juice, is composed of the same two simple sugars, glucose and fructose, joined together to form a single molecule containing one glucose molecule and one fructose molecule. Unlike sucrose, for the high fructose corn syrup there are no chemical bonds joining the glucose and fructose (the 2 sugar molecules are separate). Nearly every cell in your body can use glucose for energy. In contrast, only liver cells break down fructose. One of the end products is triglyceride, a form of fat. If you are on a low-fat diet, while also consuming a lot of refined sugar (glucose or fructose), the excess sugar gets processed into fat.
An important part of this discussion is understanding what high fructose corn syrup is and where it feeds into your metabolic pathways. Fructose is a simple sugar and is also called a “fruit sugar” because it occurs naturally in fruits and berries. The difference between eating lots of fruits and berries versus a drinking a soda containing high fructose is the concentration of the simple sugar. The chemical identity of the fructose in berries and fruits is identical to the fructose found in foods where fructose is added. OK, now let’s discuss metabolism.
Fructose enters the glycolytic pathway in the liver through the fructose 1-phosphate pathway. Glycolysis is metabolic pathway utilized by most microorganisms [bacteria and fungi (yeast)] and by all metazoans (humans). During glycolysis (see where it fits into your catabolic pathways which simply means a metabolic pathway involved in the break down food molecules to produce energy), 1 molecule of sugar is degraded into 2 molecules of pyruvate.
Pyruvate then enters the Krebs cycle, and finally the electron transport and oxidative phosphorylation (in your mitochondria aka ATP energy power plants) to produce the energy unit of the cell, ATP (see diagram below of an overview of metabolism and cellular respiration).
Fructose is metabolized, primarily in the liver, through phosphorylation on the 1-position, resulting in a bypass of the rate-limiting phosphofructokinase step. Hepatic metabolism of fructose thus favors lipogenesis or fat production. It is not surprising that several studies have found changes in circulating lipids when subjects are feed high-fructose diets. Unlike glucose, fructose, does not stimulate insulin secretion from pancreatic βeta cells. This lack of stimulation is likely due to the low concentrations of the fructose transporter GLUT5 in pancreatic βeta cells. Given the available data on the metabolic effects of consuming excessive quantities of fructose as well as the potential for exacerbating insulin resistance syndromes, it is preferable to primarily consume dietary carbohydrates in the form of glucose (free glucose and starch). Although, consumption of low levels of added fructose are probably benign. Both the consumption of excessive glucose or fructose can have detrimental health effects.
Bottom line, what matters most for your health, with respect to sugar consumption, is the overall amount of sugar you are consuming per day. A diet containing an excessive intake of any sugar (fructose, glucose..) is going to lead to other health problems. The most obviously one is weight gain leading to health problems associated with weight gain (heart disease, type 2 diabetes, insulin resistance syndromes, cardiovascular disease, etc.).