Early humans were probably jacks of all trades when it came to food—they ate what was available, and the amount of carbohydrates, proteins and fats in their diet varied dramatically depending on where they lived. Except for honey, there were likely no sweeteners to “spice” up their meals. That all changed 200 years ago when table sugar—a combination of the sugar molecules glucose and fructose—began to be manufactured. This provided a steady supply of inexpensive sweeteners to the general population. From that time on, the amount of sweeteners humans ate began to rise drastically. It’s no coincidence that obesity and diabetes rates increased a few decades later. The cost of sweeteners were further reduced (and the availability increased) with the introduction of high-fructose corn syrup (HFCS) 40 years ago. HFCS is a processed form of glucose that can be easily added to many beverages and foods.
High sugar intake may cause physiological changes in the body that can interfere with the way organs are supposed to function and the way the body burns energy (metabolism) attained through food. The average non-obese person has a very low blood fructose concentration that may be as much as 100 times lower than blood glucose levels. Consuming fructose-laden desserts and sodas quickly increases blood fructose levels, flooding liver cells that are not used to such high doses. Fructose is rapidly broken down into easily processed substances (metabolites) that can be building blocks for fats.
Consuming a lot of fructose often leads to a marked increase in fat-forming enzymes and fatty deposits in the liver. Coincidentally, a decade after HFCS was widely introduced, a new metabolic disease—nonalcoholic fatty liver disease (NAFLD)—cropped up. NAFLD has been linked to overconsumption of fructose and added sugars. A fatty liver is associated with high triglycerides and “bad” cholesterol, increasing the risk for cardiovascular disease and obesity.
The good news is that these associations between added sweeteners, particularly fructose, and metabolic diseases have resulted in serious efforts to reduce consumption, like Mexico’s tax on sugary drinks and New York City’s (unsuccessful) attempt to ban sales of large sodas. In light of these efforts, people in the U.S. now seem to be eating less added sugars.
It is important to remember that moderate consumption of added fructose is most likely fine for most people. Fructose is the sweetest of the naturally occurring sugars and a little goes a long way. This is one case where “less is more.”
Ronaldo Ferraris, PhD, is a professor of pharmacology, physiology & neuroscience at the New Jersey Medical School at Rutgers University. He studies intestinal epithelial biology and cell differentiation as well as integrative regulatory processes involving sugar sensing, transport and metabolism in the small intestine.