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Delicious and Deadly

The Dangers of Fructose

Under the Radar

Nate Dutch

July 23rd, 2016

Dietary fads have always been a thing, from the carbohydrate crusades to the fat frenzy, and their merits have always been at least somewhat questionable. So what about the sugar struggle? You’ve probably heard at least something about it, likely that high-fructose corn syrup is evil or that agave nectar is the next step in healthy sweeteners. Everybody seems to have something to say on the topic, and it can be hard to decide which voice to listen to. But one thing is for sure: we are rapidly diminishing in health as a nation because obesity is still on the rise.


The problem of obesity was first addressed around 30 years ago, after the percentage of obese adults hit 15%. According to the conventional wisdom at the time, this had to mean that Americans were consuming more calories than they burned, right? Using this as their reasoning, the American Heart Association, the American Medical Association, and the U.S. Department of Agriculture issued a statement pleading for Americans to cut back on consumption of dietary fats, a calorically dense food, from 40% to 30%. Since every gram of fat contains eight calories compared to just four calories in a gram of carbohydrates or protein, reducing fat consumption should have solved the obesity crisis. Instead, the obesity rate has climbed to around 35% for today’s adults, men are eating 187 calories more per day, women are eating 335 calories more per day, and we’re all 25 pounds fatter than we were 25 years ago. So what is going on? If you break down the increase in calories, you see that 83% of the extra calories we eat now come from carbohydrates. All of these problems parallel another growing trend in the American diet: increased consumption of the carbohydrate called fructose.


To understand what fructose is and why it might be the culprit for our obesity woes, we need to start out with some biochemistry basics. Carbohydrates have gotten a bad rap in the past, but the most basic way to understand them is to think of them as your body’s energy source. So dietitians are right; carb excess causes weight gain due to excess energy, while carb reduction can be an effective fat loss method. But it’s not as simple as eating too many carbs--because not all carbs are created equal. Sugar, the topic of today’s discussion, is the common name for a disaccharide, or two part, carbohydrate called sucrose. It is composed of one molecule fructose and one molecule glucose. Fructose is found naturally in small quantities in both fruit and vegetables. It’s what gives your favorite fruit (or dessert) that sweet taste. Its counterpart, glucose, is a naturally occurring carbohydrate found in rice, potatoes, wheat, and most complex carbohydrates. The most important difference between fructose and glucose is that your body is designed to process one a whole lot more effectively than the other.


Glucose has often been called the energy of life. Literally every cell and even every bacterium in your body can utilize glucose as an energy source. Fructose can only be metabolized by your liver. So we can already see one glaring problem: fructose does not provide you with the same usable energy that you get from glucose. Recent studies have compared the body’s metabolization of glucose and fructose, and some people, like Dr. Robert Lustig, have even concluded that the effects of fructose on your body are more similar to ethanol (alcohol) than to glucose.


Dr. Robert Lustig’s findings show when glucose is consumed, 80% of the calories are used by the various organs in your body for functional purposes, leaving 20% to be metabolized by the liver. Most of that 20% is converted to a storage molecule called glycogen, while a small percentage ends up as low-density-lipoproteins, a type of fat that is a major contributor to diabetes. Fructose, on the other hand, deposits all of its calories in the liver because that is the only place the body can process it. Once there, current models suggest, about 70% of the fructose ends up as glycogen for storage, while about 30% ends up as low-density-lipoproteins. This processing is also associated with production of uric acid, which can cause gout and hypertension. Another significant difference between glucose and fructose is that while glucose can be processed by almost every cell in the body and triggers leptin, a hormone that tells your body when it’s time to stop eating, fructose can only be processed by the liver, reducing the amount of leptin produced. Therefore, you won’t fill up as quickly with fructose and will continue to eat when you should stop, a probable cause for our recent calorie increase.


So when it was declared that we needed to stop our fat levels, here is a likely progression of our obesity woes: Fat is decreased in commercial foods so they start to not taste as yummy, so the response is to replace the fat with high fructose corn syrup to add more deliciousness. Start reading labels; you’ll be very surprised to find out that some of your so-called healthy foods have fructose in abundance. More fructose, less leptin, more eating. Not only are there more calories, it is still a high fat diet in actuality because much of the calories in fructose are converted into fat. And this fat is actually more likely to cause diabetes and hypertension than the high-density-lipoproteins produced from dietary fats.


It’s important to note that most of these negative outcomes are only associated with increased fructose consumption. Very few clinical studies have been produced to show that fructose is the cause of these problems. Remember, correlation does not imply causation.


So what is my recommendation to you? Reduce fructose consumption. While it is not confirmed that fructose is the little devil it is often made to be, all sorts of red flags go off when you look at the trends between obesity and fructose consumption. Something about obesity rates increasing by 20% while fructose consumption increases by 30% doesn’t sit right in my stomach. One important exception is the fructose found in fruit and vegetables. There is a relatively small amount, and recent studies show that certain nutrients in fruits and vegetables help your body digest fructose in a beneficial way. Remember, eating one piece of cake won’t doom you to a life of fatty liver and diabetes. It’s about fructose reduction, not fructose elimination. So until studies show that something else is causing our obesity epidemic, keep reading those labels. You never know what will be hiding in your food.