The Lowdown on Fructose

What is fructose?

Fructose is a monosaccharide. It’s the simplest form of carbohydrate, containing only one sugar group, meaning it can’t be broken down any further.

Hundreds of years ago, before the mass production of sugar, we had very minimal fructose in our diets. It was only obtained in small amounts through the consumption of whole fruits, vegetables, grains, nuts/seeds and proteins. However, as the food industry refined fructose from sources like corn, and added it to a variety of processed foods, our fructose consumption increased. Many people associate fructose with fruit, but today the majority of our daily fructose comes from non-fruit sources.

Fructose vs. Table sugar

We get fructose through two main sources: high fructose corn syrup (HFCS) and sucrose.

The difference between fructose and sucrose (commonly referred to as table sugar) is the chemical structure. While fructose is a monosaccharide (one sugar), sucrose is a disaccharide (two sugars) that’s made up of glucose and fructose.

HFCS and sucrose are found in processed foods including sweets, soft drinks, and nearly every food found in a bag and/or box.

Dangers of high fructose consumption

Fructose is broken down in the liver, converted to glucose and stored as liver glycogen. However, the liver can only store so much fructose as glycogen at one time, about 100g in most people, which is not a large amount. When people eat a diet that’s high in calories and fructose, the liver gets overloaded and starts turning the fructose into fat.

A high intake of fructose can also inhibit the normal production of leptin, the hormone involved in the long-term regulation of energy balance. Leptin goes up when we get enough calories and down when we don’t. It helps signal to our bodies when it’s time to stop or start eating. So when you consume too much fructose, and your leptin production decreases, you don’t get the “I’m full” signal from the brain and you consume more food than you need.

High intakes of fructose can also lead to several other health complications, including, but not limited to, high blood pressure, increased risk of type 2 diabetes, heart disease or cancer.

When you combine artificially high fructose levels with a diet already high in other sugar and processed foods you have a potential problem.  The HFCS from the occasional soda won't disrupt anyone's normal metabolic function.  But in the common Western diet where many foods are highly palatable, high in calories, low in fiber, protein and nutrients you create a diet where people tend to overeat...and overeat the worst possible food choices.  

For health and fat loss a diet that is balanced in calories and high in satiety creates a sound diet.  In one even higher in calories,  but LOWER in satiety is a huge issue.

Context is everything!

​​​​​​​

Fructose in fruit: Debunking the myth  

Because of these negative impacts, many people believe they should limit their intake of whole fruits. However, its actually very unlikely that consumption of whole, unprocessed, fresh fruits will promote energy imbalances or body fat gains. Our bodies have a longstanding sustainable relationship to fruit.

What’s much more likely to cause these problems is the regular consumption of fructose-rich fruit juices, sweeteners and energy dense foods.

Of course, too much of anything can be harmful. However, you’d have to eat very large amounts of fruit to reach harmful levels of fructose. In fact, it takes over 8 pounds of most fresh fruit to provide 2000 calories. And most humans usually don’t eat more than 5 pounds of food per day.

Consider that fruit is on average only 5% fructose by weight you can see the disparity compared to the above 55% in High Fructose Corn Syrup or in 52-67% in fruit juices, according to Science Direct.  

Consuming whole fruits provides an abundance of nutrients and helps control energy intake.

So next time you’re reaching for an orange, don’t stress about your fructose intake. It’s the orange juice, or even worse, the orange soda you should be worried about.

Sources:

Andrews, Ryan. “All About Fructose.” Precision Nutrition, 15 Dec. 2015, www.precisionnutrition.com/all-about-fructose.

Gunnars, Kris. “Why Is Fructose Bad For You? The Bitter Truth.” Healthline, Healthline Media, 12 Jan. 2013, www.healthline.com/nutrition/why-is-fructose-bad-for-you#section2.

Walker, Ryan PhD. "Fructose content in popular beverages made with and without high-fructose corn syrup". Science Direct Volume 30, Issues 7–8, July–August 2014, Pages 928-935. http://www.sciencedirect.com/science/article/pii/S0899900714001920