- Fructose and glucose are similar in that they are both sugar molecules, but how they're handled in the body is different
- Too much fructose can lead to a number of negative health impacts, including insulin resistance and increased levels of "bad" cholesterol
In this article, we’ll unpack what fructose actually is and what it does in our bodies. Let’s dive right in!
First things first: What is fructose?
Let’s start by getting a bit molecular, because knowing what “sugar” actually is can really help our understanding of how it impacts the body. The two most simple forms of sugars are called glucose and fructose. Both molecules are technically carbohydrates, and when you combine glucose and fructose, you get sucrose—or table sugar (i.e. the ingredient on food labels called “sugar”).
Glucose is the sugar found in most foods we think of as “carbs” (bread, pasta, etc.), and it’s what our body runs on.
This article will focus on fructose (also called fruit sugar) which is in every food that lists ‘sugar’ as an ingredient as well as in fruit, fruit juices, and virtually every other sweetener (cane sugar, beet sugar, brown sugar, white sugar, high fructose corn syrup, honey, maple syrup, you name it… except for, of course, sugar-free sweeteners).
Fructose consumption across the world has been booming in recent decades. In countries like America, sugar intake has doubled in just 30 years. In essentially every country in the world, the average person consumes more than the suggested daily intake of sugar—every single day. Almost all of our fructose consumption today comes from the refined sugars used to make breakfast cereals, pastries, sodas, fruit drinks, and other sweet, processed foods and beverages.
You probably already know that fructose is “bad”. But why is that? Let’s dive into some details of how fructose is broken down in your body.
Why is fructose bad for you?
Here’s a simplified look at what happens when you eat, say, a chocolate bar:
- The sugars (sucrose) are broken down into their component parts, glucose and fructose.
- 20% of the glucose goes to the liver to be metabolised, and the remaining 80% goes to other organs to provide energy for essential bodily functions. Let’s focus on what happens with fructose.
- A large portion of fructose actually gets turned into glucose—but only if consumed in moderation.
- However, when the body is overloaded with fructose, for example, with excessive processed sugar consumption, the fructose spillover goes to the liver.
- Instead of breaking down fructose as a carbohydrate, the liver then converts it into fat, which is stored in the liver. It is because of this fat storage in the liver that fructose is particularly dangerous, above and beyond just causing us to gain weight.
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The harmful effects of excess fructose
The consistent overconsumption of sugar (and subsequent storage of fructose as fat), leads to three major health problems:
More fat around and inside of our organs
- When our bodies cannot store any more fructose in the liver and muscles, it gets stored in other places. The “fat” we usually think about is stored under our skin. However, invisible to the naked eye (and more damaging to our health) is the fat stored around and inside our organs.
- This is the problematic fat that is seen in type 2 diabetes (and interestingly the fat that, when lost, seems to lead to remission of type 2 diabetes). For example, fat deposits around the pancreas are toxic to the cells which produce insulin. Fat deposits around the heart can also cause heart disease (mentioned below) and reduce the ability of these organs to do their job well.
Increased “bad” cholesterol deposited in the arteries
- Excess fat from the liver can be deposited as cholesterol inside the walls of your arteries. This makes it more difficult for oxygenated blood to move through the body and back to the heart muscle (Picture 1), increasing blood pressure.
- If the plaque (the collection of cholesterol) ruptures, it can block the artery altogether, causing a heart attack (Picture 2).
Insulin resistance and type 2 diabetes
- In response to fructose intake, the pancreas releases a hormone called insulin, which prompts the body to take the energy out of the blood by shuttling it into cells that need it. If there’s too much, the excess gets stored in cells as fat (e.g. around and inside of your organs, in your muscles, and under the skin). This storage brings the blood glucose levels down and, voila, back to a normal, healthy range.
- The more extreme the fluctuations in fructose, the harder your pancreas needs to work to maintain a healthy, consistent sugar level. Excessive fructose consumption will eventually overwhelm your pancreas with fat storage, and blood sugar levels will rise. When your body’s ability to secrete insulin is impacted, this can lead to type 2 diabetes and a heightened risk of its associated problems e.g. blindness, heart disease, kidney problems
- Rapidly elevated levels of insulin can also have short-term consequences: 1) When a spike in insulin occurs, our bodies efficiently put all of that glucose into our cells, leading to rapidly dropping blood glucose levels—and yet another physiological response to eat sugar, fast. Sugar crash, anyone? 2) Elevated levels of insulin can lead to leptin resistance, making you hungrier (leptin is one of the hormones that makes you feel “full”), leading to further weight gain.
As you can see, fructose is not only “empty calories”, but can actually have incredibly harmful effects on our bodies. Scary, right?
We’re not trying to intimidate you into never eating sugar again. Instead, we’re here to help educate you about what goes on in your body, and to help you understand the science behind the recommendations we make. So, where else is fructose hidden away?
The dangers of added sugar
In two words: Added sugar. The food industry hides sugar in all types of products, both as a preservative and a flavour enhancer—even in things marketed as “healthy”. Unfortunately, the responsibility lies on individuals to be aware and read food labels of what they’re consuming.
Some common sources of hidden sugar include:
- Premade pasta sauces and salad dressings
- Sauces like ketchup, sweet chilli, and brown sauce
- Granola and granola bars
- Flavoured yoghurt
- Canned fruits (the fruit is often preserved in syrup)
- “No sugar added” foods (this just means that they didn’t add table sugar—instead, they use concentrated fruit juice, which, as we just learned, isn’t much better)
- Nut butters
- Non-dairy milks
- Bread (particularly longer shelf-life breads—whether or not they’re whole grain)
- Processed meats, including deli meat
How to avoid added sugars
Awareness is key here. No sugar added versions of everything above often exist, but there will likely be fewer of them, so you may have to do some hunting. Keep in mind that it’s not just the “sugar” ingredient to look out for: Juice concentrates, agave, honey, high fructose corn syrup, etc. all contain equally damaging amounts of fructose. It can be helpful to start by looking at the grams of sugar on the Nutrition Facts. If it seems high, you’ll probably be able to identify a sweetener in the ingredients list.
So… How much sugar should I have per day?
The American Heart Association recommends no more than 25 grams of sugar per day for women and 37.5 grams for men. For perspective, 25 grams of sugar is about two and a half apples—or about one normal sized Mars bar.
However, keep in mind that there are other sources of sugar you might not account for, such as hidden added sugars in savoury products or sugars in some vegetables. The point here isn’t that you need to measure out exactly your daily gram intake of sugar, but rather that it’s important to be aware of what sugar is, where it is found, and how it can impact our bodies. Now that we know this, how can we respond? Here are some simple steps to cutting down on sugar intake.