Fitness Nutrition

Is Fructose Actually Bad For You? 5 Truths You Need to Know

Brad Dieter
Brad Dieter
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Over the last 10-15 years, there has been a lot of discussion about the role that fructose plays in many of our chronic health issues, including obesity, diabetes, non-alcoholic fatty liver disease, and many others.

However, most of these discussions are a lot of hype and some hyperbole. Here are five things you should know about fructose and if it is bad for you.

1) What is fructose?

Fructose is a sugar that is found in fruit and gives it its sweetness. It is also a type of sugar that we see in our table sugar (sucrose) and is one of the leading industrial sweeteners in the form of high-fructose corn syrup.

2) What does your body do with fructose?

The question is one of the most significant “hot topics” surrounding fructose, and there has been a lot of misinformation spread about precisely what happens to fructose when you consume it. For example, how many people have heard the following: fructose gets converted to fat in your liver? I would guess that most of us have heard this. However, the truth of what happens to fructose is much different.

Your liver is indeed the primary organ that handles fructose, and almost all fructose you consume does pass through your liver. But it doesn’t really turn to fat; instead, here is the real breakdown of what happens in your body when you consume fructose.

  • Roughly 45% of it is immediately “burned” as fuel and turns into ATP and carbon dioxide.
  • ~30% of it converts into glucose and then metabolized.
  • ~25% of it is converted into lactate and shipped out of the liver.
  • <1% is converted into fat, glycerol, or glycogen.

These stats tell us that fructose does not really “turn to fat” in your liver; instead, it mostly gets used for fuel or converted to glucose or lactate.

3) What dose of fructose causes problems?

One of the most interesting aspects of the science surrounding fructose is that there is a lot of research showing what “dose” can cause health issues. One study found that consuming 255 grams of fructose per day did lead to an increase in liver fat and reduced insulin sensitivity. It also showed the same result if you consumed 255 grams of straight glucose as well, suggesting it may not be just the fructose that is the issue.  This study also showed that if you consumed 128 grams of fructose, there was no increase in liver fat or reduction in insulin sensitivity.

These studies were not the only ones to show that high doses are required for fructose to cause issues. A systematic review found that people had to be in the 95th percentile of intake for fructose to create metabolic problems. A meta-analysis found that individuals had to consume >100 grams of fructose per day to see adverse effects on body fat or metabolic markers.

To summarize this, it appears that for most of us, fructose intake between 0 and ~80-90 grams per day does not convey a substantial health risk.

4) What is the typical daily intake?

If you look at data from the US population, the average American consumes about 55 grams of fructose per day. This data is about 60% of the “problematic” dosing. It suggests that looking at fructose intake in isolation is not likely a good way to quantify the potential risks of fructose on our health.

If you are a nutrition specialist, be sure to check the rate your clients are ingesting fructose. It may be more than they realize. 

5) How should we think about fructose and our health?

There are two reasonably clear data points that seem at odds in the scientific literature.

First, we know that reasonable amounts of fructose intake don’t cause health issues.

Second, some observational data show that high fructose intake is associated with metabolic syndrome, obesity, and liver disease.

So how do we square these two ideas? Well, the main reason appears to be that unhealthy behaviors cluster. For example, people who consume higher amounts of fructose are also more likely to smoke, drink alcohol, carry a higher BMI, and be less physically active. So it may be that high fructose intake correlates to a generally unhealthy lifestyle pattern. We see this occur in most studies, wherein the highest fructose intake occurs not from high fruit intake but high consumption of sugar-sweetened beverages and highly processed foods.

The Wrap Up

Based on most evidence, it appears that modest fructose intake (~0-80 grams per day) does not pose substantial health risks. However, typically, as fructose intake gets higher, it is associated with a higher intake of fructose from processed, energy-dense foods and not from fruit. It is also associated with other unhealthy behaviors, such as smoking, alcohol consumption, and low physical activity.

We should look at fructose in the context it is being consumed and how it fits into the lifestyle of an individual. If someone is getting ~30-50 grams a day from apples, watermelon, blueberries, etc., there is no real reason to be concerned with their intake. If they are getting ~30-50 grams a day from soda, other sugar-sweetened beverages, and other processed foods, it may be worth discussing the context of their dietary choices and less about the actual fructose content of those foods.

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The Author

Brad Dieter

Brad Dieter

Brad is a trained Exercise Physiologist, Molecular Biologist, and Biostatistician. He received his B.A. from Washington State University and a Masters of Science in Biomechanics at the University of Idaho, and completed his PhD at the University of Idaho. He completed his post-doctoral fellowship in translational science at Providence Medical Research Center, Providence Sacred Heart Medical Center and Children’s Hospital where he studied how metabolism and inflammation regulate molecular mechanisms disease and was involved in discovering novel therapeutics for diabetic complications. Currently, Dr. Dieter is the Chief Scientific Advisor at Outplay Inc and Harness Biotechnologies, is co-owner of Macros Inc and is active in health technology and biotechnology. In addition, he is passionate about scientific outreach and educating the public through his role on Scientific Advisory Boards and regular writing on health, nutrition, and supplementation. Want to learn more in Brad's areas of expertise? Check out his NASM product recommendations.


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