Along with glucose, fructose is one of the two major components of added sugar.
Some health experts believe fructose is the worse of the two, at least when consumed in excess.
Are these concerns backed by science? This article reviews the evidence.
Fructose is a type of simple sugar that makes up 50% of table sugar (sucrose).
Table sugar also consists of glucose, which is the main energy source for your body’s cells.
However, fructose needs to be converted into glucose by the liver before it can be used by the body.
It’s also found in various sugary sweeteners like high-fructose corn syrup and agave syrup. If a product lists added sugar as one of its main ingredients, you can be pretty sure it’s high in fructose.
Before the mass production of refined sugar, humans rarely consumed it in high amounts. While some sweet fruits and vegetables contain fructose, they provide relatively low amounts.
Some people do not absorb all of the fructose they eat. This condition is known as fructose malabsorption, which is characterized by excessive gas and digestive discomfort (1).
Unlike glucose, fructose causes a low rise in blood sugar levels. Therefore, some health professionals recommend fructose as a “safe” sweetener for people with type 2 diabetes (3).
However, others are worried that excessive fructose intake may contribute to several metabolic disorders. These concerns are discussed in the next chapter.
Summary Fructose is a type of sugar that makes up around 50% of table sugar and high-fructose corn syrup. Scientists are concerned that excessive intake may cause metabolic disorders.
Glucose and fructose are metabolized very differently by the body.
While every cell in the body can use glucose, the liver is the only organ that can metabolize fructose in significant amounts.
When people eat a diet that is high in calories and high in fructose, the liver gets overloaded and starts turning the fructose into fat.
Many scientists believe that excess fructose consumption may be a key driver of many of the most serious diseases of today. These include obesity, type II diabetes, heart disease and even cancer.
However, more human evidence is needed. Researchers debate the extent to which fructose contributes to these disorders (4).
Summary Many health professionals have claimed that excessive fructose intake is a major cause of metabolic disorders.
While excessive fructose is undoubtedly unhealthy, its health effects are controversial.
Nevertheless, there is a considerable body of evidence justifying the concerns.
Eating a lot of fructose in the form of added sugars may:
- Impair the composition of your blood lipids. Fructose may raise the levels of VLDL cholesterol, leading to fat accumulation around the organs and potentially heart disease (5, 6).
- Increase blood levels of uric acid, leading to gout and high blood pressure (7).
- Cause deposition of fat in the liver, potentially leading to non-alcoholic fatty liver disease (8, 9).
- Cause insulin resistance, which can lead to obesity and type II diabetes (10).
- Fructose doesn't suppress appetite as much as glucose does. As a result, it might promote overeating (11).
- Excess fructose consumption may cause leptin resistance, disturbing body fat regulation and contributing to obesity (12, 13).
Note that not all of this has been proven beyond a shadow of a doubt in controlled studies. However, the evidence is still there, and more studies will paint a clearer picture in the coming years and decades.
Summary Many studies suggest that a high fructose intake may contribute to chronic diseases in humans.
It's important to realize that all of this does not apply to whole fruit.
Fruits aren't just watery bags of fructose, they are real foods with a low calorie density and lots of fiber.
They're hard to overeat on and you would have to eat very large amounts to reach harmful levels of fructose. In general, fruit is a minor source of fructose in the diet compared to added sugars.
The harmful effects of fructose apply to a Western diet supplying excess calories and added sugars. It does not apply to the natural sugars found in fruits and vegetables.