Fructose: Friend or foe to your waistline?

According to experts, there may be a downside to having too much ‘fruit sugar’ in your diet. Here’s why.

Whether you’re looking to regulate your blood glucose levels or protect your waistline, finding sugar-free alternatives can be tough when it can be found in almost anything you eat.

So, what exactly is fructose and how much of it is too much for our body?

What is fructose?

Sugar is made up of two components – glucose and fructose.

The difference between the two lies in their chemical structure, registered dietitian and certified exercise nutrition coach Catherine Gervacio says.

“To simply explain, glucose is directly absorbed into the bloodstream after digestion,” Catherine says.

“Fructose on the other hand, is metabolised first in the liver to be converted to glucose.

The body uses glucose to fuel different processes in the body.”

Research also suggests fructose is generally considered much sweeter than its glucose counterpart.

What are the main sources of fructose?

Fructose can naturally be found in mainly in fruits.

While Catherine says it can also be found in apples, pears and grapes, the most popular main source of fructose is honey – which, according to research, has been used as a natural sweetener since the ancient times.

“Certain vegetables like onion, artichokes and asparagus can also contain fructose.”

Is fructose bad for you?

In a typical western diet – where the main sources of fructose are from processed foods and drinks containing sugar derived from sugar cane or sugar beet – that could lead to problems.

Naturopath Dr David Jivan tells The House of Wellness TV that consuming excessive amounts of fructose can create free fatty acids, if your body can’t break it down.

“These form like little droplets or globules of fat in your liver, and it may lead to a condition called non-alcoholic fatty liver disease, and or type 2 diabetes,” Dr Jivan says.

One recent study also found that excessive fructose consumption could lead to issues such as obesity, arterial hypertension and even increased cardiometabolic risk factors in children.

What is fructose malabsorption?

Up to one in three of us also experience a common condition known as fructose malabsorption or dietary fructose intolerance (DTI), which occurs when cells on the surface of the intestines can’t break down fructose efficiently.

“This can result in an increased concentration of fructose in the entire intestine, which can lead to bloating, discomfort and other issues,” Dr Jivan says.

“According to analysis of clinical trials evaluating fructose intake, 25-40g of fructose per day is totally safe.

“However if you have fructose malabsorption you need to keep your fructose intake to less than 25g a day. That’s three to six bananas or two to three apples per day.”

Signs of fructose malabsorption

Besides bloating, Catherine says other signs and symptoms of fructose malabsorption can include abdominal pain, gas, diarrhoea or nausea.

What is fructose intolerance?

“Fructose intolerance is a disorder in which the body lacks the enzyme needed to break down fructose,” Catherine says.

Otherwise known as hereditary fructose intolerance (HFI), this condition is recessively inherited and can lead to toxic impacts on the liver, intestines and kidney.

Signs of fructose intolerance

“The signs and symptoms are similar to fructose malabsorption,” Catherine explains.

“Along with liver dysfunction and blood sugar fluctuations.”

What are high-fructose foods?

Other fruits that are high in fructose include mangoes and watermelon, Catherine says.

“Some fruit juices are added with fructose as a sweetener, and dried fruits like raisins and dates also contain fructose.

And some processed foods such as sweetened cereals, granola bars, and other foods have added high-fructose corn syrup, Catherine says.

What are low-fructose foods?

According to Catherine, some low-fructose fruits include:

  • Berries (strawberries, blueberries, raspberries and blackberries)
  • Oranges
  • Lemons
  • Limes
  • Grapefruits
  • Melons
  • Pineapple
  • Avocado
  • Tomatoes
  • Bell peppers

What is high-fructose corn syrup?

A sweetener made from cornstarch, high-fructose corn syrup (HFCs) undergoes processing to convert some of its glucose components into fructose, Catherine explains.

“It is used to sweeten different products as a cheaper alternative to table sugar.

“But it is typically associated with different metabolic diseases due to fat accumulation in the liver when taken in excess.”

Excessive HFCs intake could potentially lead to an increased risk of obesity, insulin resistance, cardiovascular diseases and reproductive system diseases.

For more on dietary choices:

Originally published in June 2018. Updated January 2024.