Fructose: Is this fruit sugar bad for you?

5 min

©istetiana

By Alisa Voltermann
September 29, 2020

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In the food industry, there’s a highly concentrated isolated form of fruit sugar that is used in addition to natural fruit sugars. Before you cut juicy fruits from your diet, let’s talk about fructose.

What is fructose?

The freshly squeezed orange juice in the morning, the sweet berry mixture, the pre-workout banana – all these foods contain fructose. Fruit sugar (known as fructose) is a naturally occurring chemical compound. As a monosaccharide, this carbohydrate is a sugar found exclusively in ripe fruits and honey in nature.

In addition to natural fructose, however, there’s also a highly concentrated, industrially produced, form of simple sugar. The sweetness of this isolated pure fructose is twice as strong as that of glucose and is therefore used worldwide for the production of sticky lemonades and soft drinks, sweet baked goods and snacks, and even ready-made dishes like pizza. The use of fructose in the food industry has increased dramatically, particularly due to the introduction of high fructose corn syrup in the USA. The sugar content of high fructose corn syrup, which is made from corn starch, can vary. In Germany, the sweetener can be found as glucose-fructose syrup or as fructose-glucose syrup, depending on the proportions on the ingredients list.

White crystal table sugar, sucrose, found in packets in the baked goods section of supermarket shelves, is typically about 50% isolated fructose. The other 50% is made up of the simple sugar glucose.

The metabolism of fructose

Just as with the metabolism of our main energy supplier glucose, there’s a sophisticated system behind the breakdown of fructose – the two metabolisms are closely linked. But don’t worry, we don’t juggle with technical terms, but will stick to the simple terms.

Unlike glucose, fructose is metabolized independently of insulin. This means that the pancreas doesn’t secrete insulin into the blood when we consume foods high in fructose. This is true for natural fructose from fruits and vegetables as well as for artificial fructose in its form as a sugar found in processed products.

Once it reaches the small intestine, it’s absorbed by the cells of the intestine and released into the tissue via the blood. The most important organ for the metabolism of energy-rich fructose is the liver. The liver can either use the energy generated by the breakdown of fructose for its own needs or convert it into glucose, which can then leave the liver and be sent into the blood.

However, as soon as more energy is produced from fructose than the liver can process, this energy is stored in the liver as fat.

How unhealthy is fructose?

Before we discuss its downsides, we have good news for you: Fructose in its natural form is not inherently harmful.

A bowl of freshly picked strawberries, a juicy nectarine, your favorite smoothies – you can and should enjoy them without a guilty conscience. But on one condition: Your average sugar intake shouldn’t exceed ten percent of your daily calorie requirement. This corresponds to about 50g per day, depending on your basic needs and activity level.

Market-fresh fruit and vegetables have long since ceased to be our main source of fructose, however, in favor of sweet and savory ready-to-eat products high in fructose. What are the health effects when people consume far more over a longer period of time than their liver can break down? As already noted, fructose that is not needed to provide energy is broken down into fat in the liver. In the long term, this can lead to fatty degeneration of the liver, similar to how severe alcohol consumption can affect the body over time. This is called fatty liver.

There are numerous studies that show that high weight gain is due to the consumption of fruit sugar from processed products. As fructose and glucose metabolism are closely linked, this can not only lead to a fat metabolism disorder, but can also cause diseases such as insulin resistance, type 2 diabetes, and cardiovascular disease.

How much fructose is in fruit?

If we remove any products containing artificial fructose from our shopping list, we are left with juicy fruit and crunchy vegetables. Apart from natural sugars, apples, cherries, mangoes, and all other foods from the produce department contain numerous vitamins and nutrients that we don’t want to do without in our daily diet. To keep from exceeding the general recommendation for sugar – which includes fructose – here’s a look into low and high fructose fruits and vegetables.

Note: The data are average values per 100g. Depending on variety and degree of ripeness, the amount of fructose may vary.

List of fruit and vegetables high in fructose

Food	Fructose content
Persimmons	10g
Mangoes	8g
Grapes	8g
Bananas	7g
Apples	6g
Pineapple	5g
Kiwis	4g
Red Peppers	4g

By the way: dried fruits, like apricots, plums, and figs, contain a higher percentage of fructose than fresh fruit and should be enjoyed in moderation. The same applies to fruit juices, which, unlike whole fruit, contain no fiber, while also delivering larger amounts of fructose.

List of fruit and vegetables low in fructose:

Food	Fructose content
Lemons	1g
Rhubarb	1g
Broccoli	1g
Asparagus	1g
Zucchini	1g
Strawberries	3g
Raspberries	3g
Grapefruit	3g
Papaya	3g

You don’t have to do without fruit and vegetables, or even fruit juices, to consume less fruit sugar. Before you go throwing out your fruit basket, start by cutting packaged foods out of your diet. A glance at the list of ingredients will always tell you if they are sweetened with artificially produced fructose.

Tip: If you like structured lists with exact numbers, then we have a table for you about sugar substitutes.

Is fructose healthier than other kinds of sugar?

At first glance, fructose sounds healthier than dextrose. However, it’s now clear that the term generally refers to highly concentrated industrially produced fructose, which in large quantities can be a burden on the liver. The decisive difference of fructose vs glucose: Our body doesn’t depend on fructose as an energy supplier, but cannot do without glucose. So the answer to whether fructose is better for your health is no.

On the topic of sugar-free eating, here’s a challenge: try going 5 days without any processed sugar at all.

Fructose intolerance and fructose malabsorption

A bloated stomach, audible tummy grumbles, uncomfortable bowel movements – many people suffer from these problems when they consume fructose.

One reason for the symptoms can be a fructose allergy or fructose intolerance. Occurring to one in 20,000 people, fructose intolerance isn’t very common. Nevertheless, the clinical picture has already been extensively researched. The disease is a congenital metabolic disorder, which is based on a genetic defect. This defect affects the liver enzyme fructose-1-phosphar-aldolase, which, in a healthy person, initiates the breakdown of fructose. Patients with fructose intolerance can absorb it into the liver, but cannot metabolize it afterwards.

Besides hereditary fructose intolerance, there are also people who suffer from fructose malabsorption. The cause of abdominal pain, nausea, and bloating in this case is poor absorption of fructose, where the transport of simple sugars from the intestine is limited or even non-existent. As a result, more and more fructose passes straight into the colon. The result is a generally restless metabolism. To this day, scientists still disagree on the exact cause, but suspect that excessive fructose consumption may contribute to this. With three out of ten people affected, the disorder is far more widespread than the congenital intolerance and can have different degrees of severity.

Fructose: Our summary

Not all fruit sugars are the same. While the natural form from ripe fruit and vegetables is harmless in moderation, avoid fructose from processed foods.

What you should remember about fructose:

It’s a carbohydrate and is largely metabolized in the liver.
An artificially isolated form of fructose is used in the food industry for the production of processed products.
On German labels, highly concentrated fructose is labeled as glucose-fructose syrup or fructose-glucose syrup.
Overall, daily sugar consumption should not exceed 10 percent of your calorie requirement, including fructose.
There are two types of disordered fructose metabolism: fructose intolerance, in which fructose cannot be broken down, and fructose malabsorption, in which fructose cannot be absorbed into the cells efficiently or completely.

Sources for this article

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