The consumption of fruits can be harmful

Can fruit be unhealthy?

Sugar should only be consumed in moderation, that much is known. In 2015, the WHO issued a recommendation in this regard: an average adult should not consume more than ten teaspoons of sugar - equivalent to around 50 grams - per day to prevent weight gain and tooth decay. According to the WHO, a maximum daily sugar consumption of five teaspoons would be even better.1 It is difficult to adhere to this because the industry likes to give sugar other names. Names like glucose, sucrose, maltose or dextrose mean nothing other than sugar. Fructose (fruit sugar), which occurs naturally in fruit, is also a certain type of sugar

"Sugar" at a glance

From a purely scientific point of view, sugars are a specific group of organic compounds, the so-called low molecular weight carbohydrates. Depending on the number of individual building blocks (saccharides) lined up in a row, a distinction is made between simple sugars (monosaccharides), double sugars (disaccharides) and multiple sugars (oligo- and polysaccharides) .³ ​​In common parlance, sucrose, the granulated sugar, is a representative the double sugar.

To the Monosaccharides counts for exampleGlucose (Glucose, dextrose) found in fruits, vegetables and honey. This sugar reaches the bloodstream directly from the intestine and serves as the body's fastest supplier of energy.Fructose (Fructose) is found in fruits and is converted into glucose in the liver.Galactose is part of lactose and is mainly found in milk and dairy products. At Tagatose it is a simple sugar that was only recently approved in the EU. This is produced industrially from galactose, but it also occurs naturally in dairy products. Tagatose is only absorbed by the small intestine to about 20 percent, has a lower calorific value than glucose and is primarily used in diet food

To theDisaccharides one calculates Maltosewhich consists of two glucose molecules. In the human body, this sugar is created during the digestion of starchy foods, but it can also be produced artificially. Because of its caramel-like taste, Maltose often used for baked goods.lactose consists of glucose and galactose and is mainly found in milk and dairy products. Sucrose (Table sugar, granulated sugar, beet sugar, cane sugar) is either used directly for sweetening or added to food. This disaccharide is obtained from sugar beet or sugar cane and consists of one half of glucose and the other half of fructose.

Polysaccharides (Polysaccharides) taste less sweet. They include starch, glycogen, pectin, chitin, callose and cellulose. Polysaccharides serve as fiber, reserve materials and nutrients. They can be found in cereal grains or potatoes, for example

Different fructose content in fruits

The fructose content in fruits is generally relatively low, but can vary greatly depending on the type of fruit. Here is a brief overview - the average values ​​for fructose (fruit sugar) per 100 grams of fruit for the respective fruit are always given: dates (31 grams), persimmons (eight grams), grapes (seven grams), apples, cherries (six grams), oranges , Bananas (three grams), watermelon (five grams), lemon (one gram), papaya, rhubarb (less than 0.5 grams).

In order to exceed the recommended maximum amount of 50 grams of sugar per day through the consumption of fruit, one would have to consume unusually large amounts of fruit. For example, to get into an area of ​​health concern, one would have to eat a large watermelon or six medium-sized apples at once. From this amount you would get around 50 grams of fructose, which can put a heavy strain on the small intestine and liver.⁶ However, there are no serious evidence studies that state that above this amount fruit is classified as unhealthy and has a harmful effect.

Industrial fructose: Popular in food production

Fructose occurs naturally in fruits, but it can also be obtained artificially. For example, a special fructose syrup is made from corn starch, which is marketed as a highly concentrated, industrially produced fructose under the name High-Fructose-Corn-Syrup (HFCS). Its sweetening power is many times higher than that of beet sugar. The food industry likes to use the advantages of synthetic fructose: it does not crystallize and retains a smooth consistency. For example, baked goods with fructose browns more evenly, and ice crystals do not form in frozen foods. Despite these advantages, it can be problematic for the end user because large amounts of HFCS are often ingested unconsciously. A ready-made smoothie sweetened with HFCS, for example, contains up to 40 grams of fructose per liter, which corresponds to a small watermelon.

Too much fructose can make you sick

Since fructose can only be metabolized via the liver, larger amounts of around 50 grams or more put a strain on this organ. Excess fructose is released into the blood, which increases cholesterol and blood fat levels. The sugar is then stored in the body as fat. Long-term consumption of large amounts of fructose can therefore lead to obesity and the risk of fatty liver disease. Metabolic diseases such as type 2 diabetes, obesity or gout can also be possible consequences. There are some studies that show a connection between the consumption of fructose and these diseases. However, it could not be clearly confirmed that the fructose alone is responsible for the health problems.⁷ ⁸

Digesting with stomach ache

However, consuming fructose in large quantities can become uncomfortable for another reason: too much of it can in some cases cause indigestion. This can be explained as follows: Fructose absorbed by the body first reaches the small intestine. If large amounts are involved that overwhelm the small intestine, it cannot use the entire amount of fructose. In this way, fructose subsequently also reaches the large intestine, and the intestinal flora changes. Bacteria in the large intestine use large amounts of fructose as a reason to over-multiply and produce acids and gases in the process. Many people feel this in the form of stomach pain, gas or diarrhea. The tolerance threshold here is very different from person to person. If it is severe, one speaks of fructose intolerance, which can be tested by a doctor

Fructose in beverages

In addition to fructose, fruit also contains fiber. Since these have to be broken down in the digestive tract, fructose is slowly broken down after eating fruits. The absorption of fructose into the blood is delayed and the blood sugar level rises only slowly. Fiber, such as pectin, also binds water and swells up in the stomach. This delays gastric emptying and makes you feel full longer.

If you consume the fruit juice made from it instead of fruit, it behaves differently: Fruit juices without added dietary fiber make the blood sugar level rise faster, and you feel hungry again more quickly after consuming them. Since the feeling of satiety does not set in so quickly due to the lack of fiber, you can quickly drink larger quantities of fruit juices than you would in the form of fruit. So it makes a big difference to the body in which form you eat fruit.

An overview of fruit drinks

In the trade you can find different names of fruit drinks¹⁰: Under fruit juice one understands a liquid product made from fruits, in which the fruit content has to be 100 percent. A distinction is made between not-from-concentrate juice and fruit juice made from concentrate, whereby in the case of concentrate the fruit juice is concentrated in the country of origin and diluted back in the country of destination. A fruit juice made from oranges, for example, contains around 40, apple juice even up to 68 grams of fructose per liter. At Fruit nectar the legally prescribed minimum content of fruit juice or fruit pulp varies depending on the type of fruit. For mango, for example, this must be 25 percent, for nectar made from peach 50 percent. Up to 20 percent of the total weight of sugar or honey can be added to fruit nectar.Fresh juice is 100 percent freshly squeezed juice made from fruits.

Fruit juice drinks are among the soft drinks and contain only small amounts of fruit juice. For citrus fruits, for example, it is six percent, and for grapes or pome fruit, 30 percent. Sugar and flavorings may also be added. At Smoothies the whole fruit, sometimes even with the skin, is processed. It is based on fruit pulp or fruit puree, which is mixed with water, dairy products or vegetable milk to achieve a creamy consistency. Smoothies taste good and they also convey the feeling of doing something good for the body. However, the enjoyment of a smoothie can quickly add up to large amounts of fructose: For example, a smoothie made from three apples, two oranges, a banana and 100 grams of strawberries contains around 40 grams of fructose - which means that the fructose account for that day would almost be full.

Pesticides - the dreaded chemistry in fruit

Since the introduction of the glyphosate ban in Austria in July, consumers have been particularly sensitized to the subject of pesticides, and reports on pollutants in food have aroused great interest. You can't tell the fruit has been treated with pesticides, and you can't taste it either, which is why these substances are often feared. On average, conventional fruit - from small plants to ripe fruit - is sprayed up to 53 times before it hits the supermarket shelves.¹¹ In Europe, around 290 different substances are currently approved that are used in agriculture, and conventional farmers come hardly without pesticides. In the event of criticism, farmers and supermarkets usually refer to limit value regulations that are seldom exceeded in Austria. However, the limit values ​​apply to individual pesticides and not to the total exposure to all pesticides used. The entire cocktail of pollutants that results from the spraying can in some cases very well have an impact on health.

Studies on Pesticide Exposure

A 2015 study from the USA¹² showed that the male sperm count and the proportion of morphologically normal sperm cells decrease when fruit with high pesticide loads is consumed. A Danish long-term study published in 2017 examined the long-term effects of pesticide residues from various substances in food. The study concluded that the effects would be negligible for health.1³

At the end of 2018, a random test by the Vienna Chamber of Labor showed that 88 percent of the fruit tested contained residues of harmful substances. However, all values ​​for individual pesticides were below the legal limit. When added up, however, the total amount of pollutants on a fruit resulted in a high level of pollution. It would therefore be more helpful to disclose the total exposure to all pollutants in the fruit to the consumer in order to be able to better assess the health consequences.¹¹ A survey by Global 2000 in 2015 showed that organically grown fruit has little or no pesticide exposure.¹⁴


A healthy, balanced diet should definitely include fruit. Anyone who eats normal amounts of fruit is doing something good for their body and does not risk stomach ache or other health problems - provided there is no intolerance. When consuming finished beverages made from fruit, however, you have to be more careful: Large amounts of fructose can be quickly absorbed through fruit juices, smoothies and the like. Here you should make sure to stay below the recommended maximum values ​​for fructose in order to avoid discomfort. And if you are afraid of pesticide pollution and want to be on the safe side, it is best to choose organic fruits, because organically grown fruit must not contain any non-natural pesticides. ¹⁵ ¹⁶ ¹⁷ (Linda Naar, 4.9.2019)

Linda Naar is a biologist and works as a project employee at Open Science - Life sciences in dialogue with natural science topics in science communication. She is also one of the bloggers who write the articles for the Hungry for Science blog from Open Science as a "better know".


¹ AGES: Guideline: Sugars intake for adults and children (2015)

² German consumer organization, food clarity: sugar has many names

³ Lifeline, the health portal: glucose plus fructose equals sucrose: an overview of the types of sugar

⁴ Science Direct: Tagatose

⁵ Science direct: Polysaccharides

⁶ Stanhope Kl: Sugar consumption, metabolic disease and obesity: The state of the controversy (2016). Crit Rev Clin Lab Sci. 2016; 53 (1): 52-67.

⁷ Chiu S, Sievenpiper JL, de Souza RJ et al .: Effect of fructose on markers of non-alcoholic fatty liver disease (NAFLD): a systematic review and meta-analysis of controlled feeding trials (2014). Eur J Clin Nutr. 2014 Apr; 68 (4): 416-23

⁸ Sievenpiper JL, de Souza RJ, Mirrahimi A. et al .: Effect of fructose on body weight in controlled feeding trials: a systematic review and meta-analysis (2012). Ann Intern Med. 2012 Feb 21; 156 (4): 291-304.

⁹ Austria's public health portal: fructose intolerance

¹⁰ Federal legal information system: Fruit Juice Ordinance

¹¹ Chamber of Labor Vienna: pesticide residues on fruit and vegetables from Viennese supermarkets and markets (2018).

¹² Chiu Y., Afeiche M., Gaskins A., et al .: Fruit and vegetable intake and their pesticide residues in relation to semen quality among men from a fertility clinic (2015). Hum Reprod. 2015 Jun; 30 (6): 1342-1351.
Published online 2015 Mar 30.

¹³ Larsson M., Nielsen V., Bjerre N., et al .: Refined assessment and perspectives on the cumulative risk resulting from the dietary exposure to pesticide residues in the Danish population (2018). Food and Chemical Toxicology, Volume 111, January 2018, Pages 207-267.

¹⁴ Global 2000: organic vs. conventional (2015)

¹⁵ Global 2000: Pesticides

¹⁶ Bio Austria: Organic legislation

¹⁷ Consumer Health Communication Platform: Publications on Organic Production (2019)

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