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Fructose: Is Fructose Really Harmful?

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Fructose stands for fruit sugar. Fructose has had a bad rap for a while. It is said to be harmful, promote cancer, cause fatty liver, make you fat, and much more. Fruits naturally contain fructose. Is fruit also harmful? We present fructose-rich foods and clarify in which form fructose is harmful.

Fructose is said to be harmful

Fructose is a sugar that was once thought to be very healthy and recommended for diabetics because it is metabolized independently of insulin, and has a low glycemic index (GI), while glucose has a GI of 100) and therefore has little effect on blood sugar levels.

In the meantime, however, the tide has turned and fructose is considered harmful. It is said to make the liver fatty, promote gout and kidney stones, damage the cardiovascular system and the intestines, make you fat and promote cancer and even diabetes. Let’s take a look at whether fructose is actually that harmful, or maybe just in a certain form and amount.

First of all, there is an explanation of the term, then the potentially harmful effects of fructose. If you want to know straight away which foods contain how much fructose, simply scroll down to «These foods contain fructose».

Fructose and fructose: The definition

Fructose (or fructose) is fruit sugar. It belongs to the group of carbohydrates and, like glucose (dextrose), is one of the so-called simple sugars (monosaccharides). Simple sugars are made up of many individual sugar molecules. In the case of fructose from many individual fructose molecules, in the case of glucose from many individual glucose molecules. Glucose, also known as blood sugar, is generally our body’s main source of energy.

Why is fructose called fructose?

The term fructus comes from Latin and means fruit – and since the sugar in question is naturally found in fruits, in particular, it was called fructose for fruit sugar.

Fructose and Glucose: The Calories

Fructose, glucose, and also sucrose (normal household sugar) contain about the same number of calories (around 400 kcal or 1673 kJ per 100 g). Since fructose tastes twice as sweet as pure glucose and has a higher sweetening power than table sugar, you need less of it.

However, this is one of the reasons why the food industry is increasingly turning to sweeteners with a high fructose content. The only problem is (for the consumer, of course, and not for the food industry) that fructose is also less filling, so you tend to eat more of it.

The benefits of fructose for the food industry

While we know and use normal sugar as a crystalline powder, the food industry usually uses fructose in the form of syrup. This syrup is not pure fructose, but a mixture of fructose and glucose. Apart from the stronger sweetening power of such a fructose-rich syrup, the production of fructose-containing syrup from corn starch is also cheaper than importing sugar from sugar cane. In addition, fructose syrup has a number of technological advantages over conventional sugar:

Fructose syrup intensifies the taste of both fruity and spicy dishes. It creates an increased volume in baked goods and intensifies their browning, prevents harmful ice crystal formation in frozen foods, has excellent solubility, and does not crystallize. These properties of fructose syrup make it extremely versatile, so it is no longer surprising that it can be found in numerous finished products. Of course, the food industry is not interested in the health-endangering effects of fructose.

The disadvantages of fructose for the consumer

The disadvantages of fructose for the consumer include the digestive and metabolic pathway of fructose, which is very different from that of glucose:

The metabolism of fructose

Glucose is the body’s most important supplier of energy and therefore quickly enters the bloodstream from the intestine. Glucose is then called blood sugar. From here, the glucose is channeled into the cells with the help of insulin. Excess is stored in the liver and muscles in the form of glycogen, which can be converted back to glucose when needed. Only when the glycogen stores are full is the excess glucose converted to fat and stored in the fat cells.

In contrast to glucose, which is indispensable for generating energy in the cells, the body does not depend on the supply of fructose. It is therefore only very slow to get from the small intestine into the blood. In the intestinal mucosa, there are certain transporter proteins (they are called GLUT-5) that can be used to transport fructose into the bloodstream.

However, the number of these transporter proteins is limited, so only a limited amount of fructose can get into the bloodstream. No insulin is needed for the fructose to get into the cells. It is therefore said: fructose is metabolized independently of insulin, which is why it was recommended to diabetics as a sweetener for a long time, which was bad advice, as you will read below.

Fructose intolerance and fructose malabsorption

A healthy organism is well equipped to break down normal amounts of fructose (such as those found in fruit and vegetables). However, if large amounts of fructose from drinks or confectionery get into the intestine, many people react with an intolerance. This is called fructose malabsorption. The term “malabsorption” comes from Latin and means “bad absorption”.

In this case, the small intestine cannot completely transfer excessive amounts of fructose (more than 50 g per hour) to the blood. There are too few GLUT-5 transporters. And so some of the fructose ends up in the large intestine.

For some of the resident bacteria, the unexpected arrival of fructose is a real feast. They multiply at lightning speed and produce a lot of gases at the same time. Stomach pain, flatulence, and diarrhea are the consequences.

Fructose intolerance (FI), on the other hand, is an intolerance and metabolic disorder in which even small amounts of fructose from fruits or vegetables lead to the symptoms mentioned. Here you will find all further information on fructose intolerance and what you can do about it from a naturopathic point of view. A special form of fructose intolerance is hereditary fructose intolerance, hereditary fructose intolerance.

Hereditary fructose intolerance

So-called hereditary fructose intolerance is a hereditary disease in which almost no fructose is tolerated at all. The cause is an enzyme defect. That affected lack the enzyme called aldolase B so that the fructose that comes with the food cannot be completely broken down in the liver cell. There, the fructose is now – thanks to the enzyme ketohexokinase – present as fructose-1-phosphate and should now be broken down further by aldolase B.

If this does not happen, fructose-1-phosphate accumulates in the liver, which has a toxic effect and can lead to life-threatening hypoglycemia, since fructose-1-phosphate inhibits the conversion of glycogen into glucose. As explained above, glycogen is the storage form of glucose.

Fructose and the Leaky Gut Syndrome

If too much fructose is ingested, it can also directly damage the mucous membrane of the small intestine. There it leads to inflammatory processes (via the intestinal flora disturbance described below and via the formation of uric acid) and in this way can promote the development of the so-called leaky gut syndrome (LGS).

The LGS describes an increased permeability of the intestinal mucosa so that not only intestinal bacteria and their bacterial toxins but also particles from the food pulp can get into the bloodstream. Once in the blood, these foreign substances activate the immune system and promote the development of allergies and autoimmune diseases.

Fructose damages the intestinal flora

With a high-fructose diet with foods sweetened with industrial fructose, the intestinal flora changes in a negative way, it loses its healthy balance. The numbers of bifidobacteria and lactobacteria are declining, while enterococci and Escherichia coli are increasing. The latter in particular release so-called lipopolysaccharides (LPS), which promote inflammatory processes and insulin resistance (type 2 diabetes) and can pass through the intestinal mucosa in the case of the leaky gut syndrome described above. Studies indicate that the LPS are significantly involved in the development of the non-alcoholic fatty liver.

Fruits promote a healthy intestinal flora

Despite the fructose content, fruits do not harm the intestinal flora. On the contrary. With an increasing proportion of fruit and vegetables in the diet, there are positive changes in the composition of the intestinal flora. A study from 2020 even showed that increased fruit consumption in particular promotes the diversity of the intestinal flora.

Fatty liver caused by too much fructose

With the increasing consumption of industrial fructose worldwide, the number of people affected by the fatty liver is also increasing. A connection is obvious. Not only because of the intestinal flora disturbance and polysaccharide formation of some intestinal bacteria described above but also because fructose stimulates the formation of new fat in the body and at the same time blocks fat breakdown.

Blame for this misery should be in particular the oxidatively effective and pro-inflammatory uric acid, which is produced during the metabolism of fructose. The leaky gut syndrome caused by them and the subsequent influx of foreign substances into the blood stimulates the formation of new fat. In addition, there is a mitochondrial dysfunction in the liver, so that less ATP (energy) is formed there. However, the less energy can be formed, the more nutrients are naturally stored in the form of fat.

In the meantime, even children’s livers have become fatty. This is usually the case with overweight children, children born to overweight mothers, and children who were not breastfed or only briefly breastfed. Children become overweight particularly often when they are given sweetened drinks.

No fatty liver from fruits and vegetables

Anyone who thinks that they also get fatty liver from eating fruit and vegetables is wrong. A study from December 2020 with over 52,000 participants showed that the risk of fatty liver decreased with increasing fruit and vegetable consumption. So it’s again about the isolated fructose from the food industry in finished products and drinks, which makes you ill, but not about the natural fructose content in fruit and vegetables.

Fructose and the risk of gout and kidney stones

The uric acid produced when fructose is broken down causes the uric acid level in the blood to rise, but only if there is an excess of fructose, i.e. if you eat a lot of it. At the same time, fructose – like alcohol – inhibits the excretion of uric acid in the urine. This effect is particularly pronounced in people whose uric acid levels are already significantly elevated.

An increased uric acid level can now lead to gout or kidney stones (uric acid stones). It is less well known that high uric acid levels can apparently also lower vitamin D levels (according to a study from 1993). Because if you give people with high uric acid levels allopurinol (a uric acid-lowering gout medication), then the uric acid decreases, and at the same time the level of the active vitamin D (1,25 (OH)2D) increases significantly.

So if you suffer from gout, are prone to kidney stones, or are wondering about an inexplicable vitamin D deficiency, consistently avoid processed products containing fructose, sweets, and especially soft drinks. Because it is believed that it is mainly drinks sweetened with fructose that leads to the undesirable increase in uric acid. But what about fruits?

No gout and no kidney stones from fruit

A study from 2008 said: On the one hand, fruits and fruit juices seem to theoretically be able to increase uric acid levels due to their fructose content. However, since an elevated uric acid level increases the cardiovascular risk, people who like to eat fruit should also suffer from cardiovascular disease more frequently. But that is just not the case. This is because it has been proven that increased fruit and vegetable consumption lowers cardiovascular risk.

In July 2019, a review article in Nutrients read that a plant-based diet can reduce the risk of rising uric acid levels or gout – and that when plant-based diets are rich in fruit and purine-rich legumes (urine is produced in the body from purines). The study mentioned, i.a. presented a study in which people with elevated uric acid levels were switched to a healthy Mediterranean diet (more olive oil, legumes, grain products, fruits, vegetables, and at the same time only a little meat and only moderate amounts of dairy products). Her uric acid levels dropped by a third.

In May 2012, Canadian scientists wrote in the Journal of Nutrition that fructose negatively impacts uric acid levels even if you’re on a hypercaloric diet, meaning you’re simply eating too much overall, regardless of the source fructose comes from.

When it comes to kidney stones, Kidney International already stated in 2004 that the consumption of fruit and vegetables dilutes stone-forming factors in the urine without at the same time affecting the concentration of stone-protecting citrates and potassium. On the other hand, if fruits and vegetables are eliminated from the diet, even healthy people can develop kidney stones.

Fructose promotes the development of the metabolic syndrome

High fructose consumption can not only cause gout via the rising uric acid level (hyperuricemia). According to animal studies, it is known that hyperuricemia can cause the typical diseases/complaints of the so-called metabolic syndrome. This syndrome consists of the four most common phenomena of civilization, which in turn massively increase the risk of cardiovascular disease (and thus the most common cause of death of our time):

  • high blood pressure
  • Lipid metabolism disorders (excessively high blood lipid levels)
  • Pre-diabetes (high insulin and/or blood sugar levels; insulin resistance)
  • overweight

Fructose leads to diabetes

Increased uric acid levels caused by fructose can impair the cells’ sensitivity to insulin. NO (nitric oxide) is required for insulin to dock onto the insulin receptors in the cells. However, uric acid reduces the bioavailability of NO and thus also the insulin sensitivity of the cell. As a result, the cells gradually lose their ability to respond to insulin. It’s called insulin resistance. Pronounced insulin resistance is the main feature of type 2 diabetes. Here, too, fruit does not increase the risk of diabetes.

Fructose promotes cardiovascular disease

The NO mentioned not only makes the cells receptive to insulin but also ensures that the flexibility of the blood vessels is guaranteed. If the high concentration of uric acid caused by fructose impairs the production of nitric oxide, the blood vessels lose their elasticity.

High blood pressure develops, which significantly increases the risk of cardiovascular disease. A study published in the journal Nature also showed that fructose is harmful to the heart. The research team led by Professor Wilhelm Krek from the Swiss Federal Institute of Technology in Zurich (ETHZ) found that fructose can also cause an enlargement of the heart muscle in people with high blood pressure.

Fructose makes you fat

Fructose can promote obesity via at least three mechanisms, i.e. make you fat:

  • Fructose is converted into fat and stored in the fat deposits.
  • Fructose prevents fat burning by increasing insulin levels while at the same time increasing fat build-up.
  • Fructose blocks the feeling of fullness.

Fructose is converted to fat

When fructose is broken down into fat in the liver, some of this fat gets back into the bloodstream and now raises blood fat and cholesterol levels before it is finally stored in fat deposits (belly, hips, legs, bottom, etc.). Losing weight is anything but easy if you regularly consume too much fructose.

Fructose blocks the feeling of fullness

Since fructose causes so-called leptin resistance, there is a blocked feeling of satiety after fructose consumption. Leptin is a hormone and messenger substance that is mainly produced in fat cells. One of its tasks is to tell the brain how full the fat deposits are. If there are sufficient fat reserves, leptin inhibits the feeling of hunger. You feel full. In the case of leptin resistance, however, the body no longer reacts to leptin – and there is no feeling of satiety. In the corresponding studies, however, the participants only received industrial fructose. So they didn’t get fruit. Because fruits make you slim despite their fructose content!

Fruits make you slim

In a review from 2016 one read that it has long been known how well fruit can reduce obesity and improve the diseases associated with obesity (diabetes, coronary heart disease). Numerous studies have shown that people are slimmer the more fruit they eat – even though some fruits contain large amounts of fructose and glucose. Yes, low fruit consumption is even considered one of the most important risk factors for being overweight and for high blood sugar and cholesterol levels. The reasons for the anti-obesity effect of fruit are as follows:

  • Those who eat fruit usually take in fewer calories overall.
  • Fruit fills you up.
  • Fruit contains fiber that is healthy for the intestines and ensures healthy intestinal flora.
  • Fruit provides important micronutrients and secondary plant substances.
  • It is suspected that there are other, but as yet unknown, mechanisms.

So if you want to lose weight, you can eat fruit without any problems, yes, you should eat fruit and you don’t have to worry that you might gain (even more) weight from fruit.

Fructose and Alzheimer’s

Fructose is also associated with Alzheimer’s disease and declining cognitive abilities in old age (thinking, language, memory, information processing, etc.). In Alzheimer’s, the internal structures of the nerve cells (the neurofibrillary tangles) change, deposits form around the nerve cells (Alzheimer’s plaques) and communication between the nerve cells is gradually lost.

Insulin resistance and impaired mitochondrial function in the brain are considered to be important contributory causes of Alzheimer’s. Both problems are fueled by fructose. Insulin resistance means that the cells in the brain can no longer be supplied with sufficient glucose and less energy is produced with reduced mitochondrial function. However, the nerve cells in the brain in particular require a high supply of energy. If this is missing, the activity and performance of the nerve cells decrease or they even die.

(Excursion: If you are now wondering whether the cells in the brain cannot be supplied with glucose independently of insulin, then the following explanation is for you: for a long time it was actually believed that glucose uptake in the brain is completely insulin-independent. There are indeed insulin receptors in the brain, but it was always assumed that these have other functions in the brain. It was also assumed that only the glucose transporters GLUT1 and GLUT3 supply the brain with glucose and thus also that the brain is supplied with glucose independently of insulin since GLUT 1 and GLUT3 act insulin-independent. But then studies raised doubts because they also found GLUT4, an insulin-dependent transporter in the brain, so different research teams came to the conclusion that an insulin-dependent glucose uptake must also take place in the brain, at least in part.

Sugar-sweetened beverages have also been shown to be particularly harmful in terms of Alzheimer’s risk, so affected or at-risk people should avoid drinking sugar-sweetened soft drinks. The fructose in fruit or fruit juice, on the other hand, has no harmful effects on the brain.

Fruits protect against Alzheimer’s

A 2006 study showed that those (predisposed to Alzheimer’s) who drank three or more servings of fruit juice per week developed Alzheimer’s later than those who consumed fruit juice less frequently. A 2010 study also found that high fruit and vegetable consumption appeared to protect against Alzheimer’s. The same result was shown in a 2015 study: fruit consumption (and exercise) reduce mortality from Alzheimer’s.

Fructose and cancer

Since obesity and the other characteristics of the metabolic syndrome increase the risk of cancer and fructose can promote the metabolic syndrome, fructose indirectly prepares the ground for cancer in this way alone. However, fructose also directly increases cancer growth. Malignant tumors have a particularly large number of fructose transporter molecules so that they can absorb as much fructose as possible. Because tumors are often poorly supplied with oxygen and fructose can be metabolized even with a low oxygen supply. Oxygen-poor tumors in particular form metastases more frequently. Acids (uric and lactic acid) are also formed during the metabolism of fructose, which also promotes cancer growth.

Fruits protect against cancer

Only industrial fructose has such a carcinogenic effect. Despite their fructose content, fruits have a protective effect against cancer. For example, high citrus fruit consumption protects against stomach cancer. High fruit consumption also reduces the risk of prostate cancer – to name just two examples.

These foods contain fructose

Fructose is naturally present in many foods, especially in fruits and vegetables and in the corresponding juices. Honey and thick juices (e.g. maple syrup, agave syrup, apple syrup, etc.) also contain plenty of fructose. In addition, the food industry uses various industrially produced high-fructose syrups for a wide variety of finished products.

Fructose in fruits and vegetables

Some example fructose values of fruits can be found in the table below. Vegetables, on the other hand, contain significantly less fructose, usually only between 0 and 1.5 g per 100 g. Exceptions are e.g. E.g. carrots with 2.4 g fructose or red peppers with 3 g fructose per 100 g.

Fructose in dried fruits

Dried fruits naturally contain more fructose per 100g than fresh fruits because most of the water has been removed from them and the nutrients are therefore in a concentrated form. However, since dried fruit also contains many valuable vital substances, they do not pose a problem in manageable quantities and as part of an overall healthy diet.

Prunes, for example, have been shown to be beneficial for bone health and digestion, and help prevent colon cancer. Dried apricots are extremely rich in beta-carotene and are therefore healthy for the eyes, bones, and mucous membranes.

In fact, a 2020 study by researchers at the University of Missouri and Harvard TH Chan School of Public Health in Boston found that the risk of colon polyps increased by 24%, prostate cancer by 49%, nasopharynx cancer by 76%, and stomach cancer by up to 96% and reduced risk of death from pancreatic cancer by 65% when eating 3 to 5 or more servings of dried fruit per week.

A portion is about 3 figs/apricots/dates or 1 heaped teaspoon of raisins so that you can see from this information alone which quantities of dried fruit are helpful and what may be too much.

Fructose in fruit juices

By drinking fruit juices, you can quickly consume a large amount of fructose that would be difficult to achieve by eating fruit alone. Fruit juices (if unsweetened) do not contain more fructose per 100 g than the whole fruit, but a liter of fruit juice (or more) is drunk faster than you could eat the amount of fruit it contains (usually several kilograms).

Fruit juices are better than soft drinks

A 2016 study found that when 2- to 9-year-old children drink a lot of soft drinks (five drinks a week or more), their risk of developing asthma increases fivefold compared to children who drink no more than once a week drink a soft drink – which is probably due to the fructose, which is used to sweeten soft drinks, especially in the USA (in the form of high-fructose corn syrup HFCS).

When the kids drank five or more servings of 100% apple juice a week, their risk of developing asthma only doubled. Orange juice, on the other hand, had more of a protective effect against asthma.

  • Orange juice contains per 100 ml: 2.3 g fructose and 2 g glucose.
  • Apple juice contains per 100 ml: 5.3 g fructose and 1.9 g glucose.
  • Coca-Cola Classic contains 100 ml: 5 – 5.5 g fructose and 4.5 – 5 g glucose.

Overall, cola is clearly the worst choice. The fructose content is high, the glycemic index is also high due to the additional high glucose value. In addition, cola (and other soft drinks) contain no vitamins or antioxidants.

Fructose more harmful than a high glycemic index

It is interesting in this context that the glycemic index of orange juice (GI 50) is even slightly higher than that of apple juice (GI 41). So the harmful effect of fructose appears to be higher than that of the higher GI. Yes, it even seems that despite the higher GI, orange juice is not harmful at all, but beneficial.

Only a minimal risk of obesity from fruit juices

In 2017, a meta-analysis from 8 cohort studies with a total of almost 35,000 children showed that the consumption of 100% fruit juices (maximum 240 ml daily) in children aged 7 to 18 does not contribute to obesity. A slight increase in BMI was only observed in children under the age of 2 when they drank fruit juices.

No increased risk of diabetes from fruit juices

As far as the diabetes risk from fruit consumption is concerned, we report here (fruit protects against diabetes) that people who like to eat fruit are less likely to develop diabetes. In terms of diabetes risk from fruit juice consumption, a study with over 27,000 participants (40-59 years) was published in 2013, which stated that drinking soft drinks but not consuming 100% fruit or vegetable juices increases the risk of diabetes.

Fruit juices protect – albeit weakly – against cancer

What about the risk of cancer and cardiovascular disease? Freshly squeezed fruit juices (and of course also vegetable juices) are known to be an important part of naturopathic therapy concepts.

A review from 2006 states that although fruit and vegetables reduce the risk of cancer and cardiovascular disease, it is not known whether juices also have a protective effect. Because maybe it is precisely those substances that protect against diseases that are removed during juice production (roughage). It turned out, however, that the antioxidants (less fiber) have a protective effect – and it is precisely the antioxidants that are still contained in the juices.

Fruit juices reduce cardiovascular risk

Overall, it was found in the study mentioned that pure fruit and vegetable juices only have a weak protective effect in relation to cancer, but significantly reduce the risk in relation to cardiovascular diseases – regardless of whether the people also like it Eating fruits and vegetables or not.

The rules for healthy fruit juice consumption

Fruit juices therefore only pose a certain health risk if you overdo it with the quantity or do not drink 100% pure juices. There is a high probability that there are also differences in the effect of purchased (i.e. pasteurized) juices and freshly squeezed juices, which was unfortunately not taken into account in the studies.

The following general rules apply to the consumption of fruit juice:

  • In any case, only drink fruit juice as a (between) meal or as a kind of appetizer (not as a thirst quencher).
  • Only drink fruit juices in small quantities (e.g. 200 ml per serving).
  • Don’t drink fruit juices every day.
  • It is best to only drink freshly squeezed fruit juices, as all of the fruit’s own vital substances are then still contained in the juice and the advantages of consuming juice can therefore outweigh them.

Table sugar consists of 50% fructose

Ordinary table sugar (sucrose) is a double sugar (disaccharide) because it consists of many double molecules, each of these double molecules in turn consisting of one fructose and one glucose molecule. This means that half of the table sugar consists of fructose. Anyone who cannot tolerate fructose because of fructose intolerance usually also has problems with normal table sugar and products sweetened with it.

Honey

You should also only use honey in small quantities, preferably as a remedy rather than as a food: honey usually contains more fructose (approx. 40%) than glucose (approx. 30%). Moreover, the more liquid a natural honey is or the longer it remains liquid during storage, the higher its fructose content. The liquid acacia honey, for example, is rich in fructose with almost 44% fructose and 27% glucose. The firmer honey made from dandelion and rapeseed, on the other hand, contains slightly more glucose than fructose.

Agave syrup

Agave syrup consists of about 55% fructose (and 12% dextrose), so it contains even more fructose than honey and is, therefore – if you want to avoid fructose – not so ideal or should really only be used in small quantities, but certainly not for baking or as a spread or as a sweetener for jam.

For comparison: Maple syrup consists of 30% fructose and 30% glucose, so it is a little lower in fructose, but overall it is by no means lower in sugar.

Thick juices

In addition to agave syrup, there are other syrups that are often advertised as healthy sweeteners in the alternative trade but should in fact be consumed with caution. Some thick juices are thickened, i.e. boiled down, fruit juices, and are therefore even richer in fructose than fruit juices, e.g. B. concentrated apple juice, concentrated pear juice, or concentrated date juice.

Of course, if you eat a spoonful of it every now and then, that’s no problem. However, if you would like to use them regularly to sweeten desserts and cakes, for example, and are perhaps already overweight and/or suffer from a chronic illness that could be aggravated by fructose, then you should use the thick juices mentioned better (if it must be thick juices must) replace with low-fructose syrups, e.g. B. rice syrup, yacon syrup or barley malt syrup.

Inulin and FOS consist of fructose

Fructose is also part of certain natural multiple sugars (oligo- or polysaccharides) called inulin and FOS (fructo-oligo-saccharides). These consist of two or more linked fructose molecules attached to a glucose molecule. Their connection is so tight that it would take a specific enzyme to break it. Since the human digestive system does not have this enzyme, no free fructose is produced when these polysaccharides are digested.

Many oligo- or polysaccharides are readily eaten by the intestinal bacteria, which can lead to increased activity, which is why inulin and FOS are considered valuable prebiotics that can contribute to a healthy intestinal flora. Inulin is therefore available as a powder for oral use, e.g. B. accompanying an intestinal cleansing.

However, the more active intestinal flora can lead to flatulence or discomfort, especially in sensitive people (independent of fructose), so inulin and FOS should be used carefully.

Inulin is found in larger amounts in Jerusalem artichoke, and smaller amounts are found in onions, garlic, leeks, and asparagus. Here is a list of foods rich in inulin. For FOS, on the other hand, Yacon is one of the best sources, e.g. B. in the form of yacon powder or yacon syrup. In the meantime, there are also producers in Germany for the South American tuber, so that Yacon can also be ordered and prepared fresh.

Industrially produced fructose

Fructose is also produced industrially – and used to sweeten a wide variety of finished products. So pay attention to the list of ingredients in soft drinks, chocolate bars, sweets, ready-made cakes, fruit gums, ice cream pralines, milk slices, semolina desserts, mixed pickles, pickles, ketchup, dressings, nut biscuits, and much more.

So when we talk about fructose, we are no longer talking about the fruit sugar in cherries, apples, or bananas, but much more often about the highly concentrated and industrially produced fructose in the finished products or drinks mentioned.

This is how fructose is labeled and declared in finished products

If you no longer want to eat fructose in finished products, pay attention to the list of ingredients. Fructose or sweeteners containing fructose can be declared there as follows (of course, the spelling with “k” is also possible, i.e. fructose or glucose):

  • fructose
  • fructose syrup
  • Glucose-Fructose Syrup: Sugar syrup that contains more glucose than fructose
  • Fructose-glucose syrup: Sugar syrup that contains more fructose than glucose
    HFCS (High-Fructose Corn Syrup): High-Fructose Corn Syrup means high-fructose corn syrup. It consists of a mixture of glucose and fructose and is usually made from corn starch. If you were to eat cornstarch, it would be broken down into glucose in the body. Corn starch, therefore, contains no fructose and can therefore be used in the case of fructose intolerance, e.g. B. be used as a binder or thickener. To produce the HFCS, however, complex enzymatic processes are used that create fructose from the starch. There are different HFCS. They differ in their fructose content. The higher the fructose content, the stronger the sweetening power of the syrup. HFCS 42 consists of 42% fructose, and HFCS 55 55% (based on dry weight). HFCS 42 is more likely to be mixed into breakfast cereals, and HFCS 55 into soft drinks.
  • Isoglucose: Collective term for types of syrup made from corn, wheat, or potatoes. These include the already listed glucose-fructose syrups and fructose-glucose syrups (HFCS). These are sugars with different proportions of glucose and fructose. In German-speaking countries and in the EU, the term isoglucose is more commonly used, and in the USA the term HFCS.
  • Corn Syrup or Corn Syrup/Corn Syrup: An isoglucose made from corn
    Invert sugar (invert sugar syrup): Invert sugar is sucrose that has been enzymatically treated in such a way that the bond between the fructose and glucose molecules has been broken and both simple sugars are now free.
  • Fruit sweetener: Fruit sweetener is an industrially produced sweetener. It consists of pure sugar, namely a mixture of fructose, glucose, and sucrose. If a product is sweetened with fruit, the manufacturer can write “Natural sweetness made from 100% fruit” on the product, which of course is extremely sales-promoting. However, the advertising slogan only came about because the sugar is obtained from fruit and no chemicals are used in the manufacturing process, but this does not change the fact that it is an industrially produced isolated high-fructose sugar with known disadvantages.
  • fruit juice concentrate
  • Sugar, sucrose, sucrose, beet sugar, cane sugar, brown sugar, refined sugar, refined sugar, and sugar syrup are all terms for the same thing: ordinary table sugar that’s half fructose

Low fructose syrup types

The types of low-fructose syrup include the syrups mentioned above, i.e. rice syrup, yacon syrup, and barley malt syrup. A low-fructose syrup or sweetener is low in fructose and therefore does not have the health effects typical of fructose, but it does not have to be healthy.

Rice syrup, for example, contains almost no fructose and is therefore usually well tolerated by people with fructose intolerance. But instead, it contains 23% glucose and 30% maltose (malt sugar, a disaccharide that consists of pure glucose, with two glucose molecules always connected to each other, so that the malt sugar is ultimately split into glucose in the intestine). So here we have an almost pure glucose syrup, which is also a highly concentrated sugar and consequently has its disadvantages.

The situation is very similar with barley malt syrup. Here, too, the fructose content is negligible (approx. 3.2%), while glucose (12%), maltose (53%), and long-chain sugars (31%, fructooligosaccharides, etc.) predominate.

In the case of yacon syrup, the proportion of free fructose can be up to 15%. There are also 5% glucose and 5 to 15% sucrose. The rest are fructooligosaccharides, the fibers described above under “Inulin and FOS” with a prebiotic effect, which means that they have a beneficial effect on the intestinal flora. Read more about the health benefits of yacon syrup in our yacon syrup article. We present healthy sweeteners in our article on sweeteners.

Conclusion: fruit is healthy despite the fructose it contains!

If you eat fruit and vegetables and small amounts of dried fruit and occasionally drink a glass of freshly squeezed fruit juice, you don’t have to worry about the possible harmful effects of fructose. These foods are healthy—and even though they contain fructose, fructose can’t be harmful as part of an overall healthy diet. On the contrary. It is easily used by the body for energy, provided of course you don’t consume more calories than you can burn.

For sweetening, we recommend low-fructose sweeteners, especially if you have a sweet tooth. If you only eat something sweet now and then, high-fructose concentrated apple juice or agave syrup won’t do any harm either.

Fructose only causes health problems when consumed in excessive amounts and/or in the form of isolated, concentrated, industrially produced fructose, which is found in confectionery, soft drinks, juices, and convenience products.

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Written by Bella Adams

I'm a professionally-trained, executive chef with over ten years in Restaurant Culinary and hospitality management. Experienced in specialized diets, including Vegetarian, Vegan, Raw foods, whole food, plant-based, allergy-friendly, farm-to-table, and more. Outside of the kitchen, I write about lifestyle factors that impact well-being.

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Generation Chips

Sick From Food Additives