What is fructose?
Fructose is a monosaccharide, the simplest form of carbohydrate. As the name implies, mono (one) saccharide (sugar) contains only one sugar group, so it does not break down further.
Each subtype of carbohydrates has a different effect on the body depending on the structure and source (i.e. what food it comes from). The chemical structure affects how quickly and / or easily a carbohydrate molecule is digested / absorbed. The source determines whether other nutrients come along with the carbohydrate.
For example, both corn syrup and fruits contain fructose, but their effects on the body vary. Corn syrup is the simplest system for delivering carbohydrates to the body - there is nothing else in it, while fruits contain other substances, such as fiber, these are dietary fibers that affect the digestion and absorption of fructose. Plus, the amount of fructose in an average apple is much less than, say, in a regular can of soda.
Fructose has a unique texture, taste, digestibility and digestibility, which is different from glucose, sugar, which is the majority of the carbohydrates we consume when they get to the circulatory system.
Fructose, unlike glucose:
- Absorbed by the intestine using mechanisms other than glucose
- Absorbed more slowly
- Does not cause significant release of insulin
- Gets into cells by other means of delivery than glucose
- When it enters the liver, it provides the production of glycerin, a substance that increases the formation of fat and its basis
- Some people are unable to fully digest fructose when losing weight in a dosage of over 50 grams (Note: this is a very large amount. This is found in 4-5 apples. Although half a liter of corn syrup is about 45 grams of fructose.)
- Consumption of both glucose and fructose accelerates the absorption of the latter. This is one of the reasons why many sports drinks contain a mixture of sugars.
Why is fructose important?
500 years ago, before the era of mass production of sugar, fructose was at a minimum in the human diet. She acted only as part of ordinary food. Fruits, vegetables, grains, nuts / seeds and proteins contain a limited amount of fructose and provide a moderate amount of it. When the food industry isolated fructose from sources such as corn, and when it began to be added to a variety of processed foods, our fructose consumption increased.
In particular, it increased between 1970 and 2000. Although many people associate fructose with fruits, most of it comes to organisms from sources unrelated to them. A survey conducted in the 1990s showed that an average person consumes ~ 80 grams of added sugar (which is ~ 320 calories or 15% of energy consumption); approximately half of this amount is fructose.
We get fructose not only from fruits, but also from sucrose (tableted sugar). Sucrose is a diasaccharide (two sugars) consisting of glucose + fructose. It is found in processed foods, including sweets, soft drinks, and just about any packaged “edible food substance.”
What you need to know
Our liver is the main center of fructose metabolism. In the liver, it is processed into glucose derivatives and stored in the form of hepatic glycogen. At one time, the liver can process and store a limited amount of fructose as glycogen. The rest will be stored in the form of fat, so a large single dose of fructose is likely to settle on your sides. This is more pronounced in people with high blood lipids, insulin resistance, or type 2 diabetes.
High consumption of fructose (unlike other dietary carbohydrates) can lead to the fact that leptin will not be produced in normal quantities.
Leptin is a hormone involved in the long-term regulation of energy balance. Its level increases when we get enough calories / energy, and decreases if not, so it lets us know when to start and finish eating.
A decrease in leptin production associated with chronic high fructose intake can have a detrimental effect on the regulation of food intake, as well as the percentage of body fat. In other words, when there is an excess of fructose, your brain will not send you “I have enough” signals, and you will continue to eat, although you have already received more than enough calories.
Since fructose is delayed in the liver, it does not cause a strong glycemic response. And if it can be good when consuming whole fruits, then if you eat added fructose-based sweeteners, the effect is reversed. Although fructose is quite low on the glycemic scale and can help restore hepatic glycogen during physical activity, excessive consumption of it can lead to the formation of fat in the liver, as well as to an upset of the energy balance and system of regulating body fat. As a result, consuming large amounts of fructose-based sweeteners can lead to obesity in the abdominal region, low levels of healthy and high bad cholesterol in the blood, high levels of triglycerides and loss of appetite control.
Clinical studies show that people who have a lot of fruits (and vegetables) in their diets are usually more lean, it’s easier for them to maintain a healthy weight and overall well-being than those who do not.
Worried about fruits? Relax. Experts concluded: "Consumption of fructose from naturally untreated food sources is low enough and hardly likely to have negative metabolic effects."
Consuming fruits (and vegetables) can help prevent chronic diseases and even cancer.
Dr. Vioke, the author of a study in which he monitored the effects of fruit consumption on adults for more than 10 years, argues that one should not be afraid to gain excess weight from fruits: “There is no data that would indicate any significant weight gain as a result of eating a lot of fruit. "
If you are worried about your health and optimal physique, boldly eat an orange, but better think twice before drinking a bottle of orange juice, or, even worse, a can of orange soda.
Conclusions and recommendations
When it comes to fructose, its source is important. It is highly unlikely that by consuming fresh unprocessed fruits you will gain energy imbalance and begin to gain weight. However, if fructose-rich juices, sweeteners, and energy-intensive foods regularly appear in your diet, you will most likely come to these problems. Our bodies have a long and lasting relationship with fruits, but this does not apply to fructose and sweeteners.
Eating fresh fruits in abundance will provide you with nutrients and help control the flow of energy. 2000 calories is almost 3.5 kilograms of fruit. Usually a person does not eat more than ~ 2.5 kilograms of food per day.
Avoid foods / drinks with added fructose sweeteners; replacing sugar with it is generally a very bad idea. .
Ask yourself - does my fruit abuse lead to digestive problems like chronic illnesses or weight gain?
Benefits and side effects of fructose
Do not really trust what is written on the label about the sugar content in soda. The Center for Research on Childhood Obesity says there is a frightening difference between what is said on the packaging and how it really is. In fact, in corn syrup with a high content of fructose, it is 18% more than what is written in the composition.
But let's figure it out.
Fructose, glucose and sucrose are types of simple sugars that are naturally present in foods. In fact, many people believe that fructose is not a cause for concern, because it is present in fruits. Consuming fructose with fruits is basically acceptable, since with it you get more fiber, vitamins and minerals such as iron and calcium. They help process fructose in the body.
But if you isolate fructose and add it to food that does not contain fiber and vitamins, then we find ourselves in unhealthy territory. The body has to deal with too much fructose, without fiber, which can mitigate its effect.
You really cannot distinguish between these three types of simple sugar to taste, but your body considers them to be completely different things. As a result, it treats each type very differently. This discovery was made only a few years ago, and therefore there are still misconceptions about the difference in the effect of different types of sugar.
The path that fructose takes in the body is completely different from glucose and sucrose. The only body cells that can handle fructose are liver cells. Fructose produces much more fat than glucose, and scientists believe that the body perceives it more as fat than as carbohydrate. In liver cells, it also turns into uric acid and free radicals. And this is bad (uric acid enhances inflammation, and free radicals cause cancer and other diseases).
Your body loves glucose, its alternative name is "blood sugar". The body uses glucose to produce energy and releases insulin in response to an increase in blood sugar. The body processes the carbohydrates you consume into glucose, from which energy is obtained. But what if you don’t need energy right now? It is stored in muscle or liver cells for later.
Drain fructose and glucose together, what happens? That's right, sucrose. This is another name for table sugar, which is naturally present in fruits and vegetables. The body breaks it down into two components: fructose and glucose. When you eat sugar, the body takes glucose and uses it to generate energy or stores it in the muscles or liver (see above). And, if you are not really crazy training hard, fructose goes straight to fat synthesis.
High fructose corn syrup
Since it is hotly debated by people associated with healthy eating, I decided to include it in the list. Like sucrose, syrup is glucose + fructose, but it contains slightly more fructose (55%) than glucose (45%). In this sense, syrup is no more dangerous than "real" sugar, or sucrose. There is even a study on this subject.
A few kind words about fructose.
Supporters of fructose argue that, since it is natural, it means healthy. They also point to the fact that fructose is much sweeter than table sugar, so much less is needed to sweeten it. As a result, with the same level of sweetness, fewer calories enter the body.
They also argue that the national obesity epidemic is not so much related to fructose, as obesity is the result of many factors, not just one. They cite several studies supporting this idea. We consume too much fructose. Much more than it would be necessary to just make something sweet: we need it to be SUPER sweet, and we will eat it in incredible quantities.
If you are overweight, fructose is best avoided. Your body is able to perfectly process all three types of sugar. But when you overload the system, then things get out of hand.
In short: fructose turns into fat. Glucose - no.
And this process affects not only the liver. Scientists are exploring what large doses of fructose do with your brain.
Yale University conducted a study where they watched what happened to 20 average adults who were given glucose or fructose-rich drinks. Before and after taking them, they underwent an MRI.
Participants who drank drinks with sucrose showed a decrease in the activity of the center of hunger in the brain. Their brain signaled "fullness." Those who drank fructose drinks didn’t.
In short: Fructose affects the brain in a different way than sucrose and this can lead to overeating.
No kidding, the liver turns fructose into fat. When liver cells break down fructose (if you remember, I mentioned above: this is the only type of cells that can cope with it), they synthesize fat stored in fat cells.
When you consume too much fructose, it becomes a toxin for the liver. This leads to insulin resistance and liver steatosis.
In short: For the liver, fructose is similar to alcohol: very toxic if you consume too much.
Most people are better off avoiding fructose, especially if they are overweight. Since your body perceives fructose as fat, processes it in the liver and synthesizes new fat, misfortune happens. Obesity is only part of the problem. The Harvard School of Public Health published an excellent article outlining the results of an in-depth analysis of the danger of steatosis.
Fructose in foods
Fructose-rich foods include many sweetened drinks and snacks, fruits, especially in concentrated juice or dried fruit form, and honey (see table below). Chains of molecules of fructose, fructooligosaccharides or fructans are present in high concentrations in some vegetables and grains, which often causes an allergic reaction in people with fructose intolerance.
Fructose or fructans contain many foods, and despite the overall decrease in the amount of fructose in the diet, it is important to monitor the quality of the diet to keep you feeling under control.
To achieve this, seek the help of an experienced nutritionist who is competent in fructose intolerance. It is also often useful to drink vitamins.
In the case of hereditary fructose intolerance, it may be necessary to exclude sucrose (which, when split, produces fructose and glucose).
A sweetener such as tagatose is processed into fructose and is present in drinks (non-alcoholic, instant, teas, fruit or vegetable juices), breakfast cereals, cereal bars, confectionery and chewing gum, sweets and fillings, jams, marmalades and dietary products. Levulose and invert sugar on the labels indicate the presence of fructose.
Fructose is more easily tolerated in the presence of glucose. This means that for products containing as much glucose as fructose, the body is more likely to respond normally (in the table, this is the F / G value, which should be less than 1).
In some products, regardless of glucose content, a lot of fructose is also naturally present, i.e. more than 3 grams per serving, or more than 0.5 grams of fructans per serving.
These are two criteria that are considered most useful when choosing candidate products for removal from the diet.
According to these criteria, the following foods are most likely to be poorly tolerated and should be excluded from the diet or consumed in limited quantities:
- Fruit and fruit juices: apple, cherry, grapes, guava, lychee, mango, melon, watermelon, orange, papaya, pear, persimmon, pineapple, quince, carambola.
- Most dried fruits, including currants, dates, figs, raisins, even if it is a fitness bar.
- Processed fruits: kebab / grill sauce, chutney, canned fruits (often made in peach juice), plum sauce, sweet and sour sauce, tomato paste.
- Berries in large quantities: blueberries, raspberries.
- Sweets, foods and drinks with a very high content of sucrose (table sugar) and fructose corn syrup.
- Honey, maple syrup.
- Large quantities of vegetables (containing fructans or inulin: artichoke, asparagus, beans, broccoli, cabbage, chicory, dandelion leaves, garlic, leeks, onions, peanuts, tomatoes, zucchini.
- Sweet wines: for example, dessert wines, a butcher, port, sherry.
- Wheat and rye products (with fructan content): flour, pasta, bread, wheat bran, whole breakfast cereals.
- Wholemeal foods in large quantities.
- Since people with fructose intolerance react poorly to sorbitol (code E420) and xylitol (E967), it is better to check whether the following foods cause undesirable symptoms: diet / light drinks and drinks for diabetics, chewing gum and diet sweets / candies without sugar , stone fruits (e.g. apricots, cherries, quinces, prunes and peaches), pears, dried fruits (e.g. apples, apricots, pigs, figs, nectarine, peaches, plums, raisins). Beer in large quantities can also cause problems.
Examples of well-tolerated fruits and vegetables are:
Eggplant, banana, Brussels sprouts, carrots, clementine / mandarin, corn, cucumber, fennel, grapefruit, lemon, potatoes, pumpkin, radishes, red currants, rhubarb, sauerkraut, spinach and sweet potatoes / pits.
In the case of multiple carbohydrate / sugar intolerances, FODMAP intolerance (fermentable oligo-, di-, monosaccharides and polyols) may occur, which requires a general decrease in the content of FODMAP, at least during the trial period of 4-6 weeks and with observation for a diet. For a significant group of patients, however, this is not necessary, since individual intolerances are more common.
The following information contains details on reducing the amount of fructose in your diet. However, it is recommended that you consult a nutritionist to maintain a healthy and balanced diet.
The table below shows the content of fructose and glucose, as well as their ratio in the most common products. The numbers are rounded, and therefore discrepancies between the values of fructose and glucose and their ratio are possible. Keep in mind that when comparing tables from different sources, certain variations are possible. This is due to differences in measurement methods, the actual sugar content in different types of fruits, as well as ripening and growth conditions. Therefore, these tables should always be considered as rough recommendations.
First step: we look at the ratio of fructose and glucose (F / G value), it should be less than 1 (i.e., the fructose in the product is less than glucose).
Second step: the absolute fructose content in the product should not exceed 3 grams per serving. Small portions of border products are acceptable, but not on an empty stomach.
Content per 100 g of product (in grams):
|Berries||Fructose (F)||Glucose (G)||F / G ratio|
|Black currant, fresh||3||3||1|
|Currant red, fresh||2||2||1.2|
Content per 100 g of product (in grams):
|Dried fruits||Fructose (F)||Glucose (G)||F / G ratio|
Honey and fruits
Content per 100 g of product (in grams):
|Honey, fruits||Fructose (F)||Glucose (G)||F / G ratio|
|Grapefruit juice, fresh||2||2||1|
|Fresh orange juice||3||3||1.2|
Vegetables and mushrooms
Content per 100 g of product (in grams):
|Vegetables, mushrooms||Fructose (F)||Glucose (G)||F / G ratio|
|Whole rye bread||1||1||1.5|
Sweeteners: aspartame, acesulfame K, saccharin, cyclamate, stevia and thaumatin do not cause problems for people with fructose intolerance, including hereditary.
Sorbitol decreases, and glucose increases fructose tolerance.
Glucose (e.g. glucose / dextrose-containing preparations, drinks, syrups) can be consumed with fructose-containing foods to increase tolerance.
Fructose-containing foods are best tolerated in small portions throughout the day and not on an empty stomach.
About 30% of people with fructose intolerance also suffer from lactose intolerance. They are likely to be sensitive to the entire FODMAP group.