Fructose: good or bad?

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Sugar is also in foods that are natural and healthy like fruits and vegetables. This can make it hard for us to really understand the dangers of consuming too much sugar and reminders are often a good idea.

There are dozens of different sugars in the world, but for the purpose of this article what we need to understand are sucrose, glucose, and fructose. Sucrose (aka, table sugar) is a disaccharide — this means it is made up of two sugar molecules joined together. These two molecules on their own are called glucose and fructose. We were never in contact with as much sweet fruit than today’s diets. The problem in sugary fruits is the fructose.

Glucose, besides being present in sugar, honey, and other sweeteners, is derived from starch — when we eat starches, our bodies convert them into glucose, which we use for energy. The body metabolizes glucose in the intestinal tract, where it gets absorbed into the blood stream causing a rise in blood sugar levels. To get the sugars where they need to go, the pancreas releases insulin, this lowering the blood sugar by letting glucose in the body cells. One part of the absorbed glucose is used directly as energy and another part is stored as glycogen in our liver. Also our muscles store glucose as glykogen but they are not able to release the glucose into the blood stream. They rather keep it and use it as fuel for sudden activities. Glucose is the body’s number one source of energy, and is an important part of healthy functioning (in moderation). As of course an excessive intake will be converted to body fat.

Fructose is a naturally occurring sugar present in fruit, honey, and cane sugar, among other things. Fructose is about twice as sweet as glucose. It is often thought of as a healthier type of sugar because it has a low glycemic index, meaning it has a very small impact on blood glucose and insulin levels. This is because fructose doesn’t get absorbed in the intestinal tract the way glucose does. Instead, fructose travels further down the intestines and on to the liver. The breaking down of fructose in the liver triggers the production of uric acid, among other things, which in excess can cause gout and kidney stones.

We would like to explain further why too much fructose is bad for you.

  1. Fructose can only be metabolized by the liver and can’t be used for energy by your body’s cells. It’s therefore not only completely useless for the body, but is also a toxin in a high enough amount. Normally the liver convert the fructose into fat acids and transport it over the blood stream in the whole body. If there is an overload the liver will produce too much of these fat acids and at one point they could not get convert properly so the liver becomes fatty.
  2. So excess fructose damages the liver and leads to insulin resistance as well as fatty liver disease. In fact, fructose has the same effects on the liver as alcohol, which is already well known as a liver toxin.
  3. While most of your body’s cells cant use fructose as a source of energy, the bacteria in your gut can do this so that’s why excess fructose can create gut flora imbalances, promote bacterial overgrowth and promote the growth of pathogenic bacteria.
  4. Fructose rapidly causes leptin resistance. Leptin is a hormone that controls appetite and gives our brain information about fat reserves in our body and regulates the food intake on long-term. Leptin resistant people tent to gain fat and become obese really easily.
  5. Cancer cells thrive and proliferate very well with fructose as their energy source.
  6. Excess fructose also affects brain functioning, especially as it relates to appetite regulation.

I hear can hear you think, ‘Does this mean fruit is bad?’. The biggest difference between a piece of fruit and for example a can of soda is that fruit contains vitamins, minerals and other nutrients our bodies need. But that does not mean you can guiltlessly eat endless amounts of fruit. Your fructose intake will add up. Especially if you combine consuming fruits with other hidden sugary foods and drinks. Most healthy people are eating around 50 grams of fructose per day. Most fruits are half glucose and half fructose. Consuming over 100 grams sugar from fruits every day can become problematic. To have an idea how much fructose is in different kind of fruits have a look at the chart below.


                               Fruit                    Gram fructose
                 1 average mango                              30
                 1 cup blueberries                              22
                 1 Asian pear                              19
                 1 average banana                              16
                 1 wedge watermelon                              15


We know it can be so difficult to understand the world of health and nutrition especially with so many articles telling us what to believe. But it is important to try to understand what types of foods do to our bodies and make your own conclusions and decisions.

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