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  • Writer's pictureCecilia Rockford

All you ever wanted to know about fructose

Updated: Mar 20, 2021

One of the most popular question in the comments. Briefly: there is a popular thought that fructose is a “bad” carb, which goes directly into the body fat. This idea seemed always strange for me, cause only fat transforms directly into the body fat - it’s the aim of fat. 

But to say sth more concrete, I was forced to look through tons of researches. It turns out this question is relevant for everyone. Healthy lifestyle tries to declare that even fruits are unhealthy - every single gram of body fat is dreadful for people.

What have I found?  «Effects of glucose or fructose feeding on glycogen repletion in muscle and liver after exercise or fasting» - fructose renews the supply of glycogen in the liver. In this research, the effect of glucose and fructose on glycogen renewal after physical training were compared. 

According to the protocol, there was 90-minutes training and then consuming glucose/fructose. Results - glucose was better for the muscle glycogen renewal, while fructose shows better results in liver glycogen regeneration.

But we are frightened of fructose for other reasons, right? We think that the metabolism of fructose is ended by the lipid cells and the phrase “gained weight after 1 apple” makes us panic. Let’s investigate the metabolism of fructose.

Buy the way, all the data below can be found in the  «Health implications of fructose consumption: A review of recent data» article. It is obvious that fructose overcomes the glycolysis phase much faster than glucose. Yes, the part of fructose metabolism is the synthesis of fatty acids. But in real life, everything is easier than in healthy blogs. 

Fructose in the body transforms into 1,3-Bisphosphoglyceric acid. Part of 1,3-Bisphosphoglyceric acid transforms into pyruvic acid and acidates to the CO2 and H2O. The other part forms lactate. The main part of  1,3-Bisphosphoglyceric acid transforms into glucose and glycogen. And only a small part of received fructose forms fatty acids. One tiny part. It is nothing. Because it’s widely known that approximately 25% of body energy is taken out of fatty acids.

Pyruvic acid is a popular BAD, by the was. Thus,  «An apple a day keeps the doctor away» is always actual!

And a bit about fructose and obesity. Direct quote from the research:

Fructose can correlate with obesity, but it’s not its reason. Obese people receive too many calories, including carbs, fats and proteins. It’s obvious that for most people obesity correlates with high-calorie proficit. Focus on excluding 1 element from the diet won’t solve the problem.

Regardless of the obesity reason  Centre of Food Nutrition and Agriculture Policy states that fructose itself doesn’t cause obesity.

Thus, relax. Take it easy.

And math for brains. For instance, you’ve eaten 1kg of bananas. 1 banana have 4,7% of glucose, 8,6% of fructose and  13,7% sucrose. 1 banana = 21,8 gr of carbs per 100gr, which gave use 218gr of carbs per kilo and 18.7gr of fructose. I can’t count how much fatty acids we’ll receive from eat, thus, let’s assume that 5gr of fatty acids because the main part of fructose will transform into the glucose. 1 kilo of bananas - 950kcal, fatty acids are almost absent. The main problem with the fructose are not fruits, but sweet soda - the fructose there is uncountable. 

The problem is not in fructose - it’s in calories. Eat fruits to be happy!

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