Fructose, which is natural sugar from fruit has been reputed to be the factor responsible for gathering fatty tissue and having negative influence on our health. It is admitted, that excessive amount of fructose may cause problems connected with the metabolic syndrome, and may have negative influence on functioning the brain and memory. Does it mean we should resign from eating fruit, then?
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Fructose, when eaten in excess amount, may really have negative influence on our health, it may contribute to the development of diabetes, lead to fattening the liver, cause dyslipidaemia, increase the risk of heart diseases and cause increasing weight.
It is confirmed in many studies. For example, in the one below, it was observed, that 200g of fructose a day caused occurring the symptoms of the metabolic syndrome (increased triglycerides, lowered level of HDL, lowered insulin sensitivity).
This is how fruit gained bad fame. It happens very often that the dietetic gurus and people who are preparing to fitness competitions eliminate fruit from their diets, or they limit their intake drastically.
But remember, that fructose present naturally in fruit and all kinds of fructose or glucose-fructose syrup is a totally different group of products.
Overeating fructose in diet is mainly connected with eating processed food, rich in glucose-fructose syrup. Nowadays, you can find it almost everywhere, in yoghurt, cereal, fruit juice, ketchup, sweetened beverages, bakings, bread, and in the products you would never expect to find any source of sugar.
The main sources of fructose in diet are: glucose-fructose syrup, beet sugar, cane sugar, honey, fruit juice and, at the end, fruit and vegetables.
A typical fruit contains, on average, from 5 to 10g of fructose. It's not much. Not all the carbohydrates found in fruit come from fructose.
Below, you can find a list of popular fruit and the content of fructose in 100g.
(Product → the amount of sugar in 100g/ the amount of fructose in 100g)
grapefruit (pink) 6.2/2.9
Fructose is sugar, which builds up the liver glycogen at first. Liver has the ability of storing glycogen, but it's limited. It is estimated, that the daily dose of fructose over 50g is transformed into fatty acids.
Concerning the statement above, it is admitted that 50g of fructose is a safe dose to be consumed. Young healthy sporty people will, of course, eat more of that without any harm for their health.
Knowing that an average fruit contains from 5 to 10g of fructose, you can see, that fruit may not be the threat for you. 25g of fructose eaten from fruit is a large orange, 200g of strawberries, an average banana and kiwi.
Don't forget about the fact, that fruit is not only sugar, but also food rich in vitamins, minerals, carotenoids, flavanoids and polyphenols. Majority of fruit has low calorific density and high content of fibre and water. Thanks to that, it influences the feeling of satiety after meal.
A study done in Spain at the Navada University showed, that eating fruit influences positively the loss of body mass and health. Two groups of women were compared. Both groups used low-calorific diets, where one of them supplied 5% of energy from fruit, the other one supplied 15% from fruit. The second group maintained higher level of lean body mass. The improvement of the lipids and lowering the oxidative stress were also observed.
Of course, on the other hand, it's easy to consume 50g of fructose from processed food. Especially in a form of fruit juice and sweet sparkling beverages. Only two cans of some sweet fizzy drink supply 50g of fructose.
To sum up, fructose is not pure evil, but eaten in excessive amount, influences negatively our health. Therefore, the consumption of processed food, rich in additional sugar and glucose-fructose syrup should be limited. You don't have to be afraid of eating fresh fruit too much, as they will not cause the increase of body fat, under the condition that the negative calorific balance is sustained.