How is fructose different from glucose?

Take home message

"With few exceptions, existing studies do not support a benefit of replacing fructose with glucose. Over consumption of fructose above the daily energy requirement has adverse effects on liver fat, but no more than when other carbohydrates are over consumed.  Hence, the existing scientific literature does not justify a particular focus on fructose. . . .

It is very difficult to over eat sugar by consuming fruits. For comparison, three pieces of fruits (for example: a banana, an apple and an orange) contain about the same amount of sugar as 16 oz (500 ml) of coke. By choosing fruits you usually leave out other food items, such as a cookie or a sugar-loaded beverage. The appeal of fruits is that they also contain fiber, vitamin C, potassium, foliate and several other valuable nutrients. Because of the intrinsic brake on fruit consumption, there is no need to worry about fruits contributing to a fatty liver. Nutrition 101, Wagengenin University


What causes fructose to taste sweeter?

All three sugars contain the same 24 atoms (6 carbon, 12 hydrogen, and 6 oxygen) and have four calories per gram. 

However, the atoms are arranged in different patterns.
molecular structure fructose glucose glacatose

The patterns result in different levels of sweetness.
Fructose is twice as sweet as glucose. Galactose is barely sweet.

How are they different in the body?
Digestion glucose fructose galactose glycogen insulin

Why did some people think glucose was better than fructose?

•  Excess fructose led mice to develop fatty livers. However, not all animal studies apply to humans.

•  When manufactures increased their use of fructose, doctors diagnosed more fatty livers. However, correlation does not prove a cause and effect relationship.

Why did some people think the fructose was better?

•  Because it doesn't cause a spike in insulin.

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