Fructose is always bad, or not?!?

Just had a brief though that I wanted to throw out there: there might be occasions where fructose is actually rather good.

I am referring to the fact that fructose is only metabolised in the liver which is generally considered a bad thing. Well, often considered a bad thing; some people like it because it means that the  glucose only enters the bloodstream very slowly (low GI). The issue though is that (a) the liver can be put under significant stress metabolising all this fructose, and (b) if its glycogen stores are full and the glucose can’t be shoved out into the bloodstream (no demand for that when sitting on a desk) then the liver makes fat from the glucose, and this fat might lead to inflammation, and fatty liver and all that.

But … (a) and (b) can be dealt with: (a) consume sugar moderately, and (b) only when your liver glycogen stores need refilling. When is this the case? Certainly at the first meal of the day (unless you are snacking on chocolate in bed through the night). So maybe a glass of orange juice at breakfast, (or at lunchtime break-fast for IF’ers) is maybe not that bad.

Some data:

  • The liver has ca 100g of glycogen storage capacity (depends quite heavily on the amount of carbs consumed)
  • Usually the brain needs ca 150g of sugar / day, which makes it 50g during 8h night
  • Juices tend to have 10g of sugar per 100ml
  • Table sugar is 50/50 glucose/fructose; grape sugar, milk sugar and maltose are 0% fructose
  •  Fructose content of fruit (juice) varies, but is is between 30-70%, with oranges being 50%

Conclusion: if you drink 200ml of orange juice (20g sugar, 10g fructose) with your Paleo bacon and egg (no bread or potatoes, of course) this might not be too bad after all. Maybe you can even afford an apple as dessert….

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