Lots of people write about fructose. From Lustig to Sisson and just about everyone in between. Currently, I’m reading Robb Wolf’s, “The Paleo Solution“, and was quite taken by this little quote that summarizes some of the problems with our infamous little sweetener:
Fructose preferentially fills liver glycogen. That means fructose accelerates the process described above in which liver function is destroyed due to carbohydrate overfeeding. This happens directly because the liver is the only tissue that can handle fructose, but it also happens indirectly because eating fructose increases the amount of glucose the liver absorbs. Fructose up-regulates the glucose transport molecules in the liver, making the liver “hungry” for sugar. This leads to increased Palmitic Acid production, which leads to leptin resistance. Oh, yeah, since we were talking about AGEs, fructose is seven times more reactive than glucose in forming AGEs…
So let’s recap. Fructose:
- Is solely metabolized by the liver
- Preferentially fills liver glycogen
- Increases the amount of glucose the liver absorbs by up-regulating glucose transport molecules
- Increases production of Palmitic Acid (leads to leptin resistence)
- Is 7-times more reactive than glucose in forming advanced glycation end-products (AGEs) responsible for damaging a host of tissues and are a causative factor in many diseases.
- Up-regulates glucose transport molecules in the liver
When I have experimented with eating high-carb/low-fat but getting fructose to the absolute
minimum and using starch (white potatoes or white rice) for the carbs, I find I get anxious.
So, for some people like me, it may be necessary to have a small amount of fructose in order
to have enough liver glycogen. I suggest 50 grams a day.