Is all sugar equally bad? If not, what makes the sugar in fruit different?
In: 1508
TL:DR: Fructose actually IS METABOLIZED DIFFERENTLY. Yes it is. Everyone saying it isnt is dead wrong.
Okay, actually people are getting it wrong here. So, I don’t feel like writing something super long but it is a little confusing so any other physiologists feel free to eli5 though so I’m sorry. I can’t sit by while people are being so misinformed though.
So without going too in depth, modern day humans can’t properly metabolize fructose. It is theorized that, as great apes, we knocked out (inhibited) the genes to make uricase (Nox4?) due to environmental pressures such as food shortages. So fructose metabolism stops at the synthesis of uric acid. The implications of high uric acid serum can cause oxidative stress that increases fat synthesis and lowers ATP production. It does more than that but I’m trying to keep the scope a little focused. It inhibits fat oxidation, upregulates fructose uptake receptors, upregulates endogenous fructose synthesis, oxidizes intracellular and mitochondrial environments via NADPH oxidase and more. There are various steps that I’m very sure are positive feedback mechanisms. All of this can be expressed as metabolic disorder, hypertriglyceridemia and non-alcoholic fatty liver disease. Fructose also has other effects like leptin resistance, a hormone responsible for satiety, and insulin resistance. There’s a lot more going on than what I mentioned and I’m pretty rusty on biochem.
Related readings:
https://pubmed.ncbi.nlm.nih.gov/31621967/
https://en.m.wikipedia.org/wiki/Fructose
https://en.m.wikipedia.org/wiki/Urate_oxidase
https://www.wikigenes.org/e/gene/e/50507.html
Latest Answers