Is all sugar equally bad? If not, what makes the sugar in fruit different?
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Fructose specifically is bad for you given its metabolic pathways. [See this article](https://www.nih.gov/news-events/nih-research-matters/how-high-fructose-intake-may-trigger-fatty-liver-disease)
There is a misconception that sugar is one thing.
Sugar is actually a bit of a catch all term for a range of related chemicals that are forms of stored energy. These are generally falling into two categories: monosaccarides (single molecule sugars) and polysaccharides (complex molecule sugars)
Glucose is the simplest molecule that falls under the sugar umbrella. It is the simplest form of sugar, and it’s the preferred form of energy at the cellular level. In nature, glucose is very abundant as a product of photosynthesis, but is also commonly converted to more complex sugars for storage or other cellular functions.
Other common forms of simple sugars in nature are molecules like fructose or galactose, which are easily digestible.
After the simple sugars there are more complex sugars. Things like sucrose (a combination of 1 glucose and 1 fructose molecule) and lactose (1 glucose and 1 galactose) are simple disaccarides, as they are formed from a combination of two simple sugars. These are denser in energy than simple sugars whe still being easily broken down into their components for a quick energy release during digestion.
White table sugar is generally refined sucrose, and lactose is primarily found in milk.
After these you get into larger more complex sugars known as polysaccharides. These are often combinations of simpler sugars used primarily for storage, which are broken down as part of digestion at a slower rate. These include things like glycogen (a long chain of glucose molecules) and starch which are digestible; or cellulose and chitin which are used for structural purposes.
There are also forms of sugar that may taste sweet but are not easily digestible for humans.
So not all sugars are equal.
In the case of fruit, they are often high in fructose due to selective breeding. This high level of easily digestible sugar means that you get a rush of sugar in your bloodstream that can give you a short burst of energy, but if you don’t need it those sugars are often converted to more complex sugars or fats for later storage.
Fructose (and ofc also HFCS) was recently highlighted for being responsible for gut expansion and engorgement of villi in the intestinal tract.
https://news.weill.cornell.edu/news/2021/08/research-uncovers-how-fructose-in-the-diet-contributes-to-obesity
It has also been linked to reduced dopamine signaling leading to greater ease of metabolic disorders and overeating/food addictions.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5747444/
Ugh, I can’t be mad at people for being misinformed but please see my other comment. Fructose IS METABOLIZED DIFFERENTLY. This thread is making me pull my hair out.
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
Some sugars are worse than other and how you eat/drink the sugars matters too. The sugar in a can of cola is worse than the sugar in a potato.
Each type of sugar is processed in a different way in the body. These differences cause some sugars to be healthier than others.
This thread is an absolute disaster of misinformation.
Different sugars affect our body in different ways. Some of them contain fructose – and this includes fruit – which is metabolized by your liver, and is an endocrine (hormone) disruptor. It can supress the feeling that you’re full thus make you still feel hungry and contribute to over-eating.
Fruit contains fructose, but there are good things in whole fruit that make it worth eating. It’s worth noting, however, that the fruit you buy at the supermarket today has been altered over decades of selective breeding (even if organic) to contain more sugar and less fiber, meaning the cost/benefit isn’t so simple. Things like grapes cause a big insulin spike. Look at what a banana used to be. The fruit we eat today is nothing like the fruit we used to eat.
High-fructose corn syrup is not good for you, but it’s only 5% more fructose than the sugar in fruit. Drinking orange juice is just as bad for you as drinking Coke or Pepsi when it comes to your metabolism (orange juice at least has vitamins in it)
Also worth noting is emerging research around artificial sweeners that is suggesting that if you consume them at the same time as other food, you can still experience insulin spikes in your body because of the complexity of how our guts and brains work.
See: https://www.nakoo.net/social/videos/video/70-fat-chance-fructose-2-0
All forms of sugar are processed by your body differently
Fructose is by far the worst of the sugars but it’s also really cheap and it’s natural form is more of a syrup. Sucrose is a glucose and fructose bound and has a lower sweet taste then fructose and is more expensive. Natural cane sugar is probably the best kind for you as it has other compounds present but it also adds taste.
One thing to remember though is the end products , glucose is the basic sugar your body uses for everything so your body is capable of using it directly. Fructose however can’t be easily used directly so it generally is turned into fat but if your body needs carbohydrates it “will” use fructose but in general most organisms are glucophilic.
Lastly the biggest problem sugars are the ones people don’t realize they are eating, it takes a lot of carbohydrates to make you sick over a long period of time and our diets do need some , the problem is if you mix sugary drinks + carb rich foods + lack of exercise it’s just a terrible spiralling problem for your health. Some of the biggest foods to look out for (that are not inherently sweet or meant to be desserts ) are rice (which triggers a bigger insulin spike then pure white sugar), pasta and noodles , breads , super starchy potatoes.
I won’t touch on 5 unit sugars as our bodies process those in even more fancy ways but those usually are pretty simple
Sugar isn’t bad.
Too much sugar is bad.
Too much sugar without fiber to go with it (e.g. fruit) is worse.
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