1mo ago

What purpose do carbohydrates OTHER than sugars serve in the body?

On every nutrition label (on the ones i've seen at least) there's a section called "Carbohydrates", and right under it is "of which sugars"

For example, this pack of chips I have lists that in 100g there's 61g of carbohydrates, of which 2.4g are sugars (speaking of which, what sugars are these, even? monosaccharides? polisaccharides? both?)

And that made me wonder - what makes up the other 58.6 grams, and what purpose do those carbohydrates serve in the body? I'll admit that I'm really inexperienced when it comes to stuff like this, so apologies in advance if this is something really obvious.

11 comments

Gonna try to give a very general ELI5 sort of answer
There's basically 3 main types of carbohydrates
Simple carbs- basically sugars (mono- and di-saccharides)
Complex carbs- starches, whole grains, etc. (polysaccharides)
Fiber- arguably these are just really complex carbs that your body can't really break down
In general, sugars are the source of energy your body actually runs on, especially glucose. Everything else basically gets broken down into glucose.
Your body can pretty much use simple sugars as-is or can easily break them down into a form it can use. There's some variation just how quick and easy it is for your body to use different sugars, but in general your body will start to feel the effects of eating sugar in the space of a few minutes, and the effects will peak within about an hour or two.
Complex carbs take a little more digesting to break down into a form your body can make use of. They're basically being turned into simpler sugars, but that process takes a while. You might hear about athletes carbo-loading with a big spaghetti dinner or something the night before a big competition. The idea there is that the energy from that big, complex carb-heavy dinner won't really hit them for a few hours or even until the next day, and it will keep providing that energy for a longer period of time.
Fiber is, for the most part, indigestible, your body can't really break it down into simpler sugars that it can make use of. It goes in your mouth, through your digestive tract, and out the other end relatively unchanged. That doesn't mean it's useless though, it still plays an important role in digestion. It takes up space in your stomach helping you feel more full. It absorbs water and helps keep your stool soft and helps waste move through your intestines, and it minds to things like bile acids and cholesterol so that they can be passed as waste.
Again, this is meant to be a very general answer, there's a lot of details I'm glossing over both just to keep things simple, and because I'm not a doctor or anything of the sort and I'm not 100% sure myself.
- Fiber is, for the most part, indigestible, your body can’t really break it down into simpler sugars that it can make use of.
  And just for clarity, just because humans can't break those down doesn't mean the entire animal kingdom can't. So its fiber to us, but usable carbs for lots of other creatures.
  
  True, I did think about mentioning that but decided to skip over it to keep things simple.
  Animals like cows for example, can get by almost entirely on fiber. Stuff like grass doesn't have much in the way of carbs we can use, but it contains a ton of fiber, and cows digestive systems are set up to actually do something with them.
  The extra "stomachs" they have allow for some extra fermentation and such to happen so they can break down that fiber into simpler carbs.
- To perhaps lean more into why complex carbs are useful:
  Your body can't really not digest something you've eaten. Once it's in your stomach, it will be broken down and gets put into your blood. With the simple carbs, you get a lot of blood sugar very quickly and your body then has to deal with that. It does so by producing insulin, which tells the rest of your body to take sugar out of the blood. It's put into either a limited, temporary storage (glycogen) or, once that's full, into more permanent storage (body fat).
  Eating lots of sugar can also lead to your body producing too much insulin, which will cause too much sugar to be taken out of the blood, so you often have a high and then a crash/low after ingesting sugary foods.
  Ideally, you want blood sugar to always stay at a reasonable level, where it can supply your brain and muscles, but where your body does not have to start storing lots of it. And that's where complex carbs are neat, because they don't get broken down all at once, when they're in your stomach/intestines, meaning their sugar enters your blood at a more sustainable rate. By eating them instead of sugar, you're less likely to put on fat and less likely to have a crash.

For the info on why there are different descriptions of carbs: https://www.fda.gov/food/nutrition-facts-label/how-understand-and-use-nutrition-facts-label
What are Added Sugars and How are they Different from Total Sugars?
Total Sugars on the Nutrition Facts label includes sugars naturally present in many nutritious foods and beverages, such as sugar in milk and fruit as well as any added sugars that may be present in the product. No Daily Reference Value has been established for total sugars because no recommendation has been made for the total amount to eat in a day.
Added Sugars on the Nutrition Facts label include sugars that are added during the processing of foods (such as sucrose or dextrose), foods packaged as sweeteners (such as table sugar), sugars from syrups and honey, and sugars from concentrated fruit or vegetable juices. Diets high in calories from added sugars can make it difficult to meet daily recommended levels of important nutrients while staying within calorie limits.
Note: Having the word “includes” before Added Sugars on the label indicates that Added Sugars are included in the number of grams of Total Sugars in the product.
For example, a container of yogurt with added sweeteners, might list: Total Sugars on Sample Label
This means that the product has 7 grams of Added Sugars and 8 grams of naturally occurring sugars – for a total of 15 grams of sugar.
As to what various carbohydrates do? That's a biochemistry semester, mate, but a quick look can be had here: https://rimgo.vern.cc/0EQF3.jpg
with a simplified version here: https://i.pinimg.com/originals/55/8f/f3/558ff3406b063c99f1868ef903217be9.jpg
Here's a medium complexity: https://redlib.nadeko.net/img/yepntxvf89t71.jpg
If I'm going to give you a short, two sentence summary? Most organic molecules in the body can be broken down to a two carbon molecule attached to a coenzyme that we call acetyl CoA, and that can be used to build most products in the body when combined with other substances like nitrogen and sulfur. Carbohydrates typically go down one of three paths, either 1.) broken down to pyruvate before entering the Kreb cycle, where we produce most of our energy, 2.) broken down to pyruvate and then switched over to acetyl CoA and used to build lipids (fats), typically as a triglyceride, or 3.) shunted through the pentose pathway and used for various purposes, including killing pathogens and building/modifying nucleic acids.

Complex carbohydates
https://www.ncbi.nlm.nih.gov/books/NBK459280/

There is no difference between carbs as sugar and carbs. They all end up in the blood stream as glucose.
Fructose is really bad and usually doesn't get converted to glucose.
Fiber is not absorbed by the body and just passes through.
Carbohydrates are not essential for human life. You can be perfectly healthy without eating them. The body does use glucose for blood cells and about 15% of brain metabolism, but that can be created by the liver on a as needed basis.
There are people who differentiate carbohydrates based on how quickly they arrive in the blood stream as glucose, in my view that's a unnecessary distinction. Elevated blood glucose is really dangerous for the body, regardless of how delayed it is. That's why the body prioritizes burning the glucose off first when it's elevated in the body.
What function does elevated glucose have? (I.e. why eat carbohydrates)
increase blood sugar for hypoglycemia
raise insulin levels
some athletes believe it helps their performance
The sports term is carb loading, and for non-fat adapted athletes it does help their endurance, prevents bonking. But for fat adapter athletes who don't eat carbs, it's unnecessary as they don't bonk. The blood only carries 5g of glucose, and when you use it all up you can bonk, the body does not store glucose at all.. the body stores fat. So people who burn fat don't bonk because they don't run out of energy
What benefit does fiber have?
reduces transit time of all food
reduces absorption of other food
can be converted into short chain fatty acids in the intestines
Obviously, reducing the nutrition from the food you eat is only a "good" thing if your diet is unhealthy.
The SCFA's are interesting, you can eat fiber and have some of it turn into fat by bacteria, or you can just eat fat directly and skip the middle man. This is the whole "fiber feeds the gut" argument you hear, gut research is still early stages. Its not clear what the ideal biome is, but whatever you eat will determine what lives in the gut. The bacteria will adapt to your diet and stabilize in about 9 months.
Some people believe fiber helps with constipation because of the reduced transit time, that isn't actually true. Fiber is actual causal of constipation (in one RCT, the only fiber RCT that exists...)

I assume these other answers are correct because I don't understand them at all.
I've always been told that carbs are full of energy (the keep your body moving kind), which is great if you need to use it, but if you don't, it just makes you fat.
- If energy in is greater than energy out, over time the extra is stored as fat. It doesn't really matter what form that energy takes. You can get fat from eating too many carbs, fats, or proteins.
  
  Right. I meant that there is more energy per gram in carbs, not that it's the only way to get fat.

The brain runs on carbs.
Which definitely explains some people.

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