What the heck are carbohydrates?

Fair warning, this is going to be long. Stop now if you don't have a few minutes to read and digest (pardon the pun) this topic.

OK so everyone talks about them, everyone has an opinion on how many we should eat and what types are “good carbs” and “bad carbs”, but very few 'non-sciency' people understand truly what carbohydrates are and how the body uses them. I’ll try and give the layman’s soup-to-nuts on carbs so that the rest of us can understand what the heck carbohydrates are, why they are important for most people, and maybe give you a leg up on all the buzz about diets and nutrition. This post won’t try to convince you one way or the other, eat how you like, it’s none of my business, but I figured I’d put this out there just so that when we talk about stuff in someone’s diet, you might have a clearer understanding of why we say what we say.
What really are carbohydrates?
Technically speaking a carbohydrate is just what the name implies, it’s a long carbon chain containing carbon atoms, hydrogen atoms, and oxygen atoms all chemically bonded together in a molecule. There are many different types of carbohydrates out there and different carbs (as I’ll call them from this point forward, just to make my typing a little easier) produce different results and have different characteristics. In essence carbs are either sugars or starches (cellulose) which means they can either be broken down by humans to use as energy or they can’t be completely broken down and used as energy. But just because a carb can’t be broken down for energy, doesn’t mean it’s useless in the body, many types of indigestible or semi-indigestible carbs are important for helping the body digest food, fiber acts as a medium to help clean up and break down other molecules in the digestive tract of humans and thus is very important to keeping us healthy, even though we can’t use it for energy, it’s important to take in a certain amount of fiber just to keep our “plumbing” working correctly. I won’t go into details, just know that without fiber, we’d have lots of issues.
The other types of carbohydrates, sugars, come in many different forms; monosaccharides like galactose, fructose, and glucose are single molecule structures that form the simplest of the carbohydrates that we can use as energy. While only glucose is used by the body, galactose and fructose can be broken down and reformed in our liver as glucose usually using chemical processes such as galactokinase and lactokinase. All sugars are broken down into glucose for energy before being used; this becomes important later when we talk about milk and fruit so store it away for later use. Polysaccharides are larger molecules made up of multiple monosaccharide groupings chemically bonded together. Sucrose (table sugar) and Lactose (milk sugar) are disaccharaides. Because the human body can use glucose as energy, polysaccharides that contain glucose are broken down in the intestines and shunted to the liver where the glucose is either siphoned off to the blood stream for immediate use, or stored as glycogen (which is just a special long chain of glucose in a water matrix) for later release. Since glycogen is big and bulky, it’s not efficient for long term storage, so the human body has found a different way to store energy for the long term….. FAT. When glucose enters the blood stream, it’s either taken up by cells that need it, or it travels around until they are corralled and stored either as cholesterol (Free fatty acids) or adipose tissue (the body fat we all know and love). That’s all I’ll say about conversion to fat as it’s a whole other topic.
So we now know that all the different types of carbs out there are all made up of the same stuff. So why the “good carb”/”bad carb” hype? Well, even though the molecules are all the same in the end, the way food is constructed drastically effect how fast or slow it is broken down. This is where fiber comes into play, fiber and cellulose to be exact. Cellulose is large polysaccharides that cannot be broken down by the body at all, and the more you have, the harder it is to extract the smaller molecules that can be used. Most organic (grown) material has cellulose in it, and the breakdown of that cellulose takes time, giving your body a chance to meter out energy in a more controlled fashion, allowing the energy to be released slowly and thus give you a constant stream of energy. Remove the cellulose and fiber, and you speed up the digestion process. Essentially, the less “other stuff” in the food, the faster it’s converted to sugar. That’s why table sugar is so bad, it isn’t what’s in it, and it’s how fast we can use it. If you dump a lot of sugar in your body, some of that will be stored as fat because essentially our bodies just don’t burn it fast enough. The more processing done to a food product, the faster it can be digested. So white flour, processed sugar, and white rice are all fast energy foods that would be good after say a 10K run, but not so good for every day two or three times a day meals. That doesn’t mean you can never eat them again, it just means that if it’s your staple, you should either eat smaller amounts with time between them, or maybe eat them far less often than you do now (if you do it often). Nobody can tell you how much is right for you, but generally to be safe most experts say try to keep your complex carbohydrates to around 80 to 90% of your carbohydrate intake if possible.
The last thing I’ll mention is why other types of sugars are (usually) not as bad for you as sucrose. Because sucrose is 50% glucose and 50% fructose, ½ of it is shuttled directly into the blood stream immediately (or converted to glycogen if necessary), the other half is transported to the liver for conversion, fructose takes much longer to enter the blood stream as glucose. Because once fructose hits the liver, it then needs to be broken down into its component atoms and reformed as glucose and if you eat enough of it and it’ll be converted to glycerol (a fat derivative) which is a component in triglycerides. It also forces the liver to work relatively hard; this can, over the long term, generate issues such as scarring and damage the liver. Thus High Fructose Corn Syrup is not so good for us. Please note that fruit, while containing large quantities of fructose, are not free of sucrose, different fruits have different ratios of fructose to sucrose, thus different fruits are better for regulating blood sugar than others (this is important to those with insulin sensitivity or diabetes). Lactose is another disaccharide that we can eat (and drink) which has to be broken down before being used. Similar to fructose, lactose is cleaved in the intestines and brought to the liver, the glucose molecules are used, and the galactose molecules (the other monosaccharide in lactose) are converted to glucose for use. Again because of the processes required to cleave the molecule it’s slower acting than sucrose. Thus in normal quantities are not as quickly converted to energy.
To conclude, the idea of good carbs vs. bad carbs is an artificial construct that we give sugars simply to identify how the body will use the food we give it. Generally, I believe the best food you can eat is food that has been processed as little as possible, when you see grains that still have the germ and husk; you’re probably choosing a “good” carb. Of course the drawback is that those extras they leave in these types of carbs spoil faster, and are heavier to transport, and don’t cook up as quickly or stick together as easily as highly processed things. So you get a society with billions of people needing to eat, and food that is sometimes thousands of miles away from them, you must make it the most transportable and quickly administering that you can. Thus processing is, in fact, quite important in some situations and shouldn't always be demonized as it is. I’d rather have a loaf of white bread than nothing.


hope this clears things up for some. Please note, to any biologists or "sciency" people out there, I've simplified some of the chemistry here to make it easy to understand, please don't debate the finer points of the chemical breakdowns the point is moot. Of course if I got something wrong (which is very possible), please feel free to point it out. I'd rather not have bad information out there and will do my best to correct any mistakes.