Posted May 7, 2011
Carbohydrates are something you hear about constantly as an American. There are simple carbohydrates and complex carbohydrates, where complex carbohydrates are supposed to be better for your health than simple. There are low-carb diets like the Atkins Diet or the Dukan Diet that are supposed to help you lose lots of weight. Then there are more esoteric things like the glycemic index of foods, and this has to do with carbohydrates as well. Let’s take a look at how carbohydrates work and why you should care about them.
You have probably heard of things like glucose and fructose. These are the simplest carbohydrates. They are molecules containing six carbon atoms, six oxygen atoms and 12 hydrogen atoms. And this is where the name carbohydrate comes from – “carbo” represents the carbon atoms, while the oxygen and hydrogen atoms represent water, or “hydrates”.
Plants make carbohydrates from sunlight and animals eat the plants. Pure glucose or pure fructose, being the simplest carbohydrates, can be immediately absorbed by the small intestine into the blood stream. Table sugar, or sucrose, is a disaccharide – one glucose and one fructose molecule bonded together. An enzyme in your small intestine can break the pair apart and then they can be immediately absorbed.
A starch, like the starch found in wheat or potatoes or rice, is a longer chain of glucose molecules connected together. Your body has enzymes that can break apart the chain into individual glucose molecules for absorption. Starch molecules are known as complex carbohydrates, and this is where the idea of the glycemic index comes from. In general, things like glucose and table sugar come into your body and enter the blood stream very quickly. They have a high glycemic index and cause a spike in the amount of glucose in your bloodstream. White bread, because the wheat is so highly processed, also has a high glycemic index. Whole grains, beans, nuts and vegetables do contain carbohydrates, but these carbohydrate chains take much longer to break down. So the glucose from these foods enters the bloodstream much more slowly and evenly. These foods have a low glycemic index and are therefor much healthier.
Many diets are low-carb diets. They ask you to restrict the carbohydrates you eat. Why? Keep in mind what a “typical American diet” looks like. A bowl of cereal, a slice of pizza, a can of ravioli, a bottle of soda, a bag of potato chips, a package of cookies, a bowl of ice cream … these are common foods in the typical American diet. These foods typically contain something like 40 to 50 grams of carbs per serving. Therefore, a typical American eating a typical American diet can easily consume 300+ grams of carbs per day without even thinking about it. A lunch consisting of two slices of pizza, a chocolate chip cookie and a big soda – that is 200 grams of carbs right there. The surge of glucose that a meal like this pumps into the bloodstream requires your body to use a lot of insulin to handle the spike. Over the years, the spikes can cause Type 2 diabetes. In addition, a meal like that contains a lot of calories, leading to obesity over time.
A low-carb diet restricts your carbohydrate intake – say 50 grams of carbs per day rather than 300. This restriction can decrease the spikes in blood sugar, which tends to lower hunger pangs and reduce the calories you consume per day.
Will a low-carb diet hurt you? For example, you may know that your brain and nervous system require glucose. If you take in no carbohydrates, will your brain die? No. Your body, when necessary, can manufacture its own carbohydrates in your liver through a process called gluconeogenesis. This process is important if, say, you are lost in a forest with no food for three days, or if you are fasting for some reason, or if you get so sick that you cannot eat, or if you are living in an extremely cold climate and meat is your only source of food. Glucose is essential, so your body is able to supply glucose even if you have no carbohydrates coming in through your food.
The whole thing is fascinating really. Carbohydrates are one source of food energy, but there are all these different aspects to it and carb consumption can have a huge impact on your overall health. The more you learn about carbohydrates, the more interesting it gets.
(Looking for more? For extra info on this or the scoop on other fascinating topics, go to HowStuffWorks.com. Contact Marshall Brain, founder of HowStuffWorks, at marshall.brain@howstuffworks.com.)
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