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All About Carbs

What do sugar, fiber, glucose, saccharides, dextrose, starch, and high-fructose corn syrup have in common?  As you might have already guessed, they are all examples of carbohydrates (aka “carbs”).  A lot has been said about carbs in popular media in recent years, but in my experience most people have a poor understanding about what carbs actually are and the important role they play in one’s diet.

What are carbs?

Carbohydrates are compounds consisting of carbon and water (H20) – ie. a “hydrated carbon”.  The simplest forms of carbohydrates are called monosaccharides, which cannot be broken down to smaller carbohydrates.  Common examples of monosaccharides are glucose and fructose.  Next we have disaccharides, which contain two monosaccharides that are bound together.  Lactose and sucrose (table sugar) are two common types of disaccharides found in our diets.  Finally we have complex carbohydrates, or polysaccharides, which are long chains of monosaccharides.  Polysaccharides include starches, which we can digest, and fibre, which we can’t.

Why do we need them?

Carbohydrates are one of the body’s main sources of fuel, with fat being the other.  However, unlike fat, which human’s store in abundance, the body has relatively small reserves of carbohydrates.  That means if you completely cut-out carbs from your diet or engage in intense physical activity for an extended period of time you can actually deplete your carbohydrate stores.  Big deal, you say?  If your body has an ample supply of fat why can’t it just use that for energy instead?  The simple reason is that our bodies function better when they’re able to burn a mix of carbs and fat for energy.  When you force your body to rely exclusively on fat for energy you’re likely to experience a myriad of side effects including headaches, weakness, physical and mental fatigue, constipation or diarrhea, and bad breath.

What foods contain carbohydrates?

A common misconception is that grains and grain products are the only source of carbohydrates in people’s diets.  The truth is that carbs are found in most of the foods we eat including fruits, vegetables, dairy products (mostly in the form of lactose), legumes, nuts and seeds.

Are there good carbs and bad carbs?

From a metabolic perspective there is no such thing as a good or bad carbohydrate*.  For example, our bodies digest, store and utilize the sugar from a cookie the same way as the sugar found in an apple.  The difference between these foods isn’t the carbs but rather the fact that an apple is low calorie and contains many other vitamins, minerals and fibre, whereas cookies do not.

*Fructose may be the exception.  It is metabolized a bit differently than other monosaccharides and there is emerging evidence that diets high in fructose may lead to elevated triglyceride levels, insulin resistance, poor appetite regulation and obesity.

What about low-carb diets for weight loss?

Despite the potential for the side effects listed above, low-carb diets can work for some people provided they are low calorie.  The biggest problem with low-carb diets is that they are notoriously difficult to stick with long term and diets that are especially strict may cause deficiencies in certain nutrients.  Ultimately the goal for most people shouldn’t be to avoid carbohydrates, but instead try to limit the consumption of high calorie, carbohydrate-rich foods that are otherwise nutritionally void (ie. high-carb processed foods).


*originally published on on March 5, 2015

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