Nutrition Basics: Carbohydrates
Carbohydrates are the next macronutrient on our list. Like protein, carbohydrate provides 4kcal per gram. Carbs, as they are colloquially called, are comprised of carbon, hydrogen, and oxygen. More specifically, they are made up of CH2O, or hydrates of carbon. Carbon hydrates, carbohydrates. Pretty neat. For this reason, they are sometimes abbreviated CHO. CHO are often categorized based on their size: simple carbohydrates and complex carbohydrates. Simple carbohydrates are mono and disaccharides (saccharide is just another name for sugar) and complex carbohydrates are oligosaccharides and polysaccharides. If this sounds confusing, you can think of them as one sugar, two sugars, few sugars, and many sugars, respectively. The monosaccharides are the simplest form of carbohydrate in that they are only one unit in size. The two most important examples of monosaccharides in human diets are glucose and fructose, though galactose may also be important. The disaccharides are made up of two monosaccharides. For example, glucose and fructose makes sucrose, or table sugar. Glucose and galactose make lactose, the sugar in milk that some people have a problem digesting. This is why galactose can be important. Oligosaccharides have 3, 4, or 5 sugars linked together, and polysaccharides are more than 5 linked units. The polysaccharides that are of most interest to nutritionists are chains of glucose molecules: the polysaccharides in certain animal products and the starches in plants are all chains of glucose arranged in different ways. All these different forms of CHO provide an average of 4kcal per gram. There are slight differences, but these are not worth thinking about outside of a lab. CHO supplies most people with 50% or more of their daily calories. The Recommended Daily Allowance (RDA) for CHO is 130 grams per day for both men and women (other than during pregnancy and lactation) after the age of 1 year. Alternatively, a general recommendation is for CHO to provide 45-65% of daily calories. 130 grams × 4 kcal/gram = 520 kcal If you are following closely, you will notice that 130 grams per day recommendation and the 45-65% recommendation are incongruent. The recommendation of receiving 45-65% of your daily kcal from CHO means that you would need to eat 260 grams per day on a 2000 kcal diet. The RDA of 130 grams per day was created to meet the needs of 97-98% of the population. How much carbohydrate you should consume, however, is based largely on your activity level, the intensity of your activity, your total energy expenditure, etc.: the more activity, the higher the level of activity, and/or the more energy you expend in a day generally means there will be greater consumption of carbohydrates. Besides providing energy, carbohydrates also help the body metabolize (use) fat and it helps to spare muscle protein. So, even if your goal is fat loss, it may behoove you to include carbohydrates in your diet. If you’re trying to build or maintain muscle, it is easier while consuming adequate CHO. Besides the prefixes mono-, di-, oligo-, and poly-, there are other ways to classify carbohydrate. There’s the Glycemic Index (GI) and the Glycemic Load (GL), which will be discussed in a future post. Carbohydrates can also be split into digestible and indigestible. Fiber is carbohydrate that we cannot digest. Though it does not provide us with calories, it has an important role in maintaining and improving our health that we will also discuss in a future post.