Carbohydrates and your body
First of all, what are carbohydrates and where do we get them from? The term carbohydrate literally means “hydrated carbon.” As you may know, water is made of hydrogen and oxygen, and when something is said to be hydrated, it contains water. Thus, the chemical abbreviation for carbohydrate (CHO) indicates the atoms it contains: carbon, hydrogen and oxygen.
We get carbohydrates efficiently from plant foods, such as fruits, vegetables, and grains. Plants produce the most abundant form of carbohydrate, called glucose, through a process called photosynthesis. During photosynthesis, the green pigment in plants, called chlorophyll, absorbs sunlight, which provides the energy needed to fuel the manufacture of glucose. Plants continually store glucose and use it to support their own growth. Then, when we eat plant foods, our body digests, absorbs, and uses the stored glucose.
Carbohydrates can be classified as simple or complex. Simple carbohydrates contain one or two molecules, while complex carbohydrates contain hundreds or thousands of molecules. Let’s break this down a bit. Simple carbohydrates are commonly known as sugars. Glucose, fructose, and galactose are the three most common sugars in our diet. Most Canadians eat too many simple carbohydrates. Data from the 2004 Canadian Community Survey (CCHS v.2) show that, on average, Canadian adults get half of their energy (50.1%) from carbohydrates and children get 55.4% of your energy from carbohydrates. Both values are well within the recommended range. On average, 31.8% of men 19 years and older and 21.5% of women 19 years and older had less than 45% of their total energy from carbohydrates. Simple sugars account for approximately 21% of carbohydrate calories (Statistics Canada, 2011). Where does this sugar come from? Some of the sugar comes from healthy food sources, such as fruit and milk. However, much of our sugar intake comes from added sugars. added sugars they include white sugar, brown sugar, honey, maple syrup, and corn sweeteners that are added to foods during processing or preparation (Canadian Sugar Institute, 2006). A common source of added sugar is regular soft drinks; Canadians drink an average of 72 liters per person per year (Statistics Canada, 2009)
Complex carbohydrates, on the other hand, consist of long chains of glucose molecules called polysaccharides. They include starch, glycogen, and most fibers. Starch includes grains (wheat, rice, corn, oats, and barley), vegetables (peas, beans, and lentils), and root vegetables (potatoes and sweet potatoes). Glycogen is the storage form of glucose for animals, including humans. And finally the fiber, which could walk all day, is the indigestible part of plants. Sources include whole grains, vegetables, fruits, nuts, and legumes. Most North Americans eat very few of these complex carbohydrates. Many people eat a lot of breads, pastas, and cereals, but most don’t consistently choose whole grains.
Why do we need carbohydrates?
Carbohydrates are an excellent source of energy for all our cells, and provide 17 KJ (4 calories) of energy per gram. Some of our cells can also use fat and even protein for energy if needed. However, our red blood cells can only use glucose, and our brain and other nerve tissues rely mainly on glucose. This is the reason why we get tired, irritated and shaky when we haven’t eaten any carbohydrates for a long period of time.
Carbohydrate fuel exercise. When we exercise, whether it’s running, walking, biking, or doing any other activity that makes us breathe harder and sweat, we begin to use more glucose than fat. While the breakdown of fats is a slow process and requires oxygen, we can break down glucose very quickly with or without oxygen.
How many carbohydrates should we eat?
The recommended daily amount of carbohydrates is based on the amount of glucose used by the brain (Institute of Medicine, 2002). The current RDA for adults age 19 and older is 130 grams of carbohydrates per day. It is important to emphasize that this RDA does not cover the amount needed to support daily activities; it covers only the amount of carbohydrate needed to supply adequate glucose to the brain. About 45-65% of total energy intake should come from carbohydrates, with added sugars providing 25% or less of total energy intake. Most health experts agree that most of the carbohydrates you eat every day should be complex carbohydrates, or whole and unprocessed. Keep in mind that fruits are made up mostly of simple sugar and contain little to no starch. However, they are healthy food choices, as they are good sources of vitamins, some minerals, and fiber, especially if the skins are eaten.
Resources
1.) International Food Information Council (IFIC) Foundation http://www.ific.org
2.) Nutrition: A Functional Approach – Janice Thompson, Melinda Manore, Judy Sheeshka