Understanding Dietary Sugars
by Professor Jay
In a mind boggling process, plants make sugars. They capture the light energy from the sun (which is 92,955,807 miles away from us) and then add that energy to carbon dioxide (which we exhale) and make sugar. Wow! We then eat that sugar, use the energy that it contains, and then exhale it back as carbon dioxide. Oh, and if that’s not enough, a waste product that plants get rid of during their whole sugar making process is oxygen; which we just happen to need in order to make use of the energy in the sugars that we eat. Yes, that is why we need oxygen. Somehow I missed this in high school biology, as it took studying it as a biology major in college before I really appreciated the craziness of it all.
Sugars are classified as a carbohydrate. There are 3 classes of carbohydrates that we get in our diets. They are sugar, starch, andfiber. Let’s explore sugars.
On a food label you will see the amount of sugars listed in grams. 1 gram of sugar provides 4 Calories. A Calorie is a unit of energy. There are several different kinds of dietary sugars. The most common are glucose, sucrose, lactose, and fructose. Let’s spend some time with each of these.
Glucose is the most common sugar in nature. Fiber and starch are both made of glucose. When someone talks about blood sugar they are referring to glucose. Glucose is the sugar that floats around in your blood. The hormone insulin then allows glucose to enter your muscle and fat cells. This is why a person with diabetes type 1, who doesn’t produce insulin, will have high blood glucose levels; that is, because the glucose cannot enter into the cells and therefore remains in the blood.
Glucose is not a very sweet sugar. It is fructose that stimulates our sweet taste buds the best. Adding fructose to any food will satisfy even the most demanding sweet tooth. Sucrose is table sugar. Sucrose is made from 1 glucose linked to 1 fructose. Because sucrose contains a fructose, it is sweet. Sucrose and fructose are natural sweeteners. They are what make fruits and certain vegetables sweet. Interestingly enough, a recent study has shown that higher concentrations of fructose (i.e. high fructose corn syrup) can contribute more to obesity than sucrose. Therefore, a goal in achieving family weight loss should be to decrease the household intake of high fructose corn syrup.
Lactose is a milk sugar. It is made of 1 glucose linked to 1 galactose. In the small intestine there is an enzyme called lactase that breaks lactose into glucose and galactose. Glucose and galactose are then absorbed into the blood. Some people do not produce the enzyme lactase and therefore cannot break down lactose. Since the lactose is not broken down it cannot be absorbed, and therefore moves through the small intestine to the large intestine. Bacteria in the large intestine then feed on the lactose, and unfortunately produce by-products, such as gases, that upset the person’s GI tract. This is what causes the symptoms of lactose intolerance.
Hopefully this gives you some insight to different kinds of dietary sugars.
Read about Fiber – The Miracle Substance
Read about Starch – What is Starch?