A Review of Carbohydrates
Content by: Erin (Nugent) Bern, RD
A deeper look into the function of carbohydrates. Carbohydrates are the primary fuel source for all cells, and are necessary to fuel the central nervous system. Consuming fiber rich carbohydrates helps to maintain a healthy GI tract.
❋ Carbohydrate family includes sugar, starch, fiber
❋ Primary fuel source for cells
❋ Provide 4 kcal/g
❋ Plants are the main source of carbohydrates: plants produce glucose during photosynthesis
❋ Plants store glucose in the form of polysaccharides as starches - therefore the best sources of dietary starches are in plant based foods (grains, legumes, and tubers)
🥔 What is starch?
Complex carbohydrates made of multiple molecules of glucose attached together in a form that the body can digest
🥑 What is fiber?
Complex carbohydrates found in plant based foods, made up of polysaccharides that cannot be broken down in the digestive process
Carbohydrates in Foods
🔶Many starchy foods also contain significant amounts of dietary fiber
🔶Much of the fiber in whole grains is found in the outer layers - when processed these layers are removed, thus reducing the fiber content
🔶Glucose - the most abundant monosaccharide. Most of the glucose we eat is linked together with additional sugars to form disaccharides or polysaccharides
🔶Fructose can be found in fruits, vegetables, honey, and high fructose corn syrup
🔶Galactose, most commonly consumed in combination with glucose to form lactose - Which is found in milk and dairy products.
🔶There are 2 broad categories of sweeteners that can be used and occur naturally in foods
🔸Nutritive sweeteners: can be metabolized and provide energy
🔸Non-nutritive sweeteners: provide no food energy
🔶On average, an adult requires ~130g/day of carbohydrates to provide adequate glucose as fuel for the brain and central nervous system
🔶Despite differing opinions between health professionals on the recommended daily amount of carbohydrates needed for optimal health outcomes, it is universally agreed on that carbohydrates should largely be consumed in the form of fiber rich fruits, vegetables, and whole grains. And to limit the amount of added sugars and caloric sweeteners.
🔶The Dietary Guidelines for Americans 2020-2025 recommends limiting added sugar to no more than 10% of daily calorie intake.
Functions of Carbohydrates
🔶Most of the digestible carbohydrates in our diets are broken down into glucose.
🔶Main function of glucose is to fuel the body’s cells, primarily the red blood cells and central nervous system
🔶When inadequate carbohydrates are consumed to produce glucose - the body is forced to break down amino acids in the muscle tissue and organs to make glucose
🔶Indigestible carbohydrates, or fiber, contribute to maintaining the integrity of the GI tract and overall health
🔶Fiber helps to prevent constipation and diverticular disease, and research indicates a connection between increased fiber intake and a decreased risk for colon cancer.
🔸Although some researchers dispute the connection with a decreased cancer risk and fiber itself. And connect this decreased risk with other nutrients commonly associated with high fiber foods: such as the vitamins, minerals and phytochemicals in fruits & vegetables.
🔶A high fiber diet promotes weight management and reduces the risk of obesity: high fiber foods add bulk to a diet while yielding a low amount of energy, they also absorb water and expand in the GI tract - aiding in the sense of fullness and satiety.
🔶Soluble fiber slows glucose absorption from the small intestine - contributing to better blood glucose regulation
🔶Glycemic index is a tool used by researchers to classify the glucose response to various foods. It is defined as the blood glucose response of a given food compared with a standard (typically glucose itself)
🔶Glycemic load better reflects a food’s effect on blood glucose than the glycemic index alone
🔸To calculate glycemic load: take g of CHO in a serving of food multiplied by the glycemic index then divided by 100
🔸This shows that although some foods may have a high glycemic index, the load calculation shows that the impact on blood sugar is not always equally high