Carbohydrates include starches, sugars, and fibers.
Foods primarily made of carbohydrates are mainly from the plant kingdom: vegetables, fruits, grains, beans, peas, and legumes.
These foods contain small amounts of protein and fat as well.
Recent trends in low-carb diets have caused carbohydrates to receive a bad reputation.
Ideally, carbohydrates should make up around 60% or more of a balanced diet with emphasis on whole food carbohydrates.
Many diets currently contain poor-quality carbohydrates, high in sugar and processed grains.
Focus should be on consuming whole food carbohydrates like vegetables, fruits, whole grains, and legumes.
Monosaccharides: single sugar molecules.
Glucose: primary energy source for the body and brain.
Fructose: sugar found in fruits; sweetest sugar.
Galactose: component of other sugars; less common in foods.
Composed of two monosaccharides:
Maltose: two glucose units; related to starch breakdown.
Sucrose: glucose + fructose; table sugar.
Lactose: galactose + glucose; milk sugar.
Formation: Via condensation reaction (water is released).
Breakdown: Hydrolysis requires water to separate disaccharides into monosaccharides.
Composed of long chains of glucose linked by glycosidic bonds.
Types of polysaccharides include:
Glycogen: storage form of glucose in animals; stored primarily in liver and muscles.
Starch: plant energy storage.
Fiber: structural component of plants.
Recommended fiber intake: about 28 grams per day; Average American consumes around 15 grams.
Two main types:
Soluble Fiber:
Fermentable, helps maintain gut microbiome.
Lowers blood cholesterol and slows glucose absorption.
Holds moisture in stools and increases feeling of fullness.
Insoluble Fiber:
Less fermentable, does not dissolve in water.
Increases fecal weight and speeds up passage through the colon.
Helps alleviate constipation and lowers the risk of certain diseases.
High fiber foods include grains, vegetables, fruits, and legumes.
Recommendations: Consume six to eight servings of vegetables and two to four servings of fruit daily.
Legumes (beans, peas, lentils) are excellent sources of fiber and protein.
Digestion begins in the mouth with amylase breaking down starches.
Stomach provides some bulk but limited digestion occurs here.
Small intestine is the primary site for starch breakdown:
Enzymes for each disaccharide break them into monosaccharides.
Fiber slows absorption and helps nutrient absorption through slower transit.
Monosaccharides are absorbed into capillaries of intestinal villi and transported to the liver via the portal vein.
Excess glucose is converted to glycogen or fat for storage.
Common health issue; approximately 75% experience some form.
Symptoms include gas, bloating, cramping, diarrhea, and constipation.
Often goes undiagnosed due to mild symptoms.
Characterized by a genetic component and varies by ethnicity.
Treatment usually involves reducing or eliminating dairy products from the diet.
Understanding carbohydrates is essential for health and nutrition.
Emphasizing whole food, plant-based sources can improve dietary fiber intake and overall health.
Next part of carbohydrate lectures will continue to explore the topic.