(34) Carbohydrates Part 1

Introduction to Carbohydrates

• 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.

Quality of 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

• 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.

Disaccharides

• 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.

Polysaccharides

• 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.

Types of Fiber

• 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.

Sources of Fiber

• 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.

Carbohydrate Digestion

• 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.

Lactose Intolerance

• 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.

Conclusion

• 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.