(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.

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