Understanding Carbohydrates: Nutrition Basics

Introduction to Human Nutrition

• Human nutrition is the study of how the human body uses nutrients from food.
• Carbohydrates, proteins, and fats are essential nutrients.

Macronutrients - Carbohydrates

• Carbohydrates are a major source of energy for the body.
• Human body cells require energy to function.
• Humans consume carbohydrates to produce glucose, used for energy.
• Carbohydrates are also converted to glycogen to store energy.
• Carbohydrates are composed of carbon, oxygen, and hydrogen.

Macronutrients - Carbohydrates - Classification

• Carbohydrates are categorized as simple and complex.
• Simple carbohydrates include monosaccharides and disaccharides (e.g., sugars).
• Complex carbohydrates include polysaccharides (e.g., starch and fiber).

Carbohydrate Types

• Monosaccharides: Single sugar units
  • Glucose: important energy source; also known as blood sugar or dextrose.
  • Fructose: the sweetest of sugars; found naturally in fruits and honey.
  • Galactose: found in lactose (milk sugar).
• Disaccharides: Two sugar units linked together
  • Sucrose: table sugar; composed of glucose and fructose.
  • Lactose: milk sugar; composed of glucose and galactose.
  • Maltose: composed of two glucose units; product of starch digestion.
• Polysaccharides: Many sugar units linked together
  • Starch: storage form of glucose in plants; a major source of carbohydrates in human diets.
  • Glycogen: storage form of glucose in animals; found in liver and muscles.
  • Dietary fiber: structural part of plants; provides no energy.

Monosaccharides

• The most important monosaccharides in nutrition are hexoses.
• Monosaccharides are the simplest form of carbohydrates that cannot be broken down into smaller units.
• The three monosaccharides, glucose, fructose, and galactose, all have the same number and kinds of atoms (C6H12O6), but arrange them differently, this is important for their different functions and properties.
• Glucose has a mildly sweet taste.
• Galactose has a hardly sweet taste.
• Fructose has a very sweet taste.

Glucose

• The fundamental sugar in human metabolism.
• Primary fuel for cells.
• Often derived from the digestion of starch.
• Also known as blood sugar or dextrose.
• A component of many disaccharides and polysaccharides.

Fructose

• The sweetest of the sugars.
• Has the same chemical formula as glucose, but with a different structure.
• Naturally present in fruits and honey.
• The amount of fructose in fruits depends on the degree of ripeness.

Galactose

• Found naturally occurring as a single sugar in few foods.
• Has the same number and kind of atoms as glucose and fructose, in a different arrangement.
• Usually part of the disaccharide lactose (milk sugar).
• Milk is the primary food source of galactose.

Disaccharides

• Disaccharides are pairs of monosaccharides linked together.
• The pair can be glucose and fructose (sucrose), glucose and galactose (lactose), or two glucose units (maltose).
• Disaccharides are broken down in the process of hydrolysis, liberating monosaccharides.

Sucrose

• Common table sugar.
• Found naturally in fruits, vegetables, and grains.
• Made commercially from sugar cane or sugar beets.

Lactose

• Milk sugar, found predominantly in milk and milk products.
• Composed of glucose and galactose, linked together.

Maltose

• Product of starch breakdown.
• Composed of two glucose units.
• Found in small amounts in some foods.
• Often produced during the fermentation of grains.

Polysaccharides

• Composed of many single sugar units linked together
• Starch, glycogen, and dietary fiber are the main polysaccharides in human nutrition.

Starch

• A storage form of glucose in plants.
• Found in grains, legumes, and tubers.
• Broken down into glucose which is absorbed by the body.
• Has long chains of glucose molecules. This can be branched or unbranched.
• The longer chains, and more branched structures, mean starch breaks down more slowly than simpler sugars. This enables a sustained energy release.
• Starch is insoluble.
• Cooking converts insoluble starches to soluble, making it easier for the body digest.

Glycogen

• Storage form of glucose in animals (including humans).
• Found primarily in the liver and muscles.
• Highly branched structure, which enables rapid hydrolysis when the body needs glucose quickly..

Dietary Fiber

• Structural part of plants, found in vegetables, fruits, whole grains, and legumes.
• Cannot be broken down by human digestive enzymes.
• Passes through the digestive system, providing no energy.
• Two main types: Soluble and Insoluble.

Soluble Fiber

• Dissolves in water, forming a gel-like substance.
• Often associated with lowering blood cholesterol and glucose levels.
• Found in oats, barley, legumes, and some fruits/vegetables.

Insoluble Fiber

• Does not dissolve in water.
• Promotes bowel movements, reducing constipation.
• Found in whole grains, vegetables, such as bran.

Clinical Importance of Fibers

• Constipation relief
• Colon cancer prevention
• Weight management
• Blood sugar regulation

Carbohydrate Sources

• Table (1) displays carbohydrate sources categorized by chemical class.
• Sources include grains, fruits, vegetables, milk, and other food products.

Recommended Daily Intake

• Dietary recommendations suggest that carbohydrates provide a substantial portion of daily energy requirements.
• The FDA recommends a daily intake of fiber, and the American Dietetic Association suggests an intake range..

This quiz explores the fundamental roles of carbohydrates in human nutrition, focusing on their types, functions, and metabolic processes. Test your knowledge on monosaccharides, polysaccharides, and other essential carbohydrate-related concepts.