Carbohydrates Overview and Recommendations

Study Notes

Carbohydrates

Carbohydrates are a primary energy source in the human diet.
Learning outcomes for carbohydrate instruction include classifying carbohydrates, identifying chemical structures of carbohydrates in food, listing main dietary sources, and describing metabolic roles and dietary recommendations.
Macronutrients account for a large minimum daily requirement, with carbohydrates comprising 50% of food energy. Carbohydrate, fat, and protein are important.
Gross energy of a substance is measured using a bomb calorimeter.
Atwater factors provide approximate ratios of usable energy from different food sources.
Some foods contain intrinsic sugars while others contain extrinsic sugars.
Daily intakes of carbohydrates for different groups are specified.
Recommended carbohydrate intakes are much higher for good overall health, this includes consideration of different intake for different needs.
The National Diet and Nutrition Survey (NDNS) data shows specific carbohydrate intake values for men and women.

Carbohydrate Classification

Carbohydrates are categorized into several groups (monosaccharides, disaccharides, oligosaccharides, and polysaccharides) based on the number of sugar units.
Monosaccharides include glucose and fructose, which are the simplest forms of carbohydrates.
Disaccharides, such as sucrose, maltose, and lactose, form from two monosaccharides bonded together.
Oligosaccharides contain 3-9 monosaccharides.
Polysaccharides contain 10 or more monosaccharide units and are categorized into storage polysaccharides (starch and glycogen) and structural polysaccharides (cellulose, pectin, and chitin).

Function of Carbohydrates

Carbohydrates are a crucial source of energy for bodily functions.
Carbohydrates provide vital fuel for the brain.
Non-digestible carbohydrates play a role in maintaining gastrointestinal health.

Role of Carbohydrates in the Body

Carbohydrates provide the body with energy needed for everyday functions.
Carbohydrates are an essential component in the creation of RNA and DNA and glycoproteins and glycolipids.
Carbohydrates participate in structural and cell signaling.
Adequate Carbohydrate consumption contributes to gastrointestinal health.

Classification of Carbohydrates - Structure

Monosaccharides are the simplest forms of carbohydrates (e.g. glucose, fructose).
Disaccharides are formed by combining two monosaccharides through a glycosidic bond (e.g. sucrose, maltose, lactose).
Oligosaccharides comprise 3-9 monosaccharides linked together.
Polysaccharides are composed of 10 or more monosaccharides bonded together.

Energy from Food, Carbohydrates

Energy from food is measured in kilocalories or kilojoules.
Bomb calorimetry is used to measure this energy.
Atwater factors are used to estimate the total energy or calories obtained from foods.
Losses from faeces and urine need to be considered when working with Atwater factors.

Glycemic Carbohydrates

Glycemic carbohydrates cause blood glucose to rise after consumption, measured using the glycemic index (GI) scale (0-100).
GI is influenced by factors like absorption rate, intestinal structure, enzyme susceptibility, and component composition of the complete meal.

Low Glycemic Index

Foods with a low GI cause a slower and more moderate rise in blood glucose levels following consumption.
Unprocessed grains (oats, quinoa, brown rice) are often associated with low GI values.
Fruits and vegetables have variable low GI values, with the skin or more mature fruit often showing a higher GI value than less mature versions.

Dietary Fiber

Dietary fiber is a non-glycemic, indigestible carbohydrate with health benefits.
Dietary fiber includes non-starch polysaccharides (NSPs), resistant starches, and non-carbohydrate components.
Older terminology also uses "unavailable CHO" to describe fiber.

Processing Steps in Flour Production

Different types of flour (white, brown, wholemeal) are obtained in flour production.
Production involves various steps including inspection, washing, conditioning, breaking, milling, and sieving.

Soluble/Insoluble Fiber

Soluble fiber (viscous) slows gastric emptying and binds to cholesterol, reducing absorption and blood glucose rises.
Insoluble fiber increases faecal bulk. Foods high in insoluble fiber include wheat bran and whole grains.

Specific Carbohydrate Food Sources

Different food groups (starchy foods, fruits, vegetables) contain different types of carbohydrates (energy sources, intrinsic sugars, dietary fiber) leading to different impacts.

Types of Non-Digestible Carbohydrates

Table of non-digestible carbohydrates (source example: cellulose from fruits and vegetables).

Resistant Starch

Resistant starch (RS) is a type of carbohydrate that isn't digested in the small intestine.
Fermentation in the large intestine produces short-chain fatty acids (SCFAs).
RS may have benefits for colonic health.

Sources of Fiber (examples)

Amounts of fiber in different types of food, presented in tabular format.

Recommended Carbohydrate Intakes

Specific recommendations for carbohydrate intakes, covering total carbohydrates, free sugars, and fiber. Specific figures are from the SACN Report (2015)
Dietary recommendations exist based on the National Diet and Nutrition Survey (2019).

Practice Multiple Choice Questions (MCQs)

Examples of multiple choice questions covering various aspects of carbohydrates. Includes calculation of energy percentages, identifying storage compounds e.g., polysaccharides, and discerning intrinsic or extrinsic sugars.

Next Steps

The next lesson will cover fats and protein, with potential further analysis in a macronutrient quiz.

Description

This quiz covers the essential role of carbohydrates in the human diet, including their classification, chemical structures, and dietary sources. You will learn about the recommended intakes for different populations and the importance of carbohydrates as a primary energy source. Test your knowledge on this vital macronutrient and its metabolic functions.

Carbohydrates Overview and Recommendations

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Questions and Answers

Which type of polysaccharide is primarily used for energy storage in animals?

What distinguishes intrinsic sugars from extrinsic sugars?

What type of linkages primarily characterizes cellulose?

What is the recommended daily intake of carbohydrates for general health?

Which of the following is a characteristic of starch?

What is the primary source of energy in the human diet?

Which of the following is not a type of carbohydrate?

Which carbohydrate consists of 3 to 9 monosaccharides joined together?

What is the role of non-digestible carbohydrates in the body?

Which of the following is a common monosaccharide found in food?

What is the condition represented by the loss of N in urine when calculating metabolizable energy?

Which of the following is considered a disaccharide?

What is the structure of carbohydrates primarily responsible for cell signaling?