1. Jamie Pope, Steven Nizielski, and Alison McCook
NUTRITION
for a Changing World
FIRST EDITION
Chapter 4
Carbohydrates
Whole Grain Hype
© 2016 by W. H. Freeman and Company & Scientific American

2. Chapter 4
Objectives
Define “whole grain,” and explain what occurs when grain is refined
Identify the primary functions of carbohydrates in food and in the body
Describe the classifications of dietary carbohydrates and their chemical compositions
Explain how carbohydrates are synthesized in plants and animals
Identify the types and sources of fiber, and describe the health benefits of fiber
Identify the sources of carbohydrates in foods, and describe the dietary recommendations for carbohydrate intake
Outline the steps in carbohydrate digestion
Describe the difference between nutritive and non-nutritive alternative sweeteners, and identify examples of each category

3. Whole Grains Are foods with whole grains good for you?
Consumption of whole grains that are high in fiber reduces the risk of heart disease and diabetes
What is a whole grain?
To be called a whole grain, the grain does not have to be intact; its parts all just have to be there. So many processed foods are ground or separated during refining, with all the bits thrown back together afterward. This processing can lower the fiber, vitamin, mineral, and phytochemical content of the whole grain.
A Harvard study in 2013 showed that the relation of fiber to carbohydrate provides the benefit to whole grains. The beneficial whole grains have a ratio lower than 10-to-1 of total carbohydrate to fiber.

4. What Is a Carbohydrate? Hydrated carbons
Made of carbon, hydrogen, and oxygen
One or more sugar molecules together
Found in plant foods and milk
Major fuel source for the body
Provide 4 kcal of energy per gram
Recommended intake is 45% to 65% of total daily calories

5. Simple Carbohydrates

6. Complex Carbohydrates
Oligosaccharides: 3 to 9 linked sugars
Polysaccharides: 10 linked sugars

7. Complex Carbohydrates
Plants
Photosynthesis
Link glucose together
Starch
Fiber

8. Glycogen Stored glucose in the body Liver Muscle
Broken down to provide glucose in the blood
Muscle
Broken down to provide energy to do work

9. Carbohydrate-Rich Foods
Complex carbohydrates
Grains
Legumes
Some vegetables
Simple carbohydrates
Fruits
Many vegetables
Milk

10. Sugars Added to Food Refined sugars added to processed foods
Add flavor
Increase energy density
Decrease nutrient density
Contribute to obesity
Benefit of avoiding excess added sugars
Reduce risk of dental caries
Possible different names of sugars on ingredients lists are sugar, brown sugar, invert sugar, high fructose corn syrup (HFCS), corn syrup, malt syrup, maple syrup, concentrated fruit juice, honey, molasses, or dextrose.

11. Carbohydrate Intake Recommendations
2010 Dietary Guidelines for Americans
Total: Consume at least half of all grains as whole grains. Increase whole grain intake by replacing refined grains with whole grains.
Added Sugars: Reduce the intake of calories from added sugars
Institute of Medicine Recommendations (DRIs)
Total: RDA, 130 g/day; AMDR, 45% to 65% of total calories
Fiber: AI, 14 g per 1,000 kcal/day
Added Sugars: ≤25% of total calories consumed
American Heart Association (2009)
Added Sugars: Women, ≤100 kcal/day (25 g); Men, ≤150 kcal/day (38 g)
World Health Organization (2003)
Added Sugars: ≤10% of energy intake

12. Carbohydrate Digestion
Enzymes digest to monosaccharides
Amylase
Sucrase
Maltase
Lactase

13. Carbohydrate Digestion
Mouth
Amylase
Breaks starch into smaller links of glucose
Small intestine
Continue digestion of starch into maltose and glucose

14. Carbohydrate Digestion
Small intestinal cells
Maltase
Hydrolyzes maltose to produce two glucose monosaccharides
Sucrase
Hydrolyzes sucrose to produce one glucose and one fructose monosaccharide
Lactase
Hydrolyzes lactose to produce one glucose and one galactose monosaccharide

15. Carbohydrate Absorption
Monosaccharides are absorbed by small intestine then transported to the blood

16. Carbohydrate Use Energy for body Fructose and galactose Glucose
Carried to the liver and converted to glucose
Exported back into the blood as glucose
Glucose
Primary fuel for cells
Stored as glycogen in liver and muscles
Excess made into fat to store

17. Fiber Solubility Dietary fiber Functional fiber
Soluble
Form viscous gels
Insoluble
Increase fecal bulk
Dietary fiber
Functional fiber
Total fiber = dietary fiber + functional fiber
Soluble fibers can decrease gastric emptying and give a feeling of fullness. They can also bind bile in the intestine, helping decrease body cholesterol.
Insoluble fiber is not fermented and persists in the colon, increasing fecal bulk, softening stools, and reducing constipation.
Dietary fiber is undigested carbohydrates and lignin in intact plant foods.
Functional fiber is nondigestible carbohydrates synthesized or extracted from plants or animals.

18. Fiber

19. Fiber in the Body Insoluble fiber Soluble fiber
Softens stool and decreases constipation
Decreases hemorrhoids and diverticular disease
Soluble fiber
Slows stomach emptying
Slows digestion and absorption
Reduces the risk of coronary artery disease

20. Health Benefits of Fiber
Soluble fiber may reduce the risk of cardiovascular disease.
High-fiber foods promote satiety and may reduce the risk of obesity.
High intakes of insoluble cereal fiber may reduce the risk of type 2 diabetes.
Soluble fiber slows the increase in blood glucose following carbohydrate ingestion.
High insoluble fiber intake softens stools and reduces the occurrence of constipation.

21. Lactose Intolerance Low lactase activity Lactose maldigestion
Diarrhea
Gas, cramps, abdominal pain
Treatment
Decrease dairy intake
Lactase pills
Calcium-rich foods
Without lactase, the lactose doesn’t get broken down into glucose and galactose and absorbed, so the lactose passes through the intestine and draws water, causing loose stools or diarrhea. The lactose is metabolized by the bacteria forming gas and causing cramps and abdominal pain. Treatment is to decrease lactose intake or dairy products. Some people can tolerate small amounts as they have low levels of lactase. Some can tolerate yogurt or cheese because bacteria in the processing metabolize the lactose.

22. Sugar Alternatives Regulated
Generally recognized as safe (GRAS) by the FDA

23. Nutritive Sweeteners
Sugar alcohols are naturally occurring sugars in plants and berries that are poorly absorbed so they provide fewer calories. Overconsumption can cause diarrhea.

24. Non-Nutritive Sweeteners

25. Carbohydrates in the Diet
Important source of energy
Some choices are better than others
Provide vitamins, minerals, fiber, and phytonutrients
Best sources
Minimally processed whole grains
Vegetables
Fruits
Beans

26. Summary
Carbohydrates, which are composed of carbon, hydrogen, and oxygen, contain 4 kcal/g and are found in plant foods and milk products
In addition to serving as a primary energy source, carbohydrates are a source of fiber, act as added sweetness and flavor for food, and reduce the use of protein for energy
The Institute of Medicine recommends that carbohydrate intake comprise 45% to 65% of total daily calorie intake
Carbohydrates can be classified as simple (sugars) or complex (starch and fiber)

27. Summary (Cont’d)
Simple carbohydrates include single sugar molecules, called monosaccharides (glucose, fructose, and galactose), or two-sugar units, called disaccharides (sucrose, lactose, and maltose)
Monosaccharide glucose is the most abundant sugar circulating in the blood and serves as an essential energy source for the cells of the body
Disaccharide sucrose (table sugar) is composed of glucose and fructose
Lactose is the primary form of sugar found in milk; some individuals lack or have decreased levels of lactase, the enzyme needed to breakdown lactose, so they experience lactose intolerance

28. Summary (Cont’d)
Complex carbohydrates are composed of linked monosaccharides that function as a stored form of energy “starch” or structural material “fiber,” depending upon how the sugars are linked
Carbohydrate digestion is accomplished through the action of enzymes, and the carbohydrates are absorbed in the small intestine
Fiber is indigestible by humans and has many health benefits
Insoluble fiber aids in digestive health, and soluble fiber may lower risk of cardiovascular disease

29. Summary (Cont’d)
Dietary fiber is the nondigestible fiber naturally found in plant foods; functional fiber is extracted or synthesized and added to foods during the manufacturing process; together they make up total fiber
The DRI for fiber intake is 25 grams for woman and 38 grams for men
Glycogen, a highly branched polysaccharide, is the storage form of glucose in humans and animals; stored primarily in the liver and muscles; liver glycogen can help maintain blood glucose
The Dietary Guidelines for Americans recommend that we reduce intake of added sugars, which increase the risk of dental caries and provide empty calories
Alternative sweeteners are regulated and considered “generally recognized as safe” (GRAS) by the FDA. Alternative sweeteners include nutritive sweeteners (sugar alcohols) and several non-nutritive sweeteners that are calorie-free and hundreds of times sweeter than sucrose.