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Human Nutrition > Lecture 4: Carbohydrates- Sugars, Starches, and Fiber > Flashcards

Lecture 4: Carbohydrates- Sugars, Starches, and Fiber Flashcards

1
Q

Carbs

A
  • The brain and body’s best
    fuel source
  • Provide 4 kcal per gram
  • Broken down into glucose
    molecules in the body
  • Made through
    photosynthesis
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2
Q

Classifications of Carbohydrates

A

Based on # of units linked together
Can be simple or complex
(Simple carbs: mono or disaccharides, oligosaccharides, complex carbs: polysaccharides)

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3
Q

Simple Carbs

A

Monosaccharides
Disaccharides
Perceived as sweeter than complex carbohydrates
* Mix with saliva and react with taste buds

Basic unit of carbohydrates: monosaccharide
* Glucose
* Fructose
* Galactose

Disaccharides: 2 monosaccharides linked together through condensation
* Maltose
* Sucrose
* Lactose

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4
Q

Complex Carbs

A

Polysaccharides

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5
Q

Condensation Reactions

A

Links monosaccharides to form disaccharides
Glucose + Glucose = Maltose
Glucose + Fructose = Sucrose
Glucose + Galactose = Lactose

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6
Q

Complex Carbs

A

Made up of many monosaccharides linked together in
chains
* Oligosaccharides: 3-10 monosaccharides.
~In foods: Legumes, beans, cabbage, brussels sprouts,
broccoli
~Found in breast milk
* Polysaccharides
~Glycogen (animals)
~Starch, fiber (plants)

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7
Q

Polysaccharides

A

Starch
~Plant glucose storage in two forms:
-Amylose
-Amylopectin

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8
Q

Amylose

A

Straight chain of polysaccharides found in starch

  • More resistant to digestion than amylopectin – “resistant
    starch” is not digested in the GI tract.
    ~May improve health of digestive tract
    ~May improve glucose tolerance
    ~May stimulate growth of beneficial intestinal bacteria
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9
Q

Amylopectin

A

Branched chains of polysaccharides found in starch
* Easier to digest

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10
Q

Where to get starch from in diet?

A
  • Toots and tubers
  • Grain seeds
  • Legumes
  • Cornstarch
  • Many processed foods
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11
Q

Glycogen

A
  • Storage form of carbohydrates in animals
  • Stored in liver and muscles in limited amounts
  • Source of glucose for body
  • Dissipates with rigor mortis, therefore is not present in
    animal products that humans consume
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12
Q

Fiber

A
  • Most forms of fiber are nondigestible polysaccharides and occur naturally as a structural component called cellulose.
  • We cannot digest or absorb fiber
  • Only found naturally in plant foods, not foods of animal origin
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13
Q

Dietary Fiber

A

Natural Fiber

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14
Q

Functional Fiber

A

Added Fiber

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15
Q

Total Fiber

A

Dietary + Functional Fiber

Listed as dietary fiber on food labels

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16
Q

Soluble Fiber

A
  • Dissolves in water to form viscous solutions
  • Can be fermented by intestinal bacteria
  • Includes: pectins, beta-glucans, mucilages
  • Food sources: oats, apples, beans, seaweed

Benefits:
* Helps lower cholesterol
* Slows gastric emptying
* Control appetite
* Normalizes blood sugars

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17
Q

Insoluble Fiber

A
  • Cannot be fermented by bacteria in the large intestine
  • Does not dissolve in water
  • Derived from structural parts of plants such as cell walls
  • Includes: cellulose, lignin, some hemicelluloses
  • Food sources: wheat bran, rye bran, fruit & vegetable peels

Benefits:
* Increases bulk of stool
* Helps relieve constipation

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18
Q

Apple

A

Skin= Cellulose: insoluble fiber
Inside apple= Pectin: soluble fiber

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19
Q

Why is dietary fiber so important?

A

Benefits:
* Helps lower risk of
~Bowel irregularity
~Constipation and diverticulitis
~Obesity
~Heart disease
~Cancer
~Diabetes

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20
Q

What can fiber help prevent?

A

Heart Disease
Diabetes
Cancer

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21
Q

How does fiber prevent heart disease?

A
  • Soluble fiber helps decrease blood cholesterol levels.
  • Soluble fiber may reduce the rate at which fat and
    carbohydrate are absorbed.
  • Insoluble fiber has been shown to promote heart health
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22
Q

How does fiber prevent diabetes?

A
  • Soluble fiber helps slow digestion and absorption of glucose,
    helping control blood glucose levels.
  • Higher consumption of fibers from cereals has been shown to reduce the risk of developing diabetes
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23
Q

How does fiber prevent cancer?

A
  • Fiber helps reduce the incidence of several cancers.
    ~Decreases the amount of time cancer-promoting substances spend in contact with the intestinal lining
    ~Encourages the growth of colon-friendly bacteria and their
    fermentation by-products
    ~Reduces concentration of bile acids in the colon
24
Q

How does fiber prevent obesity?

A
  • Increases satiety, resulting in reduced food intake
  • Some cautions about fiber
    ~Introduce fiber into the diet slowly.
    ~Initially, a high-fiber diet can cause flatulence and bloating.
    ~It may reduce the absorption of some minerals
25
Q

How are carbs digested and absorbed?

A
  • Disaccharides and starch are digested into monosaccharides.
  • Monosaccharides are easily absorbed by the small intestine.
  • Fiber passes through the GI tract undigested.
26
Q

Where are carbs digested?

A

Mouth:
~Saliva contains amylase enzyme, which starts breaking down amylose and amylopectin into smaller starch units and maltose
~Mechanical digestion of fiber
* Stomach:
~HCl inactivates salivary amylase
~Fiber delays gastric emptying
* Small intestine
~Pancreatic amylase breaks down remaining starch into disaccharides (maltose)
~Maltose and other disaccharides are broken down to monosaccharides and absorbed into blood
* Large intestine
~Fiber continues to the large intestine, where some is metabolized by bacteria in the colon and the majority eliminated in your stool
~Production of short-chain fatty acids by fiber metabolizing bacteria

27
Q

How are carbs absorbed?

A

After carbohydrates are digested to monosaccharides they are:
* Absorbed through the intestinal cell mucosa
* Transported to the liver via the portal vein
* Metabolic needs direct the fate of the monosaccharides

28
Q

Absorption of galactose and fructose

A

Used by the liver for energy

Converted to glucose

29
Q

Absorption of Glucose

A
  • Used for energy
  • Converted to glycogen through glycogenesis
  • Excess glucose is converted to glycerol and fatty acids for storage in adipocytes.
30
Q

Functions of Carbs

A
  • Provide energy
    ~4 kilocalories per gram
  • Maintain blood glucose levels
    ~Glucose is the primary fuel for the brain.
    ~Glycogenolysis occurs 4 hours after a meal.
    ~Muscle glycogen cannot be used to raise blood glucose levels.
  • Spare protein
    ~Prevents the need for gluconeogenesis
    -Occurs mainly in the liver but can occur in the kidney
  • Prevents ketosis
    ~Ketosis is an elevated number of ketone bodies in the
    blood that occurs after approximately 2 days of fasting
    -Protein from muscle and organs broken down to make
    glucose
    -Brain switches to using ketone bodies for fuel to spare
    protein-rich tissues
    -If fasting continues, protein reserves are depleted and
    death occurs
31
Q

Ideal blood glucose level

A

The body wants to keep blood glucose between 70 milligrams/deciliter and 110 milligrams/deciliter to ensure availability to cells

32
Q

Hormones responsible for maintaining blood glucose level

A

Insulin
Glucagon

33
Q

Insulin

A
  • Released from pancreas
  • Lowers blood glucose level
    ~Needed for glucose to enter the cell from the bloodstream
    ~Liver, kidney, and brain cells can use glucose without insulin.
    ~Stimulates glycogenesis (liver and muscle)
    ~Stimulates lipogenesis (liver and adipose)
    ~Inhibits lipolysis
    ~Inhibits gluconeogenesis
34
Q

Glucagon

A
  • Released from pancreas
  • Target organ is the liver
  • Increases blood glucose level
    ~Stimulates the release of glucose into the blood
    -Stimulates glycogenolysis
    -Stimulates gluconeogenesis
35
Q

Fed (postprandial) state

A

Blood glucose increases
* Pancreas releases insulin
* Insulin allows for the uptake of glucose by peripheral tissue (glucose travels from the blood into tissue = drop in blood glucose)
~Muscle stores glucose as glycogen (glycogenesis)
~Adipose stores glucose as fat (lipogenesis)
* Liver will store as glycogen and then fat lipogenesis; reduces glucose output
* Reduction in blood glucose signals `pancreas to reduce insulin secretion

36
Q

Fasting State

A
  • Blood glucose drops
  • Pancreas releases glucagon
  • Glucagon stimulates the breakdown of glycogen into glucose (glucose travels from the tissue into blood = increase in blood glucose)
  • Stimulates gluconeogenesis in the liver; increases glucose output
  • Increase in blood glucose signals pancreas to reduce glucagon secretion
37
Q

Hypoglycemia

A

Low blood glucose below

  • Occurs with excess insulin production

Symptoms:
Hunger, dizziness, feeling light-headed, confused, weak, or
beginning to sweat

Treatments:
* Eat or drinking
carbohydrate-rich foods
* Eating smaller, well-balanced meals throughout the day

38
Q

Glycemic Response

A

Blood glucose response

  • How quickly and how high blood glucose level rises after
    consuming carbs
  • How quickly it returns to normal

Affected by:
* type and amount of carbohydrate consumed - refined sugars
and starches raise blood sugar levels faster than unrefined
carbohydrates and fiber
* amount of fat and protein consumed
* Genetics
* Microbiome
* Sex
* Anthropometrics
* Other environmental factors (sleep, physical activity, meal
timing)

39
Q

Glycemic Index (GI)

A

A rating scale of the likelihood of foods to increase the levels of blood glucose and insulin.

Concerns:
* Does not account for the amount of carbohydrate
consumed.

40
Q

Glycemic Load (GL)

A

The amount of carbohydrate in a food multiplied by the amount of the GI of that food.

  • Adjusts the GI to account for the amount of carbohydrate
    typically eaten
41
Q

DRI Carb Recommendation

A

130 grams/day

42
Q

MyPlate Carb Recommendation

A
  • 6 servings of grain/day
  • 3 servings of vegetables/day
  • 3 servings of dairy/day
  • 2 servings of fruit/day
43
Q

AMDR carb recommendation

A

45-65% of total kilocalories/day

44
Q

Overconsumption of carbs

A

Most adults in the United States consume well over the
minimum DRI: 180-330g/day (~50% kcal)
* Primarily from refined bread, soda, baked goods

45
Q

Daily Fiber recommendations

A

DRI: 14 grams per 1,000 kilocalories consumed
AI: 25 to 38 grams per day

46
Q

Best sources of carbs

A

Whole foods

Some sources are better than others such as grains, vegetables, fruits, and beans

Best choices should include:
* Nutrient-dense, low-saturated-fat foods, with low amounts of
simple carbohydrates
* Higher amounts of fiber and complex carbohydrates

47
Q

Parts of a whole grains

A

Endosperm
Bran
Germ

48
Q

Endosperm

A

Largest part of kernel.
Made up primarily of starch
Contains most of kernel’s protein + some vitamins and minerals

49
Q

Bran

A

Outermost layer
Contains most of the fiber
Good source if many vitamins and minerals

50
Q

Germ

A

Located at the base of kernel
Embryo where sprouting occurs
Source of oil
Rich in vitamin E

51
Q

Whole-wheat flour

A

Missing folic acid
Uses who kernel

52
Q

Enriched flour

A

Only uses Endosperm

53
Q

Wheat flour (not enriched)

A

Uses only endosperm
No nutrients added back

54
Q

Enrichment

A

Adding nutrients back

Riboflavin
Niacin
Thiamin
Iron

55
Q

Fortification

A

Adding extra nutrients

Folate

56
Q

Whole Grains

A
  • Decrease risk of stroke
  • Decrease risk of dying from cancer or heart disease
  • Fiber linked to lower risk of diabetes
  • More satiating
57
Q
A

Human Nutrition (6 decks)

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