Download Chapter 16 lecture file (Nutrition: the basis of health living)

Chapter 16
Nutrition: The Basis
of Healthy Living
16-1 Digestion
Digestion: The breakdown of food into substances small
enough to be absorbed from the digestive tract
Nutrition: The science of diet and health
Nutrient: Chemical substance in food that provides energy
and raw materials required by chemical reaction

 Monosaccharides
Digestion
Proteins 
 Amino acids
Digestion
Fats 
 Glycerol + fatty acids
Carbohydrates
Digestion
Small molecules produced may undergo
(1) Complete breakdown to produce energy, CO2, and H2O;
(2) Recycling into new biomolecules; or
(3) Placement into storage as triglycerides (fat) for future use
The Release and Use of Chemical Energy in the
Breakdown and Synthesis Of Biomolecules
16-2 Sugar and Polysaccharides:
Digestible and Indigestible
Digestible carbohydrates:
• Simple sugars – glucose and fructose
• Disaccharides – sucrose, maltose, & lactose
• Polysaccharides – amylose and amylopectin
in starch from plants, & glycogen from meat.
Digestion:
• In mouth: enzyme α-amylase
breaks glycogen into smaller
polysaccharides.
• In acidic stomach: further digestion.
• In small intestine: debranching
enzyme & β-amylase break down
remaining polysaccharides to
glucose.
• Glucose (major fuel molecule)
transported across the intestinal
lining into bloodstream.
Indigestible carbohydrates (dietary
fiber):
• Cellulose and its derivatives
(insoluble)
• Pectin (the substance that makes
jam and jelly gel, soluble)
• Plant gums (soluble)
Health benefits of fiber: decreases
constipation & blood cholesterol levels,
may prevent colorectal cancer
16-3 Lipids: Mostly Fats and Oils
• Triglycerides in fat cells hydrolyzed to give glycerol & free fatty acids
• Transported to liver
• Fatty acids broken down to 2-carbon molecular fragments that enter main
energy-producing pathway
Recommended dietary fat content: 20% - 35% of daily calories
Today’s diet: 40% saturated, 40% monounsaturated, & 20% polyunsaturated
High saturated fat and cholesterol leads to atherosclerosis
Cholesterol is transported in the bloodstream by
lipoproteins (clusters of lipids, cholesterol, & watersoluble proteins); water soluble because of their many
NH3+ and COO− ions on proteins.
Low-density lipoproteins (LDLs): ~65% of blood
cholesterol; “bad” cholesterol; distributes cholesterol to
arteries, where it can form the deposits of atherosclerosis
High-density lipoproteins (HDLs): ~ 25%; “good”
cholesterol; transports excess cholesterol from body
tissues to the liver, where it is converted to bile acids that
are needed in digestion.
16-4 Proteins in the Diet
Dietary proteins provide amino acids for new protein synthesis
and N for synthesis of other kinds of N-containing biomolecules
Cooking → denatures proteins (first step of digestion)
Stomach: proteins → polypeptides
Small intenstine: polypeptides → amino acids
Excess amino acids not stored in body, so need to eat some protein every day.
16-5 Vitamins in the Diet
Vitamin: organic compound essential to health that must be
supplied in small amount by diet
•
•
•
•
Don’t provide energy
Aren’t digested
Can’t be synthesized by body
Needed by body to function as coenzymes
Coenzyme: A non-protein molecule that makes enzyme
function possible
Fat soluble – A, D, E, K
Water soluble – B, C
Test Your Knowledge
Which of the following is the body’s
major fuel molecule?
A) LDL Cholesterol
B) Glycine
C) Glucose
D) Vitamin C
16-5a Fat Soluble Vitamins
Vitamin A, D, E, and K stored in fatty tissues; nonpolar
hydrocarbon chains. Want enough stored; but too much is toxic
Vitamin A: essential to vision;
prevention of infection
Vitamin D: UV light converts steroid to
vitamin D; lack of exposure to sunlight
leads to vitamin D deficiencies
Vitamin E: antioxidant; found
distributed among fats in nature
Vitamin K: involved in blood clotting;
overdoses are dangerous so need a
prescription; given to newborns
16-5b Water Soluble Vitamins
Vitamins B & C: Have polar groups: -OH, -NH2, -COOH; Not
stored; must be consumed regularly
B-vitamins: B6, B12, folic acid, niacin, thiamin, riboflavin,
biotin, panthothenic acid
Vitamin B6 (“master vitamin”): involved in 60
enzymatic reactions, many involving metabolism
and synthesis of proteins
Niacin deficiency common in
countries with corn-based diet.
Folic acid: should be taken before conception;
can reduce risks of birth defects (spina bifida)
Enriched flour contains riboflavin, thiamin, niacin,
folic acid (and iron)
Vitamin C
Vitamin C
• Anti-oxidant
• Helps destroy invading bacteria
• Prevents the entrance of viruses into cells
• Combats effects of drugs and pollutants
• Aids in synthesis of collagen (in cartilage,
bone, tendons)
• Important in healing wounds for infants and
pregnant women
Prevent the common cold?
More evidence in favor of its ability to decrease the severity
of cold symptoms than for any ability to prevent colds
Diets low in vitamin C result in scurvy, characterized in its early
stages by lack of energy, and which can ultimately result in
death
Test Your Knowledge
For which of the following vitamins could an
overdose be a great concern?
A) Vitamin A
B) Vitamin B
C) Vitamin C
D) RIboflavin
16-6 Minerals in the Diet
• Elements other than C, H, N, and O that are needed for good
health
• Mostly present in foods, supplements, and our bodies in their
ionic state (e.g. Ca2+, not Ca; Na+ not Na)
• Many excreted daily and so need daily replenishment
Seven macronutrients:
Make up 4% of body weight
1. Ca
2. Mg
3. Na
4. K
5. Cl
6. P
7. S
Micronutrients:
1. Fe: deficiency causes anemia
2. Cu
3. Zn: deficiency causes poor growth and
development; poor wound healing
4. I: Essential for thyroid gland function
5. Se
6. Mn
7. F
8. Cr
9. Mo
The Macrominerals
Test Your Knowledge
Which of the following is considered a
macronutrient?
A)
B)
C)
D)
Copper
Iodine
Iron
Phosphorous
16-7 Food Additives
Food additives with little/no nutritional value;
added to processed food
16-7a The GRAS List
GRAS: Generally recognized as safe
• 100s of substances
• Published in 1959 and 1960
• Compiled from questionnaire asking experts in nutrition &
toxicology to give opinions about the safety of additives.
• Since publication, some substances have been removed
(suspicion that they are cancer-causing) e.g. sweetener
cyclamate, which was correlated with an increase in
bladder cancer
• FDA must approve new items for list based on test
results
16-7b Food Preservation
Preservatives: additive that prevents the growth of microorganisms or
slows the oxidation process
Other approaches: drying, salting, sugared solution
Prevents multiplication of microorganisms during shelf life of food.
Food is spoiled by toxic substances secreted by the microorganisms.
Sometimes preferred because sterilization by heat or radiation, or freezing,
may affect the quality of the food
Two common chemical preservatives (both are esters):
• Sodium benzoate (nonalcoholic beverages, fruit juices, fountain
syrups, margarines, pickles, relishes, olives, salads, pie fillings, jams,
jellies, and preserves)
• Sodium propionate (bread, chocolate products, cheese, pie crust, and
fillings)
16-7c Antioxidants
Action of O2 in the air is the chief cause of the destruction of
the fats in food
Antioxidants (reducing agents): molecules able to donate
an electron to a free radical before it can do any damage.
BHA and BHT donate a H● from their OH groups.
16-7d Sequestrants
Cu, Fe, Ni, and their ions
catalyze the oxidation of fats.
Trace amounts of metals are in
food from soil or harvesting or
manufacturing machinery
Sequestrant: molecule that
ties up a metal atoms or ions
by forming bonds with them
The Na and Ca salts of
ethylenediaminetetraacetic
acid (EDTA) are common
sequestrants
Metal atom is
bound here
16-7efg Food Flavors, Enhancers
and Color
• Food flavors (most originally derived from plants e.g.
peppermint oil)
• Flavor enhancers: no taste but enhance other flavors (e.g.
MSG, 5’-nucleotides, and maltol)
• Food colors: some from lab, some from nature
• Large organic molecules with several double bonds and
aromatic rings
• β carotene: example of a natural food color that may be
noted on ingredient list as “artificial color.”
• Synthetic food colors must be tested by FDA to ensure
safety, quality, consistency, and strength of color
Other Food Additives
•pH control:
• Weak acids added to give acidic taste or to mask aftertaste
• Buffers added to resist changes to pH
• e.g. Citric Acid
• Anticaking agents: prevent caking in humidity (e.g. MgSiO3)
• Stabilizers and thickeners: improve texture
• Mostly polysaccharides (e.g. guar gum)
• OH groups form H-bonds with H2O and help to provide a
more even blend of water and oils throughout the food
Test Your Knowledge
Which of the following food additives is
paired correctly with its role?
A) Guar Gum – Anticaking agent
B) EDTA – flavor enhancer
C) BHA – antioxidant
D) MSG – food preservative
16-8 Energy: Use It or Store It
Basal metabolic rate (BMR): The
minimum energy required to
sustain an awake but resting body
• Affected by body weight and
activity level
Energy from Foods
Fats: 9 kcal/g; 9 Cal/g
Carbohydrates: 4 kcal/g; 4 Cal/g
Proteins: 4 kcal/g; 4 Cal/g
Food Calorie (Cal) =1000 calories (cal)
= 1 kilocalorie (kcal).
Energy taken in (food) = Energy
used + Energy stored (fat)
Test Your Knowledge
What kind of molecule will provide the most
energy per gram?
A) Fats
B) Carbohydrates
C)Proteins
D)Vitamins
Approximate Percentages of Carbohydrates, Fats,
Proteins, and Water in Some Whole Foods
16-9 Our Daily Diet
The percentage of daily values
on a label (the DVs) are based
on a 2000-Cal daily diet
16-10 Some Daily Diet Arithmetic
A moderately active 100 lb. woman would get 30% of her daily 1750 food
Calories by consuming 53 g of fat per day.
How many cookies can she eat and leave 33 g of fat for other foods to be eaten
that day? (Their nutrition label says that there are two cookies per serving and
45 Cal from fat per serving.)
What percentage of her 53 g of fat will the cookies provide?
To leave 33 g of fat: 53 g fat − 33 g fat = 20 g fat from cookies can be eaten
With 9 Cal/gram of fat, the grams of fat per “serving” of two cookies is
45 Cal
1g
5g fat
×
=
2 cookies
9 Cal 2 cookies
2 cookies
20 g fat ×
= 8 cookies
5 g fat
20g fat
× 100 = 38%
53 g fat
Test Your Knowledge
Estimate the daily caloric needs of a 150 lb freshman
who runs 3 miles at least 5 days a week and plays
racquetball once or twice a week.
The estimated BMR is
150 lb × 10 kcal/lb = 1500 kcal = 1500 food Calories
The activity level is moderate.
Therefore, using the factor of 1.6 from Table 16.4, the
estimated daily caloric needs are
1500 kcal × 1.6 = 2400 kcal = 2400 food Calories