2. Learning Objectives
• List the three nutritional needs common to all animals.
• Define the basal metabolic rate and explain how energy is obtained and
stored in the body.
• Describe the four classes of essential nutrients.
• Describe the types of information found on food labels.
• Describe the causes of dietary deficiencies and obesity.
• Explain how diet can influence the risks of cardiovascular disease and
cancer.
3. An animal’s diet
must provide
sufficient energy
• An animal’s diet must provide:
• Fuel to carry out activities
• Raw materials for making
body’s own molecules
• Essential nutrients that the
body cannot make
• A nutritious diet provides all the
nutrients our body needs
in appropriate amounts.
4. Energy for the body’s activities
• Animals require energy for our cells to do work
• Basal metabolic rate (BMR) – energy a resting animal requires to stay alive each day
(~75%: heating, cooling, digestion, etc)
• Energy needed to perform “extra” activity (~25%: standing, thinking, sleeping, sports)
Energy needs are expressed in terms of Calories
Energy content is measured in kilocalories; 1 kcal = 1000 cal; Dietary calories
are actually kcal and are written as Calories
E.g. 417 Calories = 417 kcal
5. Chemical energy powers the body
Cellular respiration produces ATP by breaking down fuel molecules
• Cells use carbohydrates and fats as fuel sources
• Fat gives double the amount of energy per gram compared to
carbohydrates and protein
6. Energy is expressed in calories
• Calorie: a unit that describes the potential energy content of foods
• Tells us how much cellular work can be powered by the energy released from
the breakdown of that food
• A person’s daily caloric needs vary greatly by age, sex, height, and
physical activity levels
7. An animal’s diet must supply essential nutrients
• Essential nutrients are substances that an animal requires but cannot
assemble from simple organic molecules.
• There are 4 classes of essential nutrients:
• Essential fatty acids, such as linoleic acid, are
• used to make phospholipids of cell membranes and
• found in seeds, grains, and vegetables.
• Essential amino acids are
• used to make proteins
• found in meats, eggs, milk, and cheese.
• A vitamin is an organic molecule required in very small amounts in your diet.
Most function as coenzymes.
• Minerals are inorganic nutrients, required in small amounts, that play a variety
of roles.
8. Dietary deficiencies can
have a number of causes
• Malnutrition, a diet insufficient in
nutrients or calories, can cause
significant health problems.
• Protein deficiency is the most common
cause of malnutrition worldwide.
• With severe deficiency, the body breaks
down its own proteins for energy,
eventually causing irreversible damage
9. Macronutrients
• Macronutrients are the nutrients that our body requires in large amounts
• These provide the vast majority of the energy we require
There are 3 macronutrients
1. Carbohydrates
2. Proteins
3. Lipids
11. Monosaccharides
• Single sugar units
• E.g. Glucose, Fructose, Galactose
• Glucose is most easily used by the body.
• It is a simple carbohydrate.
• It circulates in the blood.
• It is the main source of energy for
the muscles, central nervous system, and is
the ONLY source of energy for the brain.
12. Fibre
• Fibre consists of carbohydrates that cannot be digested.
• There are two main ways of categorizing fiber types:
– Soluble fibre - absorbs water.
Oat bran, barley, nuts, seeds, beans, lentils, peas, and some fruits and
vegetables.
– Insoluble fibre - do not absorb much water.
• Wheat bran, vegetables (e.g., celery), and whole grains.
• .
13. Benefits of Fibre
• Normalizes bowel movements and maintains bowel health
• Fibre decreases risk of constipation, diverticular disease, and colon cancer
• Lowers cholesterol levels, blood pressure and inflammation
• Fibre decreases risk of heart disease
• Helps control blood sugar levels by slowing the absorption of sugar
• Fibre decreases risk of Type II Diabetes
• Aids in achieving a healthy weight
• foods high in fibre are more filling, less energy dense
14. Glycemic Index
• Glycemic index measures how
fast and how far blood sugar
levels will rise after eating
carbohydrates
• High GI foods are digested
quickly and converted to blood
sugar immediately, causing blood
sugar levels to spike
• Low GI foods are digested
more slowly, causing
a slower rise in blood sugar
• Especially important for
people with diabetes
15. Review of Proteins
• List the 4 elements proteins are composed of:_________________________
• Proteins are relatively large molecules made up of amino acids joined
together by peptide bonds.
• Functions of proteins:
• Structural (silk, hair, tendons)
• Contractile (actin, myosin)
• Storage (ovalbumin)
• Defensive (antibodies)
• Transport (hemoglobin)
• Signaling proteins (hormones)
• Enzymes
16. Amino acids
• There are 20 standard amino acids used
by cells in making proteins
• Our bodies can synthesize 12 amino acids
from other starting materials
• There are 8 amino acids that our bodies
cannot make so we must get these amino
acids from our diets
• They are easily obtained from animal protein
• They can also be obtained from the proper
combination of plant foods (important
for vegetarians!!)
• A complete or whole protein contains
an adequate proportion of all eight of
the essential amino acids necessary for
the dietary needs of humans.
17. Review of Lipids
• Functions:
1. Stored energy (adipose tissue).
2. Organ protection.
3. Derivatives of vitamins and hormones.
4. Temperature regulator.
5. Insulation such as myelin that covers nerve cells.
6. Lipid membrane around cells.
7. Emulsifiers to keep fats dispersed in body fluids.
18. Types of Lipids
1. Triglycerides
• Composed of three fatty
acids and one glycerol
molecule.
2. Saturated fatty acid
• Fatty acid with carbon chains
• fully saturated with hydrogen.
3. Monounsaturated fatty acid
• Fatty acid that has a carbon
chain with one unsaturated
double bond.
4. Polyunsaturated fatty acid
• Fatty acid that has two or
more double bonds on the
carbon chain.
19. Essential fatty acids
• Essential fatty acids are required for good health but
the body cannot make them (therefore, we need to
ingest them!)
• Only 2 fatty acids are known to be essential for humans
• Alpha-linolenic acid (an omega-3 fatty acid)
• Used to make phospholipids of cell
membranes and are converted into other
important molecules (i.e. anti-inflammatory
molecules)
• Found in seeds (especially flax and chia), nuts, and vegetable oils
• Linoleic acid (an omega-6 fatty acid)
• Used to make phospholipids of cell membranes and are converted into
other important molecules (i.e. pro-inflammatory molecules)
• Found in vegetable/plant and nut oils
• These two fatty acids cannot be synthesized by humans because humans lack the
specific enzymes required for their production.
20. Diet can influence risk of cardiovascular
disease and cancer
• Two main types of cholesterol occur in the blood.
1. Low-density lipoproteins (LDLs) correlate with
a tendency to develop blocked blood vessels, high
blood pressure, and heart attacks.
2. High-density lipoproteins (HDLs) may decrease
the risk of vessel blockage, perhaps because
HDLs convey excess cholesterol to the liver,
where it is broken down.
• The ratio of HDLs to LDLs is influenced by diet.
21. Major and minor dietary elements
• Dietary elements aka minerals
• Inorganic elements that are essential for body processes
• Humans need seven major dietary elements:
• Calcium, phosphorus, potassium, sulfur, sodium, chlorine, and
magnesium
• Require more than 200 mg/day
• Other dietary nutrients, such as vitamins and trace elements,
are needed by the human body in very small quantities
• Called micronutrients
• Generally need less than 100 mg/day.
• Include elements such as iron, cobalt, chromium, copper, iodine,
manganese, selenium, zinc, and molybdenum
• Nine of the essential minerals in the body account for less
than 0.01% of your body weight.
23. Functions of Dietary Elements
• Ions are found in blood plasma and cell cytoplasm (e.g., sodium, potassium,
and chloride).
• Minerals represent much of the chemical composition of bones (e.g., calcium
and phosphorus).
• Ions contribute to nerve and muscle activity (e.g., sodium, potassium,
calcium).
24. A healthful diet includes 13 vitamins
• Vitamins: are organic compounds that are
essential for our body to function properly but
required in very small amounts.
• Most vitamins are obtained from what you eat,
because the body is unable to manufacture most of
the essential vitamins needed to survive.
• Most vitamins function as, or as part of, coenzymes
and have catalytic functions that are used in
metabolic reactions.
• Severe problems can result if the diet is deficient or
if these vitamins are consumed in excess.
• Vitamins are either fat soluble or water soluble.
26. Water soluble vitamins
• Vitamin C:
• required for collagen synthesis
• Vitamin B12:
• Required for red blood cell
formation
• only in animal by-products
Scorbutic gums, a symptom of scurvy
27. Folic Acid decreases risk of birth defects and cancer
• People who get more than the
recommended amount of folic
acid have lower the risk of
developing colon or breast
cancer.
• Sources of folic acid:
• Dark green vegetables like
broccoli and spinach
• Dried legumes such as chickpeas,
beans and lentils
• In Canada, folic acid is added to all
white flour, enriched pasta and
cornmeal products
¨ Folic acid is required in the first four weeks of pregnancy for proper
development of the brain, skull, and spinal cord.
¤ Prevents spina bifida and neural tube defects
¨ The current recommended intake for folic acid is 400 mg/day
28. Fat Soluble Vitamins
• Include vitamins A, D, E, and K
• You need to have fat in your diet to absorb these vitamins
• Dietary fat à bile secretion à absorption of vitamins
• Fat soluble vitamins are stored in “fatty organs” including liver, spleen, and
adipose tissue
• Excessive amounts of fat soluble vitamins can accumulate and result in
toxicity
• Toxicity rarely results from excessive dietary intake, but rather from improper use of
vitamin supplements.
30. Fat soluble
vitamins
• Vitamin D:
• Increase absorption of calcium and
phosphate in small intestine
• Vitamin K:
• Required for blood clotting
Rickets - the softening and
weakening of bones in children
31. Vitamin D and Cancer Risk
• Low vitamin D levels and inadequate calcium intake are
important risk factors for various types of cancer
• Strongest evidence links vitamin D to decreased risk of
colorectal cancer
• How can you get vitamin D?
• Skin cells exposed to sunshine can make vitamin D.
• Dietary sources include a few foods that naturally contain
vitamin D, such as fatty fish, fish liver oil, and eggs.
• However, most dietary vitamin D comes from foods fortified
with vitamin D, such as milk, juices, and breakfast cereals.
• Vitamin D can also be obtained through dietary supplements but
too much can cause toxic effects
• Too much calcium à deposition in tissues and excessive levels in
blood
33. Water
• Water is the main component of
your body!
• Makes up 60% of your body weight!
• What purposes does water serve?
• Carries nutrients to your cells
• Required for cell metabolism
• Provides a moist environment for ear,
nose, and throat tissues
• Allows kidneys to expel toxins/wastes
• Prevents kidney stones and
constipation
• Improves digestion
• Can help decrease food intake
34. How much water should you drink?
• Depends on:
• Your size and weight
• Your activity level
• Where you live
• The “current” rule of thumb: 0.5-1 oz. per pound of body mass
• If you weigh 150 lbs = 2.2-4.4 L water/day
• How can you tell if you’re dehydrated?
• Urine color/odor
35. Reading Food Labels
• Food labels provide important
nutritional information about
packaged foods
• Ingredients are listed from
greatest to least amounts
• Nutrition facts include:
• Serving size,
• Calories per serving,
• Amounts of selected nutrients
per serving and as a percentage
of daily value (based on a 2000
cal/day diet)
• Recommendations for daily
minimums of selected nutrients. Determined by a
national scientific panel
36. Where do scientists get our information
about nutrition from?
• Many insights into human nutrition have come from
epidemiology, the study of human health and diseases
within populations.
• The essential need for vitamin C was revealed by the high incidence
of scurvy in sailors on long sea voyages.
• Early epidemiologic research showed that incidence and death rates
for certain cancers were lower among individuals living in southern
latitudes, where levels of sunlight exposure are relatively higher
than among those living at northern latitudes.
¤ The need for folic acid to prevent
neural tube defects in newborns was
revealed by studies of pregnant
women of low socioeconomic
status. Since 1998, folic acid has
been added to foods such as bread
and cereals sold in the United
States.
37. The human health problem of obesity may reflect
our evolutionary past
• Obesity is defined as a too-high body mass index (BMI), a ratio of weight
to height.
• Obesity is linked to a lack of exercise and an abundance of fattening foods
and may partly stem from an evolutionary advantage of fat hoarding.
• The hormone leptin is produced by adipose (fat) cells and suppresses appetite.
• Researchers discovered that mice who inherit a defect in the gene for leptin become
very obese.
• Obese children who have inherited a mutant form of the leptin gene lose weight
after leptin treatments. But relatively few obese people have such deficiencies
