Download Option D1: Human nutrition - Ms. Richards IB Biology HL

Option D.1 Human nutrition
Essential idea: A balanced diet is essential to human health
D.1 Human nutrition
Nature of science: Falsification of theories with one theory being superseded by another—scurvy
was thought to be specific to humans, because attempts to induce the symptoms in laboratory rats
and mice were entirely unsuccessful. (1.9)
Understandings:
• Essential nutrients cannot by synthesized by the body, therefore they have to be included in the
diet
• Dietary minerals are essential chemical elements
• Vitamins are chemically diverse carbon compounds that cannot by synthesized by the body
• Some fatty acids and some amino acids are essential
• Lack of essential amino acids affects the production of proteins
• Malnutrition may be caused by a deficiency, imbalance or excess of nutrients in the diet
• Appetite is controlled by a centre in the hypothalamus
• Overweight individuals are more likely to suffer hypertension and type II diabetes
• Starvation can lead to breakdown of body tissue
D.1 Human nutrition
Application and skills:
• Application: Production of ascorbic acid by some mammals, but not others
that need a dietary supply
• Application: Cause and treatment of phenylketonuria (PKU)
• Application: Lack of Vitamin D or calcium can affect bone mineralization
and cause rickets or osteomalacia
• Application: Breakdown of heart muscle due to anorexia
• Application: Cholesterol in blood as an indicator of the risk of coronary
heart disease
• Skill: Determination of the energy content of food by combustion
• Skill: Use of databases of nutritional content of foods and software to
calculate intakes of essential nutrient's for a daily diet
What is nutrition?
• Nutrition is the act of taking food in (ingestion), breaking it apart
(digestion), and cellular uptake (absorption)
• Our food provides the nutrients and minerals that we are incapable of
synthesizing on our own.
• Nutrients: chemical substance found in foods and used in the human body
• Minerals: inorganic substances that living things need for a variety of
purposes
Essential Nutrients vs Non-Essential Nutrients
• Nutrients are used in a variety of ways by the body, including
providing energy and biosynthesis
• Some nutrients can be made by cells, but many cannot
• Those nutrients that cannot be made by our bodies are called
essential nutrients
• Other nutrients are non-essential, either because another nutrient
can be used for the same purpose or because they can be made in
the body from another nutrient
Essential Nutrients vs Non-Essential Nutrients
• Glucose, starch, and other carbohydrates are non-essential because
they are used in respiration to provide energy and lipids can be used
instead. In fact amino acids can be fed into both glycolysis and the
Krebs cycle
• Some essential nutrients are conditionally essential. In adults,
vitamin K is produced by the metabolism of symbiotic bacteria in the
intestine. Infants do not have colonies of such bacteria at birth, they
are often given supplementary injections of vitamin K
• Essential nutrients include: essential amino acids, essential fatty
acids, minerals, and most vitamins
Minerals
• Minerals are inorganic substances which are needed in small
amounts by humans (milligrams or micrograms per day rather than
grams)
• They can be distinguished from vitamins by their chemical nature
• Minerals are chemical elements, usually in ionic form
• Examples of minerals include calcium, iron, sodium, magnesium,
iodine, and chloride.
• Minerals are fairly long-lived, so a large quantity is not necessary, but
the supply must be constant to replace those that are used by the
body
Minerals
• Minerals can be used for biosynthesis (building bones, hemoglobin
etc.) and for sending chemical messages (synaptic transmission,
action potentials etc.)
• Deficiencies cause disease. The consequences of deficiency diseases
can be serious. An example is the mineral iodine. It is needed by the
thyroid gland for synthesis of the hormone thyroxin. This hormone
stimulates metabolic rate
• If a pregnant woman has this deficiency, her baby may be born with
permanent brain damage. If an adult has this deficiency, they may
develop a goiter
Mineral Deficiency: Goiter
Mineral Deficiency: Goiter
Vitamins
• Vitamins from the words “vital amine”
because the first vitamins discovered
contained an amino group
• Vitamins are essential organic (carbon
compounds) molecules with diverse
functions that cannot be synthesized by
the body
• Vitamins, like minerals, are only needed in
small amounts, due to their long-lived
nature. They must be obtained from the
diet
Vitamins
• Some of their functions include co-factors for enzymes, anti-oxidants,
and hormones
• Vitamins can be classified as either water soluble or fat soluble.
Water soluble vitamins have to be constantly consumed and any
excess is lost in urine. Fat soluble vitamins can be stored
• Some people who are deficient in vitamin intake will consume multivitamins
• It’s unclear whether massive doses of vitamins provides any health
benefits or are even safe
Vitamin Deficiency: Vitamin C
• Vitamin C is needed for the synthesis of collagen
fibers that form part of many tissues including skin
and blood vessel walls
• In most plants and animals, vitamin C (ascorbic acid)
is non-essential. Teleost fish (e.g. cod, salmon,
herring) and many primates cannot synthesize this
vitamin. This is the result of a mutation of a gene that
codes for the last enzyme in the final reaction of this
pathway
• In humans, some other primates, and guinea pigs, it
is needed to avoid a disorder known as scurvy
• Scurvy is characterized by anemia, debility,
exhaustion, ulceration of the teeth and gums, and in
some cases, death
• It is because of scurvy that we have the term “limey”
Vitamin Deficiency: Vitamin D
• Vitamin D is also an important component of human diets
• Sources: oily fish, eggs, liver, and artificially fortified milk
• Vitamin D helps with the absorption of calcium in the
intestines which is then used for bone formation
• In children, vitamin D deficiency can cause rickets, a
disease that leads to irregular bone growth along growth
plates
• In adults, vitamin D deficiency (which has same symptoms
as calcium deficiency) can lead to osteomalacia, or soft
bones
• Osteomalacia is inadequate bone mineralization due to
calcium salts not being deposited or being reabsorbed, so
bones become softened
Vitamin D
• Does not fit the definition of a vitamin very well, as it can be
synthesized in the skin
• Vitamin D can be synthesized by cells in the skin when exposed to UVB radiation from the sun (290-310 nm)
• UV light has some harmful consequences, including mutations that
lead to skin cancer. Melanin intercepts and absorbs light
• The intensity of UV is too low in winter in high latitudes for much
vitamin D to be synthesized, but the liver can store enough during
the summer to avoid a deficiency in winter
Essential Fatty Acids
• Humans can make most of the fatty
acids that are needed for survival
• However, omega-3 and omega-6 fatty acids, which are unsaturated,
cannot be made
• Omega-3 and omega-6 refers to the position of a double bond in relation
to the end of the molecule. Development of the brain and eye involve
particularly large quantities
• For those who don’t like oily fish like salmon, sunflower seeds are a good
source of these essential fatty acids
• Flaxseeds, chia seeds, hemp seeds, and walnuts are also a good source
Essential Amino Acids
• Essential amino acids are needed for protein synthesis
• There are several (8, 9 in infants) amino acids that humans cannot
synthesize
• There is no way to store amino acids therefore all essential amino acids
must be included in the diet
• Some cultures rely on a specific type of agricultural crop, such as corn,
which may be deficient in several amino acids
• In these populations, a higher rate of amino acid deficiencies are seen
• Protein deficiency malnutrition (cannot make enough proteins) causes a
lack of blood plasma proteins, which results in fluid retention in tissues
which causes swelling (edema) and may be often seen in the abdomen
• Through the use of biotechnology, scientists are genetically modifying
certain crops to produce the essential nutrients needed for proper
nutrition
Phenylketonuria (PKU)
• Some individuals lack the ability to convert the amino acid phenylalanine
to the amino acid tyrosine
• This is an autosomal recessive disorder (genetic)
• This leads to a build up of phenylalanine in the blood and tissues, which
can lead to mental retardation, seizures, and a variety of other problems
• There is no cure, but in developed countries where infants are tested soon
after birth, a diet that limits certain proteins (high amounts of
phenylalanine like meat, fish, nuts, cheese, peas and beans) can be
established and the individual can live a normal life
• Children are normal prior to birth because the mother’s metabolism has
kept phenylalanine and tyrosine at normal levels
• Newborn genetic screen can pick up this disorder at about 24 hours after
birth
Appetite
• Appetite is the desire to eat
• A person’s appetite is controlled by the hypothalamus in the brain
• The feeling of being satiated is a complex system of negative feedback
loops between the nervous, digestive, and endocrine system
• The small intestine secretes the hormone PYY3-36 when it contains food
• The pancreas secretes insulin when the blood glucose concentration is
high
• Adipose tissue secretes the hormone leptin when amounts of stored fat
increase
• If the appetite control center receives these hormones, it reduces the
desire to eat
• This helps us to avoid health problems due to overeating, including
excessive blood glucose levels, and obesity
Appetite
• There are a variety of hormones and
other signals the brain uses to detect
hunger and fullness
• There are also physical cues, such as
when the stomach expands, it sends
a message to the brain that it’s full
and to stop eating
Eating and Nutritional Disorders
• There are many issues that play a role in eating and nutritional
disorders
• In some cases, the brain’s appetite control center is not properly
functioning, and the individual may lose weight if they have no
appetite, or become obese if they cannot be satiated
• Some disorders are a result of social, cultural, and economic factors
Malnutrition
• A lack of quantity or quality of food can lead to nutrition problems,
collectively called malnutrition, which can be classified as a
deficiency, imbalance, or excess of nutrients
• Deficiencies can occur not just with nutrients but with calories as
well
• When the body is deprived of energy in the form of calories, it will
begin to break down glycogen stored in the liver, then lipids, and
finally proteins
• Typically skeletal muscle is the protein that gets broken down for
energy, and leads to thinner, less efficient muscles
Malnutrition: Anorexia
• Anorexia means reduced appetite
• It is a psychiatric illness with complex causes. Involves starvation and loss of
body mass
• Anorexia is an eating disorder in which the individual may have an ideal body
image for themselves and will not eat in order to obtain this mental image
• When an individual restricts essential nutrients, they can damage their bodies,
including the muscle and valves of the heart
• The amounts of carbs and fat consumed are too small to satisfy the body’s
energy requirements, so proteins and other chemicals in the body are broken
down. There is a wasting of muscles. Hair becomes thinner and can drop out.
Skin becomes dry and bruises easily. Blood pressure is reduced, with slow
heart rate and poor circulation. Infertility with no ovulation. Heart muscle
deteriorates
• If untreated, anorexia can result in death
Anorexia
Starvation
• Caloric deficiency leads to starvation
Nutritional Excess
• When individuals consume more nutrients or calories than needed
for metabolic processes, obesity can occur
• There are a variety of factors that have lead to the increase in obesity
rates world-wide. These include:
• Migration to urban centers
• Less time and energy prepping and making food
• The consumption of high-calorie, low nutrition pre-packaged
foods
Obesity: Hypertension
• There are many complications that arise from obesity
• Obesity is defined as having a BMI (Body Mass Index) of 30 or greater
• Obese individuals have a greater chance to develop hypertension or
high blood pressure
• This occurs because as the size of the body increases, more blood is
needed to carry the necessary oxygen, and this increases the
pressure on the artery walls
Obesity: Type II diabetes
• In addition to the risk of hypertension, there is a positive correlation
between obesity and the development of type II diabetes
• Type II diabetes is when the body develops a resistance to the
hormone insulin as well as a decrease in the production on insulin
• This leads to high blood glucose levels
• Unless carefully managed, diabetes can cause other health problems
to develop: atherosclerosis (narrowing of arteries by fatty deposits),
hypertension and coronary heart disease (narrowing of the coronary
arteries with the associated risk of heart attacks)
Correlation between high levels of cholesterol in blood plasma
and an increased risk of coronary heart disease (CHD)
• Cholesterol in blood is an indicator of the risk of coronary heart
disease  Positive correlation
• Cholesterol is a normal component of plasma membranes in human
cells and is synthesized by the liver in hepatocytes
• It turns out that cholesterol is transported in lipoproteins, which are
small droplets coated in phospholipid
• LDL is the so-called “bad cholesterol” because it carries cholesterol
from the liver to body tissues.
• High density lipoprotein (HDL) is “good cholesterol” as it collects
cholesterol from body tissues and carries it back to the liver for
removal from the blood
• As a result, dietary cholesterol intake appears to have a very small
effect on blood cholesterol levels and therefore little effect on CHD
• Genetic factors are more important than dietary intake
• 5% of population has a dominant gene for hypercholesterolemia
• Drugs (statins) can be more effective at reducing blood cholesterol
levels than reductions in dietary intake
• Positive correlation between dietary intake of saturated fats and
intake of cholesterol, so it is possible that saturated fats, not
cholesterol, cause the increased risk of CHD in people with high
cholesterol intakes. (Saturated fats are solid at room temperature)
Nutritional Imbalances
• In some parts of the world, single food crop
staples can leave members of the population
in a state of nutritional imbalance
• This is because the staple crop is missing one
or more essential nutrients for human health
• To fight this, scientists have genetically
modified certain types of food
• Golden rice, which features the addition of
beta carotene, helps alleviate Vitamin A
deficiency, which can lead to blindness and
death
Calorimetry- determination of the energy content of
food by combustion
• The simple calorimeter is based on the knowledge of the specific heat
capacity of water
• It takes 4.186 J of heat energy to raise the temperature of 1 gram of water
by 1 degree Celsius
• Q = mass of water x specific heat capacity x change in temperature
• Q= m x C x ΔT
• The apparatus consists of thermometer to detect the change in
temperature and a vessel containing a known mass of water (1 ml of water
= 1 gram)
• The sample to be tested is ignited and placed below the container with
water and the change in temperature is noted
• Specific heat = 1 cal/g/oC or 4.186 J/g/oC
Calorimeter
Problem
• Using the experimental results below, estimate the energy content of the
nut per gram.
• Sample data:
• Mass of nut = 0.60 grams
• Volume of water = 25 mL
• Initial water temperature = 20oC
• Final water temperature = 65oC
• Q= 25 mL x 4.186 J/g/oC x 45= 4709.25 J/1000= 4.70 kJ/0.6 g= 7.85 kJ/g
• Q = 25 mL x 1 cal/g/oC x 45 = 1,125 little calories/1000 = 1.125 kcal
• 1.125 Kcal/ 0.6 grams = 1.875 kcal/gram of nuts
Problem
• Using the experimental results below, estimate the energy content of the
food per gram in kJoules and calories
• Sample data:
• Mass of food= 0.89 grams
• Volume of water = 50 mL
• Initial water temperature = 10oC
• Final water temperature = 80oC
• Q= 50 mL x 4.186 J/g/oC x 70= 14651 J/1000= 14.651 kJ/0.89 g= 16.46 kJ/g
• Q = 50 mL x 1 cal/g/oC x 70 = 3500 little calories/1000 = 3.5 kcal/0.89 g=
3.93 kcal/g
Problem
• Using the experimental results below, estimate the energy content of the
food per gram in kJoules and calories
• Sample data:
• Mass of food= 1.5 g
• Volume of water = 75mL
• Initial water temperature = 10oC
• Final water temperature = 75oC
• Q= 75 mL x 4.186 J/g/oC x 65= 20406.75 J/1000= 20.40675 kJ/1.5 g= 13.60
kJ/g
• Q = 75 mL x 1 cal/g/oC x 65 = 4875 little calories/1000 = 4.875 kcal/1.5 g=
3.25 kcal/g
Monitoring personal dietary intake
• It is possible to use databases of nutritional content of foods and
software to calculate intakes of essential nutrients from a daily diet
• “Super Tracker” available from the US Department of Agriculture
(USDA) and is free
• https://www.supertracker.usda.gov
• Assignment- Print out an image of a day of eating that you analyzed
with this website!
• 25 points
Super Tracker screenshot example
Definitions
1. Nutrition: the act of taking food in (ingestion) breaking it apart (digestion) and
cellular uptake (absorption)
2. Nutrient: chemical substances found in foods and used in the human body
3. Mineral: inorganic substance which are needed in small amounts in humans
(mg) that living things need for a variety of purposes. Chemical elements
usually in ionic form
4. Vitamin: chemically diverse carbon compounds needed in small amounts that
cannot be synthesized by the body
5. Malnutrition: a deficiency, imbalance or excess of specific nutrients in the diet
6. Obesity: excessive storage of fat in adipose tissue, due to prolonged intake of
more energy in the diet than is used in cell respiration
7. Anorexia: condition in which an individual does not eat enough food to sustain
the body even thought it is available. Voluntary starvation
8. Starvation: prolonged shortage of food. Once glycogen and fat reserves are
used up, body tissues have to be broken down and used in respiration
Definitions
8. Phenylketonuria: an autosomal recessive genetic condition in which the
level of phenylalanine (amino acid) in the blood becomes too high due to
the lack of a functional phenylalanine hydroxylase due to a mutation of
the gene coding for the enzyme.
9. Rickets: a disease that leads to irregular bone growth along growth
plates due to a deficiency of Vitamin D
10. Coronary heart disease: narrowing of the blood vessels that lead to
cardiac muscle. Risk factor for heart attack
11. Osteomalacia: inadequate bone mineralization due to calcium salts not
being deposited or being reabsorbed, so bones become softened.
Vitamin D deficiency implicated
Distinguish between essential and nonessential nutrients
• Non-essential nutrients can be made by cells or because another
nutrient can be used for the same purpose
• Example: glucose
• Nutrients that cannot be made by our bodies are called essential
nutrients
• Essential amino acids, essential fatty acids, minerals, and most vitamins
Consequences of a deficiency in the diet of an
essential amino acid
• If you are missing one of the 8 (9) essential amino acids, amino acid
deficiency results in protein deficiency malnutrition
• Amino acids cannot be stored and must be included in the diet
Outline 2 conditions that might cause the
breakdown of heart muscle tissue
• Anorexia: restriction of essential nutrients can lead to damage of the
body including the muscle and valves of the heart
• Fats and carbohydrate intake too limited to satisfy body’s energy
requirements, so proteins and other chemicals in the body are
broken down
• Starvation: prolonged shortage of food leads to body tissues break
down
Outline 2 conditions caused by being
overweight
• Hypertension: high blood pressure
• As size of the body increases, more blood is needed to carry the
necessary oxygen, and this increases the pressure on the artery
walls
• Increased capillary network to move blood through
• Can lead to strokes and heart attacks
• Type II Diabetes: body develops a resistance to the hormone insulin
as well as a decrease in the production of insulin
• This leads to high blood glucose levels
• Can lead to atherosclerosis and chronic heart disease
Outline the mechanism that can prevent the
body from becoming overweight
• Appetite control is the negative feedback mechanism that the body uses to
prevent it from becoming overweight
• Control center is in the hypothalamus of the brain
• Negative feedback loops between the nervous, digestive, and endocrine
systems
• Hormones secreted: PYY from intestines when it contains food; insulin
from pancreas when blood glucose level is high; leptin from fat cells
(adipose) when the amounts of stored fat increase
• Target: hypothalamus. Effect: reduces desire to eat
• Brain also uses other signals such as physical cues, such as when the
stomach expands and sends message to brain that it is full and to stop
eating.
Explain how the content of energy and
essential nutrients in a diet can be assessed
• Energy content of food = calories
• Determined using a calorimeter which is based on the knowledge of
the specific capacity of water and the combustion of food
• In this method, a known quantity of water of known initial
temperature, is heated by the combustion of a known quantity of
food and the temperature difference measured.
• Q = Mass of water x specific heat of capacity x change in
temperature
• Nutrients: monitoring personal dietary intake ex: super tracker. Data
base.
Outline the cause and treatment of PKU
• PKU: autosomal recessive condition due to the lack of the enzyme
that breaks down the amino acid phenylalanine to the amino acid
tyrosine or due to the presence of defective enzyme.
• As a result, phenylalanine accumulates in blood and tissues which can
lead to mental retardation, seizures, and a variety of other problems.
• Treatment: Screening at birth for the disorder. Switching infant to a
low phenylalanine/ low protein diet.
Evaluate the research that has shown a correlation between
high levels of cholesterol in blood plasma and an increased risk
of coronary heart disease
1. Positive correlation with the blood plasma cholesterol level and
increased risk of CHD.
2. This correlation may not be causative.
3. Cholesterol is made by liver. It is used to synthesize bile, steroid
hormones, plasma membranes.
4. Reducing dietary cholesterol does not reduce blood cholesterol
levels greatly.
5. Genetic factors are more important than dietary intake.
All cholesterol is not created equal
• Turns out that cholesterol being carried by Low Density Lipoproteins
(LDL cholesterol) is correlated with CHD risk while High Density
Lipoproteins (HDL cholesterol) is correlated with reduced risk.
• Drugs (statins) can reduce blood cholesterol and risk of CHD.
• Positive correlation between dietary intake of saturated fats and
intake of cholesterol, so it is possible that it is the saturated fats, not
the cholesterol, that causes the increased risk.
Explain how the lack of vitamin D or calcium can affect bone
mineralization and cause rickets or osteomalacia
• Vitamin D helps with the absorption of calcium in the intestines which
is then used in bone formation.
• Without Vitamin D, calcium is either not absorbed or is resorbed from
bones so that bones become softened. So mineralization due to
calcium salts is deficient.
• Vitamin D helps with the absorption of calcium in the intestines which
is then used in bone formation
• Without Vitamin D, calcium is either not absorbed or is resorbed from
bones so that bones become softened
• So mineralization due to calcium salts is deficient