Transcript Nutrition Part 1 Powerpoint

Nutrition
Vital Nutrients
• The small intestine absorbs all
the nutrients required for life
• Some nutrients are required for
energy and for building blocks
for more cells and cell parts
– Carbohydrates
– Proteins
– Lipids
• Other nutrients are required for
homeostasis but not energy
– Water
– Vitamins
– Minerals
Carbohydrates
• A single carbohydrate molecule is
called a simple carbohydrate or a
monosaccharide (such as glucose)
– Starches are made of many bound
together and are called complex
carbohydrates
– Some are more complex than
others, and the more complex the
branching, the longer the digestion
takes
• “White” starches such as white
rice and pasta contain simpler
chains
Glycemic Index
• The faster a food breaks
down into glucose
molecules, the higher the
glycemic index
– Pure glucose has a
glycemic index of 100
• People with diabetes and
pre-diabetes must eat only
foods with lower glycemic
indices so as to not spike
the blood sugar
– People with a family
history of diabetes should
probably do so as well…
Insulin Spike
• Insulin is released in
response to glucose
– Insulin stimulates the
liver and fat cells to
absorb glucose
• A rapid release of
glucose followed by
an insulin spike can
cause the blood sugar
to crash
Indigestible Carbohydrates
• Some branch-chain
carbohydrates are completely
indigestible to humans (such as
cellulose)
• These are still useful to the
body as dietary fiber
– They add mass to your food
(causing you to eat less overall)
– They retain water in the feces,
making it easier to pass
Proteins
• Proteins must be broken down to
the individual amino acids
• The human body can synthesize
many of the amino acids from
other amino acids (so they are
nonessential), but there are
certain ones that cannot be
synthesized
– These are called essential amino
acids
• If even one of the essential amino
acids is missing, the diet is
incomplete and no new protein
can be made
Lipids
• There are many classes of lipids
– Some vitamins (A, D, E, K) and
cholesterol are lipids, but cannot be
burned for energy
• The energy-storing lipids are fatty
acids, and these fats can be saturated
or unsaturated
– Saturated fats have no double bonds
and so pack together more tightly than
unsaturated fats
– Treating unsaturated fats with
hydrogenation can create trans fats,
which are very difficult to metabolize
and therefore very unhealthy
Vitamins and Minerals
• Vitamins are organic
compounds that serve key
purposes in cell
mechanisms but only in
small amounts
– Example: vitamin A used in
your retina
• Minerals are inorganic
elements and compounds,
such as sodium, potassium,
calcium, iron, and iodine
– Also necessary for life
Sample Vitamins and Minerals
• Vitamin A: used in the retina,
can be synthesized from
carotene (in carrots and
tomatoes); deficiency can
result in blindness
• Vitamin D: important for bone
growth, produced by sunlight
on skin from cholesterol;
deficiency called rickets
• Vitamin C: found in citrus
fruits, boosts collagen
production and immune
system function; deficiency
called scurvy
• Niacin: vital for processing
energy-storing molecules;
deficiency called pellagra
• Sodium: Vital for maintaining
osmotic balance and key
component of action
potentials
• Potassium: Vital for action
potentials, must be in
proportion to sodium
• Iron: Used in hemoglobin, lack
of iron in diet results in irondeficiency anemia
• Iodine: A key component of
the thyroid metabolic
hormones T3 and T4
(thyroxine)
• Zinc: functions as a cofactor in
many metabolic enzymes
Alcohol Dehydrogenase
• The liver must metabolize
alcohol into acetic acid using
an enzyme called alcohol
dehydrogenase
– This requires energy and uses
some of the liver’s resources
– Most women and some ethnic
groups such as East Asians have
less enzyme, making them have
a lower tolerance for alcohol
• Acetic acid can then either be
converted to fat or burned for
energy as needed
Dietary Proportion
• Opinions vary wildly on the
“optimal” dietary proportions
of carbs, proteins and fats
• A major reason for this is the
different efficiencies of
enzymes in different people
– Genetics in action!
– What is healthy for one person
may be unhealthy for another!
Example of Enzyme Action
• Carbohydrates and lipids are
interconvertible, meaning carbs can be
changed to lipids and vice versa
– These are accomplished using enzymes
• If a person’s enzymes to change
carbohydrates into lipids are more
efficient, then that person may
preferentially build fat more than
someone else
– Someday genome sequencing will make
nutrition much more personalized
Essential Macronutrients
• New cells must be formed
every day
– Mostly epithelial cells (skin, GI
tract, etc) and blood cells
• All cells require fat (cell
membrane) and protein (for
cell structures)
– Carbohydrates are also used
structurally for skin
glycoproteins
– Carbohydrates are also used as
the energy source for mitosis
Nutrient Use
Friday: Metabolism!
• Then kidneys, then reproduction, then no new
lessons!