Chapter 4/5 Flashcards
Why are carbs the highest nutrient in most diets, cross-culturally?
> Carbs are in most foods
>The body prefers glucose for energy
What are food sources of carbs?
vegetables, fruit, starch, and dairy
What does it mean to refine carbs?
to separate carbs from their vitamins, minerals, and fiber
What are examples of refined carbs?
white flour, white rice, all sweeteners
What are structural components of whole grains?
> endosperm (starch)
bran (fiber, vitamins, minerals)
germ (oil and vitamin E)
What are structural components of refined grains?
only ENDOSPERM (starch)
What are some vitamins/minerals refined grains are enriched and fortified with?
Enriched (replaced): thiamin, riboflavin, niacin, iron
Fortified (added): folate
Why is folate added to refined grains?
Folate is found in fruits and vegetables; refined grains are fortified w/ folate bc ppl under-consume these other foods
What is the significance of folate deficiency?
Folate deficiency = neural tube defects
What vitamins/minerals do refined grains lack relative to whole grains?
magnesium, Vitamin E, some B vitamins
What is a monosaccharide?
a single sugar molecule
3 most common monosaccharides in diet?
> Glucose - most important,”blood sugar”
Galactose - “milk sugar”
Fructose - highest form of sugar in fruits, vegetables, honey, high-fuctose corn syrup
What is a disaccharide?
simple carbs made up of TWO monosaccharides linked together
3 most common disaccharides in diet?
> Maltose – 2 glucose units, formed in digestive tract when starch is digested
>Mostly in BREAD products
Sucrose – glucose + fructose
>White table sugar
>Only sweetener that can be labeled “sugar” (U.S.)
Lactose – glucose + galactose
>Milk sugar
What are the 2 simple carbs?
> Monosaccharides - a single sugar molecule
>Disaccharides - two monosaccarides linked
What are complex carbs?
> Made up of many (>2) monosaccharides linked in chains
>Oligosaccharides and Polysaccharides
What are oligosaccharides?
> short chains of less than 10 monosaccharides
>Found in legumes/beans
What are polysaccharides?
> long chains of monosaccharides and include
>Glycogen found in animals
>Starch and fiber found in plants
How are carbs stored?
As glycogen in liver (with water) and in skeletal mscls
> Liver: maintains blood glucose
Skeletal mscls: used for movement (only in mscl)
What are symptoms of low glycogen stores?
> Impaired brain fxn
Confusion
Irritability
What happens when mscl glycogen stored are reduced?
Decrease in work capacity
What is carb loading?
increasing glucose stored as glycogen on a working muscle
What are the two types of fiber?
Soluble (gel-like) and insoluble
> Water-soluble fiber binds dietary cholesterol and reduces abspt.
What are food sources of soluble fiber?
legumes, raisins, bananas, oats, flaxseed
What are food sources of insoluble fiber?
wheat bran, broccoli, corn, nuts, seeds
In what form do we absorb carbs?
As monosaccharides
>Disaccharides are broken into monosaccharide
What is lactose intolerance?
Inability to digest milk sugar, lactose
What causes lactose intolerance?
Absence or lack of lactase enzyme needed to digest lactose
Symptoms of lactose intolerance
cramping, abdominal distention, diarrhea
What are some indigestible carbs?
Resistant starch, fiber, oligosaccharides
What are food sources of indigestible carbs?
Resistant starch: seeds, legumes, unrefined grains, cooked/cooled potatoes, pasta, sushi rice
Fiber: only in unrefined plant foods (soluble and insoluble)
Oligosaccharides: only in legumes
What do indigestible carbs do in the body?
> Decrease transit time, i.e. make you poop faster
Improve health of intestinal microflora
Increase amount of intestinal gas
High amounts can decrease abspt of minerals
How is blood glucose regulated?
> Pancreatic hormones (insulin and glucagon) regulate blood glucose lvls
What are the pancreatic hormones and their fxns?
> Insulin (after meals) – secreted w/ rising blood glucose → leads to storage of glucose
> Glucagon (between meals) – released w/ decreasing blood glucose → leads to increasing blood glucose lvls
What is the glycemic response?
How quickly and how high blood glucose rises after carbs are consumed
What is the glycemic index?
a ranking of how a food affects the glycemic response
Glycemic load
(a food’s glycemic index) * (number of available carbs in a serving)
What are effects of low carb diet?
> Body uses amino acids to make glucose
We don’t have protein stores, so where do the amino acids to make glucose come from?
amino acids come from (muscle!!) tissue
Ketogenesis
Prodxn of ketones from incomplete fat catabolism
>Glucose needed for complete fat catabolism
Ketones
>made when there's glucose deficit, survival mechanism >Short term energy use by brain, heart >Will suppress appetite >Create unhealthy LDL >Acidify body
Longer term compliance is poor
How many carbs needed to avoid ketosis?
50 to 100
What are 2 health outcomes of Diabetes Mellitus?
> Blindness
>Kidney failure
What are the 2 types of Diabetes Mellitus?
> Type 1: Insulin not made in body
>Need insulin injection or pump
Type 2: Insulin is made, but receptors on cells not fxning properly
What are symptoms of Type 1 Diabetes?
excessive thirst, frequent urination, blurred vision, weight loss
What are symptoms of Type 2 Diabetes?
no obvious symptoms,
has genetic component,
long term complications are damaging to: heart, blood vessels, kidneys, eyes and nervous system
Diabetes treatment?
> Diet: moderate intake of carbs and healthy fats (fats slows digestion), moderate protein (diminish stress on kidneys)
Exercise
Monitoring blood glucose lvls
Medication
Reactive hypoglycemia
Oversecretion of insulin in response to carb intake
Treatment of Reactive hypoglycemia
frequent small meals; moderate carbs
Fasting hypoglycemia
Low insulin secretion unrelated to food intake
Fiber and Bowel Disorders
Diets high in fiber and indigestible carbs can relieve or prevent certain bowel disorders, including hemorrhoids, diverticulosis, diverticulitis
Hemorrhoids
> Broken bits of skin near anus
>Caused by straining and high pressure
Diverticulosis
> Broken skin (small pockets) in large intestine
>Also caused by straining and pressure
Diverticulitis
> Inflammation of small pockets in large intestine
Colon Cancer and Fiber Intake
incidence of colon cancer is lower in popul’ns that consume diets high in fiber
Lipid (fats)
> contribute texture, flavor, aroma to foods
>9kcal per gram
How much do fats contribute to typical American diet?
> 34% of energy from fat
3 types of lipids
> Monoglyceride - one fatty acid attached to glycerol
Diglyceride- two fatty acids “ “ “
Triglycerides- three “ “ “ “ “
»_space;Stored in adipose tissue
How does fatty acid chain length affect form?
> As fatty acids increase in length, they tend to be solid at lower temps (e.g. when refrigerated)
Short-chain fatty acids
4 to 7 carbons
Remain liquid at colder temps
E.g. Milk
Medium-chain fatty acids
8 to 12 carbons
Solidify when chilled
Liquid at room temperature
E.g. Coconut oil
Long-chain fatty acids
> 12 carbons
Solid at room temp
E.g. Beef fat
Saturated Fatty Acids
> Carbons in a chain that are bound to 2 H
>Don’t oxidize (breakdown, become rancid)
Saturated fatty acids food sources
Most animal fats Tropical oils (coconut and palm)
Unsaturated Fatty Acids
Has some carbons that are not saturated w/ H
Result = double bond
Types Unsaturated fatty acids
Monounsaturated = 1 double bond Polyunsaturated = at least 2 double bonds
2 families of essential unsaturated fatty acids
>Omega-3 >Linoleic acid >Omega-6 >LinoLENic acid >long chain, “Length” (len)
Trans Fatty Acids
created by hydrogenation
Hydrogenation
chemical process that adds H to unsaturated fatty acids
>Double bonds become saturated
>Makes products more shelf-stable
>BUT adversely related to health
Trans Fats and health outcomes
Trans fats strongly linked with increase in risk of heart disease and cancer
>In 2010, NYC banned trans fats
Steps to reduce trans fat content in food
> By 2018, all food manufacturers will be forced to remove partially hydrogenated oils from their food
>Trans fats will be considered adverse to human health
Phospholipids
diglycerides w/ a phosphate group
>Fxn: emulsifiers – transport lipids through water substances in body (diffusion)
>Lipid bilayer in cell membranes
What’s one major class of Phospholipids and general structure of phospholipids?
> Lecithin
>Hydrophobic tails, hydrophilic heads
Sterols
> Lipid found in plants and animals
Cholesterol is a sterol found only in animal foods
>over 90% is found in cell membranes
Bile and micelles
> > > Forms micelles (“my-cells”), which prevent triglycerides from clumping up together
»Lipases, which break down lipids, have more surfaces to act on
Lipases
> break down lipids
[enzyme that remove fatty acids from triglycerides]
Amount of digestion by lipases in stomach and pancreas?
> Gastric lipase – Minimal digestion
>Pancreatic lipase – digests TG to monoglyceride + 2 free fatty acids
How does fat digestion occur?
> Some fat is digested in stomach by gastric lipase
Most fatty acid digestion occurs in small intestine
>Bile acts as emulsifying agent and creates micelle
>Lipase break down fats
Lipoproteins
> Transport water-insoluble lipids (TG, cholesterol), phospholipids, proteins, fat-soluble nutrients
Chylomicrons
Key fxn: deliver triglycerides from intestines to body’s cells.
[Chylomicrons are lipoproteins that consist of triglycerides, cholesterol, phospholipids, and protein.]
Chylomicron Transport Mechanism
Transport long-chain fatty acids → lymphatic system → blood stream
Very low-Density Lipoproteints (VLDL)
Not heavy, floats, lots of triglycerides in it
VLDL Synthesis
VLDL are made in liver
VLDL Synthesis Mechanism
> Extra energy from carbs (glucose) and protein (amino acids) are catabolized to 2 carbon acetic acid
Used for fatty acids anabolism (building)
Released as very-low-density-lipoproteins (VLDLs) → deliver lipids to cells
What are you measuring when you measure someone’s fasting triglycerides?
VLDL
What are you measuring when you measure someone’s triglycerides after a meal?
> Chylomicrons (triglycerides from food)
Lipoprotein lipase
removes triglycerides from VLDLs, creating intermediate-density lipoproteins (IDLs)
Low-Density Lipoproteins (LDL)
> 1/3 of IDL have additional TG removed → low-density lipoproteins (LDLs)
LDL is main carrier of blood cholesterol
>If someone has high cholesterol, they have high LDL
Elevated LDL
Primarily due to genetic defect in LDL receptor of cells
Elevated OXIDIZED LDLs
increased risk for heart disease
>Polyunsaturated fats will oxidize in the body
>Main source of polyunsaturated fats are vegetable seed oils
3 Fxns of stored fat
- Provide stored energy
- Insulate the body from temp changes
- Protect internal organs against physical shock
Fxns of Cholesterol
> Used to make several hormones, including sex hormones and cortisol
Vitamin D prodxn
Bile prodxn
Component of cell membranes
Fxns of Essential Fatty Acids
growth, skin integrity, fertility, and the structure and fxn of cell membranes
Eicosanoid Synthesis
SEE SLIDES
Omega 3 and omega 6 fatty acids: competition at first enzyme
Dietary Sources of Eicosanoids
> Hormone-like: Act where they’re synthesized
>
Which of the 2 essential fatty acids are highest in American diet? Why?
Omega-6 bc we eat a lot of vegetable oils and meats
Beneficial sources of omega 3
Fish oil – for EPA (20 carbon)
> Humans very inefficient at converting 18c to 20c
>Walnuts, flax, soy = bad sources
3 Risks of Oxidation
Excess oxidation means oxidation of:
- DNA → Cancer
- LDL → atherosclerosis/heart disease
- Cell membranes
Ratio of omega 3:6 in blood
Determines health
Lipids: Feasting/Fasting
> Feasting – excess energy is consumed and stored as TG in adipose tissue
Fasting – TG from adipose tissue are broken down, releasing fatty acids as an energy source
