major reasons why people make food choices

• preference
• habit
• ethnic heritage / regional cuisine
• social interactions
• marketing
• availability/convenience/economy
• positive and negative associations
• emotions
• values
• body weight / health
• nutrition

preference (reasons why people make food choices)

• how something tastes, if they like the flavor (ie. sweetness of sugar, savoriness of salt, high fat)
• may be influenced by genetics or pregnancy hormones (which alter food cravings and aversions)

habit (reasons why people make food choices)

• eating familiar foods / not making decisions = comforting
• people correlate certain foods / beverages with certain times of day

ethnic heritage and regional cuisines (reasons why people make food choices)

• people tend to prefer the foods they grew up eating (but also may be willing to be adventurous)
• developing “cultural competence”

social interactions (reasons why people make food choices)

• meals as “social events,” sharing food as hospitality
• people tend to eat more food when socializing with others
• eating similar foods to people in one’s social circle (ie. why obesity can be seen spreading in social networks)

marketing (reasons why people make food choices)

• food industry persuades people to eat more, and more often
• generates billions in sales for these companies each year
• brand loyalty, convenience, etc.

availability, convenience, and economy (reasons why people make food choices)

• food within financial means, quick and easy to prepare, and accessible is preferred
• fewer adults learning how to cook due to more convenient options
• people who cook for themselves and eat at home more make healthier choices
• choosing cheaper, fast food options when eating out rather than higher end restaurants which possess saturated fats, sodium, and other ingredients overconsumed by Americans
• healthier diets are more expensive (ie. fruits, vegetables, nuts, etc.)
• strategies to change this?: reducing prices of fruits and vegetables, taxing processed foods, strategic placement of healthy options, limiting discounts on less-healthy foods

positive and negative associations (reasons why people make food choices)

• people liking to eat foods they associate with happy occasions
• people often dislike foods they ate when sick, forced to eat in negative situations
• also, parents using certain foods as rewards / punishments

(example: WWII vets who fought in the Pacific disliking Asian food more than others)

emotions (reasons why people make food choices)

• may eat more or less when emotionally upset
• may eat more when bored/lonely, to ease anxiety
• carbs / alcohol = calm, protein / caffeine = more likely to stimulate
• can lead to overeating / obesity, but can also be helpful

values (reasons why people make food choices)

• food intake influenced by political views, religious beliefs, or environmental concerns

body weight and health (reasons why people make food choices)

• selecting food and supplements based on health, body weight, allergies, etc.
• helpful when based on nutritional science, based on fads can be detrimental

nutrition (reasons why people make food choices)

• making choices based on what seems nutritious, healthy
• harder to make good food choices with introduction of processed foods (ultra-processed being worse than minimally processed)

nutrient (definition)

substances that the body uses for the growth, maintenance, and repair of its tissues

• may also reduce the risk of developing certain diseases

six major nutrients

• water
• carbohydrates (including fibers)
• lipids
• proteins
• vitamins
• minerals

energy-yielding nutrients (or macronutrients)

• carbohydrates
• fat
• protein

how many calories are provided by carbohydrates?

4 kcal

how many calories are provided by fats?

9 kcal

how many calories are provided by proteins?

4 kcal

what are the different types of nutrition research study designs?

Epidemiological Studies

• Cross-Sectional Studies
• Case-Control Studies
• Cohort Studies

Experimental Studies

• Laboratory-Based Animal Studies
• Laboratory-Based In Vitro Studies
• Human Intervention (or Clinical) Trials

epidemiological study (or observational study)

research the incidence, distribution, and control of diseases in a population

strengths of an epidemiological study

• narrows down list of possible causes
• raises questions to pursue through other research

weaknesses of an epidemiological study

• can't control variables that may influence development or prevention of a disease
• can't prove cause and effect

cross-sectional study

type of epidemiological study

• observing how much / what kind of food groups people eat & how healthy they are
• can find connections to disease incidence

case-control study

type of epidemiological study

• comparing people who do have a given disease and people who do not, matching other key variables (age, gender, etc.)
• looking at the differences to better understand why they may occur

cohort study

• analyzing data from a select group of people over a period of time

experimental study

test cause-and-effect relationships between variables

• include laboratory-based studies– on animals or in test tubes (in vitro) – and human intervention (or clinical) trials

strengths of experimental studies

• can control conditions (for the most part)
• can determine effects of a variable
• can apply some findings on human beings to some groups of human beings

weaknesses of experimental studies

• can’t apply results from test tubes/animals to human beings
• can’t generalize findings
• ethical and clinical constraints on certain treatments

laboratory-based animal studies

type of experimental study

• observing changes in animal health when giving diets with certain nutrients, and excluding certain nutrients
• controlled conditions, testing possible disease causes

laboratory-based in vitro studies

type of experimental study

• studying effects of variable on tissue, cell, or isolated molecule from living organism

human intervention (or clinical) trials

asking people to adopt a new behavior, examining how it affects health

dietary reference intakes (DRI)

a set of nutrient intake values for healthy people in the United States and Canada

• these values are used for planning and assessing diets

four parts of the DRI (dietary reference intake)

• EAR - estimated average requirement
• RDA - recommended dietary allowance
• AI - adequate intakes
• UL - tolerable upper intake levels

estimated average requirement (EAR)

average daily amount of a nutrient that will maintain a specific biochemical or physiological function in half the health people of a given age and gender group

• needed to set the recommended allowance

recommended dietary allowances (RDA)

the average daily amount of a nutrient considered adequate to meet the known nutrient needs of practically all healthy people

• a goal for dietary intake by individuals

adequate intakes (AI)

average daily amount of a nutrient that appears sufficient to maintain a specified criterion

• used as a guide for nutrient intake when an RDA cannot be determined (insufficient evidence to make a stronger conclusion)

tolerable upper intake levels (UL)

• the maximum daily amount of a nutrient that appears safe for most healthy people and beyond which there is an increased risk of adverse health effects

estimated energy requirement (EER)

the average dietary energy intake that maintains energy balance and good health in a person of a given age, gender, weight, height, and level of physical activity

acceptable macronutrient distribution ranges (AMDR)

ranges of intakes for the energy nutrients that provide adequate energy and nutrients and reduce the risk of chronic diseases

4 parts of a nutrition assessment for individuals (ABCD)

• A: anthropomorphic measurements
• B: biochemical tests (lab. tests)
• C: clinical exams (physical examinations)
• D: diet history (historical information)

anthropomorphic measurements

height, weight, and other measurements taken and compared with previous results overtime may indicate trends in nutritional status overtime

• can attach physical manifestations to maybe some sort of nutrient issue

clinical exams (physical examinations)

looking for physical symptoms that may be the result of a nutritional issue, imbalance

biochemical tests (laboratory tests)

looking at samples of blood, urine, etc. to uncover early signs of malnutrition before the symptoms appear

diet history (historical information)

using health history (medical record, may have condition that interferes with ability to use nutrients), family history of certain diseases, economic status which may impede ability to have good nutrition, social factors, diet history (what you are eating on the daily)

major national nutrition surveys used to assess the nutritional status US population

• What We Eat in America
• National Health and Nutrition Examination Survey

What We Eat in America

collects data on the kinds and amounts of food people eat

National Health and Nutrition Examination Survey

examines people using anthropomorphic measurements, physical examinations, and laboratory tests

major chronic diseases that are linked to diet

• heart / cardiovascular disease
• some kinds of cancer
• strokes
• diabetes mellitus

accurate sources of nutrition information

• nutrition and food science departments at a university or community college
• local agencies such as the health department or County Cooperative Extension service
• government resources (ie. CDC, USDA, etc.)
• volunteer health agencies (AHA, etc.)
• reputable consumer groups (ACSH, etc. )
• professional health organizations (AMA, etc.)
• journals

8 red flags that identify nutrition misinformation

• satisfaction is guaranteed
• one product does it all
• time tested or newfound treatment
• paranoid accusations
• personal testimonials
• meaningless medical jargon
• natural
• quick and easy fixes

six principles of diet planning

• adequacy
• balance
• kCalorie (energy) control
• nutrient density
• moderation
• variety

adequacy (principles of diet planning)

reflects a diet that provides sufficient energy and enough of all the nutrients to meet the needs of healthy people

balance (principles of diet planning)

consuming enough – but not too much – of different types of foods in proportion to one another

kCalorie / energy control (principles of diet planning)

amount of energy coming into the body from foods should balance with the amount of energy being used by the body to sustain its metabolic and physical activities

nutrient density (principles of diet planning)

selecting foods that deliver the most nutrients for the least food energy

• to eat well without overeating, kind of like “budgeting” getting the most for your dollar
• provide vitamins, minerals, and other health-promoting components with little to no added sugar, saturated fat, and sodium

moderation (principles of diet planning)

eating foods that have adverse health effects on occasion, regularly selecting more nutritious options

variety (principles of diet planning)

selecting foods from each of the food groups daily and varying choices within each food group from day to day

Dietary Guidelines for Americans

an evidence-based document used to develop federal food, nutrition, and health policies and programs

• tells people what they should eat to stay healthy
• turns nutrient recommendations into food recommendations

MyPyramid / MyPlate

seeks to help Americans make better food choices by illustrating recommended portions from the five food groups (fruits, vegetables, grains, protein, and dairy) on a simple plate or pyramid

summary of the Dietary Guidelines for Americans (2020-2025)

• follow a healthy dietary pattern at every life stage
• customize / enjoy nutrient dense food and beverage choices to reflect one's budget, cultural traditions, and personal preference
• meet food group needs with nutrient dense foods and beverages while staying within calorie limit
• limit foods and beverages higher in added sugars, saturated fat, and sodium, and alcohol

what are the components of the MyPyramid graphic and what do the colors, bandwidth sizes and shapes all mean

• multiple colors of the pyramid illustrate variety - each color represents one of the five food groups + one for oils
• widths of the different colors suggest proportional contribution of each food group to a healthy diet
• narrow slivers of color at top imply moderation of solid fat and added sugar rich foods
• wide bottom = nutrient dense foods should make up bulk of diet
• person climbing up steps = reminder to be physically active every day
• greater intakes of grains, vegetables, fruits, and milk encouraged

what are the components of the MyPlate graphic

• make half your plate fruits and vegetables
• move to low-fat or fat free dairy milk
• make half grains whole grains
• be active to help prevent disease and manage weight
• vary protein routine
• vary vegetables
• focus on whole fruits

nutrient density

provide vitamins, minerals, and other health-promoting components with little to no added sugar, saturated fat, and sodium

• "most bang for buck"

foods that are nutrient dense

• vegetables and leafy greens
• fruits
• seafood / lean meat
• legumes, nuts, and seeds
• dairy
• eggs

energy density

a measure of the energy a food provides relative to the weight of the food (kcal per gram)

• more fat content = more _______

foods that are energy dense

• nuts
• seeds
• avocados
• oils
• nut butters
• fatty meats
• cheese
• pastries
• other processed snacks

information that is required on a food label

• product name
• manufacturer’s name and address
• amount in the package
• ingredients in descending order by weight
• allergens (milk, eggs, fish, wheat, nuts, soy)
• nutrition facts panel

information that is required on a nutrition facts panel

• serving sizes
• nutrient quantities
• daily values

daily value (DV)

help consumers readily see whether a food contributes a little or a lot of a nutrient

• how much you should aim for or limit in a day
• compares key nutrients in a serving of food with the goals of a person consuming 2,000 calories a day

how is the daily value used on food labels

%DV appears next to each nutrient on the nutrient facts label

• 5% DV or less - low in that nutrient
• 20% DV or more - high in that nutrient

nutrient claims (on food label)

characterize the level of a nutrient in a food

• ex. “fat free” or “less sodium”

health claims (on food label)

characterize the relationship of a food or nutrient to a disease or health-related condition

• ex. “a diet low in total fat may reduce the risk of heart disease”

structure/function claims (on food label)

describe the effect that a substance has on the structure or function of the body and do not make reference to disease

• ex. “supports immunity and digestive health” or “calcium builds strong bones”

parts of the gastrointestinal (digestive) tract

• mouth
• esophagus
• stomach
• small intestine
• large intestine (colon)

mouth

chews and mixes food with saliva

esophagus

passes food to stomach

stomach

adds acid, enzymes, and fluid

churns, mixes, and grinds food to a liquid mass

small intestine

secretes enzymes that digest carbohydrate, fat, and protein

cells lining intestine absorb nutrients into blood and lymph

large intestine (OR colon)

reabsorbs water and minerals

passes waste (fiber, bacteria, any unabsorbed nutrients) and some water to rectum

organs that assist in digestion but are not a part of the digestive tract

• salivary glands
• liver
• gallbladder
• bile duct
• pancreatic duct
• pancreas

salivary glands

• donate a starch-digesting enzyme
• donate a trace of fat-digesting enzyme (important to infants)

liver

manufactures bile, a detergent-like substance that facilitates digestion of fats

gallbladder

stores bile until needed

bile duct

conducts bile to small intestine

pancreatic duct

conducts pancreatic juice to small intestine

pancreas

• manufactures enzymes to digest all energy-yielding nutrients
• releases bicarbonate to neutralize stomach acid that enters small intestine

mechanical digestion

physical breakdown of food components

chemical digestion

chemical breakdown of food components

what are the components of mechanical digestion?

• segmentation and peristalsis (GI tract)
• sphincter contractions
• stomach action

segmentation

inner circular muscles contract and relax, churning chyme

peristalsis

outer longitudinal muscles rhythmically contract in a way that moves chyme forward

• general propulsion

mass movement

strong, forceful contractions in large intestine

stomach action

• three sets of muscles in the stomach work together to force chyme downward
• pyloric sphincter which sits at bottom of stomach is closed, prevents it from moving into small intestine
• result: chyme is churned

sphincter contractions

sphincter muscles periodically open and close

• allows contents of GI tract to move along at a controlled pace
• located throughout digestion process

upper esophageal sphincter

opens in response to swallowing

cardiac sphincter

prevents reflux of stomach contents

pyloric sphincter

prevents intestinal contents from backing up into the stomach

ileocecal sphincter

prevents large intestine content (bacteria) back up into the small intestine

anal sphincters

controls feces elimination

what are the components of chemical digestion?

• salivary gland secretions
• stomach secretions
• pancreatic secretions
• liver via gallbladder secretions

enzyme action

speed up / catalyze chemical reactions in the body

*facilitate hydrolysis in digestion which breaks down molecules into smaller pieces

• lower activation energy needed for action to occur
• acts on specific substrate, convert substrate into products

salivary gland secretions

squirt just enough saliva to moisten each mouthful of food so that it can pass easily down esophagus

initiates digestion of carbohydrates

stomach secretions

gastric glands in stomach secrete gastric juice

• water, enzymes, HCl

mucus prevents gastric juice from eroding walls of stomach

pancreatic secretions

in small intestine, pancreatic juice act on all three energy nutrients

• cells of intestinal wall possess more enzymes
• contains sodium bicarbonate

liver via gallbladder secretions

• liver produces bile, concentrated and stored in gallbladder
• gallbladder squirts bile into small intestine when fat arrives
• emulsifier, not an enzyme

emulsifier

disperses fats into watery solutions, makes them more accessible for digestive enzymes

where does the digestion of carbohydrates start?

the mouth

• via salivary gland secretions

where does the digestion of fats / lipids start?

the small intestine

• bile emulsifies fats and then pancreatic lipase breaks them down
• via pancreatic secretions & liver / gallbladder secretions

where does the digestion of proteins start?

the stomach

• via stomach secretions

what are the three ways that nutrients can be absorbed into the cells lining the GI tract after digestion?

• simple diffusion
• facilitated diffusion
• active transport

simple diffusion

• cross into intestinal cells freely across phospholipid bilayer
• move with concentration gradient

water, small lipids

facilitated diffusion

• need carrier to transport them from one side of the cell membrane to the other
• or, carrier can change cell membrane in some way so that nutrient can enter

water-soluble vitamins

active transport

• requires energy to move nutrients against the concentration gradient

glucose, amino acids, minerals

circulatory system and nutrient transport

• transports water-soluble and small particles directly from intestine to body blood from intestines → portal vein → liver
• rapid nutrient distribution and regulation of nutrients – liver processes and stores them as needed

sugars & proteins --> blood (liver first)

lymphatic system and nutrient transport

• fat-soluble and large particles
• intestines to thoracic duct to subclavian vein
• enters bloodstream, eventually reaches liver
• efficient transport of large lipid molecules that cannot directly enter blood capillaries

fats → lymph → bloodstream later

three major hormones that control digestion and absorption

• gastrin
• secretin
• cholecystokinin

gastrin

• responds to food in the stomach
• secreted from stomach wall
• stimulates the stomach glands

response: HCl secreted into stomach, maintains acidic pH

secretin

• responds to acidic chyme in small intestine
• secreted from small intestine wall
• stimulates the pancreas

response: bicarbonate-rich juices secreted into small intestine to neutralize stomach pH

cholecystokinin

• responds to fat or protein in small intestine
• secreted from intestinal wall
• stimulates gallbladder pancreas

response: bile secreted into small intestine to emulsify fats

bicarbonate-and enzyme rich juices secreted into small intestine to maintain slightly alkaline pH, digest fats and proteins, and slow GI tract motility

common digestive tract problems in humans

• choking
• heartburn
• ulcers
• constipation
• diarrhea
• vomiting
• gas

choking

food gets lodged in trachea and blocks passage of air

heartburn

acidic stomach contents flow backward into esophagus

• lower esophageal sphincter relaxes, weakens, stomach contents flow upward

ulcers

sore in lining of digestive tract

• caused by damage to protective mucus layer in stomach

constipation

bowel movements too infrequent, difficult, or painful

• stool moving too slowly through large intestine
• can increase pressure on wall of colon
• diverticula become inflamed – diverticulitis

diarrhea

increased fluidity, frequency, or amount of bowel movements compared to usual pattern

• most often due to bacteria or viruses
• consumption of substances not readily absorbed – ie. sorbitol
• fluid loss / dehydration can occur
• need oral rehydration solutions or other remedies to replace fluid loss from diarrhea in infants / elderly

vomiting

expulsion of stomach contents up through esophagus to mouth

“reverse peristalsis”

• body’s adaptive mechanism to rid itself of something irritating
• results in loss of fluids, electrolytes
• repeated vomiting can irritate and infect esophagus, pharynx, salivary glands, erode gums and teeth, rupture or tear esophagus or stomach

gas

undigested CHOs enter colon

colonic bacteria break it down, producing gas

• consume troublesome foods in moderation

simple carbohydrate

digested quickly, raise blood sugar quickly

• rapid energy for the body provided
• includes monosaccharides (single sugars) and disaccharides (pairs of monosaccharides)

complex carbohydrate

digested more slowly – provides longer-lasting energy, more blood sugar stability

• polysaccharides (starches and fibers – chains of monosaccharides)

major sources of simple carbohydrates

• honey
• table sugar
• syrup
• milk and yogurt (from lactose)
• candy
• soda
• pastries
• cookies
• fruit (fructose)

major sources of complex carbohydrates

• whole grains
• starchy vegetables
• legumes
• other vegetables (ie. broccoli, spinach)

monosaccharide

single sugar

disaccharide

pairs of monosaccharides

examples of monosaccharides

• glucose (blood sugar)
• fructose (sweetest)
• galactose (usually bound with lactose)

examples of disacchrides

• maltose (2 glucose– produced during fermentation)
• sucrose (glucose + fructose – table sugar)
• lactose (glucose + galactose – milk)

polysaccharide

>10 monosaccharides in length

examples of polysaccharides

• glycogen (main storage site in animals and humans)
• starch (storage form of carb in plants)
• dietary fiber (cannot be digested and absorbed due to its bonds – source of food for gut bacteria)

how are disaccharides formed?

• made by condensation, H and OH combine, making H2O, linking together with oxygen
• break into two via hydrolysis: splits into H and OH (water molecule)

two different types of dietary fiber

• soluble fiber
• insoluble fiber

soluble fiber

soluble in water

• lowers blood cholesterol levels
• delays gastric emptying
• decreases blood glucose levels

insoluble fiber

insoluble in water

• decreases intestinal transit time
• decreases constipation
• lowers risk for diverticulitis
• lowers risk for colon cancer

examples of soluble fiber

• fruits
• beans
• oats
• barley

examples of insoluble fiber

• vegetables
• whole grains

how are sugars and starches broken down in the digestive tract?

mouth

• saliva breaks down starch into small polysaccharides & maltose

stomach

• stomach acid inactivates salivary enzymes, halting starch digestion

small intestine / pancreas

• pancreas produces amylase that continues digestion
• enzymes on small intestine surface hydrolyse disaccharides into monosaccharides
• absorbed into intestine

digestion of fiber

fiber --> bacterial enzymes --> short-chain fatty acids / gas

mouth

• mechanical action of mouth tears fiber, saliva softens for swallowing

stomach

• fiber is not digested -- delays gastric emptying

small intestine

• fiber is not digested -- delays absorption of other nutrients

large intestine

• fiber passes intact into digestive tract where bacterial enzymes digest it

lactose intolerance

inability to digest significant amounts of lactose, predominant sugar of milk

• due to deficiency of lactase enzyme
• symptoms appear 30 mins to 2 hours after ingestion

major functions of glucose in the body

• energy source
• short-term energy storage (long-term when converted to fat)
• blood glucose maintenance
• supplies energy
• protein sparing
• prevents ketosis

how do hormones insulin and glucagon maintain blood glucose at a constant level in the body?

insulin (pancreas)

• lowers blood glucose by promoting glucose uptake and storage

glucagon (pancreas)

• raises blood glucose levels, stimulates glucose release and production

glycemic response

• how quickly glucose is absorbed after eating
• how high glucose rises
• how quickly it returns to normal

glycemic index

blood glucose response to a given food compared with a standard

• influenced by amount of starch, fiber, processing, structure, and presence of other macronutrients in a food

major sources of added sugar in diet

• MOST: soda, energy drinks, sports drinks
• grain-based deserts
• fruit drinks
• dairy desserts
• candy
• ready-to-eat cereals
• sugars and honey
• tea
• yeast bread

health consequences of a diet high in added sugars

• nutrient deficiencies (ie. sugars displace nutrient dense foods)
• high GI / GL
• dental carries

health benefits of diet rich in starch and fibers

reduces the risk of developing several chronic diseases

• obesity, type II diabetes, CVD, some cancers, diverticulitis

provides steady energy

helps control blood sugar

supports healthy digestion

lowers cholesterol

three major types of lipids

• triglycerides (fats, oils)
• phospholipids
• sterols

general structure of a triglyceride

1 molecule of glycerol + 3 fatty acids

monounsaturated fatty acid

a fatty acid that lacks two hydrogen atoms and has one double bond between

major food sources of monounsaturated fatty acids

some vegetable oils

• olive oil
• canola oil
• peanut oil
• safflower oil

polyunsaturated fatty acid

a fatty acid that lacks four or more hydrogen

major food sources of polyunsaturated fatty acids

vegetable oils

• flaxseed oil
• walnut oil
• sunflower oil
• corn oil
• soybean oil
• cottonseed oil

saturated fatty acid

a fatty acid carrying the maximum possible number of hydrogen atoms

major food sources of saturated fatty acids

animal fats, tropical oils of coconut and palm

• coconut oil
• butter
• beef tallow
• palm oil
• lard

trans fatty acid

has its hydrogens on the opposite sides of the double bond, more linear than cis fatty acids

• increase blood sugar more than saturated fat

main food sources of trans fatty acids

• margarine
• shortening

essential fatty acids

fatty acids that the body requires but cannot make, and so must be obtained from the diet

• linoleic acid (omega-6)
• linolenic acid (omega-3)

role of essential fatty acids in formation of eicosanoids

body uses the omega-3 and omega-6 fatty acids to make these substances

eicosanoids

biologically active compounds

• help regulate blood pressure and blood clotting

major food sources of omega-3 fatty acids

• cold-water fish (salmon, tuna, sardines, mackerel)
• walnuts
• flaxseed
• hemp oil
• canola oil
• soybean oil

major food sources of omega-6 fatty acids

• beef
• poultry
• safflower oil
• sunflower oil
• corn oil

dietary lipid digestion

mouth

• hard fats begin to melt as they reach body temperature
• lingual lipase secreted

stomach

• lingual lipase initiates digestion
• triglyceride --> diglycerides and fatty acids
• churning action mixes fat w/ water and acid
• gastric lipase hydrolyses small amount of fat

small intestine

• bile from gallbladder emulsifies fat
• via. pancreatic lipase, emulsified fat --> monoglycerides, glycerol, fatty acids

large intestine

• some fat and cholesterol trapped in fiber exit in feces

dietary lipid absorption

• large fat droplets enter small intestine after meal
• bile emulsifies fat into smaller particles
• lipase breaks down fat into fatty acids and monoglycerides
• monoglycerides and fatty acids are absorbed as micelles
• reformed into triglycerides after through
• short and medium chain fatty acids enter bloodstream
• triglycerides + cholesterol, protein, phospholids form chylomicrons which enter lymphatic system

role of lipoproteins in transporting lipids throughout the body

lipids don't mix with blood -- the body packages them into lipoproteins to move them around body safely

chylomicrons

primarily composed of triglycerides, carry dietary fat from the small intestine to cells

low-density lipoprotein (LDL)

"bad cholesterol"

• carries cholesterol made by the liver and from other sources to cells
• primarily composed of cholesterol
• excess LDL deposits cholesterol in artery walls, forms plaques

high-density lipoprotein (HDL)

"good cholesterol"

• contributes to cholesterol removal from cells and, in turn, excretion of it from the body
• primarily composed of protein
• higher HDL - protective against heart disease

major functions of fat in the body

• provide energy
• efficient storage of energy
• insulation
• protection, cushion organs
• cell membrane components
• eicosanoid production
• transport fat-soluble vitamins

role of fat in development of heart disease

• foods high in saturated fat --> raise blood cholesterol which leads to heart disease
• trans fats raise bad cholesterol and lower good cholesterol

role of fat in development of cancer

• doesn't directly cause cancer, but rather is a byproduct of obesity, inflammation, and hormone changes
• strong correlation of prostate cancer (less conclusive evidence for breast cancer)
• obesity alters hormone levels which can promote cancer cell growth / encourage tumor development

role of fat in development of obesity

• easy to overconsume fat because it is energy dense, less filling, and tastes good
• body cannot use all of these calories --> gets converted into body fat (leads to weight gain)

saturated fats effect on LDL / HDL

raises LDL, no effect on HDL

PUFAs effect on LDL / HDL

lowers LDL and HDL

MUFAs effect on LDL / HDL

lower LDL and raise HDL

trans fats effect on HDL and LDL

raises LDL and lowers HDL

major sources of fat in Mediterranean diet

• omega-3 fatty acids from fish
• MUFAs from olive oil and nuts

why is the Mediterranean diet heart healthy?

emphasizes nutrient dense whole foods and healthy fats (like olive oil, fatty fish, nuts, fruits, and vegetables)

• these lower bad cholesterol (LDL), reduce inflammation, and improve blood pressure

how is the chemical makeup of proteins different than carbohydrates and fats?

contains C, H, O, N (many also contain sulfur)

• carbs and fats only have C, H, O

protein chemical structure

• built from amino acids
• linked together by peptide bonds
• each amino acid has an amino group (-NH2) and a carboxyl group (-COOH)
• nitrogen group (amino group) varies which is why nitrogen is a defining feature of proteins

why are some but not all amino acids essential?

some proteins are non-essential, meaning that they can be synthesized from simpler molecules or by modifying other amino acids in the body if not taken in via diet

consequences when body lacks essential amino acid

• protein synthesis is limited or stops altogether
• all amino acids must be present to build proteins, the sequence will not be made at all if one needed isn't present

leads to

• poor growth, muscle wasting, weight loss
• body proteins broken down to supply amino acids, weakens tissues

digestion of proteins

stomach

• start of protein digestion
• HCl uncoils protein, begins cleaving polypeptide
• pepsinogen --> pepsin (active enzyme)
• pepsin makes polypeptide into shorter amino acid chains

small intestine

• pancreatic and intestinal cell enzymes cleave peptide chain into individual amino acids + some dipeptides and tripeptides
• enzymes in intestinal lining finish digestion into free amino acids

absorption of amino acids

• resulting amino acids are absorbed through intestinal wall into the bloodstream
• transported to liver and then distributed to body tissues

fate of amino acids once they are digested and absorbed

• absorbed amino acids travel from small intestine to liver via portal vein
• liver as control center, decides how amino acids will be used

options:

• protein synthesis
• energy source
• excess converted to / stored as fat in body
• converted to glucose if no glucose is provided in diet

does the body store amino acids?

no

• this is another reason why if one essential amino acid is missing, protein synthesis is limited

deamination

• removing the amino group of amino acids that cannot be used for synthesis / are in excess
• carbon skeleton leftover used for energy / converted to glucose or fat
• amino group becomes ammonia
• liver converts it to urea for excretion in urine

transamination

• recycling of amino group instead of wasting it
• transferred from one amino acid to a keto acid
• helps to use dietary protein efficiently
• helps to make non-essential amino acids when not readily available

major functions of protein in the body

• energy source
• growth and maintenance
• enzymes
• hormones

high quality or complete protein

has an ample amount of all 9 essential amino acids

low quality or incomplete protein

deficient or low in one or more essential amino acids

examples of complete proteins

• meat
• fish
• poultry
• eggs
• milk
• cheese
• yogurt
• soy

examples of incomplete proteins

• plants
• legumes
• grains
• seeds
• nuts
• vegetables

forming complete proteins via plant-based foods in a vegetarian diet

grains (rice) and nuts - limiting amino acid: lysine

legumes and vegetables - limiting amino acid: methionine

can combine one food lacking lysine and one lacing methionine in order to create a complete protein

common combinations of plant-based foods in order to create complete proteins

• red beans and rice
• pasta and tomatoes
• green beans and almonds
• soybeans and ground sesame seeds (miso)

health advantages of a vegan diet

• lower LDL or bad cholesterol
• lower blood pressure
• higher-fiber, lower calorie diet due to plant-based nature
• lower risk of certain chronic diseases
• reduced systematic inflammation due to abundance of antioxidants

nutritional risks of a vegan diet

• vitamin B12 - not found in plant-based foods at all, could end up with a deficiency
• bone health can be compromised
• micronutrient deficiencies
• omega-3 deficiency

two major forms of protein malnutrition

• chronic PEM: marasmus
• acute PEM: kwashiorkor

chronic PEM (or marasmus)

• deficiency of calories AND protein
• prolonged starvation / undernutrition
• little to no subcutaneous fat
• reduced brain growth
• skin and bones appearance

acute PEM (or kwashiorkor)

• severe protein deficiency despite adequate / near-adequate calorie intake
• can cause: edema (swollen belly and legs), fatty liver, skin and hair changes, impaired immunity, growth failure

why is consuming too much protein not recommended?

• increases risk for heart disease, obesity, and certain cancers
• increases kidney burden (excess protein -> increased nitrogen waste, excreted by kidneys can worsen their function
• increased calcium loss in urine (can effect bone health)
• dehydration risk (excess water required to eliminate waste products)

overall: strains body and can displace other nutrients

anabolic reaction

• small molecules are put together to build larger ones
• requires energy

catabolic reaction

• large molecules are broken down to smaller ones
• releases energy

ATP

• common high-energy compound
• used to do work in the body
• composed of a purine (adenine), a sugar (ribose), and three phosphate groups
• high energy bonds between the phosphate groups

major functions of ATP in the body

• mechanical work (muscular contraction)
• chemical work (biosynthesis)
• osmotic work (active transport)

compounds produced in cells after food is completely metabolized (other than ATP)

CO₂ and H₂O

3 major metabolic pathways through which the macronutrients are converted into energy

• glycolysis
• TCA cycle / krebs cycle
• electron transport chain and oxidative phosphorylation

glycolysis

• glucose is converted into pyruvate
• uses and generated ATP
• reversible

TCA cycle / krebs cycle

• pyruvate becomes acetyl CoA
• irreversible
• cycle generates NADH, FADH_2, GTP, and CO₂

electron transport chain and oxidative phosphorylation

• NADH, FADH₂ converted into ATP
• H₂O generated

final products: ATP, CO_2, and H₂O

where does energy metabolism occur in the cell?

mitochondria

where does the TCA cycle occur?

inner compartment of mitochondria

where does electron transport chain occur?

mitochondrial membrane

where does glycolysis occur?

cell cytoplasm

how is a carbohydrate broken down into usable energy?

source of quick energy

• glucose enters cell
• glycolysis: glucose -> pyruvate
• pyruvate enters mitochondria
• pyruvate -> acetyl CoA in TCA cycle
• ETC in mitochondrial membrane, produces ultimate products of water, carbon dioxide, and ATP (usable energy!)

how are lipids broken down into usable energy?

produces large amounts of ATP but more slowly (yields most ATP per molecule)

• triglycerides broken down into glycerol and fatty acids
• fatty acids undergo beta oxidation, converted into acetyl-CoA
• acetyl CoA enters TCA cycle and then ETC

when does fatty acid oxidation work best?

• when carbs are available
• in order for the acetyl CoA to enter the TCA cycle, oxaloacetate must be available
• it is derived from pyruvate / glucose

how are proteins broken down into usable energy?

not a primary energy source

used for energy mainly during starvation, prolonged exercise, or low carb availability

• proteins broken down into amino acids
• amino acids undergo deamination, nitrogen group removed and excreted as urea
• carbon skeletons enter metabolism in a few forms:
• pyruvate (glucogenic)
• acetyl-CoA (ketogenic)
• krebs cycle intermediates (glucogenic)

is metabolically costly and compromises body tissues

ketosis

• body lacks sufficient carbohydrates for energy and burns stored fat instead
• produces ketones for fuel

ketone bodies

• products of incomplete fatty acid oxidation
• couldn’t be broken down due to low carbohydrate intake or insufficient insulin

acetyl-CoA only enters the TCA cycle if...

there is enough oxaloacetate available when fatty acid oxidation is incomplete

• oxaloacetate gets used up to make glucose
• acetyl CoA has nothing to combine to to start the TCA cycle
• acetyl CoA - accumulate and form ketone bodies

how can ketosis be reversed?

consumption of carbohydrates

conditions in which ketosis occur

• fasting
• low-carb diets
• diabetes

fasting (ketosis)

• lack of carbohydrates
• fatty acids flood the blood stream
• no glucose to produce oxaloacetate
• TCA cycle stops
• acetyl CoA builds up
• more ketones produced

low-carb diets (ketosis)

effects:

• nausea
• fatigue
• constipation
• low blood pressure
• elevated uric acid
• bad breath
• in pregnant women can cause fetal harm and still birth

diabetes (ketosis)

• not enough insulin produced
• CHO metabolism limited
• no glucose to produce oxaloacetate
• TCA cycle stops
• Acetyl CoA builds up
• more ketones produced → spill into urine
• blood becomes acidic
• diabetic coma, death

consequences of consuming excess carbohydrates

• first stored as glycogen and then stored as fat

effects:

• elevated blood glucose
• increased insulin release
• increased triglyceride levels

consequences of consuming excess lipids

• easily and efficiently stored as body fat
• minimal conversion needed

effects

• weight gain
• increased blood lipids (LDL, triglycerides)
• increased cardiovascular risk

consequences of consuming excess protein

• cannot be stored as protein
• amino acids are deaminated, nitrogen groups removed, excreted as urea
• carbon skeletons are converted to glucose or fat

effects:

• increased kidney workload
• dehydration
• fat gain if calories remain excessive

what happens to the metabolic pathways during feasting (eating in excess)

• carbohydrates are broken down into glucose
• glucose enters liver and muscle glycogen stores
• when those fill up, converted into body fat, enter body fat stores

what happens to the metabolic pathways during fasting (food deprivation)

• liver and muscle glycogen stores used to make glucose
• used for energy in the brain, nervous system, and red blood cells & as energy for other cells
• body fat stores are used for fatty acids to provide cells with energy

how long does glycogen last?

• may be depleted after 1 hr of strenuous exercise or 24 hours of fasting
• full restoration requires 2 days
• most restored over half day

what happens to the metabolic pathways during prolonged fasting (prolonged food deprivation)

• body proteins broken down into amino acids
• amino acids lose nitrogen, converted into urea
• carbon skeletons used for glucose or become ketone bodies (no carbs to help fatty acid be processed)
• energy for brain, nervous system, and other cells
• body fat is used for fatty acids
• they become ketone bodies
• energy for brain, nervous system, and other cells

energy balance

the energy (kcal) consumed from foods and beverages compared with the energy expended through metabolic processes and physical activities

when the energy balance shifts...

weight changes

when calorie intake = calorie output

no change in weight

positive energy balance

• calories in > calories out
• increase in weight

negative energy balance

• calories in < calories out
• decrease in weight

components of 'energy in'

• alcohol
• protein
• carbohydrates
• fat

components of 'energy out'

• basal metabolism
• thermic effect of food (TEF)
• physical activity
• thermogenesis

energy received depends on ...

composition of foods and beverages and on the amount a person eats and drinks

basal metabolism

the energy needed to maintain life when a body is at complete digestive, physical, and emotional rest

BMR

rate at which body expends energy for life-sustaining activities

thermic effect of food (TEF)

an estimation of the energy required to process food (digest, absorb, transport, metabolize, and store ingested nutrients)

physical activity

voluntary movement of the skeletal muscles and support systems

thermogenesis

adjustments in energy expenditure related to

• changes in environment such as extreme cold
• physiological events such as overfeeding, trauma, and changes in hormone status

negligible effect on energy balance

relative contributions of the three major components of energy expenditure

50-70% - basal metabolism (2/3 of overall energy expenditure)

10% thermic effect of food

30-50% physical activities

most variable component of energy expenditure

amount of energy expended in voluntary physical activities

factors that can affect BMR

• age
• height
• growth
• body composition
• fever
• stresses
• environmental temperature
• malnutrition
• hormones
• smoking
• caffeine
• sleep

increases BMR

• being taller
• young age
• higher lean tissue
• being pregnant
• having a fever
• stresses (ie. disease, certain drugs)
• environmental temperature (heat and cold)
• hormones
• smoking
• caffeine

decreases BMR

• sleep
• hormones
• fasting / starvation
• more fat tissue

variables required to calculate estimated energy requirements (EER)

• height
• weight
• age
• sex
• physical activity level

body composition

the proportions of muscle, bone, fat, and other tissue that make up a person’s total body weight

3 major factors that make up a person's body weight

• fat mass (fat tissue in body)
• lean body mass (muscles, organs, skin, connective tissues, and body water)
• bone mass (weight of the skeleton)

body mass index (BMI)

a measure of a person’s weight relative to height

• determined by dividing the weight (in kilograms) by the square of the height (in meters).

equation for calculating BMI

• body weight (kg) / height (m)^2

OR

• body weight (lbs) x 703 / height (inches)^2

underweight (BMI)

BMI <18.5

healthy weight (BMI)

BMI 18.5 - 24.9

overweight (BMI)

BMI 25.0 - 29.9

obesity (BMI)

BMI > or equal to 30

health effects of having too little body fat

• unable to preserve lean tissue during wasting disease, medical stresses
• menstrual irregularities, infertility in women
• osteoporosis, bone fractures

health effects of having too much body fat

• diabetes, HTN, CVD
• sleep apnea, respiratory problems
• osteoarthritis
• some cancers
• gallbladder disease
• complications in pregnancy, surgery

common methods used to assess body fat (body composition)

• skinfold measures
• hydrodensitometry
• bioelectrical impedance
• air displacement plethysmography
• dual energy x-ray absorptiometry

skinfold measures

• estimate body fat using a caliper to gauge the thickness of a fold of skin on the back of the arm (over the triceps), below the shoulder blade (subscapular), and in other places (including lower-body sites)
• compares these measurements with standards

hydrodensitometry

• measures body density by weighing a person first on land and then again while submerged in water
• difference between actual weight and underwater weight provide body volume
• using volume and actual weight, one can determine body density
• then, percentage of body fat can be estimated

bioelectrical impedance

• measures body fat by using a low-intensity electrical current
• leaner the person, less resistant to the current
• ie. more resistant to the current, more body fat
• measurement of electrical resistance used to estimate percentage of body fat

air displacement plethysmography

estimates body composition by having a person sit inside a chamber while computerized sensors determine the amount of air displaced by the person’s body

dual energy x-ray absorptiometry

• uses two low-dose X-rays that differentiate among fat-free soft tissue (lean body mass), fat tissue, and bone tissue
• provides a precise measurement of total fat and its distribution in all but extremely obese subjects

prevalence of overweight and obesity among American adults

• around 70% of adults are either overweight or obese
• roughly 40% have obesity
• only around a third of the population is a healthy weight
• obesity rates have risen sharply since the early 90s (across all ages, sexes, and ethnic groups, making it a major public health concern)

reason for prevalence of overweight and obesity among American adults

• eating more energy dense foods (added fats, oils, and sugars)
• trend toward colossal cuisine (larger portion sizes)
• changes in diet quality

how do fat cells develop

• excess energy is stored in fat cells of adipose tissue
• during growth, fat cells increase in number
• energy intake > energy expenditure, fat cells increase in size
• once fat cells have enlarged and reach capacity, new fat cells will form
• weight loss: fat cells shrink but don't decrease in number

lipoprotein lipase (LPL)

• an enzyme that removes triglycerides from the bloodstream and directs their components into adipose and muscle cells for storage / use
• higher LPL activity = higher fat storage efficiency
• more fat cells = greater LPL activity overall (promotes fat regain after weight loss)

genetics and contribution to development of overweight / obesity

influences susceptibility to obesity through genes that affect metabolism, fat storage, and energy expenditure

• twin studies
• set point theory

twin studies

• identical twins raised apart have similar weight-gain patterns
• fraternal twins vary less in weight than two unrelated people

(shows correlation between genetics and obesity)

parents and offspring

• child with no obese parents has 10% of becoming obese
• child with one obese parent has 40% risk
• child with two obese parents has 80% risk

(shows correlation between genetics and obesity)

set point theory

genetically predetermined body weight or fat content

environment and contribution to development of overweight / obesity

• toxic food environment
• cues to overeat
• food availability
• physical inactivity

interact with genetic predisposition to influence overweight / obesity

regulation of hunger / satiety and contribution to development of overweight / obesity

• hunger and satiety are regulated by hormones such as leptin and ghrelin
• obesity --> leptin resistance reduces appetite control
• ghrelin levels rise during dieting, increase hunger and promote weight regain

together - favor weight gain and resistance to long-term weight loss

leptin

• protein produced by fat cells
• hormone that suppresses appetite and increases energy expenditure

ghrelin

• protein produced by the stomach cells
• hormone that stimulates appetite and decreases energy expenditure

health risks of fad diets

• weight cycling
• psychological problems

also: nutrient deficiencies, dehydration, loss of lean tissue, metabolic slowdown

weight cycling (health risk of fad diet)

• increased risk of premature death
• increased risk of chronic disease
• upper body fat deposition
• possibly lower HDL
• eroded self-esteem

psychological problems (health risk of fad diet)

• repeated dieting increases psychological burden

get stuck in cycle of

• ineffective treatment
• repeated failure
• leads to poor self-esteem
• disordered eating

health risks of pharmacotherapy / prescription drugs

side effects such as

• behavior change
• reduced energy intake
• increased physical activity

if these aren't maintained, weight is often regained after discontinuation ^

• increased heart rate
• GI distress

health risks of weight-loss supplements / products

• undeclared drugs
• lack of proven effectiveness (not regulated by FDA -- what is in them?)
• heart problems
• seizures
• liver damage

health risks of surgical interventions

• requires lifelong medical follow ups
• surgical complications
• nutrient deficiencies
• dumping syndrome
• psychological issues

role of diet / physical activity in managing body weight

• reduced-energy, nutrient adequate diet along with regular physical activity supports fat loss, preserves lean mass, and improves metabolic health

regular physical activity and obesity

• increases energy expenditure
• increases metabolism
• improves body composition
• improves appetite control
• has psychological benefits (combats depression, improves self-esteem)

role of behavior change in managing body weight

modifying problem (eating) behaviors

• chain-breaking (ie. not eating while watching TV)
• stimulus control (eliminating cues to eat more)
• cognitive restructuring (changing unhealthy thoughts and habits around food)
• contingency management (prizes for achieving nutrition goals)
• self-monitoring (keeping track of what you eat

characteristics of a sound eating plan for weight management

• appropriate energy intake
• emphasize nutritional adequacy
• fruits, vegetables, whole grains, lean proteins, and low-fat dairy
• eat small portions
• slow down
• low energy density (high fiber and water, lower fat)
• remember water
• focus on plant-based foods
• choose fats sensibly
• select carbohydrates carefully
• watch for empty kCals