Exam 1 - Nutrition Flashcards
Nutrition
science of food; the nutrients and the substances therein; their action, interaction, and balance in relation to health and disease
Nutrition (also)
The process by which the organism ingests, digests, absorbs, transports, utilizes, and excretes food substances
What are top 3 causes of death
- heart disease
- cancer
- stroke
Nutrients
substances essential for health that the body cannot make or makes in quantities too small to support kife
Characteristics of an essential nutrient
- Has a specific biological function
- Absence from the diet leads to decline in biological function
- Adding missing substance bac to the diet before permanent damage occurs restores normal biological function
Functional categories of nutrients
- Provide energy for the body
- Promote growth and development, maintain body structures
- Regulates body processes; help maintain homeostasis
Energy yielding nutrients
Carbohydrates
Lipids
Protein
Non-energy yielding nutrients
Vitamins
Minerals
Macronutrients
needed in large amounts
- carbohydrates
- lipids
- proteins
- water
micronutrients
needed in smaller amounts
- vitamins
- minerals
Carbohydrates
- composed of carbon, hydrogen, and oxygen
- primarily obtained from fruits, vegetables, grains, and beans
- provide 4 kcal/g
2 main types of carbohydrates
simple sugars: table sugar and glucose
complex carbohydrate: startch, glycogen, fiber
Lipids
- also composed of carbon, oxygen, and hydrogen
- insoluble in water
- provide 9 kcal/g
fats
lipids that are solid at room temperature
oils
lipids that are liquid at room temperature
triglycerides
- major form of fat in food and body
- major energy source for the body
- composed of 3 fatty acids attached to a glycerol backbone
saturated fats
- mainly solid at room temperature
- mainly found in animal sources
- raise blood cholesterol levels
- can lead to cardiovascular disease
unsaturated
- mainly liquid at a room temperature
- mainly found in plant sources
- generally healthier than saturated fats
Essential fatty acids
- unsaturated fatty acids that must be supplied by the diet: linoleic acid, alpha-linolenic acid
- have important roles in the body: being structural components of cell walls, regulation BP and nerve transmission
- can be found in vegetable oils and fish
trans fatty acids
- unsaturated fats that have been processed from cis form to trans form
- primarily found in deep-fried foods, baked snack foods, and solid fats
- Pose a health risk - intake should be minimized
- mostly removed from US food supply
proteins
- composed of carbon, oxygen, hydrogen, and nitrogen
- main structural components in the body
- provide 4 kcal/g
- formed from bonding of amino acids
Vitamins
- enable chemical reactions to occur: serve as enzyme cofactors
- do not directly provide energy (calories) but some vitamins help to break down energy-yielding nutrients
13 vitamins, 2 group
- fat soluble: vitamin A, D, E, K; more likely to accumulate and cause toxicity
- water soluble: vitamin C and B, more likely destroyed by cooking , excreted from the body more readily
Minerals
- inorganic substances
- not destroyed by cooking
- yield no energy
Major groups of minerals
- Major minerals: need more than 100mg daily, more than 5g in body
- Trace minerals: need <100mg daily, less than 5 mg in body
water
- needed in largest quantity
- several vital functions: solvent, lubricant, transports nutrients, regulates body temperature
phytochemicals and zoochemicals
- have health effect, but not essential nutrients
- phytochemicals: plant origin
- zoochemicals: animal origin
energy sources and uses
- energy is needed to preform body functions and do work
- alcohol provides energy not a nutrient
- with energy we can: build new compounds, perform muscular movements, promote nerve transmission, maintain ion balance within cells
Calorie
amount of heath energy needed to raise the temperature of 1 gram of water 1 degree Celsius
- very tiny number
Kilocalorie
- amount of heat energy needed to raise the temperature of 100 grams of water by 1 degree Celsius
- standard unit
Carbohydrate physiological fuel value
4 kcal/g
Fats physiological fuel value
9 kcal/g
Proteins physiological fuel value
4 kcal/g
Alcohol physiological fuel value
7 kcal/g
energy source calculation
grams of macronutrients x physiological fuel value = kcal
North American consume:
- 16% of energy intake as proteins
- 50% as carbohydrates
- 33% as fats
- these amounts are al within healthy ranges, but are problems
Problems with the North American Diet
- too many calories are consumed
- too much proteins from animal sources and too little from plants
- too many carbohydrate from simple sugars; too few from complex carbohydrates
- too much fat from animal sources; too little from plants
How to improve American diet
- increase intake of foods rich in vitamins and minerals (except sodium)
- decrease intake of sodium
- moderating intake of sugary soft drinks and fatty foods
- eat more fruits, vegetables, whole grain breads, and reduced fat dairy
What influences our food choices
- daily food intake is a mix of our need to satisfy hunger and social and psychological needs
hunger
physical need for food
appetite
psychological desire to eat certain foods and reject other
- for most people in Western countries, appetite is what drives eating
- availability of food allows many factors to determine what we eat
optimal nutritional health status
vitamin/ mineral/ energy needs met, including modest storage
malnutrition
undernutrition and overnutrition
under nutrition
- nutrient intake does not meet needs
- nutrient stores are depleted
- subclinical: early stage of nutrient deficiency
overnutrition
consumption of more nutrients than the body needs, most common type in industrialized nations: excess energy intake
Healthy people
- report that provides science-based, 10 year national goals for improving the health of all Americans
- main objective: help all people attain high-quality, longer lives free of disease, disability, injury, and premature death
- 355 objectives covering main aspects of health, including nutrition
Reduce…
- proportion of adults with obesity
- household food insecurity and hunger
- consumption of saturated fat, sugar, and added sugar b
- iron deficiency in children and females
Increase…
- fruit, vegetables, and whole grain consumption
- calcium, potassium, and vitamins D consumption
- proportion of students participating in school breakfast program
- proportion of worksites that offer employee nutrition programs
medical history
current and past diseases and surgeries, body weight history, current medications
Anthropometric assessment
height, weight, skinfold, thickness, arm muscle circumference, body composition
Biochemical laboratory assessment
compounds in blood and urine
clinical assessment
physical examination of skin, eyes, and tongue; ability to walk
dietary assessment
usual food intake, food allergies, supplements used
environmental assessment
education and economic background, marital status, housing condition
many sigs and symptoms of a deficiency…
are not very specific, for example:
- diarrhea
- skin conditions
- fatigue
Limitations of nutritional assessment
- may take a long time for the signs and symptoms and the clinical evidence of a nutrition deficiency to develop such as osteoporosis
genetics and nutrtion
- our genes, as well as our lifestyle and diet, affect our health
- DNA directs how the body uses the nutrients consumed
- genes dictate how nutrients will be transformed and reassembled into body structures and compounds
Nutritional disease with a genetic link
family history is considered one of the most important risk factors in the development of many nutrition-related diseases
- diabetes
- cancer
- osteoporosis
- cardiovascular disease
- hypertension
- obesity
heredity is not density
even if you have genetic risk factors, there are many other factors that you can modify
When evaluation nutrition claims, products, and advice be cautious if
- only advantages are discussed
- new or secret breakthroughs
- claim to cure a disease
- sounds to good to be true
- extreme bias against medical community
- testimonial show dramatic results
What are the scientific credentials
- registered dietitian (R.D. or R.D.N.)
- nutritionist is not a legal title - anyone can use it
What is the research behind these claims?
- size of study
- duration of study
- type of study
The dietary supplement health and education act of 1994…
- classified vitamins, minerals, amino acids, and herbal remedies as “food” however some herbal supplements contain active drugs, high doses of vitamins can also have drug-like effects and toxicity
Buying nutrition related products
- because of classification as food, regulation is much less strict compared to FDA regulation of drugs
- generally, sale will only be restricted when there are proven safety issues
- be skeptical about claims made by supplements
- be aware that some supplements can affect health just like pharmaceutical drugs
- they may also interact with pharmaceuticals (increased or decreased efficacy, different duration of action
supplements allowed to claim
- general well-being results
- how product provides benefit
- how it will affect structure or function
if claims are made…
label must display a disclaimer
tools of a healthy diet
- standards for nutrient intake
- food labels
- dietary guidelines
DRIs
Dietary reference intakes
- recommendations from the food and nutrition board of the national academy of sciences (a non-government nonprofit)
- NOT what is shown on food labels
5 different standards are part of the DRIs
- estimated average requirements (EARs)
- recommended dietary allowances (RDAs)
- adequate intakes (AIs)
- tolerable upper intake levels (ULs)
- estimated energy requirements (EERs)
dietary reference intakes
differ by life stage:
- age group
- sex (after age 9)
- pregnancy
- lactation
should be applied to dietary intake averaged over several days, not a single day
RDA
- recommended dietary allowances
- daily nutrient intake amounts that meet the needs of nearly all individuals
- this amount will prevent acute symptoms of deficiency and also promote long term health
AI
- adequate intakes
used for nutrients when there is insufficient research to establish average requirements and RDA
ULs
- upper levels
- a conservative standard: only 2-3% will experience symptoms of toxicity at these amounts
- applies to chronic daily use
- not a nutrient goal, but a ceiling for intake
EERs
- estimated energy requirements
- used for energy-yielding nutrients
- average daily energy (calories) need for each life-stage group
AMDRs
acceptable macronutrient distribution ranges
- not one of 5 DRIs
percent of calories from each macronutrient (AMDR)
- carbohydrate: 45-65%
- fat: 20-35%
- protein: 10-35%
appropriate uses of the DRIs
- intended for diet planning
- should aim to meet any RDAs or AIs set
- do not exceed the upper level (UL)
- intended for healthy people: may not meet needs of people with chronic disease
most important dietary standards to know
- recommended dietary allowance (RDA): amount that meets needs for 97-98% of a group
Adequate intake (AI)
- range that is known to be safe and provide adequate nutrition
- used when there is not enough evidence provide a specific RDA
Upper level (UL)
- highest amount that is safe in most people
Estimated Energy Requirement (EER) and Acceptable macronutrient density ranges (AMDR)
- estimated need for energy (calories) derived from macronutrients (carbs, fat, protein, alcohol)
- AMDR tells you how many calories to get from each nutrient
- RDA, AI, UL, and EER all vary based on life stage
nutrient density
what present of RDA
empty calories
some foods supply energy but very few vitamins or minerals
Putting the DRIs into action to determine the nutrient density of foods
- RDA, UL, AI, and EER are difficult for the average person to interpret
- would need different food labels from men, women, and children
- food labels use a different, more generalized system
DVs
daily values
- generic standards developed by the U.S. food and drug administration
- found on the nutrition facts panel on a food label
- compares the amount of nutrients in the food with a set of standards
Daily values (DV)
- Broken down into 4 groups: infants, toddlers, people over the age of 4, pregnant, and lactating women
- labels generally use the daily values for people over 4, unless t product is specifically marketed to one of the other groups
- DV for most vitamins and minerals come from the 2016 edition of the RDAs
- highest RDA from all life groups was used
For energy-yielding nutrients, DVs are based on a 2000-calorie diet
- fat: 30%
- saturated fat: 10%
- carbohydrate: 60%
- protein 10%
of calories - fiber is set at 11.5g of fiber per 1000 calories
putting the daily values into action on nutrition facts panels
- information related to the daily values is found on almost every food and beverage sold
- nutrients listed on nutrition facts panels tend to b the one of greatest health concern
- many people eat too much fat, saturated fat, trans far, cholesterol, sodium, and sugar
- many people are concerned that they do not get enough fiber, calcium, iron, potassium, and vitamin D
Claims on food labels
- marketing tool direct toward health-conscious consumers
- claims must comply with FDA regulations
- types of claims: nutrient content, health claims, structure-function
nutrient content claims
legally defined claims about nutrient content per serving or compared to a reference food
health claims
describe a relationship between a disease and a nutrient, food, or food constituent
- must have significant scientific agreement that they are true
- must use a “may” or “might” qualifier
structure/function claims
describe effect of a nutrient on body structure/function without referring to a specific disease
Natural
a relatively nonspecific and unregulated claim
Dietary guidelines for Americans
- the U.S. government’s foundation for nutrition policy and education
- influences nutritional assistance programs
- reflect the most accurate and up-to-date scientific knowledge about: nutritious diets, physical activity, related healthy lifestyle choices
- designed to meet nutrient needs while reducing the risk of: obesity, hypertension, diabetes
- premise is that nutrient needs should be met primarily by consuming nutrient dense food and beverages (no supplements)
2020 dietary guidelines for Americans
- follow a healthy dietary pattern at every stage
- customize and enjoy nutrient dense food and beverage choices to reflect personal preferences, cultural traditions, and budgetary considerations
- focus on meeting food group needs with nutrient-dense foods and beverages, ad stay within calorie limits
MyPlate
- depicts the key elements of a healthy diet
- emphasizes the fruit, vegetable, grain, protein, and dairy food groups
- goal is to remind consumers to think about building a healthy plate at mealtimes
food availability and access
- good nutrition status and health requires access to a safe and healthy food supply
- agriculture produces enough food to provide each person with 2940kcal daily but 1 in 9 people are undernourished, 2 billion people suffer from micronutrient deficiencies (hidden hunger)
- huger and malnutrition are most common in the developing world
- problems of malnutrition (over/undernutrition) and hunger account for over half the world’s disease burden
- industrialized countries: overnutrition results in overweight and obesity
1 in 8 people
experience food insecurity
sustainability with food
- ability to produce enough food for everyone
- those diets with low environmental impacts which contribute to food and nutrtion security
Key areas of focus for achieving global food sustainability
- promote dietary diversity to optimize nutrient density and lower environmental impact
- target food production sustainability
- reduce food loss and food waste
organic foods
- widely available but cost more to produce so are more expensive than conventional foods
- organic meat, poultry, eggs, and dairy products must come from animals allowed to graze outdoors and fed only organic feed
organic farming practices
- biological pest management
- natural fertilizer
- crop rotation
Not permitted in the production of organic food
- synthetic pesticides and fertilizers
- hormones and antibiotics
- sewage sludge
- genetic engineering
- irradiation
Consumers choose organic food is
- reduce their pesticides intake
- support sustainable agriculture
- improve the nutritional quality in their diets
Genetically modified foods
- genetic modification has been happening for as long as humans have been farming
- modern genetic engineering using recombinant DNA technology allows for direct changes to the genome
GM crops
- genetically engineering crops is used primarily to confer:
- herbicide tolerance: round up ready crops
- insect resistance: Bt corn
- increase nutrient content: golden rice
GM animals
- the AquAdvantage salon is now being sold
- advantages: grows to maturity twice as fast, land-based farming (lower carbon footprint)
- Concerns: if escape occurred, they might outcompete wild type fish, disruption of commercial fisheries and sustainable fisheries run by indigenous communities
Regulation of GM foods
- regulated by the FDA, USDA, and Environmental Protection Agency (EPA)
- FDA has evaluated all GM foods on the market and has found them safe to consume
- new U.S. law mandates labeling
Safety and other concerns about GM Foods
- addition of allergens to GM foods that previously did not contain them
- development of glyphosate-resistant “superweeds”
- transferring genes across species lines
- gene flow from GM crops to plants not intended to be modified
- development pf Bt-resistant insects
- loss of genetic diversity
- loss of cultural heritage
- insufficient regulation
Food preservation and processing
- preservation helps to extend a food’s shelf life, permit a wide variety of foods to be available year round
- original methods drying, salting, sugaring, smoking, fermenting
- newer methods: pasteurization, refrigeration, food irradiation, food additives
food irradiation
- use radiation to extend the shelf life of food and control the growth and insects and pathogens
- irradiated food does not become radioactive and has minimal nutritional differences
- irradiated food must be labeled with the Radura
food additives
- found mainly in ultra-processed food
- increase or preserve: nutritional characteristics, freshness, safety, quality and desirability
regulation and safety of food additives
- regulated by the FDA
- requires manufacturers to test and prove safety of new additives
- some additives are exempt
food and water safety
- in addition to having access to abundant, varied, and nutritious foods, we must have safe food and water supplies to support good health
- North Americans enjoy a relatively safe water and food supply, but pathogens and chemicals in foods and water still pose a health risk
foodborne illness overviewe
- annually, foodborne pathogens cause 47.8 million illnesses, though most cases go undiagnosed
causes of foodborne illness, how do they reach food
- microbes
- contamination by feces, contamination by an infected individual, cross-contamination
Norovirus
- most common cause of viral gastroenteritis
- can spread through contaminated food and surfaces, aerosolized particles
- handwashing is best; alcohol-based sanitizers not very effective
preventing foodborne and waterborne illnesses
use: good personal and kitchen hygiene, appropriate thawing, cooking, and storage procedures
prions
- infectious protein particles
- bovine spongiform encephalopathy (mad cow disease)
- resistant to heat and sterilization
toxins in food
- produced by molds, algae, and plants
- usually not destroyed by cooking
- ergot, a fungus that grows in improperly stored grain
lead
- damages every organ in the body - especially nervous system and kidneys - and impairs the synthesis of hemoglobin
- very toxic to the developing nervous system of children
- sources include: home plumbing, lead-based paints, lead-containing containers
Mercury
- converted by aquatic bacteria to methylmercury, which can cause: nerve damage, fatigue, poor learning abilities
- fish are main food source
Digestive system
- controlled by hormones an the nervous system
- has a role in the immune system: acts as a physical barrier, produces immune components
- houses bacteria: microbiota, also called gut flora
GI tract flow
Mouth/salivary glands –> esophagus –> stomach –> small intestine –> large intestine –> rectum –> anus
Basic structure of the GI tract
- also known as the alimentary canal
- long, hollow, muscular tube consisting of four layers: (in) mucosa > submucosa > muscularis externa > serosa (out)
- extends 15 feet from mouth to anus
sphincter muscle:
ring-link muscles; function as valves that regulate movement of contents through digestive tract
GI motility: movement of muscle layer that:
breaks apart food, mixes food with digestive enzymes, propels food through digestive tract
Digestive enzyme: catalyze hydrolysis reactions:
water breaks apart molecules too large to pass through the GI tract wall and yields simple molecules that are small enough to be absorbed
places digestive enzymes are produced
- salivary glands
- stomach
- pancreas
- small intestine
Digestive enzymes
- salivary glands and stomach produce small amounts of digestive enzymes
- most are synthesized by pancreas and small intestine
- disease in one of these organs can result in incomplete digestion
saliva
contributes to starch digestion, lubrication, swallowing
mucus
protects GI tract cells, lubricates digesting food
enzyme (amylases, lipases, proteases)
break down carbohydrates, fats, and protein into forms small enough for absorption
Acid
promotes digestion of protein, destroys microorganisms, increases solubility of minerals
Bile
aids in fat digestion (emulsifies fat)
bicarbonate
neutralizes stomach acid when it reaches small intestine
hormones
regulate digestion and absorption
Moving through the GI tract: mouth and esophagus
- food preparation can make food easier to digest
- in the mouth: teeth tear and grind food into smaller pieces
- saliva is mixed with food particles to create bolus
Functions of saliva
- saliva contains: mucus to help lubricate and hold bolus together, lysozyme to kill bacteria, amylase to break down starch
- water in saliva dissolves chemicals in food, contributing to taste
swallowing
- moves food from mouth to esophagus
- the epiglottis is found at the entrance of the esophagus - prevents foo from entering the trachea
- when food is swallowed, the epiglottis closes over the larynx, and then the esophagus relaxes and opens
Moving through the GI tract: stomach
- food enters through lower esophageal sphincter
- large capacity to expand
- stomach is a holding and mixing tank: little digestion occurs here, water and small amounts of fat and alcohol can be absorbed
- stomach secretes gastric juice when we see, smell, taste, or think about food
Cells that contribute to gastric juice
- parietal cells: secrete intrinsic factor and hydrochloric acid (HCl)
- chief cells: secrete pepsinogen, precursor form of pepsin and gastric lipase
- G cells: produce gastrin
HCl
kills bacteria, denatures proteins, activates pepsinogen
intrinsic factor
needed for B12 absorption
pepsinogen
after activation to pepsin, digests proteins
gastric lipase
plays a small role in fat digestion
mucus
lubricates digestive tract and protects from acid and enzymes
gastrin
hormone that stimulates digestive processes such as secretion and motility
Moving through GI tract stomach continued
- contraction of the muscle layers in the stomach mixes food with gastric secretions forming chyme
- pyloric sphincter regulates release of chyme into the small intestine and prevents backflow of bile into stomach
Moving through the GI tract: small intestine and accessory organs
- the small intestine is the major site of digestion and absorption
- divided into duodenum, jejunum, ileum
- interior of small intestine has circular folds and fingerlike projections: villi and microvilli
Small intestine and accessory organs
- circular folds cause chyme to move slowly through a spiral path, which helps mix the chyme with digestive juices and bring nutrients into contact with villi
- villi are lined with epithelial cells called enterocytes
- these cells have microvilli that form the brush border
brush border enzymes
aid in digestion
Liver, gallbladder, and pancreas
- accessory organs that enhance digestion and absorption in the small intestine
- secretion are delivered to the small intestine through: the common bile duct and pancreatic duct
- ducts come together at the hepatopancreatic sphincter (sphincter of Oddi( and empty into the duodenum
Liver produces bile:
- contains cholesterol
- emulsifies fats
gallbladder
stores and concentrates bile
bile
is reabsorbed in the ileum and returned to the liver in a process called enterohepatic circulation
sodium bicarbonate
buffering of acid chyme entering duodenum for activation of enzymes
pancreatic amylase
helps break down starches into sugar
pancreatic lipase
involved in degrading dietary triglycerides
proteases
break down proteins
gastrointestinal hormones: a key to orchestrating digestion
the work of the digestive system requires regulation and coordination of several processes
5 hormones play roles in the regulation
- gastrin
- secretin
- cholecystokinin
- somatostatin
- glucose-dependent insulintropic peptide
pyloric sphincter
regulates release of chyme into the small intestine and prevents backflow of bile into stomach
cephalic phase
the first stage of digestion, which begins before eating and prepares the gastrointestinal tract for food, the stomach responds to the mere sight, smell, taste, or thought of food
gastric phase
neural response, food is entering the stomach an semi digested proteins activate gastric activity
intestinal phase
chyme enters the small intestine from the stomach and the duodenum adjusts gastric activity through hormone and nervous reflexes
CCK + GIP
secreted in the presence of lipids and carbohydrates
secretin
decreased pH
GIP
is a hormone that stimulates insulin secretion
gastrin
- is secreted by G cells in duodenum and stomach
- promotes increased stomach motility, acid and enzyme production
- secreted when you think about or smell good
Cholecytoskinin
- is secreted in duodenum when chyme contains lipids and partially digested proteins
- accelerates pancreatic production and secretion of digestive enzymes
- relaxes hepatopancreatic sphincter and gallbladder ejecting bile and pancreatic juice into duodenum
Endocytosis
phagocytosis and pinocytosis
stomach absorbs
alcohol and water (small amount)
small intestine absorbs
calcium, magnesium, iron, other minerals, glucose, amino acids, fats, vitamins, water (70-90%), alcohol, bile acids
Large intestine
sodium, potassium, some fatty acids, vitamin K and biotin, gases, water
Moving nutrients around the body: circulatory systems
- nutrients absorbed in the small intestine go into either: blood capillaries and the hepatic portal system and lymphatic capillaries
Blood capillaries and the hepatic portal system
- water-soluble substances
- first pass effect in liver
lymphatic capillaries
- fats and fat-soluble vitamins
- released into venous circulation via thoracic duct
moving through the GI tract: large intestine
- small intestine empties into the large intestine through the ileocecal valve
- the large is referring to diameter
- 3 parts: colon, rectum, anus
colon
cecum and ascending, transverse, descending, and the sigmoid colons
large intestine 3 main functions
- house microbiota
- absorbs water and electrolytes: sodium and potassium
- forms and expels feces
Gut microbiota
- bacteria that live in the GI tract, mainly in the large intestine: ileocecal valve prevents bacteria in the large intestine from migrating into the small intestine
- colon contains up to 1000 species, but 30-40 species make up the majority
- many of the gut microbiota are beneficial: harmful strains can live there but growth is held in check by other bacteria an immune system
Dysbiosis
altered balance or change number of gut flora caused by antibiotic treatment, radiation therapy, surgery, and some diseases
Beneficial functions of micrbiota
- synthesize vitamin K and biotin
- aid lactose digestion
- ferment some fibers and starches to create short-chain fatty acids that can be absorbed and used as an energy source in the colon
- gas production can be a byproduct of these processes
probiotics and prebiotics
- consuming probiotics and prebiotics may affect the gut microbiota
- preliminary evidence has suggested benefits in treatment of: diarrhea, constipation, post-antibiotic diarrhea, GI diseases, allergies
- but other studies have shown no benefit
- there may also be risks related to over-colonization by probiotics
Probiotics
- bacterial stains that have beneficial properties to the host
- supplements usually contain one or a few species
- regulated as dietary supplements
Prebiotics
- non-digestible food ingredients
- promote the growth of beneficial bacteria
- inulin: chicory, wheat, onions, garlic, asparagus, bananas
Absorption of water and electrolytes
- 10 liters of water processes per day by digestive system (7 from secretions, 3 from drinking)
- small intestine absorbs 90%
- large intestine absorbs the remaining amount except about 1% that is excreted
Elimination of feces
- feces in rectum triggers muscle contractions in sigmoid colon and rectum, as well as relaxation of anal sphincter muscles
Composition of feces:
- 75% water
- 5% bacteria
- remainder is indigestible material and dead epithelial cells
- color due to compounds produced by bacteria
mouth and salivary glands
prepare food for swallowing: chewing, moistening with saliva, detect taste molecules, start digestion of starch with amylase enzyme
esophagus
moves food to stomach by peristaltic waves initiated by swallowing
stomach
secretes gastric juice containing acid and enzymes, mixes food with gastric juice, converting it to liquid chyme, starts digestion of protein with pepsin enzyme, kills microorganisms with acid’, secretes intrinsic factor, a protein required for vitamin B-12 absorption, slowly releases chyme to the small intestine
liver
produces bile to aid fat digestion and absorption
gallbladder
stores and concentrates bile and releases it to the small intestine
pancreas
secretes pancreatic juice containing digestive enzymes and bicarbonate into the small intestine
small intestine
mixes chyme with bile and pancreatic juice to complete digestion, absorbs nutrients and other compounds in foods, transports remaining residue to large intestine
large intestine (colon)
absorbs water and electrolyte (sodium and potassium), forms and stores feces, house most of the gut microbiota
rectum
holds and expels feces via the anus
GI pathophysiology
diarrhea
- three or more loose bowel movements per day
- secretory: increased secretion or decreased absorption of water
- inflammatory: damage to and decreased function of mucosa
- leading cause of death worldwide, especially for infants
Heartburn and gastroesophageal reflux disease
- heartburn occurs when stomach acid backflows into the esophagus
- gastroesophageal reflux disease (GERD), heartburn 2 or more times per week, also can experience hoarseness, trouble swallowing, coughing, gagging, and nausea
- serious complications of GERD include weight loss, ulceration, bleeding, anemia, and risk of adenocarcinoma of esophagus
GERD
- treated with lifestyle modification and medications
- eating small meals, avoid trigger foods, do not lay down after eating, weight loss, stop smoking, limit alcohol intake
peptic ulcers
- small erosions of the top layer of cells in the stomach or duodenum
- causes: infection with Helicobacter pylori, heavy uses of NSAIDs
- symptoms include: gnawing/burning pain, nausea/vomiting, loss of appetite, weight loss
- complications: bleeding, perforations
- treatments: antibiotics for those infected with H. pylori proton pump inhibitor to suppress acid production
Gallstons
- develop with cholesterol and bile pigments form crystal-like particles
- to prevent formation: maintain a healthy weight, avoid rapid weight loss, eat a healthy diet, exercise
food intolerances
- different from a food allergy
- lactose intolerance many adults do not make enough lactase to break down lactose
- intolerance can also occur due to a non-immune reaction to a food chemical
intestinal gas
- flatulence is a mixture of gases, fermentation of undigested carbohydrates in large intestine, performed by bacteria
- 1-4 pints per day is considered normal
- large quantities of gas can cause bloating and pain
- enzymes preparations can help prevent formation (taking lactase)
inflammatory bowel disease
- ulcerative colitis: inflammation and ulceration of the mucose in the large intestine
- Crohn’s disease: inflammation and ulceration in al layers and in any part of the GI tract
- symptoms: rectal bleeding, diarrhea, abdominal pain, weight loss, fever
