Human Nutrition Midterm

chapters 1-7

nutrition

the science of nutrients in foods and of their actions within the body; study of human behaviors related to food and eating

water, carbohydrates, lipids, proteins, vitamins, and minerals

the 6 classes of nutrients

essential nutrients

people must obtain these from food because the body can’t make them in sufficient quantity to meet physiological needs

energy yielding nutrients / macronutrients

those that we require in large amounts daily for our fuel (carbohydrates, fats, and protein)

dietary reference intakes

set of nutrient intake values for healthy people

estimated average requirements (EAR)

average amount sufficient for half of the population

recommended dietary allowances (RDA)

recommendations to meet the needs of most healthy people (98%)

adequate intake (AI)

the average daily amount of a nutrient that seems adequate; set when there isn’t sufficient evidence to set an RDA

tolerable upper intake levels (UL)

the maximum daily amount of a nutrient that is safe to consume without reaching toxic levels

malnutrition

any condition caused by lack of food energy or nutrient intake  

estimated energy requirement (EER)

average calories per day that will maintain energy balance in a person who has a healthy body weight 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

carbohydrate AMDR

45-65% kcalories

fat AMDR

20-35% kcalories

protein AMDR

10-35% kcalories

adequacy

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

balance

providing foods in proportion to one another and in proportion to the body’s needs

kcalorie control

management of food energy intake - amount of energy coming in should balance with the amount being used

nutrient density

measure of the nutrients food provides with the energy it provides; the more nutrients and fewer kcals, the higher the nutrient density

variety

eating a wide selection of foods within and among the major food groups

empty kcalorie foods

foods that contribute energy but no protein, minerals, or vitamins (ex. potato chips, candy)

moderation

only occasionally eating foods with solid fats and added sugar; providing enough but not too much

solid fats

fats that are not usually liquid at room temperature; commonly found in most foods derived from animals and vegetable oil

added sugars

sugars that are added to foods during processing, preparation, or at the table

dietary guidelines for Americans 

evidence based advice to attain a healthy weight and reduce risk of chronic disease; suggests a cup of fruit and veggies, an ounce of grains and protein, and a cup of dairy

nutrient claim

information on a food that characterizes the level of nutrient in it (ex. “good source of fiber”)

health claim

information on a food that characterizes the relationship of a food/component to a disease or condition (ex. “oatmeal can help reduce cholesterol”)

structure-function claim

information on a food that describes the effect that a substance has on a structure/function of the body (ex. “supports digestive health”)

digestion

the process by which food is broken down into absorbable units

gastrointestinal (GI) tract

flexible muscular tube that extends from the mouth, through the esophagus, stomach, intestines, and rectum to the anus

lumen

inner space within the GI tract

pharynx

long tube that food goes down after being swallowed that leads to the larynx and esophagus

epiglottis

closes the entrance to the trachea and prevents fluid/food from entering when a person swallows 

bolus

mouthful of food that has been chewed and swallowed

anus

terminal outlet of the GI tract

duodenum

top portion of the small intestine

esophageal sphincter 

circular muscle at the upper and lower ends of the esophagus that prevent back flow

esophagus

food pipe from mouth to stomach

gallbladder

organ that stores and concentrates bile

ileocecal valve

sphincter separating the small and large intestine

ileum

last segment of the small intestine

large intestine/colon

lower portion of the intestine that completes the digestive process

pancreas

gland that secretes digestive enzymes and juices into the duodenum

pyloric sphincter

muscle that separates stomach from small intestine and regulates the flow

small intestine 

major site of digestion and absorption of nutrients 

chyme

semiliquid mass that is the result of stomach acid and digestive juices

GI mobility

spontaneous movement of the GI tract

segmentation

inner circular muscles of the GI tract contract and relax to churn the chyme; mixes it with digestive juices and puts it in close contact with the absorbing cells of the intestinal wall

peristalsis

outer longitudinal stomach muscles rhythmically contract to move chyme forward

enzyme

protein that facilitates a chemical reaction 

hydrolysis

chemical reaction facilitated by enzymes that adds a water to break a molecule into smaller pieces

salivary glands

release saliva into the mouth to moisten food so it can pass easily down the esophagus

gastric glands

secrete gastric juice (mixture of water, enzymes, and hydrochloric acid) into the stomach for protein digestion

bile 

made by the liver, stored in the gallbladder, released in to the small intestine; prepares fats and oils for digestion 

simple diffusion

some nutrients (water + small lipids) can cross freely through membrane of intestinal cells

facilitated diffusion

some nutrients (like water soluble vitamins) need a specific carrier to transport them through the membrane of intestinal cells

active transport

some nutrients like glucose and amino acids move against a concentration gradient which requires energy for carriers to transport through membrane

villi

fingerlike projections on the folds of the small intestine 

microvilli

tiny hairlike projections on each cell of every villus that can trap nutrient particles and transport them

crypts

tubular glands that lie between intestinal villi and secrete intestinal juices into the small intestine

prebiotics

food components such as fiber that are not digested but used as food by GI bacteria yo promote their growth and activity

probiotics 

live microbes in food/supplements that can be beneficial for health 

gastrin

hormone that responds to food ointment the stomach and secretes hydrochloric acid for acidic pH

secretin

hormone that responds to acidic chyme in small intestine and secretes bicarbonate rich juices from the pancreas to maintain alkaline pH

cholecystokinin (CCK)

hormone that responds to fat or protein in small intestine and secretes bile to emulsify fats as well as some pancreatic juices to level pH

glucose + glycogen

molecules that provide about half the energy muscles and body tissues use

simple carbohydrates

monosaccharides and disaccharides

complex carbohydrates

polysaccharides

glucose 

monosaccharide - blood sugar 

fructose

the sweetest monosaccharide

galactose

monosaccharide - small natural sugar

maltose

disaccharide made up of 2 glucose molecules; is produced whenever starch breaks down (carbohydrate digestion)

sucrose

disaccharide made of glucose and fructose; provides the natural sweetness of foods

lactose

disaccharide made up of glucose and galactose; principal carbohydrate of milk

condensation

chemical reaction that links 2 monosaccharides together to form a disaccharide: a hydroxyl (OH) from one combines with the H from another, creating water molecule 

glycogen

polysaccharide made up of many glucose molecules; stores glucose for future use of energy for the body

starch

glucose molecules linked together in branched or unbranched chains

maltase

enzyme on the outer membrane of intestinal cells that breaks maltose down into 2 glucose during carbohydrate digestion

sucrase

enzyme on the outer membrane of intestinal cells that breaks down sucrose into 1 glucose and 1 fructose during carbohydrate digestion

lactase

enzyme on the outer membrane of intestinal cells that breaks down lactose into 1 glucose and 1 galactose during carbohydrate digestion

gluconeogenesis

the making of glucose from proteins 

protein-sparing action

the action of carbohydrates providing enough energy to allow protein to be spared for other resources

diabetes

disease that results from blood glucose rising after a meal and failing to go back down because the insulin is insufficient or ineffective

insulin

hormone that regulates blood sugar by moving glucose from the blood into cells after a meal 

glucagon

hormone that regulates blood sugar by signaling to the liver to break down glycogen stores and release glucose into the body for cells to use in between meals

type 1 diabetes

diabetes that results from the pancreas failing to produce insulin

type 2 diabetes 

diabetes that results from cells not responding to insulin - usually a consequence of obesity

hypoglycemia

disease caused by abnormally low blood glucose concentration 

glycemic response

how quickly glucose is absorbed after a person eats, how high blood sugar rises, and how quickly it turns back to normal

low glycemic response

characterized by slow absorption, moderate rise in blood glucose, and a smooth return to normal (desirable)

high glycemic response

characterized by fast absorption, surge in blood glucose, and overreaction that plunges glucose below normal after 

lipids

family of compounds that includes triglycerides, phospholipids, and sterols; composed of CHO and insoluble in water

fatty acids

organic compounds composed of a carbon chain with hydrogens attached and an acid group (COOH) at one end and a methyl group (CH3) at the other end; carbon chains can go up to 24 

saturated fatty acid

carries the maximum amount of hydrogen atoms (ex. stearic acid)

point of unsaturation

the double bond of a fatty acid where hydrogen atoms can easily be added to the structure

unsaturated fatty acid 

lacks hydrogen atoms and has at least one double bond between carbons

monounsaturated fatty acid

lacks 2 hydrogen atoms and has one double bond between carbons (ex. oleic acid)

polyunsaturated fatty acid

lacks 4 or more hydrogen atoms and has 2 or more double bonds between carbons (ex. linoleic acid)

omega number

position of the closest double bond to the methyl end of a fatty acid 

ex. omega-3 fatty acid means the closest double bond is 3 carbons away from the methyl end 

triglyercides

the chief form of fat in the diet and the major storage form of fat in the body; composed of a molecule of glycerol with 3 fatty acids attached