Midterm Flashcards
Essential Nutrient
Chemical required for metabolism, can not be synthesized or can not be synthesized rapidly enough to meed the needs of an animal or human for one or more physiological functions
1) Removing nutrient causes a decline in health
2) Putting nutrient back in diet fixes health
Deficiency
Prevention of disease associated with the nutrient
Nutritional requirement
Ensure optimal health
Limitations with nutritional recommendations
Age, gender, body size, physical activity
Nutrient requirement labels
Daily values are based on a 2 000 calorie a day diet
Made using DRIs
Dietary Reference intake (DRI)
Umbrella term, refers to set of reference values for nutrients (EAR, RDA, AI and UL
Macronutrients
Fats, carbs and proteins
Establishing nutrient requirements
Estimated average requirement (EAR): The needs of 50% of the population are met
Recommended dietary allowance (RDA): The needs of 97% of the population are met ** What organizations are going for
Some people need top consume a lot more than others to get to the same point!
RDA
EAR + 2STD dev
Upper limit (UL)
Highest level of continuous daily nutrient intake that causes no risk of adverse effects.
No one is deficient. Agencies do not strive for this, not realistic due to genetic issues, food allergies etc
Reason why we can not just overshoot requirements to make sure everyone gets enough
Each nutrient has a different sized gap
Adequate intake (AI)
When not enough info to establish an EAR and RDA
Based off of much less scientific data
Determined base on intake in healthy people who are assumed to have an adequate nutritional status. Expected to meet or exceed the needs of most individuals
Understanding a nutritions diet
Adequate: Enough calories, essential nutrients and fibre to keep you healthy
Moderate: Ensuring you do not consume too many calories, or eat too much of one food group
Balanced: Nutrient dense foods
Varied: Eating a wide selection of foods to get the necessary nutrients
Methods for studying nutrition
Cell culture models (not great because we eat food not just nutrients)
Animal models
Epidemiological cohorts studies (lifestyle in relation to nutrition) (prospective vs retrospective: Looking into the future/ looking back on old results)
Intervention studies (randomized control trial (RCT): People are placed into randomized groups and observed
ChallengesL Genetics, lifestyle, cultural habits
Micronutrients
Vitamins
Minerals
Organic (contain carbon)
Carbs/ fibre
Lipids
Proteins
Vitamins
Inorganic (no carbon)
Minerals
WATER
Metabolism
Anabolism (building up) + catabolism (breaking down)
Water
Main component of blood
Deficiency is not a huge issue as we know when we need to drink (we get thirsty)
20% will come from foods
Solvent in biochemical reactions, catabolism (hydrolysis), nutrient transport, temp regulation
Water toxicity
water intake»_space;> kidney’s ability to process
When you consume too much water and there is not enough electrolytes, sodium in cells will flow out to create a new equilibrium
Only really happens when someone is avoiding urination (water floods into cells and burst)
Hyponatremia
Water/ Na imbalance
Causes CNS edema and muscle weakness
Constituents
Nutrient breakdown
Quality control
Ensuring composition does not change overtime. Critical for a food industry perspective so raw material can be standardized (always look and taste the same
Food analysis
Development, application and study of analytical methods for characterizing food and constituents. Important, allows consumer to make informed decisions
Government regulations: Maintain high quality of food, fait competition between companies, eliminate economic fraud
Quality control
Nutrient density in food
Caloric count does not predict nutrients eg cupcakes (empty calorie) or broccoli (nutrient dense)
Moisture (water content)
Air dry food sample by putting it in hot even and heating up so evaporates.
Important because water is weight (more water= higher shipping costs)
Too much and food will spoil quicker, too little and food will be less palatable
Moisture duties energy and nutrients in food
(wet weight- dry weight)/ wet weight x 100
AG industry labelling is based more on dry matter, human food on wet weight
Possible errors: Drying can remove other volatile compounds such as short chain fatty acids and some minerals. Allows new methods being created.
Ether extract
Dry matter undergoes ether extraction
wet weight of ether extract/ wet weight of sample x100
Potential sources or error: Other things are soluble in ether extract (chlorophyll, resins, waxes) so this will over- estimate crude fat determination. We need more technologies that are more precise. Gas chromatography is a newer method
ASH
Ignite ether residue to get ash (minerals, sodium etc.) Gets rid of anything with carbon so left strictly with minerals
Important for nutritional labelling, quality and taste of food, microbiological stability, nutritional requirements, manufacture processing
weight of ash/ wet weight of sample x100
Sources of error: Volatile minerals may be lost when burning residue, possible to loose some, underestimating the mineral content
No information about individual minerals. Very significant limitation.
Kjeldahl analysis
Done to get nitrogen from the dry matter. Nitrogen is used to estimate the amount of protein
Assumptions: All nitrogen is in protein, all protein contains 16% nitrogen
Crude protein: Protein approximation
1) Digestion: Food sample is mixed with sulphuric acid, converts nitrogen into ammonia
2) Distillation: Separates the ammonia
3) Titration: Quantifies the amount of ammonia
% crude protein
(N in sample x6.25)/ wet weight of sample x100
Where is the number 6.25 from
100% / 16%= 6.25
Even though actual range is 13-19%
Other sources of nitrogen: Any nitrates, nitrites, urea, nucleic acid etc, The food in sample would therefore be part of the crude protein calculation (slight over estimation)
% crude fibre
(wt of ASH + crude fibre)- (wt of ASH)/ wet weight of sample x100
Fibre is not digestible, post ether extortion, solution which was used for fat composition would be discarded, Ppt boiled into acid and then boiled into alkaline solution to mimic digestion (through stomach to small intestine)
Crude fibre vs. dietary fibre
Crude fibre: mainly cellulose and lignin
Dietary fibre: Used to describe all fibre (both soluble and insoluble fibres) in a food. To better estimate dietary fibre content, additional analysis are necessary
Potential sources of error: unable to distinguish different fibre components
Measuring crude fibre under estimates actual dietary fibre content of feed by up to 50%. Because dietary fibre includes cellulose, hem cellulose, pectin, mucilages, gums, ligin etc. Soluble fibres are lost during the proximal analysis (lost in either acid or alkaline analysis)
Nitrogen free extract (NFE)
= digestible carbohydrate (CHO)
Estimates starch and sugar content
100- (% moisture + % crude fat + % ash + % crude protein + % crude fibre)
This accumulates all of the errors that exist for the other components. Starting point to distinguish between starches and sugars
Still used as the basis for human food labelling and animal feed analysis, no information on digestibility of food (so we do not know what will actually be absorbed)
No info on specific amino acids, minerals, lipids or carbs
Has promoted the development of more advanced analytical assays to improve food characterization
For humans we start with wet weight, ag starts with dry. Percentages will be different but weight will be the same
Dietary fibre
Non- digestible complex CHO, structural part of plants (we do not have the enzymes to break these down)
Insoluble: Cellulose, Lignin, hemicellulose. Intact through intentional tract. Does not dissolve in water
Soluble: Pectins, gums, mucilages. Forms gel, does dissolve in water
More accurate fibre analyses (to complete the proximate analysis)
Van soest method
Southgate method
Van soest method for fibre analysis in feeds (detergent fibre analysis)
Differentiates between insoluble fibres. Determines fermentable and non- fermentable CHO (when fibre is fermented it can be energy)
Very important for ag applications. Not used for human analysis because it poorly differentiates sugars, starches and soluble fibres
Cellulose and hemicellulose, lignin ( poorly fermentes, prevents fermentation of other fibres)
Southgate method
Provides information about sugars, starch and various fibres
Useful for human nutrition and food labeling.
Does not differentiate sufficiently between various insoluble fibre components adequately
GI tract
= gut. Digestive system refers to the GI tract and associated organs (liver, pancreas, gall bladder)
Soluble
Is CHO soluble in aqueous environment of digestive tract (not determined by enzymes, determined by physical and chemical properties
Digestibility
Does the host organism have the enzymes necessary to digest CHO (non digestible CHO= fibres)
Fermentability
Do gut bacteria have the enzymes needed to break it down
Sample system w/o caecum
Mono-gastric, suited for a nutrient dense, low fibre diet.
Oral cavity
Food is chewed and mixed with saliva
Stomach (mono gastric no caecum)
Cardia, funds, body and atrium are functionally distinct regions of the stomach but not anatomically distinct
Empty=5mL, filled =1-1.5L
Gastric emptying= 2-6 hours
Gastric glands secrete gastric juice
Small intestine (monogastric no caecum)
Main site for nutrient digestion and absorption (30m^2). large surface area die to colds, cilli and crips
Microvilli: Brush boorder membrane
Chyme acidity neutralized by pancreatic juice
Food digested by pancreatic juice and bile acids
Large intestine (monogastric no caecum)
Site of fermentation. Production of short chain fatty acids (SCFS) which are known as volatile fatty acids (VFA). Source of energy for bacteria
Site for water absorptopn
Nutrient transport mechanisms
Mechanism depends on nutrients solubility, concentration gradient, molecular size
Diffusion: High to low conc gradient
Facilitated diffusion: Same but requires a channel
Active transport requires every against a concentration gradient
Needs to go from intentional lumen too the enterocyte (cellular) cytoplasm
Gut bacteria
Everyone has slightly different species in their gut with similar core functions. More anaerobic than aerobic
Probiotics
Beneficial bacteria to improve gut health
Simple system with functional caecum
Pseudo ruminant, hindgut fermenter, subtle for a diet with large amounts of forage
Also known as a hind gut fermenter (fermentation takes place after the small intestine)
Caecum
Enormous hindgut filled with bacteria
SCFA provides 70% of total energy needs for host. Site for the production of vitamins
Signs of energy/ nutrient deficiency: Coprophagy (eating dung/ faces) . Young animals eating faces colonize their gifts with bacteria
Where nutrients are absorbed in horses
Small intestine: Glucose, amino acids, fatty acids
Large intestine and caecum: Lactic acid, amino acids
Ruminant
Suited for animals that eat hight quality forage. Foregut fermenters
1) Reticulum
2) Rumen
3) Omasum
4) Abomasum
Nutrients are produced by bacteria then become available for digestion and absorption by the ruminant
1) Rumination
2) Eructation (belching)
Grazers vs browsers
Horses are grazers, cows are browsers
Reticulum
Honeycomb appearance to capture nutrients and trap foreign material
Rich in bacteria (fermentation vat)
Rumen
Largest, fermentation vat
Rumen papillae increases surface area for absorption (like microvilli in human intestine)
Food is mixed and partially broken down and stored temporarily
60-80% of total energy produced here as SCFA
Omasum
Reabsorption of water and some electrolytes, filters large particles
Abomasum
Digestive enzymes secreted from gastric glands (HCl, mucin, pepsinogen, lipase etc.) true stomach
Pros of rumen system
Vitamin synthesis, non- protein nitrogen can be used for making protein
What does fermentation refer to
CARBS
Cons of rumen system
Carbs degraded into gases and lost through eructation, heat production (due to fermentation)
Avian system
Beaks and claws break for into smaller pieces
Rapid digestion: Birds can starve if deprived of food for a few hours (adapted for constant grazing)
Crop: Enlarged esophagus, storage for food so they can pick some up and fly away. Food is softened here, often regurgitated to feed to offspring
Avian stomach
Glandular portion: Proventriculus (chemical digestion. Like our stomach)
Gizzard: Physical digestion (because they have no teeth)
Avain small intestine
Similar to other systems
Avian Ceca
Minor site of bacterial fermentation, Two small caecum. Functional, just not a huge contributor
Avain large intestine
Very short, connects cloaca and small intestine
Storage or undigested material, water absorption
Caloca
Where digestive, urinary and reproductive systems meet (unite to avian, after small intestine, before recutm)
Digestibility
Calculated from the amount of nutrient in diet and the amount appearance in faces
Represents a combination of nutrient release from the food matrix, microbial fermentation and absorption
Need to prevent deficiency and ensure essential nutrients are available to the organism
Total collection method
Allow animal to adapt to a diet over 7-21 day period
Isolate animal for quantitative analysis
Measure intake over a 3-10 day period
Collect and weigh all faces \
Analyze for nutrient
Apparent digestibility coefficient= (total intake - total feces)/ total intake
Limitations of the total collection method
Accuracy in measuring food intake (animals will spill foods)
Metabolic cages creates anxiety in animals, which may make them behave abnormally
Labour intensive
Animals confined in costly equipment, not feasible for captive wild animals
Indicator method (matter technique)
Requires a marker: internal (natural component of feed) and external (a component added to the feed)
Characteristics of a marker: nn absorbable, not affected or be affected by the GIT, mix easily with the food, easily and accurately measured in samples
1) Adapt animal to test diet (which contains a marker)
2) Collect a feed and decal sample
3) Analyze each for marker and nutrient of interest relative to you indicator
Advantages of this method: Less labour intensive, ideal for wild animals
A= ratio of nutrient/ marker in feed
B= ratio of nutrient/ marker in faces
(A-B)/A
Apparent vs true digestibility
Apparent digestibility underestimates true digestibility because the following are not considered
Endogenous secretions (eg. fatty acids released from dying epithelial cells)
Bacterial growth in gut (eg. biotin produced by gut bacteria)
Digestive enzymes (eg. protein secretion, digestive enzymes released by cells)
True digestibility
1) Preform digestibility study using test diet
2) Switch to diet containing none of the nutrient of intrest (zero nutrient diet)
3) Analyze faces after test diet is cleared
4) Subtract level of nutrient in feces of animals fed the zero nutrient diet from the test diet
True digestibility coefficient formula
A= ratio of nutrient/ marker in test diet
B= ratio of nutrient/ marker in faces (after test diet)
C= Ratio of nutrient/ marker in faces after zero nutrient diet
(A-(B-C))/A
Factors that affect digestibility
Feed intake, particle size, chemical composition, climate (digestibility is higher when it is warmer), age
SI unit for energy
kJ
What is a calorie
Measure of heat to express the energy content of food
1000 chemistry calories= 1 food calorie= 1kcal= 4.18kJ
Positive energy balance
More in (food and drink) than out
weigh gain, infertility, increased blood lipids, insulin resistance
Negative energy balance
More out (metabolic and cellular function/ physical activity) then in
Calorimetry
Measure of heat production
Uses heat as an indicator of the amount of energy stored in the C-H bonds of foods
Bomb calorimeter
Works according to principles of direct calorimetry (directly measures the amount of energy stored in chemical bonds of foods
1) Put try sample in the bomb with oxygen
2) ignite sample
3) Head released is absorbed by water rand measured
Heat of combustion (gross energy)= maximum energy
Potential errors
Over estimates energy (eg. we do not digest fibre)
Does not take into account the energy needed for digestion and absorption
Physiological fuel values
Also called Atwater values, available energy or metabolizable energy. Takes into account incomplete digestion
Nitrogen makes urea with hydrogen which is excreted in urine (nitrogen is not used for anything in the body). This loss of hydrogen affects the heat of combustion
Lipids have lots of hydrogen atoms available for cleavage
(heat of combustion - energy lost in urine) x apparent digestibility
CHO- 4
Fat- 9
Protein- 4
Factors that affect heat of combustion of fatty acids
Chain length (longer chain= more energy)
Degree of unsaturation (more double bonds, the less energy released (for equal chain lengths)
When calories do not always add up
Fibre is the problem
Use of metabolizable energy
Heat increment of feeding (HIF) is also called the thermic effect of food. energy used for the digestion, absorption, disturbiution and storage of nutrients
Comprises 5-30% of daily net energy usage
Used to determine net energy
net energy= metabolizable energy- HIF
Total energy expenditure
1) Basal metabolic rate (BMR)
2) Thermal effect of food (HIF)
3) Physical activity energy expenditure (PAEE)
4) Thermoregulation (which does not really need to be considered because when we are cold we will put on a sweater. we adapt to the thermal energy around us
Basal metabolic rate (kcal/ 24h)
Measured shortly after waking, have not yet had a meal, lying down, completely relaxed, comfortable room temp
Muscle and bone are most reflective of BMR
BMR= Ax M^0.75 kcal/ day
Based on metabolic weight
Metabolically active tissue (A)= 70 for humans. each species has its one value
M= body weight in kg
0.75= kleiber’s law. Constant
Most accurate way to measure is measuring body fat percentage with specialized equipment. This is the most accurate . Uses the katch- mcardle BMR equation which is the same for both men and women
Haris- benidict equation
More refined, based off of large population based studies
Resting metabolic rate
Like BMR just experiment is not as accurate
Factors that can affect BMR
Genetics (inheritance of a fast or slow metabolic rate)
Age (young> old because of greater muscle mass
Sex (men>women (greater muscle mass)
Exercise changes body tissue proportions due to changes in muscle mass. The more fat free mass, the higher your BMR
Temperature (maintaining thermoregulation)
Measuring total energy expenditure
All metabolic processes generate heat, which can be used as a measure of energy expenditure by direct or indirect calorimetry
Calorimetry (general combustion equation)
Fuel +O2 —-(respiration)—> CO2 + H2O + Heat
Fuel= Diet (cho, fat, protein. could also be a mixed food sample or a fecal sample)
O2 and CO2 are from indirect calorimetry. This measures oxygen consumption and CO2 expenditure
Heat: Direct calorimetry
Direct calorimetry
Measures the heat a person generates, total heat loss. Very expensive and impractical as you have to lock someone in a metabolic chamber and their heat heats water in a pipe for 24h
Indirect calorimetry
Energy- releasing reactions in the body, depends on the use of oxygen (oxidation of foods in your body produces CO2.)
Estimates energy requirements by measuring: O2 consumption (L), carbon dioxide production (L), urinary nitrogen loss (g)
This method can not account for anaerobic processes (eg. production of lactic acid (lactate) from glucose during intense exercise.
people do not measure urinary nitrogen loss because protein is not usually used to produce energy so it does not really need to be considered.
Cons: Hyperventilation, hard to get an airtight seal. Masks are impractical
Advantages: Useful with animals, can determine the type of substrate being oxidized
Direct vs indirect calorimetry
Very comparable
Respiratory quotient (RQ)
Provides information about: Energy expenditure, biological substrate being oxidized (carbs or fat)
Ratio of metabolic gas exchange
RQ= CO2 produced/ O2 consumed
Non protein RQ, protein contributes very little to energy metabolism
Differs for every macronutrients
For each non- protein RQ value, their is a caloric value for each L of O2 consumed or CO2 produced
Table also tells you how much CHO and fat contribute to energy
RQ assumptions made
Only CHO and fat are metabolized
No synthesis is taking place at the same time as breakdown
Amount of CO2 exhaled= amount of CO2 produced by tissues
Changing RQ: The crossover concept
When muscle starts to use more CO2 than fat to sustain power. Endurance (fat) vs high intensity (CHO)
Training will enable a person to more the cross over to the right, meaning more fat is used than CHO
Carbohydrate classification
Monosaccharide: Naturally occurring, most common is glucose, cannot be hydrolyzed into a smaller unit. Considered a reducing sugar when the anomeric carbon is free
Disaccharide: Most common is sucrose, two monosaccharides joined by an acetyl (glycosidic) bond
Complex: Oligosaccharides, polysaccharides. Homo and hetero. Glycogen (animal) starch and cellulose (plant)
ALL CHO have a H:O ratio of 2:1 ( very oxidized to begin with)
Monosaccharides
Trioses: Metabolites of glucose. We do not consume these, but we can find them in our body as we break down glucose.
Pentose: Components of DNA and RNA
Hexose: Nutritionally, the most important
Also is any monosaccharide that has an aldehyde, same vibe applies to ketose
Sterioism
Same molecular formula and sequence, differ in 3D space
L (OH of highest chiral carbon on the left) and D (OH of the highest chiral carbon on the right) isoforms
Chiral compounds: Attached to four different atoms or groups
Number of steeoisomers for a molecule= 2^n (where n= # chiral carbons)
D monosaccharides are nutritional important, digestive enzymes are stereospecific for D sugars. We can not process L sugars
Fisher –> Haworth
1) Non- acetyl/ non- ketal Ch2Oh always points up
2) for OH groups: If it is right in the Fischer, it’s below in Haworth. If it’s left in the Fischer, it’s above Haworth
3) Hermiacetal: Alpha has the OH group pointing down, beta has the OH group pointing up
Anomeric carbon
Carbonyl group
Disaccharides (most common oligosaccharide)
2 monosaccharides attached by a glycosidic bond (formed between two hydroxyl groups) which can be alpha or beta
Polysaccharides
Min 6 monosaccharides attached by glycosidic bonds
Homopolysacharides are more abundant in food
Alpha (1,6) binds create branching. More ends there are, the more energy we get. Much more rapid way of obtaining glucose
