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What is nutrition?
- - The science of food, nutrients and substances in food.
- - Their action, interaction and balance in relation to health and disease
- - The processes by which the organism ingests, digests, transports, utilizes and excretes food substances
What is the goal of nutrition?
- modern nutrition now looks at understanding the effects of over nutrition and understanding the optimal levels of nutrients to maintain good health
What are essential nutrients?
A chemical that is required for metabolism but that cannot be synthesized or cannot be synthesized rapidly enough to meet the needs of an animal.human for one or more physiological function
What is dietary essential VS non-essential?
Has to be obtained in the diet (at least 40) VS body can produce them
How do nutritional deficiencies occur and give 3 examples
- - Occur when a person;s nutrient intake falls consistently below the recommended requirement for that nutrient
- - Ex: Anemia (Fe, folate, B12), rickets (vit D), scurvy (vit C)
How are nutrient requirements estimated? What does it show? What is the difference between a requirement and a recommendation? How can these be divided?
- - estimated using a normal distribution of percentage of pop VS [nutrient] required to satisfy the accepted endpoint
- - range of nutrient intakes required by individuals to acheive same end point of growth, storage or health
- - Requirement: what the body needs
- - Recommendation: what is told to consumme to meet requirement
- - divided by age, sex etc.
How do we study nutrition?
- - cell culture models: pick up cell type and look at how nutrients affect its function and metabolism
- - animal models
- - epidemiological: large population based studies - prospective VS intervention and difficulties (genetics, lifestyle, cultural habits)
What is the Dietary reference intakes? What are the 4 types of reference values?
- - A set of scientifically based nutrient reference values for healthy populations
- 1. Estimated Average Requirement: mean of the bell shapes curve
- 2. Recommended Dietary Allowance: set at large error margin of mean (mean + error margin)
- 3. Adequate Intake: set for nutrient when not enough data to set EAR or RDA - type of recommendation
- 4. Tolerable Upper Intake Level: amount of nutrient that can consistently consummed without adverse effects
How are the nutrient classes divided?
- 1. Macronutrients: larger organic molecules that yield a caloric intake - includes carbs, lipids, proteins
- 2. Microntrients: smaller molecules (organic and inorganic) that don't directly provide energy bu are critical in metabolic proceses - include vitamins and minerals
- 3. Organic: carbs, lipids, proteins, vitamins
- 4. Inorganic: minerals and water
What is metabolism and how is it regulated? What is anabolism? What is catabolism?
- - Meta: processes eeded to sustain life and is regualted by various hormones
- - Ana: process of using building blocks to synthesize macromolecules - requires energy
- - cata: break down of macromolecules to supply energy
Describe the nutrient cycle
Cell tissues --> nutrient building blocks --> [waste for excretion out] recycled nutrients --> [nutrient intake] nutrient building blocks --> cell tissues
Why is water important? What are the functions?
- - it is an essential nutrient and can be seen as the true macro nutrient
- - solvent, lubricant, tempurature regulation, cataboism (hydrolysis)
What is food analysis? Why is it important?
- - the development, application and study of analytical methods for characterizing foods and their constituents
- - important for diet of animal and enancing nutrional value
What is the proximate analysis schematic?
- - Basis for nutrient analysis and nutrition fact labeling
- - gives you 6 values
- - 1-5 are analytically found
- - 6 is calculated
What is the first step? How is it calculated?
- Feed sample is air dryed to release moisture (water) and leave dry matter
- %moisture = weigh loss/wet weight of sample x 100%
- %dry matter = 100 - %moisture
What is dry matter? Why is determing water content important? What are the potential sources of error? What are the differences in determining moisture content in human VS agricultural applications?
- Moisture content removed
- Water content makes up a high content and affects quality storage of food - higher water means faster spoiling
- More volatile nutrients might also evaporate off (short chain FAs) that sould be in dry matter
- Most animal feeds are expressed in dry matter - contains nutrient whereas human nutrition oftern uses wet weight (skips this step)
What is the second step if FPA? How is it performed?
- Mix the weighed and dried matter with organic solvent (ether) causing separation between lipids (react with ether and found in ether layer) from rest of dry matter
- Ether fraction transferred to a new tube and dried
- Leaves fattty residue to be weighed
What is the ether extract and how is it calculated?What are potential errors?
- Ether extract = crude fat
- %crude fat = weight of crude fat/wet weight of sample x 100%
- Other lipid based compounds might be in food and will be included in extraction although not nutrional
- Changes in current food labeling requires trans and sat. fats and cholesterol which isn't provided by this method - use advanced methods after this such as GLC
What is the third step in the FPA?
Take residue left from lipid extraction and you ignite/combust it and left with ash - ash contains inorganic material therefore you can find mineral content
What is the ash and how do you calculate it? What are the potential errors? What may it also indicate?
- Ash = mineral content
- %ash = weight of ash/wet weight of sample x 100%
- May be volatile minerals and therefore loss of nutrient and leading to an underestimation
- Limits to finding specific minerals - labeling requires sodium content therefore need more advanced methods
- Also indicates potential soil contamination if %ask is too high
What is the fourth step of the FPA? What does it assume and what method does it use?
- Measuring nitrogen content = protein
- Almost all proteins contain around the same amount of nitrogen
- If measure amount of nitrogen can extrapolate the amount of protein
- Uses the Kjeldahl Analysis
What is the main point of the Kjeldahl analysis? What are the main steps?
- Measure nitrogen content
- 1. Digestion: A homogenous food smaple mixed with sulfuric acid will break down protein and convert nitrogen to ammonia
- 2. Distillation: separating the ammonia
- 3. Titration: quantifying the amount of ammonia with a strandard solution to determine N content
How do you calculate crude protein? Where does the constant come from?
- %crude protein = (N in sample x 6.25)/wet weight of sample x 100%
- Kjeldahl assumes ALL protein is 16% nitrogen
- 100%protein / 16% nitrogen = 6.25 and Nitrogen x 6.25 = crude protein
What are the potential errors with the Kjeldahl analysis?
- Assumes all proteins have 16% nitrogen however the actual range is from 13-19% which changes the conversion factor
- There are other forms of N which get interpreted as protein (nitrates, nitrites, urea, nucleic acids)
What is the fifth step in the FPA?
- Take the dry matter and extract lipids with ether
- Boil in acid - filtrate + residue
- Boil the residue in alkali - filtrate + ASH and crude fibre
- Ignite the ash with crude fibre to separate them
What is crude fibre? How is it calculated in the FPA?
- indigestible plant material and will be burned off and lost
- Important especially in feed
- %cude fibre = (wt of ash with crude fibre - wt of ash)/ wet weight x 100%
What are potential errors associated with crude fibre analysis?
- Underestimate fibre (hemicellulose, pectin, hydrocolloids) - certain fibres are lost in harsh chemicals
- Not getting individual fibre components - are different fibre types with different health benefits
- Crude fibre isn't equal too dietary fibre
- Crude fibre (lignin and cellulose) < dietary fibre (cellulose, emicellulose, pectin, hydrocolloids, lignin) - missing nutritional information
What is the NFE and what is it mainly comprised of? How is it calculated? What are the potential errors?
- NFE = Nitrogen Free Extract or Digestible Carbs
- Mainly starches and sugars (not separated, required % sugar need advanced methods)
- %NFE = 100 - (%moisture + %crude fat +%ash + %crude protein + %crude fibre)
- Incorporates all errors from analytical components as the numbers come from other steps
What information is FPA missing? What is it used for?
- No information on digestibility or on specific amino acids, mineral, lipids or carbs (all crude methods
- Still used in food labeling and animal feed analysis
- Has provided te basis for developing more advanced analyses
What are dietary fibres? How are dietary fibres categorized? What must we keep in mind about fibres?!
- Non digestible (in human diet) complex CHO (carbs)
- Structural part of plants
- 1. Insoluble - cellulose, lignin, hemicellulose - remains in tact through the intestinal tract (does not dissolve in water)
- 2. Soluble - pectins, gums, mucilages - forms gel (does dissolve in water) (soluble in digestive tract and have their own set of health benefits)
- * All fibres are indigestible whether soluble or insoluble, by human and animal enzymes*
What are the 2 food/feed composition methods? Describe each.
- 1. Van Soest - methods for fibre analysis in feeds (neutral detergent fibre analysis)
- most important in agricultural applications
- poor differentiation of sugars, starches, cell solubles
- Differentiates between fibre components: Cellulose with hemicellulose and lignin
- Use various detergents to separate out fibre components
- In agricultural, want to know amount of lignin because animals have bacteria that can digest fibres EXCEPT lignin therefore high lignin is bad and contributes to bulk
- 2. Southgate method : inconjugtion with FPA
- provides information about sugars, starch and fibre
- Useful for human mutrition, food labeling - more specific info on sugars and starches
- Does not differentiate fibre components therefore can't be used for animals