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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
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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
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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
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What is dietary essential VS non-essential?
Has to be obtained in the diet (at least 40) VS body can produce them
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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)
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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.
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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)
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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
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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
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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
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Describe the nutrient cycle
Cell tissues --> nutrient building blocks --> [waste for excretion out] recycled nutrients --> [nutrient intake] nutrient building blocks --> cell tissues
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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)
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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
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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
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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
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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)
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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
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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
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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
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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
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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
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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
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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
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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)
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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
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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%
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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
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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
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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
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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*
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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
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