FOOD20003 Lecture Notes - Lecture 12: Antibody, Malnutrition, Protein Digestibility Corrected Amino Acid Score
28 Jun 2018
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• Generally: protein quality in meat > vegetarian sources
• Animal meat: high percentage of essential amino acids in ratios similar to the human requirement
o Relatively easily digested
Protein Quality:
• Dietary proteins must provide all the essential amino acids
o Limiting amino acids = aa in insufficient amounts to support protein synthesis (runs out)
§ As it’s not supplied in adequate levels, body must breakdown existing proteins to obtain
the needed amino acids OR simply stop making new proteins
§ Lysine, methionine, threonine, tryptophan
• Liver can produce non-essential amino acids
Measuring Protein Quality
1. Chemical Scoring – ratio of grams of limiting aa in a test diet vs amount in reference (i.e. egg) x100
2. Biological value (BV) – How readily the broken-down protein can be used for the body
(absorbed but was it used?)
3. Net protein utilisation – ratio of aa converted to proteins to the ratio of amino acids supplied
4. Protein efficiency ratio – weight gain of the animal vs intake (I.e. ate 200g, does it gain 200g in weight?)
5. Protein Digestibility Corrected Amino Acid Score (PDCAAS) – amino acid requirements & digestibility
Complementary proteins
• Incomplete protein sources à only has LOW amounts of the essential aa
• Complementary proteins:
o Combining two or more foods with incomplete proteins
o This provide adequate amounts of all the essential aa
• Do not need to be eaten together, as long as the day’s meals supply them all
Document Summary
Generally: protein quality in meat > vegetarian sources, animal meat: high percentage of essential amino acids in ratios similar to the human requirement, relatively easily digested. Protein quality: dietary proteins must provide all the essential amino acids, limiting amino acids = aa in insufficient amounts to support protein synthesis (runs out) As it"s not supplied in adequate levels, body must breakdown existing proteins to obtain the needed amino acids or simply stop making new proteins. Lysine, methionine, threonine, tryptophan: liver can produce non-essential amino acids. Severe deprivation/impaired absorption of protein, energy, vitamins, minerals. Involves: severe weight loss, muscle wasting, anxiety, apathy, hair skin problems, kwashiorkro (oedema) Inadequate protein intake: no fluid balances, skinny with large stomach, digests own tissues in order to stay alive. Apathy, misery, irritability, sadness: maramus-kwashiokor mix: Lack of antibodies infection: ****nutrition intervention must be slow and involve gradual increase in quality.
