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Medical Essential amino acids

  1. Feb 12, 2017 #1
    It is said that of the 20 amino acids that body needs to produce it's proteins, 9 are not made by the body, so they need to be given in the form food.

    My question is, is the said nine are not all produced by the body, or are the body produces them, albeit very little which is not enough?
  2. jcsd
  3. Feb 12, 2017 #2


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    I don't believe they are produced by the body at all. I don't think we have the necessary cellular machinery to produce them in any quantity.
  4. Feb 12, 2017 #3
    The wiki article is informative I think.
    Our bodies can produce a limited amount of some amino acids, but most of them are obtained by breaking down proteins consumed as food.
    The amino acids contained in our food originate in plants, then go into the food chain.
    (or for vegetarians of course, there is no chain)
  5. Feb 12, 2017 #4
    Are there any amino acids which are essential for man, but not for some other animals?
  6. Feb 12, 2017 #5
    I think all animals require the same same set of 21 amino acids for building up their own proteins and internal body structures.
    It's quite likely though that different species require different proportional amounts of them
  7. Feb 12, 2017 #6
    All animals and all plants and bacteria consist of the same 21 amino acids. Yet amino acids are not essential for plants because plants synthesize all amino acids.
    Man does not synthesize all amino acids. Man also does not synthesize ascorbate. Like most primates and guinea swine.
    But most mammals have no need of ascorbate because they synthesize them.
    Do any animals synthesize any of the 9 amino acids man does not?
  8. Feb 12, 2017 #7
    I don't know, but think it's unlikely for animals close to us in terms of DNA.
    I wouldn't be surprised if very simple organisms, particularly single celled ones can synthesize amino acids that higher organisms don't.
    Their DNA probably has as much in common with plants as is does with human DNA.
  9. Feb 12, 2017 #8
    Why is it unlikely?
    Monkeys need C vitamin, but lorises, galagos and lemurs don´t. Guinea pigs need C vitamin, but most other rodents don´t. Some bats need vitamin C, some others do not. Many passerine birds need C vitamin, but many others do not.
    In all cases, the reason is loss of function of one enzyme - which has happened independently several times.
    Are any of the 9 essential amino acids essential due to recent nonfunctionality of the ability to produce it, which ability has been preserved by closely related animals?
  10. Feb 12, 2017 #9


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    The DNA of plants and animals (both being eukaryotes) are more similar to each other than they are to bacteria (prokaryotes).

    It looks most metazoa (i.e. animals) lack the capability of synthesizing the nine essential amino acids (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4303824/).
  11. Feb 12, 2017 #10

    jim mcnamara

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    Answer to the question: humans make none of the nine AA's de novo ( from scratch or from some other molecule).
    See: http://ajcn.nutrition.org/content/87/5/1576S.full
    For non-scientists: https://en.wikipedia.org/wiki/Protein_Digestibility_Corrected_Amino_Acid_Score

    PDCAAS takes into account the effects of digestibility, availability, etc: e.g, takes into account anti-nutrients like phytates in legumes - why very well cooked beans are a better source of protein than raw, for example.

    This is the gold standard for human protein nutrition today. Protein quality is a complex subject. Lists of PDCAAS values for foods out on the internet are mostly provided by vendors of supplements and are not helpful. Most NIH literature concentrates on a specific problem. The lists there, if any, are short and also often not very helpful. Same for WHO publications, not comprehensive. The US Department of Agriculture had a decent one - cannot find it. Most calculations oddly enough are based on the USDA nutrient database, anyway.

    Plants: Soy has a high PDCAAS value=92. Dairy: milk is 100. Meats vary from 92...97. Egg=100.

    Note that the calculated values for milk and eggs exceed 100, for example. PDCAAS numbers do not exceed 100.

    If want to see what amino acids are in foods go to the source for the PDCAAS numbers above and most other places like WHO. :
    1. go here https://ndb.nal.usda.gov/ndb/search/list
    2. Bring up the food search
    3 !! SELECT STANDARD REFERENCE - otherwise you get an endless barrage of prepared foods.
    4. Use the FULL REPORT option.
    Found something: use the search option here: http://nutritiondata.self.com/ The numbers are uncorrected PDCAAS values.
  12. Feb 14, 2017 #11
    Thank you all for your reply.
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