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Longer Digestive tracts not suited for meat consumption?

  1. Mar 20, 2007 #1
    I was talking to a vegitarian friend who claimed that because humans have relatively long digestive tracts meat consumption may be harmful to us. Upon further investigation she didn't have any real science to back this up.

    As far as I know the main potential problems with meat are the saturated fat, carcinogens from overcooked/charred meat and possible stress on the kidneys if excessive protein is consumed without adequate water intake.

    Is there any truth to my friends thoughts?
  2. jcsd
  3. Mar 20, 2007 #2
    Our degestive tract evolved to digest animal tissue and plant tissue. Meat is an essential part of the diet. Our body requires amino acids which are the building blocks of protiens. There is a total of 20 amino acids. Our body can produce most of the amino acids, but there are some amino acids that cannot be assembled by our body. They are called essential amino acids. We humans usually get essential amino acids from meat. Tell your friend to talk to a doctor about being a vegetarian, because I think vegetarians that dont eat any animal products, have to take supplements to obtain essential amino acids.
    Last edited: Mar 20, 2007
  4. Mar 20, 2007 #3
    Essential? Sorry but that is basically nonsense.

    As if people who do not eat meat are less healthy because of it.
  5. Mar 20, 2007 #4
    You have to get essential amino acids somehow. I geuss you could say that in the PRESENT, animal product are not essential since someone could take amino acid supplements which would contain the essential amino acids. But in the past when those supplements did not exist, meat was indeed an essential part of a humans diet. I might be wrong but i dont think there is a plant that we can consume that contains all the essential amino acids, or a combination of plants that will supply us with all the essential amino acids.
    Last edited: Mar 20, 2007
  6. Mar 20, 2007 #5


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    Some are. But, no, it is not an essential part of the diet. The essential amino acids can also be obtained by combining vegetables and grains to balance those. Animal products are considered complete proteins, because you can obtain all of your essential amino acids from any single type of meat, and they are in the most digestible form for the human body. With a vegetarian diet, no single food item is a complete protein, and vegetable sources are not as digestible as meat sources, so one must be educated about what to combine to ensure they are getting adequate nutrients. Of course, proteins are not the only nutrients we require either, so we need more than just meats too.

    Humans are omnivores and the structure and function of the digestive tract, not its length, is what tell us that humans are not efficient at digesting vegetables (that's why they are good sources of fiber, which means undigestible matter). We are also not obligate carnivores, so need more than just meat as well. The diet that our digestive tract has evolved to digest contains a mixture of meats, vegetables and grains.

    So, one can be a healthy vegetarian if they are very careful about what they are doing, but there are also a lot of myths, such as the one the OP inquired about, that are spread among vegetarians (as well as myths spread among non-vegetarians about vegetarian diets). I would strongly suggest that anyone considering a vegetarian diet ask their physician to recommend a good nutritionist who can help them understand their dietary needs and approach their choice in a healthy and safe manner. Don't rely just on the advice of your physician...believe it or not, they do not receive much training on nutrition in medical school, so are not the best people to ask for help in formulating a diet. A registered dietician or nutritionist is a better resource.
  7. Mar 20, 2007 #6
    edit: oops, my internet didn't load those posts that came after... sorry for repeating what's already been said lol

    let's at least agree that in a "natural*" setting a human would have a pretty hard time finding proteins and certain vitamins without the aid of meat and other animal products...

    now this is no longer true thanks to the help of vitamin supplements and food additives... or things like fortified soy milk (which tastes much better than animal milk to me ... and i kind of find the idea of drinking another animal's fluids rather icky).

    but biologically, humans still are omnivores who require very high amounts of proteins -- easily found in meat.

    * I know, technically, human technology is part of nature just as much as a bird's nest is a part of nature.
    Last edited: Mar 20, 2007
  8. Mar 20, 2007 #7


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    Again, that is not correct. There are places in the world where people exist on vegetarian diets, and are just fine. For example, combining corn and beans (i.e., a bean burrito on a corn tortilla) is a complete protein. Depending on where you live and what produce is available locally, it can be very easy to find a healthy vegetarian diet. There is a lot of misinformation spread about both vegetarian diets and meat consumption alike. Sometimes the reasons people choose a vegetarian diet are misguided based on this misinformation (the environmental impact of vegetable vs animal agriculture is one example where misinformation abounds), but if that is what they choose, they can do it in a healthy way if they are careful (or, in some cases, they don't need to be very careful because their culture already includes the needed variety of foods in their normal diet). One also should not assume that if you eat meat you will automatically have a healthy, balanced, nutrient-complete diet either. A variety of vegetables is still needed.
  9. Mar 20, 2007 #8
    I don't think I was clear in what I meant to say... my point wasn't that it's impossible for a human to get his proteins and vitamins on a vegetarian diet. You've mentioned beans, you can also add certain nuts and so on.

    what I meant by natural setting was that for the primitive humans, it was much easier to get these proteins from meat (the increase in protein intake had to do with better hunting tools and techniques, not better crop production). So we've evolved to digest meat and need those high amounts of proteins that are easiest found in meat.

    agriculture came later, and now we have come to the point where we can add the nutrients we need to foods that don't even have them to begin with.

    I used to be a vegetarian with no health problems... and I'll agree that the only reason I eat meat is because I love the taste. mmmm
    Last edited: Mar 20, 2007
  10. Mar 20, 2007 #9


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    Again, not really. Before agriculture, humans were hunter-gatherers, not just hunters. Given the challenges of hunting, especially with primitive tools, it's pretty likely that the dietary staples were provided by gathering of fruits, vegetables and nuts, and meat would have been a smaller portion of the diet. It's a lot easier to catch a berry than an animal, although insects (also an animal) might have contributed to the dietary requirements for protein.
  11. Mar 21, 2007 #10


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    I once filled out an online diary where you log your daily intake of food. The website was made by several dieticians and an internist/nephrologist and is supported by the Dietician Cooperation of the Netherlands.

    I'm a vegetarian and my protein and vitamin intake was all up to the standards and I don't do any effort in planning my meals. Ofcourse this is only an indication and not scientific proof, but I think the need to eat meat is overestimated in developed countries. We have access to so much food. The fact that millions of people are vegetarians from the second they were fertilized should be proof enough that meat is not essential.
  12. Mar 21, 2007 #11

    jim mcnamara

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    For a different point of view -

    The idea of what we evolved to eat is more to the point than what we can/cannot eat. Plus, the vegetarian term spans a lot of ground.

    Milk-derived products and soy protein products (early humans did not have access to either) provide pretty good proteins; with vitamin B12 in dairy but not in soy. Both of these nutrients may be in short supply in pure vegan diets without some knowledge of what you are doing diet-wise.

    The whole problem in this debate isn't what research says. It is which pieces of research you glom onto, and what your point of view about what the human diet should be. The latter being far more important than anything else. IMO.

    Carnivores tend to suggest ideas like the research presented in the 'Huyanim Cave Fauna...' by Stiner - archeological sduies on animal bones in a cave for the past 200,000 years.

    Herbivores tend to cite longevity studies and lipid metobolism studies.

    The solution is:
    1.We need a silicon-based intelligent life form to study human diet and metabolism. This assumes the life form doens't have pre-conceived notions about what humans are "supposed" to eat. It also assumes they don't want this planet as a sand farm.


    2. We all must be aware that everything published that is on the outskirts of science (ie., non-peer-reviewed books and papers) is basically trying to sell an idea. Or sell a product. Or both.

    IMO 1 & 2 have equally likely probability :)

    It is VERY hard to objective about food. Period.
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