Better world with veggies?

  1. Recently, I read an article in a magazine which said that if all people turn vegetarian, the earth will be a better place to live. It explained that some energy is lost at each trophic level. So, due to conservation of energy, if we directly consume plants, we will get more energy for some particular mass. In this way our food requirement will lessen. So, we can get rid of the problem of food scarcity.

    So, here's the question : I agree that our food requirement will be less because we will obtain more energy for less food. But I think digesting plants directly requires more energy than digesting meat. I want to know if this notion?
     
  2. jcsd
  3. SteamKing

    SteamKing 9,138
    Staff Emeritus
    Science Advisor
    Homework Helper

    Well, one thing is certain. If everyone goes completely vegetarian, there will eventually be fewer people to worry about. It will be more difficult for people to live in places without sufficient arable land from which to grow enough crops for sustenance, and any increase in population above sustainable levels could be potentially catastrophic for such communities, although the duration of these imbalances could be brutally short as enough die off to bring about a rebalance in the number of consumers versus the amount of food available for consumption.

    Say goodbye to places like Japan, which gets a significant proportion of its dietary protein from fish, because there is not enough arable land in the mountainous Home Islands to support the numbers of Japanese currently living there. Say goodbye also to a lot of people living in tropical or very arid climates, as these areas are very poor candidates for farming. Ditto for people living near the arctic circle, since growing seasons there are very short.

    One mistake you make in your energy calculation is that kg for kg, a plant diet contains more calories than a diet of meat or other food. This is not true.

    A lot of the mass of vegetable matter is undigestible fibre, from which no nutrients or energy are extracted by the human gut. Animals like cows have specially adapted digestive tracts to allow them to survive on an all-plant diet. Even with these specially adapted digestive tracts, cows and other ruminants rely on bacteria living in their gut to ferment the plant matter so that digestion can be completed:

    http://en.wikipedia.org/wiki/Ruminant

    An all-plant diet has to be carefully monitored to make sure enough of the proper minerals and vitamins are consumed to maintain health.
     
  4. What I read was that it does not contain more calories but if we directly consume the producers, the energy lost in conversion of energy will be less and so our food requirement will lessen.

    But as you said, plants are hard to digest. So, if in future somehow we find a way to completely digest the substances found in plants, then would the claim be true?
     
  5. SteamKing

    SteamKing 9,138
    Staff Emeritus
    Science Advisor
    Homework Helper

    Perhaps, but short of genetically re-engineering the human digestive tract, I don't see us giving cows and other ruminants much competition eating grass.
     
  6. Monique

    Monique 4,700
    Staff Emeritus
    Science Advisor
    Gold Member

    1) We don't eat grass, 2) Humans cook food, which makes food more easily digestible. People eat spinach (and other vegetables) for the nutrient content.

    Yashbhatt is right about the energy conversion thing, it's in the text books.

    I can't answer the question "But I think digesting plants directly requires more energy than digesting meat. I want to know if this notion?" What energy are you talking about?
     
  7. Monique

    Monique 4,700
    Staff Emeritus
    Science Advisor
    Gold Member

    Japan could use the sea to grow protein-rich vegetables:
    Seaweed: An alternative protein source

    Indeed when I was in Okinawa there were seaweed farms off the coast.
     
  8. Pythagorean

    Pythagorean 4,609
    Gold Member

    That's true, but fiber actually helps aid digestion in several important ways:

    http://en.wikipedia.org/wiki/Dietary_fiber#Effects_of_fiber_intake

    In fact, the low-fiber diet of modern day has been associated with obesity and diabetes!
     
  9. Pythagorean

    Pythagorean 4,609
    Gold Member

    To the OP, "Better world" is a bit of a glorification of the vegetarian diet; when you make such an all-encompassing statement, you have to be careful to consider the economic and social consequences, too. There are certainly benefits, but there are also risks associated with a vegetarian diet. While protein isn't really a problem like most people think it is, B12 is one of the micronutrients that you can only get from animal products.
     
    Last edited: Apr 20, 2014
  10. Monique

    Monique 4,700
    Staff Emeritus
    Science Advisor
    Gold Member

    Actually B12 comes from bacteria, so it can be cultured without animals. Also, vegetarianism still includes animal products and thus a source of B12.
     
  11. russ_watters

    Staff: Mentor

    There's a big flaw in your premise:
    The world doesn't have a general food scarcity problem. What it has is people living in paces where food is tough to grow and political problems that prevent surplus food from other areas from getting to them.
     
    1 person likes this.
  12. @Monique I mean that we need to spend some amount of energy in converting one form of energy to another. So, as the plants molecules are more complex as compared to meat, don't we need more energy in transforming the complex molecules present in plants to simpler ones?

    @Pythagorean You are right. But here by better world I meant world without food scarcity.
     
  13. Pythagorean

    Pythagorean 4,609
    Gold Member

    But do any humans actually get B12 from bacteria? As far as I know, animals are the only human-available source. I know yeast can be fortified with B12, but it was my impression that this fortification was through animal products.

    I know vegetarians consume milk/eggs, but that doesn't seem relevant to the OP's proposition.
     
  14. Monique

    Monique 4,700
    Staff Emeritus
    Science Advisor
    Gold Member

    Plant molecules are more complex? I don't think so.

    For a fact vitamin B12 can only be synthesized by certain bacteria, the bacteria live in the guts of animals and that's how it gets into animal products.

    Scientific breakthrough reveals how vitamin B12 is made
     
  15. Pythagorean

    Pythagorean 4,609
    Gold Member

    I know B12 is only made by bacteria, but that still doesn't address my point. As far as I know, animal products are the only way humans get it (in sufficient quantities).
     
  16. @Monique They may not be that complex but they are certainly more complex than glucose and we need to convert all food to glucose to obtain energy.
     
  17. Monique

    Monique 4,700
    Staff Emeritus
    Science Advisor
    Gold Member

    Obviously if it is produced by bacteria, one can grow the bacteria and harvest the vitamin. Also, one can use the bacteria to ferment food. Indeed, vitamin B12 is present in fermented vegetables: Vitamin B12 content in Korean fermented foods and some popular foods. I'm interested to find out whether humans are able to live in symbiosis with the bacteria, I've never seen research on it.

    Considering that vegetarians don't need to eat double the amount of food, I don't think it is an issue. I don't have the knowledge or sources to back it up. Your statement that all food needs to be converted into glucose is too simplified, metabolism is very complex.

    Let's take an example and compare beans with meat, I think the cooked beans are more easy to digest. Actually they contain carbohydrates that are easily converted into sugar. Just take a bean into your mouth: it tastes sweet due to carbs being digested by your saliva. I think a steak will take longer to be digested, but don't have an appropriate source.
     
  18. Pythagorean

    Pythagorean 4,609
    Gold Member

    It's mostly a question of economic viability. Can you produce enough B12 to replace B12 from animal sources? Your own article acknowledges in the abstract that "the apparent nutritional imbalance in the traditional semi-vegetarian diet raised a special attention, especially on vitamin B12 status, supplied by animal foods" and notes the Korean fermented foods as an exception.

    But, keeping with the thread topic, we're still left with the question of viability of such alternative B12 sources.

    Not also, this issues that have arisen so far with B12 synthesis. The B12 produced by cyanobacteria like in Spirulina is well known for being a pseudovitamin. The B12 it produces is useless to humans:

    http://www.ncbi.nlm.nih.gov/pubmed/17959839

    You might be interested in this paper I came across during our discussion here:

    http://www.nature.com/nature/journal/v283/n5749/abs/283781a0.html
     
  19. So, till we don't find a way to completely digest plants we can say that being completely vegetarian would be no better than present?
     
    Last edited: Apr 21, 2014
  20. Monique

    Monique 4,700
    Staff Emeritus
    Science Advisor
    Gold Member

    Why would you say that?

    *edit* Here, does this answer your question?

    Climate benefits of changing diet. Climatic Change (2009) 95:83–10
     
    Last edited: Apr 21, 2014
  21. To put that in perspective:
    The world has a total land mass of 149,000,000 km[itex]^{2}[/itex].
    1 square kilometre contains 100 hectares.

    2,700 Mha = 27M sq km of pasture ( roughly the size of Morth America )

    for the cropland:
    100Mha = 1M sq km or roughly the size of South Africa, or Canada and Australia combined

    Worldwide:
    17,298,900 square kilometres of world land is cultivated.
    15,749,300 is used for replanted food crops such as wheat, rice, corn.
    1,549,600 is used for other agricultural food crops and industrial plant products such as fruit and rubber trees.

    If we ate veggies:
    % reduction in cropland worldwide ie replanted cropland = 1,000,000 / 15,749,300 = 6.35%

    ( I suppose that means that 93.35% of food crop land use is already used for human consumption )

    http://en.wikipedia.org/wiki/Land_use_statistics_by_country

    No breakdown on the pasture land usage at wikepedia.
    Although this site might be able to provide some correlation,
    http://data.worldbank.org/indicator/AG.LND.ARBL.ZS
     
    Last edited: Apr 21, 2014
Know someone interested in this topic? Share a link to this question via email, Google+, Twitter, or Facebook

Have something to add?

0
Draft saved Draft deleted