Comment by pron | Hacker News Reader

Comment by pron | Hacker News Reader

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sound reasons and very little magical thinking in terms of the economics of food

First, there isn't much logical thinking involved in veganism or vegetarianism. At their best, they're about ethics (which I certainly respect). At their worst, they make some very dubious claims about te economics of food and the environment.

But either way, note that people make significant and probably burdensome changes to their lives when it comes to upholding morals pertaining to food. I think that more (liberal) people would go a longer way making actual life changes when it comes to food than just about anything else. They might explain that the things you actually put into your body are the things you should care about most. Only there's little evidence to suggest that's the case. It is much more probable that national policies like increasing minimum wage or reforming education would have a bigger (though indirect) effect on your personal well being than optimizing your diet (as long as it's more or less "normal").

All religions, in this case the healthy diet religion, must not rely on facts in order to gain followers; they must rely on gut feelings, because gut feelings are much more powerful than proof when it comes to motivating life changes. And we just naturally feel that ingested food has to have a major effect on our health and general well being. It just makes sense, right? But, at least in the current state of scientific knowledge on the subject, that intuition is just superstition. After decades of research there's little consensus even on what makes us fat, let alone more subtle or indirect effects diet may have on our health. In fact, it's very probable that even if one day we do know exactly what's healthy to eat and what isn't, and at what quantities, the actual effect-size on our health will be quite small. It's quite possible that within some sane bounds, what food we eat simply does not determine our health to any large degree.

I disagree with your claim that veganism and vegetarianism can't be backed by logical thinking. Producing meat requires significantly more natural resources (land area, water) and produces significantly more pollution (methane, ground contamination) than producing fruits and vegetables.

Here is an example comparing the amount of water needed to irrigate various crops compared to the amount needed to raise beef.

US Corn Production: 9 gallons water / lb corn

US Wheat Production: 14 gallons water / lb wheat

US Barley Production: 26 gallons water / lb barley

US Alfalfa Production: 31 gallons water / lb alfalfa

US Beef Production: 441 gallons water / lb beef

http://www.journalofanimalscience.org/content/71/4/818.full....

Global Spinach Production: 2 gallons water / lb spinach

Global Potato Production: 4 gallons water / lb potatos

Global Banana Production: 13 gallons water / lb bananas

Global Apple Production: 18 gallons water / lb apples

Global Lentil Production: 64 gallons water / lb lentils

Global Cashew Production: 121 gallons water / lb cashews

Global Almond Production: 252 gallons water / lb almonds

http://www.waterfootprint.org/Reports/Mekonnen-Hoekstra-2011...

I could look for more examples, but this took me about half an hour already, and I think it pains a rather compelling picture by itself. The difference would be less extreme when looking at pork and poultry, but there is still a stark contrast.

You need to normalize to nutritional value rather than weight.

But the whole point of this thread seems to be that such an analysis is hard to do.

Exactly.

There are so many confounding variables here that it's really hard to tell. Everyone pretty much chooses to believe whatever data they like best. For example, cultivated land is probably less environmentally friendly than pasture land.

It wouldn't matter how environmentally unfriendly it was to cultivate land as long as livestock are fed cultivated crops, since they require more than one pound of food to produce one pound of meat.

If x = environmental impact of cultivating crops

then R*x = environmental impact of raising livestock

where R = pounds of feed required to produce one pound of meat

Now if we raised our meat differently, such as only on grass-fed pastures, then things might look a lot different. But in the US at least, factory farming and animal feed is the norm.

I'm not too fond of factory farming, but that has little to do with veganism. In any case, your math would be correct only if 1 pound of vegetables consumed by a person is the same as one pound of meat. I guess even vegetarians would admit that's wrong (I think humanoids started eating meat because it was the only thing providing enough concentrated nutrition to support a massive brain, at least without eating all day long).

Moreover, it's quite conceivable (again, no proof, but there's little proof af anything in this field) that herbivores would convert one pound of corn much more efficiently than we would. This might mean that humans are better off wasting energy by feeding vegetables to animals and then eating the animals, than eating the vegetables directly. Maybe we can't extract the nutrients from the vegetables as well as herbivores do, so that seemingly wasted energy is actually a net gain.

Energy is always lost as you move up the food chain, because no predator can capture 100% of the energy stored in their prey.

Consuming plants is not as efficient as photosynthesizing, and consuming animals is not as efficient as consuming plants.

In this case, the cows burn energy from the food they consume for as long as they're alive, meaning it's a physical impossibility for the meat produced from them to contain as much energy as the food they consumed.

Unless you're claiming that raising livestock violates the laws of physics, but that's an entirely different argument.

No, he's suggesting that it's possible humans digest plants much less efficiently than herbivores do, and less efficiently than humans digest meat. E.g., if the herbivore can capture 90% of the energy in a plant, and we can capture 80% of the energy in the herbivore, that may be a better deal than if we can only capture 10% of the energy in the plant directly. In the case of cows eating grass, that doesn't sound that far-fetched. They have the benefit of multiple stomachs evolved to break down fibers, and we don't. Surely you don't think that every animal digests plants more efficiently than they digest meat? What about obligate carnivores, which can extract roughly 0% of the energy from plants?

You could measure by calories, since there will not be a huge difference in the number of calories consumed by people with different diets.

Giving an incredibly quick example, wheat and ground beef have roughly the same caloric density

Wheat: http://www.fatsecret.com/calories-nutrition/usda/whole-grain...

Beef: http://www.fatsecret.com/calories-nutrition/usda/ground-beef...

But since it requires numerous pounds of wheat to create one pound of beef, you are losing overall caloric density.

I can easily eat a 1/2 lb steak for dinner and feel fine, but eating 8 slices of bread at once will make me feel very sick. so I don't think caloric density is the be all and end all of nutritional value. I mean, wheat and beef also have about the same caloric density as gummi bears...

http://www.fatsecret.com/calories-nutrition/kroger/gummi-bea... https://www.google.ca/search?q=40g*11.3+to+lb https://www.google.ca/search?q=140*11.3

    First, there isn't much logical thinking involved in veganism or vegetarianism.

I strongly dislike the flavor and aroma of meat, so it's logical that I follow a vegetarian diet.

(There are few things as useless as discussions about nutrition at Hacker News.)

But you would maybe eat meat if the flavor/aroma were OK, no? I realize this is getting into a 'duck typing' sort of question but I don't think "I just don't like the taste of meat" is really what most people think of by vegan/vegetarian.

I don't eat mashed potatoes, but it's not because of some reverence for the humble potato or concern about industrialization of farming, it's just because I don't like the taste.

That is actually NOT logical though. You have conditioned yourself to dislike the taste and smell of meat. You might as well say that a dog salivating when it hears a bell is logical.

Of course it's ok, and in a lot of cases, preferable, to not behave logically.

I consciously avoided any reference to ethics to avoid that quagmire. But unlike ethics and the effects of the complex series of compounds that are food on the complex system of tissue that is the body, the environmental economics of food are pretty much straightforward and as far as I can tell both well understood and lacking the ridiculous back-and-forth of nutritionism.

It's absolutely possible that many vegans are vegans due to some psychological pressure towards purity or ascetism, and they just coincidentally chose a pressure vent that also makes sense in an economic and environmental sense. I'm sure many of them might even be aware of that dualism.

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