Does eating (or not eating) animals have health implications?

At the request of Jim the Directrix, who has been discussing various issues of diets that don't include animal flesh in comments on "Temple Grandin's rationale for eating animals," I'm here opening a discussion on diet from the point of view of health (rather than of morality).
    It starts with an interchange begun on the Grandin post having to do with vitamin B12. Ken had commented:

Felt an obligation to do some extra research on the vitamin B12 question. I was mistaken to write that its absence would quickly cause a problem. However, predicting the point at which a problem will arise is difficult. It can be less or more than 3 years, depending on genetic factors, how much is secreted daily, and how much is absorbed. It varies from person to person. The danger is greater in a vegetarian family because the onset of vitamin B12 deficiency in children is much faster.

Jim the Directrix replied in an email directly to Ken and me:

Thanks for your response and especially for looking more into the B12 issue. Pundits for eating meat have blown the B12 issue way out of proportion to defend their position. Listening to these pundits gives the false impression that vegans are a great risk of B12 deficiency. Here's what my guru Dr. John McDougall says about the issue:

Vitamin B12 Deficiency—the Meat-eaters’ Last Stand
    Defending eating habits seems to be a primal instinct for people. These days Westerners are running out of excuses for their gluttony. Well-read people no longer believe meat is necessary to meet our protein needs or that milk is the favored source of calcium. With the crumbling of these two time-honored battle fronts, the vitamin B12 issue has become the trendy topic whenever a strict vegetarian (vegan) diet is discussed. Since the usual dietary source of vitamin B12 for omnivores is the flesh of other animals, the obvious conclusion is that those who choose to avoid eating meat are destined to become B12 deficient. There is a grain of truth in this concern, but in reality an otherwise healthy strict vegetarian’s risk of developing a disease from B12 deficiency by following a sensible diet is extremely rare—less than one chance in a million." complete article

Thanks, Ken and Jim, for getting this discussion started. I hope the neutral title I've given it meets with your approval.
    I'll return in a separate post to the question of the morality of eating animals.

Temple Grandin's rationale for eating animals

On Valentine's Day, I withheld judgment on "Temple Grandin's dilemma," pending further information.
    Further information I now have, from her wonderful book (a must read for anyone interested in other animals and our relationship with them), Animals in Translation: Using the Mysteries of Autism to Decode Animal Behavior:

If I had my druthers humans would have evolved to be plant eaters, so we wouldn't have to kill other animals for food. But we didn't, and I don't see the human race converting to vegetarianism anytime soon. I've tried to eat vegetarian myself, and I haven't been able to manage it physically. I get the same feeling you get with hypoglycemia; I get dizzy and light-headed, and I can't think straight. My mother is exactly the same way, and a lot of people with processing problems have told me they have this reaction, too, so I've always wondered if there's a connection. If there's something different about your sensory processing, is there something different about your metabolism, too?
    There could be. It's possible that a brain difference could also involve a metabolic difference, because the same genes can do different things in different parts of the body. A gene that contributed to autism might contribute to a metabolic difference, or any other kind of difference. Parents have always said that their autistic children have lots of physical problems, too, usually involving the gut, and mainstream researchers haven't paid a lot of attention to this.
    So until someone proves otherwise I'm operating from the hypothesis that at least some people are genetically built so that they have to eat meat to function. Even if that's not so, the fact that humans evolved as both plant and meat eaters means that the vast majority of human beings are going to continue to eat both. Humans are animals, too, and we do what our animal natures tell us to do.
    That means we are going to continue to have feedlots and slaughterhouses, so the question is: what should a humane feedlot and slaughterhouse be like?
    Everyone concerned with animal welfare has the basic answer to that: the animal shouldn't suffer. He should feel as little pain as possible, and he should die as quickly as possible.

...But eliminating pain isn't enough. We have to think about animals' emotional lives, not just their physical lives. We're responsible for slaughterhouse animals; they wouldn't even exist if it weren't for us. So we have to do more than just take away physical pain.
    The single worst thing you can do to an animal emotionally is to make it feel afraid.... [pp. 179-80, 189]

So, what judgment am I now prepared to make?
    An observation or too first. In the first sentence quoted, Ms. Grandin says that because we evolved a certain way, we must eat animals. Clearly that is not so; many people are vegetarians.
    She also says that, because "humans are animals...we do what our animal natures tell us to do." Not entirely. Human animals are also moral animals; the aforementioned vegetarians have chosen not to eat meat, either because they think they ought not [morality as a set of principles for avoiding evil and doing good) or because they judge that avoiding meat affords a better (because healthier) life [morality as a set of principles for attaining the good life].
    That said, I still can't bring myself to judge Temple Grandin. Who would I be to judge someone who has done far more for animals than I could ever hope to do?

A subtler, perhaps deeper read when it comes to the morality of eating animals seems to be on offer in Jonathan Safran Foer's 2009 book, uneuphemistically titled Eating Animals, which I've just begun to read, along with entering freshmen at Duke University and the University of North Carolina at Chapel Hill. It's their assigned reading for book discussion their first week on campus this fall.

The squeeze machine

One of the most fascinating things portrayed in the movie Temple Grandin was Temple's noticing the calming effect on cattle of their being constricted in a chute in order to be vaccinated, and her being led by that observation to construct a "squeeze machine" for herself, to see whether it would have the same effect on her, who as an autistic person often felt anything but calm.
    She writes about it in Animals in Translation, which I introduced here the other day:

When I saw the cattle in their squeeze chute and got inspired to build a squeeze machine for myself, at first I was thinking only about the calming effects of deep pressure. So I built it with just two hard plywood boards, without any padding or cushions. All autistic children and adults like deep pressure. Some of them will put on really tight belts and hats to feel the pressure, and lots of autistic children like to lie underneath sofa cushions and even have a person sit on top of the cushions. I used to like to go under the sofa cushions when I was little. The pressure relaxed me.
    Then gradually I started to improve my squeeze machine by adding soft padding...The pads gave me feelings of kindness and gentleness toward other people—social feelings....
    I think the squeeze machine probably also helped me have more empathy, or at least more empathy for animals. When I first started using the soft version of the machine, in my late teens, I didn't know how to pet our cats so they really liked it. I always wanted to squeeze them too tight....
    Autistic children never know how to pet animals the right way, so you have to teach them....
    Even a lot of normal people don't realize that you have to stroke animals, not pet them. They don't like to be petted. You have to stroke them the way the mother's tongue licks them.
    There have been two experiments on squeeze machines for animals....
    This research is important for people with autism. A lot of autistic children can't stand to be touched. I was like that when I was a little kid. I wanted to feel the nice social feeling of being held, but it was just too overwhelming....
    Being touched by another person was so intense it was intolerable. I would start to panic and I had to pull away.[pp. 114-117]

The squeeze machine is fascinating, especially when you've just learned of it. But what affected me the most about the chapter from which those excerpts are taken was its many examples of our being at one with other animals. Like this paragraph:

A dog's attachment to his owner is like a baby animal's attachment to his mother, or a human child's attachment to his mom or dad. Pet dogs act the exact same way children do in the strange situation test. In the strange situation test the researcher watches how a very young child reacts to a strange new environment when his mother is there with him, and when she's not. Most children will confidently explore a strange environment as long as their mother is with them, but when she leaves the room they'll stop exploring and wait anxiously for her to come back. Dogs do exactly the same thing. This has been tested formally in fifty-one dogs and owners. Most dogs stop exploring and act anxious when their owner leaves the room. Then they relax and start exploring again when their owner returns. When humans say dogs are like children, they're right. [p. 111]

    Other examples deal with clinical research into brain anatomy and chemistry. They'd be difficult to excerpt briefly. Read the book!

Temple Grandin's dilemma

Temple Grandin (born 1947) came to my attention only recently. I discovered the movie first, with Claire Danes in the title role. At the time, I thought that the name sounded familiar, and I finally remembered that a lecturer I'd heard at UNC (Dr. John Ratey, on exercise and the brain) had dedicated one of his books to her (A User's Guide to the Brain: Perception, Attention, and the Four Theaters of the Brain, 2002).
    And now I'm reading one of her books, Animals in Translation: Using the Mysteries of Autism to Decode Animal Behavior, 2005. Much more even than the books of Karen Pryor (e.g., Reaching the Animal Mind, 2009), Grandin's book thrills me on a subject that reaches to the very bottom of me.

It is a terrible irony for me, then, that Temple Grandin is a consultant to the livestock industry and well-known in those circles for her innovations in the design of slaughter systems. While I can approve taking steps to avoid alarming animals as they're herded to be killed, the whole enterprise is repugnant to me.
    I googled on "temple grandin moral dilemma" and found (on the Vegan Soapbox website) that

Temple Grandin’s reply to those who have identified the inherent contradiction in the statement “I design slaughter houses and I love animals,” is: “some people think death is the most terrible thing that can happen to an animal.” It follows according to Ms. Grandin that “the most important thing for an animal is the quality of its life.”

    Whoever's on the soapbox for the website immediately retorts:

Ms. Grandin’s argument is derived from an underlying ontological worldview that assumes a dualism between “human” and “animal.” This is a factual inaccuracy. Biological “animality” exists on a continuum: a human animal is a member of a species of bipedal primates in the family Hominidae—“higher primates.” It is from this invalid assumption that Ms. Grandin’s argument tries to follow. Her claim, then, is baseless and open to the challenge of blatant selective reasoning.

I'm not going to take a final position on Grandin's ethics, for I assume I don't know the whole story (yet). But I don't see how her reply quoted in the article could rectify her presumed cognitive dissonance. Just look at how she talks of "animals and humans" to see how closely related she acknowledges that they are:

It turns out that all animals and humans have what researchers call a built-in confirmation bias. Animals and humans are wired to believe that when two things happen closely together in time it's not an accident; instead the first event caused the second thing to happen.
    For example, if you put a pigeon in a case with a key that lights up right before a piece of food appears, pretty soon the pigeon will start pecking the lighted key to get food....
    The pigeon is acting like a person who thinks his team will win the baseball game if he's got his lucky rabbit's foot with him....
    Confirmation bias is built in to animal and human brains, and it helps us learn. We learn because our default assumption is that if Event 1 is followed by Event 2, then Event 1 caused Event 2. Our default assumption isn't that Events 1 and 2 happened at the same time by coincidence. Coincidence is actually a fairly advanced concept both for animals and for people. That's why in statistics courses you have to formally teach students that a correlation isn't automatically a cause. [David Hume argued for coincidence over causality in the eighteenth century.] Our brains are wired to see correlations as causes, period. Since in real life a lot of times Event 1 does cause Event 2, confirmation bias helps us make the connection.
    The downside of having a built-in confirmation bias is that you also make a lot of unfounded causal connections. That's what superstition is....
    ...The same part of the brain that lets us learn what we need to know and find the things we need to stay alive is also the part of the brain that produces delusional thinking and conspiracy theories. [pp. 98-100]

As a matter of fact, humans are animals. We have a common ancestor with every other animal [and life form¹] on the planet.
_______________

1. Thanks to Carolyn for reminding me that I myself had realized this later, but without doing anything about it at the time.