Well, the song in the Science section about the importance of a eating well (with the Orwellian title "I'm a Machine, You're a Machine") contains a very interesting line about what constitutes a healthful diet. Schoolhouse Rock recommends a high-protein and low-carbohydrate diet (plus exercise).
When I first heard this song, I wasn't sure that I heard that right. High-protein, low-carbohydrate? Atkins hadn't published his stuff back in the seventies when this song was written! Where did that come from?
It turns out, this is one of those cases where the "conventional wisdom" of what constitutes a healthful diet swings widely from generation to generation, and from century to century. Those big cattle drives we read about from the Old West? They were done because the US developed a huge appetite for meat in the late 19th century. In the lean years during and after the Civil War there wasn't all that much food to go around, and an entire generation grew up slightly stunted growth-wise; that generation in turn developed an obsession with protein. If you have it, better eat it, because you don't know when you'll have it again. All that meat also was a status symbol; eating meat showed that you could afford meat, which meant that you and your family weren't likely to go hungry in the near future.
By the early seventies the scientific consensus was starting to swing in the other direction. I don't remember a whole lot from the seventies--I turned nine in 1980--but I do remember growing up thinking that all that meat and fatty food would make you unhealthy; that the healthful way to eat was to eat lots of fruits and vegetables; eat pasta, potatoes, and breadstuffs for energy; and eat only a little protein and fat.
Aside from the fruits and vegetables--which just about everyone agrees are good for you--this advice was exactly the opposite of what that Schoolhouse Rock song was telling us to do.
I remember the first time I was exposed to the idea of the "High-Protein, Low-Carb diet". One of my co-workers in the late nineties would order a double hamburger, discard the top bun, cut the rest in half; stack the whole thing together, and get rid of one half of the bottom bun. He said his doctor had told him to do this, to help him lose weight. (He did have serious heart issues, and had to carry around the nitroglycerine tablets just in case.) At the time, I thought that was the weirdest thing I'd ever heard of. I'm not so sure about that anymore; I'm no weight-loss expert, and I've never dieted, but I think there's probably something to the idea that cutting the carbs from the diet will actually result in weight loss before cutting the fat will. I'm not going to get into that argument here; that's something for another time, and as I said, I'm no expert.
But a slightly larger point is that the experts don't agree with each other.
And an even more important point that, is that even when the experts agree with each other, it doesn't mean they're right!
I saw an article at the New York Times (hat tip to the Instapundit) that I found highly interesting, entitled Diet and Fat: a Case of Mistaken Consensus. This article looks into how the low-fat consensus came into being and shouldered aside earlier "conventional wisdom" regarding diet, even though there wasn't a whole lot of evidence supporting it. In a very small nutshell, the problem is that scientists are people too, and every bit as vulnerable to social and political pressure as the rest of us poor souls. In fact, scientists may even be more vulnerable to social and political pressure than the rest of us, because in order to do their jobs, they have to convince someone (often the government) to pay for their research--and they have to convince their peers that their research is actually worth publishing. The Peer Review system, which--don't get me wrong--is necessary to weed out junk science--can also weed out entirely legitimate ideas that don't match the consensus. If you make yourself unpopular among your scientific peers, you can't publish your work, and your scientific career goes kablooey.
The article charts the rise of the low-fat consensus. Basically, one strongly-opinionated proponent of the low-fat model wound up getting into positions of authority within the American Heart Association, along with some allies; then, they managed to make a consensus by throwing the weight of the AHA behind research and researchers that supported the party line. Eventually, those scientists that doubted the consensus were marginalized and ignored. All this happened without the weight of scientific evidence in favor of the consensus position.
The problem is that we mere non-scientist plebians don't often have the expertise to determine for ourselves, first-hand, what is good science and what is junk. We have to rely on experts. But there are frequently experts on every side of every argument you can think of. What do we do?
We often try to answer this question by figuring out which side has more experts than the other side. If nine out of ten dentists agree that you shouldn't chew aspen bark, then we assume that's probably good advice.
The trouble is, that's a really lousy way to conduct scientific research. Our knowledge of the world is constantly changing. Theories old and new are constantly being tested, updated, pondered, and discarded. And every new advance in science originated in the mind of some individual scientist who looked at the data in a slightly different way than those who came before, and came to new conclusions. Initially, every advance in science starts out as a non-consensus position.
Consider the recent news item that some scientists have proposed a new theory about the human appendix. As I understand it, this theory rejects the consensus notion that the appendix is just a useless organ, a leftover from far back in our evolutionary past where it actually did something that helped us survive. This theory proposes that the purpose of the appendix is to preserve some intestinal bacteria--which is crucial in helping us digest our food--in times of famine or disease, when our digestive tracts get emptied and/or flushed out. With the appendix there keeping some of these bacteria around, we can start digesting normally again the moment the food supply becomes available.
Is this theory correct? Who knows? I'm in no position to judge it. But the point is, it might be right. And if it is, then it gives a perfect illustration of one scientist having an idea that flies in the face of consensus, and the consensus being wrong.
The author Michael Crichton--who wrote the Andromeda Strain, Jurrasic Park, and many others--delivered a very interesting speech some years back warning (among other things) that the scientific community has been embracing consensus as a guiding principle of late; and that this has been degrading the quality of the science produced, and undermining the faith of the public in scientists and the in institutions of science. The speech, whimsically entitled Aliens Cause Global Warming, contained this section (which we should all memorize):
I want to pause here and talk about this notion of consensus, and the rise of what has been called consensus science. I regard consensus science as an extremely pernicious development that ought to be stopped cold in its tracks. Historically, the claim of consensus has been the first refuge of scoundrels; it is a way to avoid debate by claiming that the matter is already settled. Whenever you hear the consensus of scientists agrees on something or other, reach for your wallet, because you're being had.
Let's be clear: the work of science has nothing whatever to do with consensus. Consensus is the business of politics. Science, on the contrary, requires only one investigator who happens to be right, which means that he or she has results that are verifiable by reference to the real world. In science consensus is irrelevant. What is relevant is reproducible results. The greatest scientists in history are great precisely because they broke with the consensus.
There is no such thing as consensus science. If it's consensus, it isn't science. If it's science, it isn't consensus. Period.
This is something that we all need to remember. Any time you hear a scientist or politician say, "The science is settled!" just think to yourself that this person has lost any credibility to speak on scientific matters. Science is never settled. Declaring that it is, merely makes one impervious to any subsequently collected evidence to the contrary. The most that anyone has the right to say is, "Based on our best understanding and the evidence we've collected to date, the most likely explanation is X." Anything more leaves the realm of science.
And based on our best understanding and the evidence we've collected to date, it's not a high-fat diet that will do you in, it's a diet that consistently takes in more calories than your body burns. And it is often the low-fat diets that do this; the lack of fats leave the person hungry, causing him or her to eat a lot more than he or she would have on a richer diet. But as I mentioned above, this assessment may still change when new research comes in on the matter. In the meantime, don't let anyone browbeat you into eating what they want you to by claiming that 9 out of 10 experts agree with them. Nine out of 10 times, the research will be pointing somewhere else by the time the decade is out.