Scott and Scurvy: How the cure for scurvy was lost | Hacker News Reader

Scott and Scurvy: How the cure for scurvy was lost

idlewords.com

244 pointsmark_h36 comments

But in the second half of the nineteenth century, the cure for scurvy was lost. The story of how this happened is a striking demonstration of the problem of induction, and how progress in one field of study can lead to unintended steps backward in another.

This isn't the only time progress in one field leads to steps backward in another.

Once upon a time, the Romans knew the cause of plague: evil spirits. Evil spirits lived in the bodies of the living and the dead, but would occasionally jump from a sick person to a healthy person The health person would become sick, and further spread evil spirits.

The Romans knew how to prevent the spread of evil spirits: isolate the sick and the dead, and even burn the bodies. They even weaponized it, using the bodies of those that died of plague as a biological weapon.

Once we learned that evil spirits don't exist, we threw away this theory of disease. Instead, we believed that plague (much like flies, mold and other such unpleasantness) was spontaneously generated in matter. It wasn't until much Pasteur that we discovered the Romans were 90% correct.

Is it correct to say that the English understanding of scurvy really went backward?

They started with an incorrect theory (acidic fruit stops scurvy) which was later falsified (so does fresh meat). Their progress towards the truth is quite direct, a testament to good record-keeping and communication.

In contrast, the remedies lurch wildly around in effectiveness -- because they weren't properly tested, in isolation from other factors. Nor were they ever retested, even when they changed to the limes. That seems to be where the real failures occurred.

If their record keeping had actually been so good they would have remembered that citrus (by whatever means, and not to the exclusion of other remedies) cures scurvy and would not have wandered off into the weeds chasing spoiled meat (which, if the navies were at sea for years at a time could not possibly have been the case).

I don't see the 'direct progress' you mention, then again maybe my sarcasm detector is miss-calibrated.

No, I didn't mean that sarcastically. Their theories go like this, at least in my reading.

1 - Something about citrus fruits cures scurvy. Correct.

2 - Something about living on a diet of preserved foods causes scurvy. This is even more correct, since now we're getting at the cause.

But I agree we're seeing some interesting cognitive biases here.

Once their original theory is disproved, they focus on explaining the latest results, and seem to forget that they still have to explain why citrus fruit ever seemed to cure scurvy. (Or perhaps the story is more complex than we suppose, and they had some other explanation).

What's certain is that they don't test their ideas with enough experimentation. There seems to be a bias towards formulating theories, and trusting in the expert's judgment, without any empirical verification.

2 is more like "toxins in improperly canned meat cause scurvy".

Did you actually read the article? It isn't so simple.

They transitioned from lemons to limes without realizing that they had gone from a kind of citrus that protected from scurvy to one that didn't. Their interest in meat was due to expeditions which unambiguously demonstrated that lime juice did not protect against scurvy while polar bear meat did. And no simple categorization would have explained to them why you don't want to use copper in preparing food.

The only thing shown unambiguously was that "that juice did not prevent scurvy". Taking this to reason inductively that "no citrus juice prevents scurvy" is the real problem. They discarded documented evidence and grasped at other straws instead of stepping back and investigating history.

The problem is that they had no mental frame of reference from which to understand the importance of avoiding heat, light, and copper. Therefore even if they performed experiments and discovered the truth, they would have no theory to tell them that taking the obvious next step was a bad idea.

Witness for example Scott's ability to demonstrate that seal meat prevented scurvy, and his inability to realize that trying to preserve it by boiling it wouldn't work.

The original theory was that a shortage of some nutrient carried by acidic fruits prevents scurvy. This theory is correct.

It did go backward. The 18th century concept of the disease was as a dietary deficiency, while the 20th century concept was chronic food poisoning.

One point I was trying to stress is that "properly tested, in isolation from other factors" depends a great deal on your mental model of the thing you're testing.

I originally thought you were wrong about this, because a lot of the other articles seemed to suggest they only understood the citrus connection as a cure for some mysterious disease. Which would have made it the wrong theory, but coincidentally the right practice.

But at least according to Wikipedia, there were plenty of people who understood scurvy as a dietary deficiency, even in the 1600s. They thought it was more about acidity, but that's close enough. So, I was wrong and you are right.

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

The wikipedia article is kind of iffy, I would recommend this great overview instead:

http://idlewords.com/sailors_scurvy.pdf

Or 'The History of Scurvy and Vitamin C' by Kenneth Carpenter if you want to really dig in.

Of the four conditions he mentioned (depression, autism, hypertension, obesity), I don't suppose there is evidence to suggest that, I don't know, regular exercise would cure at least two?

But exercise doesn't come in convenient pill form.

At least three - in some people. Regular exercise has been shown[1] to reduce the signs of depression in some people (but, obviously, not others).

From what I know of hypertension (not much), it's more of a disposition - if you treat yourself poorly, and you have a disposition towards it, you might develop it later in life. Exercise and diet, of course, are preventative - but not a cure; once you are diagnosed, it's like a warning sign from your body flashing "hey you, be careful, you're hurting me!"

And it's not just regular exercise, a balanced diet is a must. If all you eat is corn (factory farmed meat; processed foods; just about everything cheap in the grocery store) - but you run on a treadmill 30 minutes a day - you're still going to put on weight.

[1] http://www.mayoclinic.com/health/depression-and-exercise/MH0...

I suffer from hypertension. I'm not currently fat and haven't been for some years, I run 35 km every week or more, but I still need the pills (with their nasty side-effects).

There is a strong genetic component to hypertension (61% heritable) so I do not think it is fair to say that exercise and diet would cure it for most people.

Perhaps the most sobering stat I learned in med school: Take everyone who is 55 years old and does not have hypertension. 90% of those individuals will ultimately go on to become hypertensive.

In atypical fashion, I can actually source this: http://www.nhlbi.nih.gov/health/public/heart/hbp/hbp_low/hbp...

It would help with some kinds of depression, somewhat help hypertension and obesity, but would not even remotely cure any of them. I'd name five factors that are strong promoters of a vast number of current widespread diseases: vitamin D deficiency, consuming grains, consuming too much Omega-6 vegetable oils, consuming too much fructose, consuming too little animal fat calories.

Right, but that's a great example. What if exercise helps because of something that is created as a side effect, and that in the future is available in pill form?

Exercise probably does help because of a "side effect", namely reducing muscle insulin resistance. The direct effect of burning calories is too small (and too easily offset by increased appetite) to have much to do with weight regulation.

In fact, there is good evidence that a few molecules are directly responsible for obesity. Fructose, ethanol, and galactose all increase appetite. http://blog.nutritiondata.com/ndblog/2007/08/fructose-swee-1... http://www.medicalnewstoday.com/articles/125848.php Appetite increases caloric consumption, which causes obesity over time. Exercise counteracts this effect.

We are in some ways in a similar mess to the scurvy problem. We've known for years that the Japanese diet, the Mediterranean diet, exercise, and the Atkins diet all work to reduce weight. We know that high fructose corn syrup is bad. And we know that fat consumption has little to do with weight gain (see Atkins diet). But despite the preponderance of evidence, I continue to hear nonsense spouted by people with MDs about how a low fat diet is the best way to lose weight. And when I tell my friends, they are amazed at how quickly they lose weight with no work other than switching fructose for glucose in the diet.

As you're no doubt aware, but your readers might not be, sucrose (table sugar) dissociates into its fructose and glucose halves pretty much as soon as it hits your stomach.

So cutting back on, e.g. high fructose corn syrup (a roughly 50/50 mix of glucose and fructose) won't help if you're replacing it with sugar.

Everybody knows that lime juice cures scurvy, and that the English navy figured out the whole thing centuries ago, and like most things "everybody knows", it's largely wrong.

Thanks for submitting this - it was a fascinating read.

Well, lime juice can prevent or cure scurvy, it's just that other things have more vitamin C. And the British navy did use lime juice. So neither of those is shown to be "wrong" here; instead, we're shown more of the story than these two facts alone can give us.

Fantastic and fascinating read. Thanks for posting this. I had no idea that lime juice only contains a fraction of the vitamin C content of lemon juice. I wonder how grapefruit fares.

Fresh lime juice actually has something like 2/3 the vitamin C of lemon juice. Grapefruit is comparable to lime. Check out table II: http://digital.library.okstate.edu/OAS/oas_pdf/v18/p36-38.pd...

For some reason, the 1918 tests showed fresh lime juice to have a quarter the antiscorbutic activity of lemon juice (when you fed it to guinea pigs, it took four times as much to prevent scurvy). It's possible the vitamin is less bioavailable in limes, but I don't know the research at all.

And of course the actual lime juice from navy and merchant ships was much worse than that.

If anyone is interested in polar exploration I strongly recommend "Barrow's Boys: A Stirring Story of Daring, Fortitude, and Outright Lunacy":

http://www.amazon.com/Barrows-Boys-Stirring-Fortitude-Outrig...

> They had a theory of the disease that made sense, fit the evidence, but was utterly wrong. They had arrived at the idea of an undetectable substance in their food, present in trace quantities, with a direct causative relationship to scurvy, but they thought of it in terms of a poison to avoid. In one sense, the additional leap required for a correct understanding was very small. In another sense, it would have required a kind of Copernican revolution in their thinking.

Fascinating.

I predict that we will eventually come to know of a few dozen different nutrient deficiencies, lifestyle habits, childhood developmental factors, neurological defects, neurotic thought patterns, and other random things that collectively account for nearly all cases of what we now call "depression".

These explanations are not widely pursued because there are no practical and rigorous experiments to verify them (no ethical way to control psychological experiments) and they don't lead to practical solutions (society does not have the wherewithall to carry out the remedies).

However, as this story illustrates, "we don't know" is never an acceptable answer when we demand from science a solution to an immediate and dire problem. The confidence of experts is fairly constant over time, while only their degree of correctness improves.

The same thing happened with concrete. The Romans knew how to make concrete, but after the collapse of the empire this knowledge was lost, only to be reinvented in the Victorian industrialist age.

In another irony, the "Worst Journey in the World" that is mentioned in the article was based on another incorrect scientific theory: recapitulation theory. They thought the emperor penguin eggs would reveal more about evolutionary theory than they actually did. (According to Wikipedia: http://en.wikipedia.org/wiki/The_Worst_Journey_in_the_World#...)

Couldn't help but notice this:

Eat a [polar] bear liver every few weeks and scurvy will be the least of your problems.

Yes, it will be the least of your problems, because you will be dead. Polar bear liver is highly toxic (30-90 grams of it will kill a man).

An ironic error, considering the article.

What's so toxic about it?

Massive amounts of vitamin A.

if the world ends, don't eat carnivore livers

If the world ends don't eat a carnivore that eats carnivores that occasionally eat animals. Generally a good idea anyway since most carnivores taste goddamned awful.

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