a little exercise in critical thinking

By Alison Campbell 11/11/2010


Grant‘s just sent me a piece that a recent Sciblog commenter posted on a US website. (Oh, all right, it was the Huffington Post. Not a place to go for good science coverage, but anyway…)

I knew a New Zealand dairy farmer who told me that her 9-year-old daughter had been growing breasts and pubic hair. Somewhat alarmed, she and her husband tried to figure out what caused the problem. It turned out that the vet had injected a few cows in ther herd which had not become pregnant in the first round of artificial insemination with a powerful hormone to induce ovulation, in the hope to impregnate them this time. The milk from these cows, along with the milk from all the pregnant cows, had been going into the tank from which the milk was collected by a milk tanker in the morning. The family had used some milk from the tank for their daughter’s breakfast every morning. Once they realised what the problem was, they stopped using the milk and their daughter reverted back to normal. So much for “100% Pure New Zealand”!

 

Let’s just sit back & have a look at the many misconceptions that this piece contains :)

Quite by coincidence there was a piece in the newspaper just a few days ago (similar to this one) about the lowering in the age at which children begin to enter puberty, over the last few decades, to the point that for many girls the related physical changes begin from about 9&1/2 years of age. The on-line encyclopaedia Te Ara tells us that “[in] 2000 puberty occurred three years earlier on average than it did in most western societies a century earlier — probably largely because of improved nutrition.” (Now, this brings with it a number of attendant problems – not least, the need to look at the sort of s*x education children receive and when they receive it; however, that’s not something I want to get into at this point.) More recently, it’s possible that increasing levels of obesity have an impact, because body fat is a source of oestrogen. (See work by Sir Peter Gluckman, for example.) And some people have also raised concerns about the amount of oestrogen and other related hormones in the environment. So it’s not completely unlikely that this apocryphal farmer’s daughter might have been entering puberty as part of the normal run of things, and that the milk she was drinking had nothing to do with it. Correlation does not equal causation.

Since dairy farmers need their cows to be pregnant and subsequently lactating, injecting hormones that induce ovulation (such as luteinising and follicle-stimulating hormones) into cows that haven’t become pregnant is a common management practice, and there’s a reasonable amount of literature on the best way to manage this (here, for example). But the hormone treatment (& the vet’s time) is going to cost money, so that it’s extremely unlikely that the family described by the HuffPo’s correspondent would be unaware that the vet had treated some of their herd in this way. Good herd managers are going to be very much aware of what’s going on with their cattle.

The other thing is, these hormones don’t last indefinitely in the body. They’re produced (injected), initiate changes, and disappear: the half-life of luteinising hormone in the human body, for example is around a couple of hours. So because the treated cows are not going to be continually expressing these hormones in their milk, it’s hard to see how this child would have been receiving a regular titre in the milk on her breakfast cereal. And if she was, then in all probability so was the rest of the family — was no-one else affected? Plus there’s the matter of dilution factors, as the milk from the few treated cows would be considerably diluted by admixture with the milk from the rest of the herd. And the principles of homeopathy apply here about as much as they do anywhere else i.e. not at all :)


0 Responses to “a little exercise in critical thinking”

  • Apart from the scientific issues you describe, this scenario is a direct lift from the award winning “My Year of Meat”, by Ruth Ozeki, published in 1998 (although I think the daughter in question was only 5 in the book) and set in the US. Sounds like someone is trying to make sure the backlash caused by this book against intensive US meat production processes is globalised??? By the way, the novel is a great yarn…

    • Hi Sally :)
      ‘Someone’ is a prolific commenter on Darcy’s recent ‘Antivaccination in NZ’ post…
      Might have a look for the book when I get half a minute :)

  • On the surface the story might sound quite convincing, if one doesn’t apply some rational thinking:
    Drank milk, breasts developed; stopped drinking milk, everything went back to normal.
    But then where is the objectivity in these observations? Did things go back to normal because that is what the farmer wanted? How was “back to normal” defined? What measurements were made? Did the pubic hair retract ,for example?
    Puberty does tend to be an intermittent process, so any perceived changes could just be coincidental.
    But then of course all of these issues come with ANECDOTAL “evidence”.

    I’m sure Fonterra wouldn’t be particularly happy with this sort of comment.

  • I’m sure Fonterra wouldn’t be particularly happy with this sort of comment.
    That thought crossed my mind when I read the previous commenter’s notes.

  • That’s a great article, Darcy, thanks for the link. I particulary liked this bit from Steven Novella:
    The primary weakness of anecdotes as evidence is that they are not controlled. This opens them up to many hidden variables that could potentially affect the results. We therefore cannot make any reliable assumptions about which variable (for example a specific treatment) was responsible for any apparent improvement.

  • Alison, the point about hidden variables and uncontrolled observation is particularly relevant to health and illness. When someone is ill there is a tendency to throw various remedies at it simultaneously which, while it gives one the impression that you are doing everything possible to feel better, makes it impossible to identify which remedy (if any) was effective. I remember a letter to the editor a while ago attributing a womans recovery from some severe infection(I think) to prayer. Apparently, she had been on antibiotics for two days which “weren’t working” but she was prayed for during the night and the following morning she recovered.
    No consideration that perhaps the antibiotics had just taken time to kick in! Sigh
    Its potentially a similar situation with high dose IV vitamin C, variables need to be removed to prove its efficacy (or not).
    Of course in medicine one then runs into the possibility that removing variables may be unethical.

  • Now I know this is 148 days old, but heck, when you’ve worked on dairy farms and seen the things that go on, you would believe the Huffington article very easily. Very very easily.

    The mythical farmer needs to be removed from the equation first. He’s sitting at the Mount in his hot tub: the manager is actually running things, except he’s at the rugby and the dairy assistant is in charge, with his two weeks of training, which he got from the outgoing assistant that was sacked for being drunk.

    The assistant got his girlfriend to inject the hormone, which the vet left there specially, and she rinsed the syringe in the house milk bucket unknowingly (her brother wanted the syringe). etc etc etc.
    Secondly, the “let’s pretend everything is fabulous” tone of all the posts, and the blog itself, are not flattering to a science site. You might actually consider that it really happened, and propose what might be done about it.
    I can imagine the scene on the Titanic being similar: “Really Bob, I heard one of the steerage passengers say we were sinking! Sinking! All that’s happening is that some bilge water has got in: Sir Peter did some research into that, didn’t you Peter, yes that’s right.”

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