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Does science “catch up”? Example: Bloodletting Works … wait, what!?

bloodletting - not what it used to be...

If there’s one statement that bothers me, it’s this:

“…the science has finally caught up…”

Or any of it’s variations. Actually, a lot of things bother me… I’m easy to troll, and I’m sure my friends will start saying this to me all the time.

It’s usually used when science confirms something that people supposedly already “knew”.

Good examples come out of exercise science all the time – a particular exercise method turns out to be better than another, or provide some fringe benefit, and suddenly the advocates of that method were “right all along”, and “science has finally caught up” to their wisdom. It’s funny how fast they forget all the other things science has debunked along the way… guess they didn’t believe those things.

I’ll talk about why this statement implies a misunderstanding of science later.

First, let’s talk about how bloodletting apparently works.


I’ve recently described bloodletting in ‘Why Science? Part 3 – What Could Go Wrong?‘, an article reviewing some examples of ridiculous / gruesome “cures” from the history of medicine (and why we should use science to see if stuff works).

Shortly after posting, my friend Aaron Bower sent me a link to an interesting Scientific American article (no, he didn’t say anything about science “catching up” to ancient wisdom, but he probably will now that he knows it bothers me).

Grandly titled ‘Bloodletting Makes Comeback for Metabolic Syndrome(we’ll explain what metabolic syndrome is in a minute), the article reports on a recent experiment that demonstrated that ‘phlebotomy’ (taking blood from a vein) actually has positive effects on cardiovascular health markers.

Cool stuff!

But does this really mean bloodletting is making a “comeback”? It wouldn’t be surprising if people get way ahead of themselves because of this one experiment. Before you know it, you’ll see “bloodletting clinics” in the hippest of our neighborhoods. But before we get too hype, let’s look at the experiment.

The Experiment

This was actually a pretty solid experiment with interesting findings. 1

METS refers to metabolic syndrome, which is a collection of medical disorders (high blood pressure, abnormal blood fats, abnormal blood sugar, etc.) that together raise the risk of cardiovascular disease significantly. It’s common in people who are overweight /obese, and/or have diabetes.

Basically, the researchers gathered 64 people with METS and randomly assigned them to either a phlebotomy group, or a control group.

On day one, the people in the phlebotomy group had various measurements taken, then gave blood through phlebotomy. The control group had measurements taken, but gave no blood (they were offered the treatment after the experiment was over, just to be fair). More blood was taken from the phlebotomy group after four weeks, and then final measurements were taken at the six week mark.

The results: blood pressure, blood iron levels, and various other markers of cardiovascular health were significantly lower in the ‘phlebotomy’ group compared with controls. For example, systolic blood pressure dropped from about 145 to 130 (mmHg), which is pretty good, since a 10 point drop can mean a 41% reduction in stroke 2, among other things.

The researchers conclude that it may be the reduction in blood iron levels that does the trick, since excess iron is associated with METS. Exactly how this works is beyond the scope of this article, but it is some interesting science!


The study was not perfect. The authors outlined their limitations (because, you know, they are scientists, and they don’t make ridiculous claims based on one experiment). One of their limitations was a lack of subject blinding.

Blinding is an attempt to keep the subject from knowing what group they’re in, which helps rule out the placebo effect. For example, they could have came up with a way to do sham phlebotomy, since it’s probably not that hard to fake – see James Randi and his debunking of “psychic surgery”:

Blinding is important… Not properly blinding an experiment can lead to overestimates of up to 40%! 3 So this experiment definitely needs to be repeated with better blinding. Fake blood drawing should be easy!

Furthermore, I have some points of my own:

  • How long do it last? Is blood pressure still decreased after a month? Six months? A year? Do people need to visit the blood clinic every three weeks?
  • Compare it to something! – Like exercise. We already know you can lower blood pressure by about 10 points with only 60 – 90 minutes of moderate intensity exercise per week, for just 8 weeks. 4
  • Would exercise plus phlebotomy work even better? Now that would be something to get excited about. But if there is no extra benefit, people should just exercise (since there are so many other benefits with exercise).

Overall, a very interesting study, but as usual, more research is needed.

Conclusions on bloodletting:

Does this experiment provide good rationale for prescribing “bloodletting” as a legitimate treatment for cardiovascular disease?

Not quite. More experiments need to be performed to address the concerns above.

It does, however, highlight a potential fringe benefit of donating blood! So by all means – go donate some blood. If it doesn’t help you, it will definitely help someone else (and possibly save their life).

Perhaps this is some scientific proof of karma!

Science does not “catch up” – it tests!

I reviewed this study to make just one main point: Things are never all that simple in science. If it was, we’d all live forever.

“I think you’ll find it’s a bit more complicated than that” – Ben Goldacre

Bloodletting was apparently the most common medical practice performed by doctors from antiquity to the 1800′s. It involved bleeding a significant quantity of blood to cure almost any illness. For different diseases, all you had to do was drain the blood from different spots, and by different amounts.

During antiquity, it was used to “balance the humors”. But even after that theory was rejected, the practice continued. It wasn’t until the 1800′s that it was abandoned (as it had a high risk of causing infection, and it didn’t seem to help anything, except hemochromatosis).

But here we are, in 2012, and a scientific study has shown that “bloodletting” might be good for a very far reaching medical condition (cardiovascular disease is the number one killer in the world).

I guess the science has finally caught up!


Science tested an idea, and confirmed it as useful in a particular situation… maybe. It didn’t prove the ancient people right – not by a long shot! What they did was far less elegant than modern phlebotomy. Bloodletting was crude and dangerous. And being based on flaky theories, they didn’t really know why they were doing it!

So what’s my point?

Science doesn’t catch up… it tests, and it’s probably the best method of testing that we’ve ever had. The results of these tests could either confirm or debunk an idea – and don’t forget, lot’s of things have been debunked by modern science.

When people say the “catch up” thing, it implies that science is somehow behind. What is it supposed to be catching up to? Using our intuition or beliefs? Well, when it comes to this kind of stuff (what works in health and fitness), we know our intuition is not very reliable – we’re usually wrong! Science isn’t the “other way” of finding things out – the way that the “establishment” uses. This belief is likely part of the problem – people think science is some sort of authority, deciding what does and doesn’t work, and what is or isn’t real. This is not true.

Science is a method of gathering knowledge by experimenting and observing. It attempts to rid us of our biases, so that we can come closer to knowing the truth. It’s not perfect, and scientists make mistakes (which other scientists enjoy pointing them out).

Science is always changing and progressing. And it keeps getting better.

There, that’s it.

Just had to get it off my chest.

The thing is, I’ve probably said it before too.

Never again!


ResearchBlogging.org1. Houschyar KS, Lüdtke R, Dobos GJ, Kalus U, Broecker-Preuss M, Rampp T, Brinkhaus B, & Michalsen A (2012). Effects of phlebotomy-induced reduction of body iron stores on metabolic syndrome: results from a randomized clinical trial. BMC medicine, 10 PMID: 22647517

2. Law MR, Morris JK, Wald NJ. Use of blood pressure lowering drugs in the prevention of cardiovascular disease: meta-analysis of 147 randomised trials in the context of expectations from prospective epidemiological studies. BMJ. 2009
May 19;338:b1665. doi: 10.1136/bmj.b1665. Review. PubMed PMID: 19454737; PubMed Central PMCID: PMC2684577

3. Schulz KF. Assessing allocation concealment and blinding in randomised controlled trials: why bother? Evid Based Med. 2000;5:2 36-38. doi:10.1136/ebm.5.2.36

4. Ishikawa-Takata K, Ohta T, Tanaka H. How much exercise is required to reduce blood pressure in essential hypertensives: a dose-response study. Am J Hypertens. 2003 Aug;16(8):629-33. PubMed PMID: 12878367

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    One Response to Does science “catch up”? Example: Bloodletting Works … wait, what!?

    1. Tom Hennessy says:

      In THIS case though, bloodletting, it IS “science catching up”, because the treatment was used for thousands of years, without actually knowing WHY it worked, it just did. Scientists, the medical profession proved, using their ‘established’ methods, that bloodletting was simple quackery, useless in most cases and dropped it completely by law from their ‘formulary’, allowing only doctors to perform it, then disallowed doctors from performing it. Now, it is shown to affect a syndrome, metabolic syndrome, which one in three is slated to manifest, and the ‘take’ of science? “Doesn’t prove anything”, when in fact it actually did prove it, scientifically using all the gadgets they could supply. Blood pressure, insulin, etc.

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