If you’ve read about alternative medicines at all, you’ll probably have heard of homeopathy. I’ve known about homeopathy for years. What I don’t understand is how normal, rational people with a modicum of scientific training can buy into it.
According to practitioners, homeopathy is “perfectly safe”–which is true, because it has no effect at all other than a placebo effect! Generally speaking, I have no problem with people taking sugar pills, but some people I know use homeopathy instead of seeking more effective treatment. For the common cold this may be fine. However, for dangerous illnesses like cancer it may mean that the person may waste valuable time; the disease may gets worse and worse, and the sufferer won’t seek out a more effective remedy until it is too late. So yes, homeopathy can be harmful.
For those who don’t know, here’s the basis behind homeopathy:
- “Like cures like”–i.e. if a substance causes symptoms in a healthy person, it will cure the same symptoms in a sick person.
- The strength of cures increase with dilution. In other words, a solution of concentration A is more potent at curing disease than a solution of concentration 1/10 of A.
- Finally, homeopaths claim that, by shaking a solution in a certain way while diluting it, the water retains the “memory” of the original substance.
I don’t know much about claim #1; it seems counterintuitive, but then some real science does without further investigation. But claims #2 and #3 can be disproven using a bit of math as well as modern science.
Let’s look at claim #2 in more detail.
A homeopathic “remedy” has been diluted many, many times before it reaches the shelf. Let’s take “coffea” (actually, caffeine) as an example. How many molecules of caffeine would be in one milliliter of a “30x coffea” remedy? Note that, according to homeopathic notation, this means that the original solution has undergone 30 ten-fold dilutions.
I’ve looked at several pro-homeopathic websites and can’t determine what solution strength is used at the outset. So for purposes of our calculation, let’s assume we start with 1 cubic centimeter (the same as one mL) of pure caffeine–giving the homeopaths the benefit of the doubt.
Caffeine has a density of 1.23 g/cubic centimeter and a molar mass of 194.19 g/mol. Toss in Avogadro’s number (6.022 x 10^23) and you find that we start with approximately 3.81 x 10^21 molecules per mL of solution.
Each ten-fold dilution would reduce the concentration by a factor of 0.1, or 10^-1. So 30 subsequent ten-fold dilutions would reduce the concentration of a solution by a factor of 10^-30.
By multiplying these two numbers together, we see that the number of caffeine molecules in a solution of 30X coffea is 3.81 x 10^-9, a very small fraction of a molecule. Obviously you can’t have a fractional molecule, though.
So what does this mean? Well, you might say that it means that the probability of finding a caffeine molecule in a milliliter of solution is .000000381 %. Or maybe you would understand this better if I were to say that there would be, on average, 3.81 caffeine molecules in a million liters of water—about one molecule in 69,000 gallons, for those of you who think in the English system of measurement.
How likely is it that 1 milliliter of this remedy would actually have an active ingredient present?
At this point the homeopaths trot out claim #3, that the water used in dilution retains a “memory” of the molecule, and it is this “memory” that cures a person. I have two responses to this claim.
The first is common sense. Most people I know take their homeopathic remedies in pill form. Perhaps water was used in the formation of these pills, but there sure isn’t much there now. So how’s the “cure” supposed to be stored?
My second rebuttal is more scientifically rigorous. There are physical chemists (e.g. Hans Andersen of Stanford) out there that actually study the kinetics of water–how it behaves, both in bulk (i.e. in a large container) as well as in tightly enclosed spaces. This is generally done via computation (molecular dynamics simulations), but at least some MD simulation results can be verified experimentally.
The MD simulation results I’ve seen show that, while water is definitely “shaped” by some organic molecules (such as proteins with hydrophobic active sites)*, as soon as the molecule is removed, the water returns to normal random behavior such as that in the bulk. There isn’t any “memory” involved, only normal principles of physical chemistry.
In other words, homeopathy is a bunch of bunk. I believe in some forms of alternative medicine, but homeopathy isn’t one of them.
*If you want to see a really cool way in which this is used, check out the work of Tom Young (Columbia/CUNY), who uses this to determine the geometry of competitive inhibitors (drugs) for proteins.