While preparing for this talk, I briefly considered diluting what I had to say. I figured that it would be a nice bit of homeopathic humour, and although the idea wasn't especially original, I felt that it had a certain amount of charm. Until some back-of-the-envelope calculations revealed that dissolving my talk to a standard homeopathic dilution of 30C would give me a little less than one femtosecond in which to speak. (If you don't know much about homeopathy, you'll get that joke later. And no, it still won't be funny.)
I sort of feel bad, picking on homeopathy—on the pseudoscience scale, it's just one notch below the idea of a flat earth. It offers the traditional alt-med package: a panacea with no side-effects. And homeopathy has a special place in my heart.
"So what is homeopathy?" you might ask. It's a common misconception that it consists primarily of herbal remedies. Homeopathy is often confused with "naturopathy", but it's not just a special blend of "herbs and spices": it's much more ridiculous than that.
Doctor Steven Novella does it no injustice when he calls it prescientific sympathetic magic.
Homeopathy was created by Christian Friedrich Samuel Hahnemann ("Sam", to his friends), a German physician, as early as 1796 (although Hahnemann did not use the term "Homeopathy" for his cures until 1807). Hahnemann was appalled by the state of medicine in his day, and rightly so. Bloodletting, purging, enemas, and the like were all still in common use at this time, and it would be more than fifty years before Ignaz Semmelweis's proposal that hand-washing significantly reduced mortality was finally accepted by the medical community (thanks to the germ theory of disease, popularised by Louis Pasteur). In those days a visit to a physician could easily kill you. Hahnemann said:
My sense of duty would not easily allow me to treat the unknown pathological state of my suffering brethren with these unknown medicines. The thought of becoming in this way a murderer or malefactor towards the life of my fellow human beings was most terrible to me, so terrible and disturbing that I wholly gave up my practice in the first years of my married life and occupied myself solely with chemistry and writing.
This seems fair. Unfortunately, this "chemistry" of his wasn't so good. Hahnemann subscribed to a vitalist philosophy in which illness is posited to be a result of disturbances in one's innate life force (miasms), and he rejected the notion that disease could be caused by invading entities: in other words, what we now call the germ theory of disease. Here's how homeopathy works (or perhaps, "here is homeopathy's proposed method of action" would be a better phrase, as the best meta-analyses seem to show no effect at all).
We begin with Hahnemann's ipse dixit "Law of Similars": this is the voodoo part. Beginning with the observation that a particular treatment for malaria (cinchona bark) produced symptoms when ingested that were similar to the symptoms of the parasitic infection that it was meant to treat, Hahnemann declared similia similibus curentur (or "let like be cured by like") to be a fundamental healing principle. Put simply, if a substance causes a symptom in an otherwise healthy individual, it can be used to treat this symptom in a diseased individual. This is presumably why rubbing minced onions in one's face is such an excellent remedy for hay fever.
Unfortunately, reality had to intrude and ruin everything. You see, many of these so-called remedies were actually highly dangerous, or at the very least distasteful. These ingredients include dog faeces, eye of pheasant, arsenic, and cobra venom, among a plethora of more mundane things. And so, in a rather generous attempt to make his remedies less dangerous, Hahneman invented the principle of serial dilution, also known as the "Law of Infinitesimals". This rule states that as a remedy is diluted, its potency is increased (in direct contradiction, I hasten to add, to the dose-response relationship on which much of modern medicine is based).
And so, as you might guess, homeopathic remedies are really quite dilute. Although the procedure may vary slightly, it goes something like this:
- Select a "remedy" (anything from grass to loon feather to red wine) and a dilutant (usually either water or ethyl alcohol).
- If the remedy is not already a liquid, put the substance in solution. This may involve grinding it into a paste or saturating water with it; insoluble solids, such as bone or oyster shell, may be ground with lactose in a process called trituration.
- Take one drop of the remedy liquid and dilute it in 99 drops of dilutant.
- The remedy must be succussed. This involves shaking it vigorously ten times. Several reports indicate that Hahnemann had a saddle-maker fashion him a leather striking board stuffed with horsehair. Hahnemann believed that this process "potentised" or "activated" the healing energy of the solution.
- You have now made a 1C homeopathic remedy. For a 2C solution, repeat steps three and four again, and again for a 3C solution, etc.
- Once dilution is completed, the remedy may be used as is, or used to saturate lactose pills.
The dilution of homeopathic remedies is measured on several scales, the most common of which are C and X (sometimes D). A 1C solution is one part "active" ingredient and 99 parts water (or alcohol), a dilution of 1 in 100. A 1X or 1D solution is one part "active" ingredient and 9 parts water (or alcohol), a dilution of 1 in 10. Consequently, a 3C solution is the same as a 6X solution: one part active ingredient in 1,000,000 parts water.
But now back to chemistry. In 1811, the Italian scientist Amedeo Avogadro proposed that the volume of any gas is proportional to the number of molecules that comprise it, irrespective of the nature of the gas in question. Avogadro's work was built upon by those who came after him, eventually resulting in the calculation of what came to be known as the Avogadro constant, which some of you may remember vaguely from high school chemistry: roughly 6.02 x 1023. This is the number of elementary entities in one mole of any substance, and specifically the number of atoms in 12 grams of carbon-12.
So what does all of this mean? Well, what it means is that you can't dilute something forever. In fact, with just a little bit of math, plus knowledge of the molecular mass of the dilutant (which can be gleaned from the nearest periodic table), it is fairly straightforward to calculate exactly how far one can dilute something before no molecules of the original substance are left at all.
After some simple back-of-the-envelope calculations, it turns out that once a substance has been diluted past 25X (or roughly 13C), the chances of the remedy having a single molecule of the orginal substance left are less than 50/50. The standard homeopathic dilution recommended by Hahnemann? 30C, a whopping thirty-five orders of magnitude more dilute!
So there's literally nothing to homeopathy. But that's not the only problem.
The Law of Similars betrays an extremely superficial understanding of medicine. So-called "allopathic" medicine (the alt-med practitioner's pejorative term for scientific medicine) is frequently accused of being concerned with only the symptoms, rather than the root cause of disease. This is patently absurd when one considers homeopathy's purported method of action, which involves the assumption that there is some fundamental connection between a disease and a substance that happens to create a similar set of symptoms. In fact, the idea of like-cures-like predates Hahnemann by quite a bit, with the German-Swiss physician Paracelsus quoted as saying "What makes a man ill also cures him," in the sixteenth century.
This fallacious argument from antiquity notwithstanding, I have heard many homeopathic practitioners argue that the Law of Similars show that homeopathic solutions function in a fashion very similar to vaccines. I can agree that someone with little or no understanding of a vaccine's method of action might see it that way; but it is clear that anyone who would make this argument has no business dispensing medical advice. A vaccine introduces and incapacitated pathogen to the body's immune system, in a very real way teaching the immune system how to deal with that particular virus. A homeopathic remedy, well... doesn't do much of anything.
To get around this inconvenient bit of math, homeopath Jacques Benveniste proposed in 1988 that water (and presumably alcohol, as this is another popular dilutant) was capable of "remembering" substances with which it had come into contact. Benveniste was a little shady on the details, and it remains unclear how, even if the water did remember the substance, it could influence the body in any way with such a "memory". While Benveniste published several trials with positive results, this "water memory" has proven irreproducible under double-blind conditions. In fact, according to the journal Nature, liquid water is incapable of maintaining ordered molecular networks for more than a fraction of a nanosecond. More recently, homeopathic proponents have opined that water memory has "something to do with quantum mechanics".
This water memory charade has been highly criticised, and in fact raises more questions than it answers. For example, its memory seems rather selective. To quote Tim Minchin: "It's a miracle! Take physics and bin it! Water has memory! And whilst its memory of a long-lost drop of onion juice seems infinite, it somehow forgets all the poo it's had in it!" To quote Richard Dawkins: "Every time you drink a glass of water, the odds are good that you imbibe at least one molecule that passed through the bladder of Oliver Cromwell." Although Benveniste claimed that succussion was necessary to initiate water memory, the mechanism of action has yet to be explained.
Benveniste is, in fact, the recipient of two Ig Nobel awards in Chemistry. The first, in 1991, was for being a "prolific proselytizer and dedicated correspondent of Nature, for his persistent belief that water, H2O, is an intelligent liquid, and for demonstrating to his satisfaction that water is able to remember events long after all trace of those events has vanished." The second, in 1998, was for a paper titled "Transatlantic Transfer of Digitized Antigen Signal by Telephone Link", in which he described a mechanism for packaging homeopathic "molecular activity" into email attachments. The award cites "his homeopathic discovery that not only does water have memory, but that the information can be transmitted over telephone lines and the Internet."
A recent, extensive review of the evidence by the Science and Technology Committee of the United Kingdom (where homeopathy is covered by the National Health Service) concluded that there was no reason to believe that homeopathy worked. While regulation of such products in the United States in nominal, Health Canada's Natural Health Products Regulations under the Canada's Food and Drugs Act is responsible for overseeing homeopathic remedies in Canada. To quote from their website:
Through the Natural Health Products Directorate, Health Canada ensures that all Canadians have ready access to natural health products that are safe, effective and of high quality, while respecting freedom of choice and philosophical and cultural diversity. [Emphasis added.]
When regulating homeopathic remedies, Health Canada mandates that evidence for efficacy be presented if the manufacturer wishes to include recommended uses for the product. These high standards of evidence may include simple references to "traditional use", or may go further, referencing either provings or the homeopathic materia medica. Note that several reference materials that Health Canada deems acceptable for evidence of efficacy predate the germ theory of disease by several decades.
For those who are wondering, a homeopathic proving involves the administration of undiluted homeopathic ingredients to one or more participants in a "trial"; in fact, Samuel Hahnemann's own ingestion of cinchona bark might be considered the first homeopathic proving. After exposure to the substance in question, subjects are prompted to describe any emotional or physiological effects that they experience. These effects are noted, as the homeopathic philosophy dictates that after dilution these are the symptoms that the remedy will treat. Note that no form of blinding or control is mandated.
One homeopathic proving describes a remedy "made by exposing powdered milk sugar to a powerful telescope in Boston, Massachusetts while it was focused on the planet Saturn during April 2009." Yes: this "proof" describes a homeopathic remedy in which the active ingredient is Saturn.
Things are further complicated when companies bypass the standard Health Canada or FDA approval process by claiming that their product is homeopathic, when in fact it contains dilutions of only 1 or 2X. This can pose a problem when the active ingredient is dangerous, as was the case with Zicam, a cold and flu remedy containing measurable quantities of Zinc, which reportedly caused 130 consumers to lose their sense of smell!
I will finish by quoting the late Perry DiAngelis, former contributor to the Skeptics' Guide to the Universe:
Are you sure the Law of Infinitesimals refers to dilution and not the IQ of adherents to this theory?
Hahnemann, Christian Friedrich Sammuel. The Organon of the Healing Art (5th/6th edition). 1833/1921.
http://www.sciencebasedmedicine.org/?cat=5 (especially http://www.sciencebasedmedicine.org/?p=3961)
Edit: Also check out this article by Dr. Steven Novella discussing Hyland’s Teething Tablets, "homeopathic" tablets for babies that "contain measurable and variable amounts of an actual drug, in unsafe doses, and without safety caps".