Animals to humans: How to adjust doses from animal studies for humans - Aspire Natural Health

Animals to humans: How to adjust doses from animal studies for humans

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I spend quit a lot of time cruising Pubmed looking at scientific studies for suggestions and hints on how I can help patients.

Recent examples include: using propolis to treat neurofibromatosis (NF), bromelain to treat cancer, as well as cocoa powder to treat intestinal inflammation.

Almost all of these studies are done on rats or mice.



A Common Mistake
And here’s where I’m happy to admit that I made a common mistake.

What I had been doing was looking at the dosing used in the studies and directly translating that to people.  Say they used 40 milligrams of substance Z per kilogram of body weight in mice.

Okay, no problem.

We take that and multiply it for a human.  The average weight of humans is considered 70kg (around 150 lbs) so 40 x 70 = 2800mgs or 2.8 gms.  Some of these conversions yield realistic possibilities for humans – 3 grams is a goodly amount, but not crazy – sometimes they don’t – such as needing to drink 100 bottles of wine.

Case closed, or so I thought.  But, now I know that’s just wrong.

Thanks to an excellent piece by a doc who uses the Internet pseudonym of ‘Dr Andro’ there’s an important element I missed entirely.  “… mice metabolise whatever supplement or medication you feed or inject them at a 12 times higher rate than human beings…”,  rats are similar.  Dogs, cats, guinea pigs, etc used in some studies also have different metabolic rates.

So the doses that are needed to have an effect in mice and rats, due to their much higher metabolism, are not the same in humans with our much slower metabolism.  We’re going to leave out the fact that the metabolism or mice and rats isn’t quite the same as humans which means that some of the effects they get are NOT applicable to us.  So, it’s possible that the doses used safely in mice and rats (such as 40mg/kg) may be toxicly high for humans.

Dr Andro goes through the math used to come up with the conversion factors to take this difference in metabolism into account.  Check out his article if you’re interested

Bottom line
After crunching the numbers, we need to use the following conversion factors when applying doses used in mice and rats to humans:  0.081 for mice and 0.162 for rats.

To take our example above of the dose of 40mg/kg used in a study applied for a 70kg human.  By direct conversion (70kg x 40 mg/kg) we came up with a dose of 2800mg.  Our hypothetical study was done in mice so we apply the conversion factor of 0.081 to come out with a human equivalent dose of 226.8mg or 227mg.  Wow!  Much more reasonable.

While most natural substances are extremely safe even at very high doses, please keep these conversion rates in mind when perusing studies.


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