Only The Dose Makes the Poison

Paracelsus, a Swiss physician and philosopher born in 1493, is credited as the father of toxicology. He coined the phrase, “Only the dose makes the poison.” Geoffrey Kabat, author of Getting Risk Right, explains the concept:

The magnitude of one's exposure matters. This is true of micronutrients, such as iron, copper, selenium, and zinc, which our bodies need…but which, taken in large amounts, are highly toxic. It is also true of lifestyle and personal exposures, if to cigarette smoking and consuming alcoholic beverages, and medications, as well as pollutants in the environment. Many toxins and carcinogens exhibit a dose response relationship: that is, as the exposure increases, so too does the observed toxic or carcinogenic effect. Even compounds and foods we think of as healthy can be lethal when consumed in excess…Clearly, consumption of excessive amounts of water can lead to an electrolyte imbalance and heart failure.

This concept applies to all aspects of life. Most decisions should involve getting the “dose” right, not making absolutist, binary claims. It’s a lazy trap to judge ideas without regard to the amount, exposure, or duration.

• Investment risk is needed to growth wealth, but excessive risk leads to ruin
• Striving for greatness is great, but demanding perfection leads to paralysis
• Working out is great, but a lack of recovery leads to injury
• Regulation is necessary, but excessive regulation crushes innovation
• Meetings are necessary, but excessive meetings are not
• Management is valuable, but micromanagement is disabling

It’s all a matter of degree. Not enough exposure doesn’t deliver any benefit. Too much exposure can literally kill us. Few things are black and white. Nevertheless, it’s tempting to label things as good or bad because it simplifies life. But it’s false simplification, because the value of most decisions is getting the dose right.

Even scientists are susceptible to this flaw. As Kabat explains, scientists ignore the dose part of the equation and only focus on the substance:

Nevertheless, what is noteworthy and disturbing is how frequently scientists examining an exposure of concern to the public can ignore the issues of dose and potency or imply that they are seeing an effect of an exposure at a dose that is so low as to make the claimed effect questionable.

In many decisions, whether political or pharmaceutical, nothing is right or wrong nor good or bad. It’s always about “how much” and “to what degree.” False dichotomies are convenient, but wrong. The next time you encounter an argument that’s framed as a dichotomy, remember that the hard part is getting the dose right.