TLDR: In studies, bacteria disappear more quickly from untreated wood than from oiled wood.
I used to listen to the advice to oil my cutting board, until I began reading the surprisingly large number of studies done on wooden cutting boards since the 1990s.
The most recent research suggests that when it comes to bacteria, it may be better to leave wood untreated and absorbent.
Wood absorbs water
Most people have a negative association with wood's ability to absorb water: they picture mold or wood rot, so it's easy to think that absorbency is a problem to be prevented.
Because of this, it can also be easy to miss that wood does not just 'hold' water, it moves it.
Picturing a tree helps make this clear: trees need to move gallons of water from their roots to their leaves each day. Under the microscope, wood is made up of a series of tiny interwoven "straws" that make that movement possible.
The same physical structure that makes water transport possible in a living tree continues to absorb and distribute moisture in cut, dried wood.
What does that mean for a cutting board?
A splash of water from the sink won't just sit on the surface; it is absorbed and distributed through the board, a process that begins immediately upon contact with water.
Where this gets interesting is the impact this simple process has had on food safety research.
Researchers have observed that bacteria move with the water. When the surface of the board gets wet, the wood begins pulling the water, and anything carried in it, through those "straws."
That's the leading hypothesis for why bacteria can sit on the surface of a plastic cutting board for days, but disappear from the surface of wood cutting boards in only minutes in some studies.
And in those same studies, the bacteria don't return to the surface. They stay trapped deep inside the wood's structure. When the wood dries out, the bacteria are left without food or water, and they eventually die.
So why don't we oil our cutting boards?
We don't oil our cutting boards because we're operating from the principle that using fewer, simpler ingredients results in better products. We can avoid petroleum products or potentially rancid oils by sticking to wood only.
But there's an added benefit:
Oil and wax can block or slow wood's ability to absorb and move water, which means they can also slow its ability to move bacteria off the surface.
This was confirmed in a 2023 Oregon State University study, which inoculated oiled and unoiled boards with bacteria and found significantly more recoverable bacteria on the oiled samples.
Keeping our cutting boards free of oil, wax, and glue means that we also do what we can to preserve the amazing capillary action that helps wood remove bacteria from its surface.
Disclaimer: The research cited here is not product specific testing on our cutting boards—I'm summarizing and highlighting it in this blog post to describe our design choices, not to make any specific product claims for Salzmark.
Sources:
- Ak, N., & Cliver, D. O. (1994). Cutting boards of plastic and wood contaminated experimentally with bacteria. Journal of Food Protection, 57(1), 16–22.
- Aviat, F., Gerhards, C., Rodriguez-Jerez, J.-j., Michel, V., Bayon, I. L., Ismail, R., & Federighi, M. (2016). Microbial safety of wood in contact with food: A review. Comprehensive Reviews in Food Science and Food Safety, 15(3), 491–505.
- Vega Gutierrez, S. M., Vega Gutierrez, P. T., Waite-Cusic, J., & Robinson, S. C. (2023). Wood cutting board finishes and their effect on bacterial growth. Coatings, 13(4), 752.