[Steven Gore]

Steven Gore  asked the Naked Scientists:

I recently learned that capsaicin stimulates the same receptors that detect hot temperatures and that menthol stimulates those receptors that detect cold temperatures.

I've noticed that I have a very strong tolerance of spicy foods, so much so that my friend and I regularly have Habenero eating contests.

My wife comes from Colombia where spicy food is almost unheard of and she can't even smell a chilli pepper without breaking into fits of coughing.

So if one can build up a tolerance to capsaicin through exposure to the chemical could tolerance also be built up through regular exposure to hot temperatures?

Thanks

Steven Gore
Dallas, Texas

What do you think?

[chris]

I don't think so; chilli (capsaicin) is detected by the capsaicin-receptor (TRP-V1) on the surfaces of (as you say) heat-sensing pain fibres. I don't think scientists entirely understand the process of habituation (tolerance) to capsaicin exposure, but it may involve down-regulation of the receptor (i.e. reduction in the numbers of receptors on the nerve cells, so the cells are harder to activate and hence the consumer can tolerate more curry).

Heat is also detected by proteins on the heat-sensitive fibres, but this time the effect is achieved by these proteins altering their shapes as the temperature changes, allowing more ions to flow into and activate the nerve. However, I'm not sure that chronic heat exposure would down-regulate these proteins in the same way that capsaicin exposure knocks down the expression of its receptor.

It's an interesting question and one I'd like to look into a bit more, if that's okay?

Chris

[DoctorBeaver]

Steven - although I have no definitive proof, I have plenty of experience of both spicy food and hot temperatures.

I lived in Uganda for 2 years and spent a lot of time in Kenya & Tanzania. While there I met plenty of people of Asian and African descent who liked their food spicy. However, I also met plenty from both ethnic groups who had no, or little, tolerance for spicy food. All of these people had been brought up in the same climate.

Also, I was raised in England (not the hottest country in the world!) yet my tolerance to spicy food is higher than most Asians I know.

So, experience tells me that hot temperatures do not increase tolerance to spicy food.

(As a point of interest, while in the USA a few years ago I ate what was called "Extra hot chilli" by the TexMex roadhouse concerned without breaking much of a sweat)

[chris]

Mmm, but you are talking about heat tolerance on a global bodily scale; I was thinking more locally - as in the same nerve fibres affected by the chilli and whether this makes them less sensitive to heat too.

I might write to a colleague I know in London who I think will know the answer to this!

Chris

[RD]

If high temperature in the mouth was gating the burning sensation of chemical irritation, then a chili/curry would taste spicier when cold.