What it does, and how sure we are
Chilli's heat and most of its effects come from capsaicin. The evidence is a mixed picture, strong in one narrow place and thin in the popular ones, so we label each carefully.
- Relieves pain, as a topical creamStrong · topical
- Small lift to metabolism & fullnessEmerging
- Chilli-eaters show lower mortalityEmerging
- "Melts fat and cures a cold"Not supported
Capsaicin's best evidence is as a topical pain cream, not a food. Eaten, it gives a small, real thermogenic and appetite effect, and big population studies link regular chilli eating to lower mortality, but those are observational, so both sit at Emerging. It does not meaningfully "burn fat" on its own.
The one thing to know
"Chilli" is doing two separate jobs, and good cooks buy for each one on purpose. Some chillies are chosen for heat, some almost entirely for colour. Reach for the wrong one and a dish is either bland and red, or painfully hot.
Heat · Teekhi mirch
high capsaicin
Guntur, bird's eye and the like. A little goes a long way; use for genuine spice.
Colour · Kashmiri
deep red, mild
Low in capsaicin, rich in red pigment. For that restaurant colour without the burn.
Two things nearly everyone gets wrong
The heat is not in the seeds. Capsaicin is concentrated in the white membrane (the placenta) the seeds cling to; removing the membrane, not just the seeds, is what tames a chilli. And water will not help a burning mouth: capsaicin is fat- and alcohol-soluble, not water-soluble, so water just spreads it around. Milk works because its casein protein lifts the capsaicin away, which is exactly why raita and lassi sit beside spicy food.
How to cook with it
Chilli is added at every stage, and the form decides the effect: whole for aroma, powder for heat and colour, fresh for a green brightness.
Whole dried in the tadka
A broken dried chilli crackled in hot oil gives a smoky aroma more than raw heat.
Powder for heat and colour
Add to the masala; hot chilli for the burn, Kashmiri alongside it for colour without overdoing the heat.
Dial the heat down
Slit and scrape out the pale membrane, or lean on Kashmiri chilli, to keep flavour while cutting the fire.
Handle with care
Capsaicin lingers on skin. Wash your hands, and keep them away from your eyes after chopping.
A note of history
For all its central place in Indian food, chilli is a relative newcomer, brought from the Americas by Portuguese traders only around 500 years ago. Before that, heat came from black pepper and ginger. It is a good reminder that "traditional" cuisines have always absorbed new ingredients, and made them their own.
Is it safe?
For most people, yes, in the amounts food uses; chilli does not cause ulcers, a common myth. But it can genuinely aggravate existing acid reflux, IBS or piles in some people, so if a dish reliably troubles you, that is worth respecting. Very high intakes cause simple stomach upset. Topical capsaicin creams are effective but should be kept well away from eyes and broken skin.
Sources
- Chopan M, Littenberg B. The association of hot red chili pepper consumption and mortality: a large population-based cohort study. PLoS One. 2017;12(1):e0169876.
- Derry S, et al. Topical capsaicin (high concentration) for chronic neuropathic pain in adults. Cochrane Database Syst Rev. 2017;(1):CD007393.
- Zsiborás C, et al. Capsaicin and capsiate could be appropriate agents for weight management: a meta-analysis. Crit Rev Food Sci Nutr. 2018;58(9):1419–1427.