If you chose stainless steel to avoid plastic, it is natural to ask one more question.
Does stainless steel itself leach anything into food?
It is a fair question. It deserves a straight answer, including the parts that are inconvenient for us.
The short version
- Yes, trace amounts of nickel and chromium can migrate from stainless steel. This is real, it is published, and we would rather you heard it from us.
- The research everyone cites is about cooking, not storing. That distinction is the whole answer.
- We are not going to tell you “steel doesn’t leach.” Nobody can honestly prove that negative, and a company built on not overclaiming must not overclaim here of all places.
- Roughly 10–15% of people are nickel-sensitive. If that is you, you should know it before you buy from us.
What “leaching” actually means
Leaching is the transfer of small amounts of a material from a container into food. It happens under specific conditions — heat, acidity, or long exposure.
The word sounds alarming. In practice, almost every material interacts with food at a microscopic level. The useful question is not whether interaction happens, but under what conditions, and how much.
What stainless steel is made of
Stainless steel is not a coating. It is not layered. It is not lined with something else. It is a solid alloy — mostly iron, with chromium, and in food-grade steel, some nickel.
The grade we use is 304, also written 18/8: about 18% chromium, 8% nickel.
Chromium is the important one. Exposed to oxygen, it forms a very thin, invisible oxide layer on the surface. That layer is what makes steel “stainless” — it protects the metal underneath, and it is self-repairing. Scratch it, and it reforms.
That stability is why steel has been standard in professional kitchens, food processing and medical environments for decades.
The study people are actually referring to
When you read that stainless steel leaches nickel, the source is usually Kamerud et al. (2013). It is a real study and its findings are real.
Here is what it did: it simmered tomato sauce — highly acidic — at around 85°C, in stainless steel, for six to twenty hours.
Under those conditions, measurable nickel and chromium migration occurred.
So the honest framing is this: that research is about cookware, not food storage. Nobody simmers sauce in a lunchbox for twenty hours. A cold container of leftovers in a fridge is a fundamentally different situation from a pan on a hob.
The study also found something worth knowing: migration drops sharply after the first few uses. New steel releases more; the same vessel, used repeatedly, releases progressively less as the oxide layer matures.
The part we cannot tell you
We would like to write “and therefore cold storage in 304 steel causes no migration at all.”
We are not going to, because no study of cold-storage migration from 304 exists that we can point you to. You cannot prove a negative by asserting it, and we are not going to be the company that does exactly what it criticises everybody else for.
What we can say is that the conditions known to cause migration — high heat, high acidity, many hours — are not the conditions inside a fridge. And that steel does not rely on plasticisers, softeners or surface coatings, so there is no additive to migrate in addition to the metal itself. There is nothing in it that is not the alloy.
Acidic foods
Tomato, citrus, vinegar-based dressings. These increase interaction, particularly with heat and particularly in lower-grade steel.
This is one of several reasons the grade matters. 304 is specifically designed to resist corrosion in kitchen environments. Some brands in this category quietly use 201 or 202 steel — both are less corrosion-resistant, and both are sold as “food grade.”
Storing a tomato-based leftover in 304 overnight is fine. We would not recommend simmering a ragù in it for a day.
If you are nickel-sensitive
This is the section most steel brands leave out, so here it is.
Roughly 10–15% of people in Europe have some degree of nickel sensitivity — more commonly women, and most often experienced as contact dermatitis from jewellery or belt buckles. A smaller number react to dietary nickel.
304 stainless steel contains nickel. That is not a secret, it is in the name: 18/8.
If you have a diagnosed nickel allergy and you have been advised to limit dietary nickel, you should talk to your doctor before choosing steel food storage — and you should probably not take our word for it, because we sell the stuff.
We would rather tell you that and lose the sale than have you find out from someone else.
What about 316?
316 steel adds molybdenum and is more corrosion-resistant — it is what you want for marine environments and certain medical uses. It also contains more nickel than 304, not less, so it is not the answer to a nickel question.
For food storage in a domestic kitchen, 304 is the right material, and the difference is smaller than the marketing suggests. We wrote about that separately.
The honest summary
Steel is not a miracle material. It is a stable one.
It does not rely on coatings. It does not contain softeners. It does not degrade the way plastics can. It is the same material in year ten as it was on day one — and that consistency is the entire point.
But it is a metal alloy, it contains nickel, and under the right conditions — hot, acidic, prolonged — trace amounts can migrate. We are telling you that up front, with the study, with the numbers, and with the caveat about who should be careful.
A company that volunteers its own inconvenient fact is a company you can believe about the rest.
See what actually touches your food →
Food should be stored without doubt.
This article is general information, not medical advice. If you have a diagnosed nickel allergy, speak to your doctor.