Stainless steel leaches nickel and chromium into foods during cooking (2013)

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4284091/

by yumraj • 4 years ago

174 298 4 years ago

ncbi.nlm.nih.gov

iab2• 4 years ago

Anybody close to just giving up at this point?

quantified2• 4 years ago

Cast iron FTW. Haven’t checked if an enamel dutch oven is naughty or nice. Slow cooker’s pottery glaze is unknown.

anonporridge• 4 years ago

This. We literally take iron as a supplement because it's an essential mineral for the body.

K.I.S.S.

carabiner2• 4 years ago

Why not carbon steel? It's lighter and just as durable, that's why it's used in restaurant kitchens.

ummonk3• 4 years ago

With cast iron or carbon steel you're getting bits of polymerized oil (i.e. seasoning) in your food.

vernie2• 4 years ago

Don't worry too much, all this stuff will take a few years off your life on average and those years would've sucked anyway.

throwaway8943452• 4 years ago

How many years are shaved off by worrying about all of the things that shave off a few years?

gilrain• 4 years ago

This is ageism which assumes that the elderly are in constant misery and would rather be, or be better off, dead.

You’re wrong. When you are older you will realize that life is worth living at every age, and you will hope the young don’t treat you too badly in their ignorance.

ciphol• 4 years ago

They'll also make you start having "old age" diseases at a younger age, on average.

jotm• 4 years ago

What's the point? Whether you just give up or try to go on, you die anyway. Might as well not give up :D

freeflight• 4 years ago

This isn't really "new news", it's been a known thing for a while [0]

Personally became aware of it when looking for camping cookware; Stainless steel or aluminum are very good materials for pots taken on trip, they sturdy but not too heavy, tho have this issue of not being good for anything acidic due to the increased leeching.

[0] https://pubmed.ncbi.nlm.nih.gov/1514841/

blarg1• 4 years ago

Yep I'm going back to my mercury and lead alloy pot.

riversflow• 4 years ago

Reminds me of one of my personal heros, Bruce Ames[1] who invented the Ames test, a relatively cheap biological assay that tests for mutagenicity[2].

Essentially it turns out that tons and tons of stuff, both synthetic and natural is mutagenic to some degree, but we tend to think about it as a binary instead of a spectrum. His argument was that some things that are technically mutagenic, like pesticides and fire retardants have a net benefit in spite of this(e.g. pesticides make a better diet more financially attainable which has a bigger impact on public health than a very small increase in the base rate of cancer), but we lump them all together. It's why California's Prop 65 is just completely stupid; we lump fairly benign things like coffee and wine in with things like asbestos.

The quote I always think of is, "if you have thousands of hypothetical risks that you are supposed to pay attention to, that completely drives out the major risks you should be aware of."

[1] https://en.wikipedia.org/wiki/Bruce_Ames

[2] https://en.wikipedia.org/wiki/Ames_test

iab2• 4 years ago

That’s some interesting stuff, thanks

hedora5• 4 years ago

Fire retardants are a net negative for public safety. Consumer protection groups, furniture manufacturers, and fire fighters all banded together to eliminate California's requirements for them. It still took over a decade. During that time, the fire retardant manufacturers were literally the only group that supported using them.

dylan6043• 4 years ago

Yup: https://news.ycombinator.com/item?id=30622479

emmelaich6• 4 years ago

:-)

Maybe you shouldn't read how new buildings poison you with radioactive gas.

https://www.epa.gov/radtown/natural-radioactivity-building-m...

DeWilde• 4 years ago

In the worst case, we're left with air-frying as a healthy way of cooking.

tus666• 4 years ago

And these things are bad for us? I mean it's not lead.

dcchambers6• 4 years ago

Toxicological studies show that oral doses of nickel and chromium can cause cutaneous adverse reactions such as dermatitis.

Literally the first sentence in the abstract when you click the link. The rest of the abstract summarizes the study nicely in a small paragraph.

lazide3• 4 years ago

How is that comparable to lead at all?

refurb3• 4 years ago

You do realize “cutaneous adverse reactions such as dermatitis” is just a rash right?

somethoughts• 4 years ago

Yes is it a feature not a bug? "Nickel is a mineral. It is found in several foods including nuts, dried beans and peas, soybeans, grains, and chocolate. The body needs nickel, but in very small amounts. Nickel is a common trace element in multiple vitamins." [1]

[1] https://www.webmd.com/vitamins/ai/ingredientmono-1223/nickel

convolvatron• 4 years ago

chromium isn't so benign, is it?

HarryHirsch3• 4 years ago

It is a feature, nickel is a cofactor in certain enzymes, and in industrial nations the main source for humans is their stainless steel cookware. On chromium being an essential trace element the jury is still out.

yumraj4• 4 years ago

Well, that is counter to what the above paper says:

Though Ni is known to be essential to the health of some species, it has not been proven to be essential to the health of humans (3). There are no known human enzymes or cofactors dependent on Ni for normal function

cyounkins5• 4 years ago

The dose makes the poison. For example, potassium is both a vitamin required for survival and what is used to stop the heart in lethal injection.

https://en.wikipedia.org/wiki/Lethal_injection#Potassium_chl...

emmelaich6• 4 years ago

Lead is mentioned too :-(

It has been demonstrated that Pb in glazed cookware and storage containers can leach with test acidic solutions and increased with duration of contact

Albeit not in steel

hollerith• 4 years ago

I heard that cheap stainless pots leach fewer toxins than the expensive ones.

cyounkins5• 4 years ago

Worth noting that this investigation specifically analyzes highly acidic tomato sauce and that is likely to be the worst case scenario. Still very valuable research!

WinterMount2232• 4 years ago

Tomato sauce is not only acidic but also has a strong chelating agent citric acid which is known to corrode stainless steel in industrial settings.

friedturkey• 4 years ago

Plenty of people eat tomatoes and pasta quite often so it’s also not an unreasonable test case.

perihelions• 4 years ago

Also, it's with factory-fresh steel. Fig. 1(b) shows something like a 10x reduction between the 1st and 6th cooking cycle (discussion suggests there's a passivating oxide layer that forms).

Like those videos of engineers breaking airplane wings at 300% design strain, this kind of paper is more reassuring than scary IMHO.

jeffbee5• 4 years ago

Yeah, and it's completely bizarre how this paper doesn't even contain the word "passivated". Stainless cookware comes from the factory passivated, because otherwise it would be highly reactive and rust immediately, violating consumer beliefs about the word "stainless". Passivated stainless is virtually all chromium oxide on the surface. So I'm not sure why the paper even mentions the bulk fraction of Cr in 304 and 316 SS.

tharkun__• 4 years ago

This is a really good thing to know about though. I love my cast iron pan. But tomato sauce is the one thing I still pull out my stainless steel pan for.

So is it better to just use my cast iron pan for tomato sauce too and just live with the fact I have to redo some of the seasoning if I happen to do multiple acidic sauces/dishes in a row?

ricardobeat• 4 years ago

Sounds like an enameled pan like Le Creuset might be the best for those. I haven’t had any issues with tomato sauce on cast iron though, probably takes some really long cooking to damage it.

froh• 4 years ago

No, you're perfectly good with the stainless steel pan, as the sibling comments clarify (essentially: passivation, chrome oxide layer, all good)

bluedino• 4 years ago

I'm using my grandmothers cast iron. She and my grandfather lived well into their 50's so I should be good.

alfalfasprout• 4 years ago

I mean, they're totally for a different purpose though. Clad stainless cookware is meant for faster reaction to changes in temperature. Cast iron is great for searing but has way too much thermal mass to finely control temperature. Hard to beat copper and stainless steel for that.

yumraj4• 4 years ago

From what I've read, cooking acidic food in cast iron can lead to iron poisoning. Though it is not clear how much dosage would be needed for that to happen..

Arrath• 4 years ago

It the other direction, if you're iron deficient it can be a good thing!

melling2• 4 years ago

Well into their 50s is not very old. 100 years ago the average lifespan wasn’t as good but there was more childhood mortality, no antibiotics, etc.

CincinnatiMan• 4 years ago

Pretend you're on Reddit and you'll realize it was a joke.

lkrubner• 4 years ago

Also, cast iron pans leach iron into food, and are therefore an effective way to treat anemia. Any one who needs a small, steady dose of iron can benefit from cast iron pans.

pphysch• 4 years ago

OTOH it can introduce dangerous amounts of iron if you cook highly acidic foods in it

_jal• 4 years ago

Your food will taste really gross well before it is dangerous.

And cooking acidic foods in cast iron ruins the seasoning, so anyone who uses it regularly already doesn't do that.

HarryHirsch3• 4 years ago

Iron toxicity isn't really a thing, uptake is active and tightly controlled in the colon. Copper toxicity on the other hand, when you cook acidic foods for too long in a copper pan, that's a distinct possibility.

There's a lesson in that: journals print what people like to read. Everyone with a mild sense of chemistry already knows that you can't prepare tomato sauce or mulled wine in copper vessels, consequently such a paper will be rejected for being plain obvious. Stainless steel on the other hand, that's pleasantly controversial and you can debate about chromium and its oxidation state and essential nature and toxic concentration until the cows come home.

That explains the nature of the investigation.

CoastalCoder2• 4 years ago

One time when I was a kid, I put a container of tomato sauce in the fridge, and covered it with aluminum foil. A few days later the foil had holes where it contacted the sauce. I still remember the nasty smell decades later.

uneoneuno• 4 years ago

I have a feeling you made an aluminum / tin battery with the tomato sauce as the electrolyte?

perilunar2• 4 years ago

See also the story of the lucky iron fish:

https://en.wikipedia.org/wiki/Lucky_iron_fish

syntaxing2• 4 years ago

I think (unglazed) ceramic is your best bet. I use ceramic pans and glass pots. The corning glass pots last forever (probably my lifetime) but I have to replace my ceramic pans maybe every year or two. Seems worth the $50 for a peace of mind.

germinalphrase• 4 years ago

What kind of ceramic pan are you describing here? My assumption was ceramic coated cast iron, but you would hardly replace that yearly.

AussieWog932• 4 years ago

I know people who've bought cheap enameled cast iron, and theirs died after around 2 years of heavy use.

hedora5• 4 years ago

There's some teflon-like substance marketed as ceramic. I doubt it lasts more than a year, despite all the marketing claims saying it is indestructible.

I accidentally bought one on Amazon once, thinking it was a ceramic coated cast iron pan. Back it went.

I guess it's not false advertising if hundreds of fly by night companies all co-opt the name of the same superior technology.

syntaxing2• 4 years ago

I use green pans. While they still “work”, the nonstick properties diminish which isn’t the end of the world, but gets annoying for things like eggs.

WinterMount2232• 4 years ago

Unglazed ceramics can leach arsenic depending on their composition, so if you are really paranoid your safest bet is new lab grade borosilicate glass.

every2• 4 years ago

That would be the original borosilicate Pyrex which is no longer made. Fortunately, I inherited a ton of it from my parents...

dylan6043• 4 years ago

Screw it. All of this tech is too much. I'm going back to wood sticks on an open fire next to the cave I'm moving into.

ycombinete• 4 years ago

ah, but the wood smoke is full of carcinogens, we're better off not eating!

dennis_jeeves1• 4 years ago

Not so fast, join the long queue...

hprotagonist2• 4 years ago

I don't know about you, but i do not regularly simmer tomato sauce for 2-20 hours at a time.

Johnny5552• 4 years ago

A long simmer really brings out the flavor, my grandmother would simmer it for hours, at least half a day if not longer. And she used fresh tomatoes out of her garden.

AussieWog932• 4 years ago

It's definitely a thing in some cultures (Italian I know for sure, possibly Mexican too?). I personally boiled down some lasagna meat for 4.5 hours just the other day.

assttoasstmgr• 4 years ago

Sounds like someone's never had Sunday gravy with braised short ribs before.

hprotagonist2• 4 years ago

you put tomatoes in your gravy? takes all kinds, i guess.

koolba• 4 years ago

That’s pretty much how you make tomato sauce and chili. Both of which are awesome.

mnw21cam• 4 years ago

Yeah, at the end of last summer, I had a whole pile of excess tomatoes from the garden that I wouldn't be able to eat before they went off, so I bunged them in a very large saucepan and simmered them until they took up 1/3 the volume, and put them in hot jars. It's a fairly common way to preserve them.

deepsquirrelnet3• 4 years ago

Oh tomatoes? Well, tomatoes love to be grown in acidic soil, which increases the uptake of nickel and chromium. And they had better be organic, because common contaminants of fertilizer salts include arsenic and cadmium. But you don't want to eat organics if they're grown from waste biproducts of animal farming, such as commonly used bone meal, because those concentrate heavy metals.

jeffbee5• 4 years ago

It is interesting that this regularly pops up on HN. People crave some kind of "aha!" subtle, gotcha explanation for why our health is falling apart, because they desperately need to ignore the quite obvious explanations of air and water pollution.

loudtieblahblah• 4 years ago

the more obvious explanation are diets that arent healthy.

donkeydoug• 4 years ago

+1 to this and your other diet related comments. think the issue in large part is insulin resistance driven by high carb processed food and replacing fat in things with sugar thanks to the (22 - 15) countries study. fasting & keto can help someone recover... but so much polarization that people don't want to hear that either. so... think _enough_ of the science is out there at this point, but things are going to keep getting worse, more obesity, type 2 diabetes, sicker. you'd think the mortality correlation with covid would have woken more people up. oh well.

yumraj4• 4 years ago

Well, since I posted this I can answer how I ended up there and the reason is rather simple.

We mostly use cast iron for cooking, except for cooking anything that is acidic (tomato, lime etc.) for which we use stainless steel. So, got curious if stainless steel reacts with tomato or lime or not, since after all it's a metal, an alloy but metal.

So while I was bored of doing what I was doing, searched and found this, which was new info for me. So, decided to post it..

As simple as that... :)

refurb3• 4 years ago

I was with you until “air and water pollution” as I expected the much more obvious cause of “obesity and lack of exercise”.

jeffbee5• 4 years ago

Some research indicates that obesity might be caused by water pollution, and the link between air pollution and lack of exercise should be clear enough.

pastacacioepepe• 4 years ago

Yeah it's absurd to worry about stainless steel pots leaking nickel in food when we all breathe heavily car polluted air daily without worry.

deepsquirrelnet3• 4 years ago

The reason why those nihilists "roll coal" is to make you worry. Or maybe it's activism in disguise.

0xbadcafebee2• 4 years ago

Supposedly anodized aluminum is nonreactive. Besides enamel-coated pans and really well-seasoned cast iron, these seem like the only pans that don't leach anything? I guess we need tests to be sure. (you can also use stoneware for cooking, but not on a range)

qbasic_forever2• 4 years ago

Carbon steel might not be as bad as stainless--it doesn't have the nickel and chrome I assume like stainless.

I'd worry with anodized aluminum that the anodization can flake off with sharp utensils. I baby my aluminum cookware and it still gets some scratches.

There's some borosilicate glass cookware too, but IIRC it went out of fashion and can be hard to find in typical cookware forms like wide pans. It had some problems with thermal shocks and shattering I believe too.

hedora5• 4 years ago

It was popular in drug labs, so they replaced the consumer stuff with something that violently explodes if used for chemistry.

Of course, people that were using it to, you know, cook food, or in research labs ended up in some pretty dangerous situations too.

Many underfunded grad students were maimed. (Really.)

ummonk3• 4 years ago

Carbon steel is the same as cast iron, just with a lower carbon content. Both are only going to leach carbon and iron directly. Arguably though, the seasoning itself is probably some kind of polymerized hydrocarbon, and so you might leach polymer into your food when cooking on a well-seasoned cookware.

carterschonwald2• 4 years ago

So there’s several details and questions that I think might be important for interpreting this study!

1) all stainless steels need to be “passivated” in order to be properly stainless. These days that process involves putting the stainless steel in a hot water bath with like a pound of citric acid for every gallon of water used. (I actually do this at home with any cookware or steel bottles where I notice a metallic taste). Chips of stainless steel that aren’t passivated will leach and or corrode!

2) I think most cookware is 304 steel. I’m not sure how often it’s 316. But also unless you control for passivation it’s still pretty uninformative.

yumraj4• 4 years ago

all stainless steels need to be “passivated” in order to be properly stainless.

Does the passivated layer survive scrubbing and dish washing?

cyounkins5• 4 years ago

It can be damaged physically or chemically but the oxide layer is self-healing upon contact with oxygen.

brador• 4 years ago

Soda is acidic and comes in Aluminum cans. Why don't the cans develop holes?

slater• 4 years ago

"The inside of the can is lined by spray coating an epoxy lacquer or polymer to protect the aluminum from being corroded by acidic contents such as carbonated beverages and imparting a metallic taste to the beverage."

https://en.wikipedia.org/wiki/Aluminum_can

iNerdier• 4 years ago

Because they’re really a plastic bag with aluminium lining. Nurdrage has a good video showing this: https://m.youtube.com/watch?v=X1pB6O6AYMU

rob743• 4 years ago

If the cans weren't lined (like other commenters remarked), the most the acid in the soda would do is dissolve a little bit of the aluminium - of course that's not necessarily healthy, but to get a hole in the can you'd need something much stronger. Despite what some urban legends claim, there is still a difference between Coca-Cola and hydrochloric acid...

hammock7• 4 years ago

Aluminum soda cans are lined with BPA or similar.

hammock7• 4 years ago

Does occasionally cleaning my cookware with Barkeeper's Friend (oxalic acid) accomplish the same?

carterschonwald2• 4 years ago

I don’t know! With citric acid and it’s predecessors, they only dissolve iron atoms but don’t react with the chromium and nickel alloying elements, which is an important combo!

luma• 4 years ago

When welding stainless used in food service, you then need to re-passivate all the joints. Can be a bit of a pain for long pipelines. You'll often see acrylic piping used in food plants partially for this reason (another reason is that it's easy to see any blockages or growths etc through the pipe walls).

senectus1• 4 years ago

can you use cast iron on an induction cooktop?

I mean, it should work... but is there any reason not to?

hedora5• 4 years ago

It works great. The reason not to use it is that it will scratch the heck out of certain (resistive or induction) cook tops. Our cooktop has little raised matte nubbies that stick out a bit over the shiny ceramic surface. The nubbies are "pre scratched", and protect the rest of the cooktop. We have no problems with cast iron on it.

Some people use silicon mats to avoid scratches. The protective mat often burns or discolor the cooktop.

If you want to immediately ruin a ceramic cooktop, put a piece of aluminum between a hot pan and the ceramic top. Some sort of ion exchange happens, and the foil embeds itself below the surface, then flakes off. (Also, it smokes a lot,)

perilunar2• 4 years ago

Yes cast iron works. Most ferrous metals do but some stainless steels don't.

agumonkey• 4 years ago

who here cooks with steam ?

faramir• 4 years ago

Wow... I use a stainless steel pan every day AND I'm covered in eczema. Maybe it's time to get a new pan.

hedora5• 4 years ago

Get an allergy screening. They can test for nickel sensitivity.

emmelaich6• 4 years ago

Some browsing lead to this interesting bit of trivia -- nickel means demon or goblin, and originates from miners mistaking the nickel ore for copper ore, calling it "goblin's copper".

As early as the 1600s, a dark red ore with a distinct green coating became a notable source of irritation for copper miners in Saxony, Germany. Believing that the dark red substance was an ore of copper, they continued mining it. As the ore was causing ailments, the miners turned to folklore and adopted a belief that it was protected by goblins. This ultimately led to the naming of the ore as “kupfernickel,” translating to “goblin’s copper.”

https://www.hmpgloballearningnetwork.com/site/thederm/site/c...

Also, (my speculation) it is the origins of the name of Copernicus.

adhesive_wombat• 4 years ago

The -nik in Kopernik (the unlatinised name) is not related to the Koper-: it makes it a agent noun in Polish (and other Slavic languages), similar to beatnik, robotnik and Sputnik. It's basically like "-er".

The Koper- could relate to copper, or dill (says Wikipedia). Then it would be copper-er or dill-er. Maybe his family once coppered pans or ships or made pickles!

emmelaich6• 4 years ago

Yes, I found that after and decided not to spoil my fun.

The area around Kopernik is rich in minerals including copper so I'm leading towards copperer. Either a copper miner or one who works with copper.

ajuc• 4 years ago

Copper in Polish is "miedź". If it was borrowed from a foreign language they would use Latin not English (there's almost no English loandwords in Polish at the time) so it would be cuprum. Or they could use German - so Kupfer. In any case the second vowel would be "u".

So "Kopernik" name is probably related to the dill plant (koper).

adrian_b12• 4 years ago

It should be kept in mind that almost any material used in contact with food will leach something, especially when it is used during cooking, i.e. at high temperatures, and, in the case of metals, when the food contains fruit juices or vegetable juices, which are acidic.

So what matters is the hierarchy of the materials from this point of view, i.e. which are better and which are worse.

The best material for food-contact is glass, but glass, while perfect for storage, is not suitable for most types of cooking (even if it is quite possible for someone to eat only food cooked in a microwave oven, in glass cookware).

The next best material is titanium (commercially pure titanium, not the frequently encountered Ti-Al-V alloy). Titanium cookware exists, but it is normally too expensive, unless it is used in some activities where its low weight can justify the high price.

After these 2 cookware materials, which unfortunately are not an acceptable choice for most people, comes the stainless steel.

Yes, stainless steel will leach a little nickel and chromium. However this leaching will be large only for new cookware and it diminishes a lot for used cookware. Even in the case of people with nickel sensitivity, most of which are women, the quantities of nickel leached from used stainless steel cookware are far too low to have any effect.

All the other materials that are used for cookware, including ceramics, can be sources of much more dangerous leaching than stainless steel (excluding glass & titanium).

Ceramics and plastics are the worst (this includes any non-sticking coatings), because, unlike for metals and glasses, their chemical composition is usually kept secret by their manufactures, so you never know what they may leach.

hawski• 4 years ago

Wouldn't iron be the best at least for pans? Also what about enamel?

adrian_b12• 4 years ago

Any kind of iron cookware leaches in food a quantity of iron that is many orders of magnitude greater than all metals leached by stainless steel.

Fortunately, excessive quantities of iron in food are not dangerous for most people, even when the quantity is great enough to give an unpleasant taste to the cooked food.

In any case, iron cookware is preferable to ceramic/plastic/non-sticking cookware of unknown chemical composition.

Etherlord87• 4 years ago

I like the way you think. If you have a pan made of food, does it matter if some food leaches to your food? For a person with iron deficiencies it's hard to argue additional iron is bad, however...

Once your iron gets into contact with oxygen, you will no longer consume iron, you will consume rust...

adrian_b12• 4 years ago

About enamel, that is a complex mixture of various oxides.

All colored enamels have undesirable components.

White enamel can be made perfectly safe for food contact. Unfortunately, being white is not a guarantee for that.

Manufacturers are tempted to include in the enamel composition various oxides that improve the manufacturing properties, e.g. which increase the fluidity of the melted enamel, or which enhance the adherence of the enamel to the base metal, and so on. These additives may leach unwanted substances.

So one may use cookware with white enamel, if they trust that the manufacturer was not too greedy to reduce their costs.

Ideally there should be a law to force all manufacturers of cookware to publish the precise chemical composition of any material used for food contact, like there are laws for labels with the approximate food composition.

Until then, it is safer to distrust any kind of coatings, plastics, enamels or glazes with secret compositions, because in the past there were many bad surprises whenever any of these were analyzed.

bagels• 4 years ago

Is iron cookware really just iron, or is it alloyed slightly?

cjg• 4 years ago

Iron pans are not the best for those with hemochromatosis (iron overload).

cycomanic• 4 years ago

The issue with iron cookware (and I'm a big fan) is cooking acidic dishes in them (which are the ones that mainly cause the leeching) you destroy the seasoning and they become a bit of a pain to clean after that.

eternityforest3• 4 years ago

I'm not entirely convinced that plastics are categorically bad. I suspect they are better than stainless for long term storage of certain things.

There's a lot of plastics that don't commonly get used but are food rated in industrial applications, it would be cool to see them thoroughly evaluated and if they are safe, made into consumer items.

Ceramics are scary because a few have lead in them, but there are safe ones(Just not that you can afford), they're used for surgical implants.

I wonder what the possibilities are with magnesium. It can be extracted from the ocean and is nontoxic enough to just put back where you found it, so it seems to be the closest we have to a renewable metal.

There's also laser etched lotus effect patterns. Do metals still leach after you make them hydrophobic like that? Could you make magnesium corrosion resistant enough?

kmmlng• 4 years ago

I suspect they are better than stainless for long term storage of certain things.

I'm confused, how is that relevant to the topic at hand?

adrian_b12• 4 years ago

The base components of many plastics, e.g. polypropylene, polyethylene, acrylic glass, are perfectly safe for food contact.

The problem is that all plastics contain various additives, which are normally not disclosed by the manufacturer, even in the plastic grades that are approved for food contact.

The risks caused by unknown plastic additives are especially large when the plastics are used above room temperature, e.g. for heating food in a microwave oven.

Storing food in polypropylene vessels or polyethylene bags in a refrigerator is likely to be perfectly safe.

adrian_b12• 4 years ago

As you have said, the problem with magnesium is that it corrodes too easily, so it is not used, even if it is perfectly safe for food contact.

aperson_hello• 4 years ago

Another potential problem with magnesium is its flammability. Look up magnesium fire and you'll understand. Maybe not that likely in most settings (it takes a bit to get it going), but a forgotten pot on a gas burner would worry me.

dataflow• 4 years ago

Where does Teflon fit in this hierarchy?

And by "ceramic" I assume you mean the faux-"ceramic-coated" ones that don't actually contain ceramic, right?

adrian_b12• 4 years ago

Pure ceramic is porous, so it is never used in direct contact with food, because the food will be absorbed in the pores.

In all cookware where the body is ceramic, the surface is covered with some glaze, enamel or plastic coating, which is the material that really counts for food contact.

mschuster91• 4 years ago

The problem with modern Teflon is mostly that people overheat their non-stick pans. The stuff is chemically inert otherwise.

Older Teflon pans and cookware have the problem of PFOA contamination, but that's IIRC been banned for years now.

api• 4 years ago

What about cast iron? It’s very nice to cook with and popular with chefs.

mrspuratic• 4 years ago

When correctly used it only leaches about the last 100 meals into your next meal :)

Maursault• 4 years ago

glass, while perfect for storage, is not suitable for most types of cooking

Such as? Could be I'm simply unaware of "most types of cooking."

curiousllama• 4 years ago

Wouldn’t a glass frying pan shatter?

hammock7• 4 years ago

Anything on a stove or in a fire

lkxijlewlf• 4 years ago

Sauteing. Frying. Well, pretty much any stove top cooking.

I mean, sure, if we want to "well technically" the hell out of it, one could probably use glass if you're careful. But one also has to consider safety and convenience.

morganslaw2• 4 years ago

Ceramics and plastics are the worst (this includes any non-sticking coatings), because, unlike for metals and glasses, their chemical composition is usually kept secret by their manufactures, so you never know what they may leach.

Again, when you refer to ceramics, are you referring to the tons of ceramic coated cookware that is now immensely popular as a replacement for Teflon? Is this stuff just as bad? https://www.goodhousekeeping.com/cooking-tools/a26078798/bes...

adrian_b12• 4 years ago

It is not clear from the advertisements of the vendors what kind of material is used for the so-called "ceramic" coatings.

I believe that they use the word "ceramic" to say that the coating is not made from an organic polymer, like Teflon, but from an inorganic oxide or mixture of inorganic oxides.

The correct meaning of ceramic is a material that before processing is soft and plastic, so you can give it any form you want. Then, after heating at very high temperature in an oven, a.k.a. burning, the finished ceramic product becomes hard.

I am pretty certain that this is not how the so-called ceramic coatings are made.

The cookware that I have seen with "ceramic" coatings had bodies made of aluminum. So I assume that the "ceramic" coatings are mostly of aluminum oxide, probably grown electrolytically or chemically.

True ceramic products consisting mainly of aluminum oxide are very common, so I assume that this is why the "ceramic" coating vendors use the word "ceramic".

Alumina, a.k.a. aluminum oxide, is inert enough in most conditions to be safe for food contact, even if not as safe in contact with acidic juices as glass.

As always, the base material is less concerning than the possible existence of undisclosed additives.

It is possible that the so-called "ceramic" coatings are perfectly safe, but nevertheless I would not buy one unless the vendor would state clearly the composition of their "ceramic".

I have seen too many contrary examples in the past, so that I cannot trust anyone who says "Trust us, it is good for you", without providing additional relevant information.

samatman3• 4 years ago

The distinction you're trying to draw between glass and ceramics doesn't exist, ceramics are generally glazed, which means "covered in a coating of glass".

Enameled pans aren't going to leach anything if you buy them from any reputable manufacturer (which is at least all of the European, American, and Japanese ones) because any colorants added to the glaze will be rated as food safe. In fact, you mentioned titanium: that's what's used to make the inside of white enameled pots look white.

Enameled cast iron (or enameled anything) is a fine choice, it comes with its own limitations culinarily (and advantages) but it isn't going leach anything into your food.

adrian_b12• 4 years ago

You are right that glaze is a kind of glass.

Nevertheless, most glazes have a much more complex composition than the standard borosilicate or soda-lime glasses.

Glazes usually contain colorants and various additives that improve certain properties useful during manufacturing, which do not exist in the glasses used for vessels.

It is possible to make glazes that are perfectly safe for food contact, but historically there were many examples of glazes with harmful components.

Unless a manufacturer provides the composition of the glaze used by them, you cannot know how safe it is.

Moreover, glazes and enamels have a problem that does not exist for stainless steel vessels. The glazes or enamels may crack and expose the base material to the food. However that is somewhat mitigated by their lower price, which facilitates the replacement of the cookware.

plasticchris• 4 years ago

Lots of old glazes used lead, so this isn’t always true. Can’t always judge by words or even appearances.

carlmr• 4 years ago

Enameled pans aren't going to leach anything...because any colorants added to the glaze will be rated as food safe

So we consider stainless steel pans as food safe generally, yet they do leach something. I don't see how food safe could imply that something doesn't leach. Only that we either think it doesn't leach too much or we don't think what it leaches is harmful.

vannevar2• 4 years ago

Enameled cast iron (or enameled anything) is a fine choice, it comes with its own limitations culinarily (and advantages) but it isn't going leach anything into your food.

Has this been verified in practice? Is enamel always pure, or can it contain contaminants that can leach?

b1123• 4 years ago

What bothers me is, people washing and scrubbing their frying pans.

I cook in stainless, and after done just put it in the sink with water. After I eat the food, maybe a half hour later, just dump the water and wipe it with a rag.

Point is, why remove the grease, why remove the seasoned crust on pan. Do people take soap and scrub brush to their bbq too?

You don't need to soap wash, or scrub a frying pan.

This sort of behaviour likely keeps leeching to a minimum, compared to vigorously scrubbing and cleaning each use.

b1123• 4 years ago

Up and down the votes do go,

Ew! Gross, down you know,

Ha, right, up they sow,

Digust is truth's foe!

dtagames2• 4 years ago

Did we skip cast iron? Iron leeching into your food is actually a good thing. There are several brands of excellent cast iron cooking products which should be safe. Staub is one I like.

christophilus• 4 years ago

I love my lodge pans. If you properly clean and oil them, they are as easy to use as non-stick alternatives. For a long while, I didn't believe this, but then I used my parent's pan one weekend, and it was a revelation. Turned out I'd never properly seasoned / kept my pans seasoned.

ramijames• 4 years ago

Curious where copper falls in this list.

giaour2• 4 years ago

Copper is more reactive than steel. Copper cookware (with some rare exceptions) is lined with another metal to prevent food from direct contact with copper during cooking. Traditionally, a thin layer of tin is used for this purpose, though modern copper cookware can sometimes use steel or anodized aluminum.

formvoltron• 4 years ago

Also cast iron and carbon steel both leach iron into food. Iron is now known to cause stress to cells and can even initiate a special form of cell death.

giantg22• 4 years ago

Iron is also known to be essential for human health and intentionally added to many foods.

I can't tell, but maybe your comment was calling that out sarcastically.

margalabargala3• 4 years ago

This is not useful information if not combined with the quantities involved. It's like warning that drinking water is known to raise your blood pressure and has even caused people to die of heart attacks. It's true, but not in the quantities a person usually encounters.

giaour2• 4 years ago

I thought this was actually an important source of dietary iron in the early modern period, though that may be apocryphal.

AlexandrB2• 4 years ago

When I was a kid I noticed that Cheerios are notably high in iron. I threw a bunch of Cheerios into a cup of water and let it mix for many hours on a chemical mixer. The iron fell out and stuck to the stirrer magnet as a small amount of iron filings.

Is this dietary iron different from the iron you get from a pan? Or do Cheerios cause stress to cells and a special form of cell death?

aceazzameen• 4 years ago

I've always wondered about the patina, or carbonized oil, on my cast iron and carbon steel pans. That stuff leeches over time too, and it's probably carcinogenic? Have there ever been any studies on the seasonings on those pans and any potential health effects?

That being said, I love my pans and probably wouldn't stop using them.

giantg22• 4 years ago

And nonstick coatings can also off-gas and be damaged or deteriorate over time.

My big thing about this study is that they claim to use realistic cooking parameters. Some dishes may be cooked 6-20 hours, but how common is that? Wouldn't most dishes be under 1 hour and contain less acid? Seems like they're targeting worst case scenarios, which are plausibly realistic but not typical.

eatbitseveryday2• 4 years ago

What of cast iron?

TAKEMYMONEY2• 4 years ago

It leaches iron. Not "heme iron" (like that found in meat), it isn't absorbed as easily.

This is affected by a number of factors including the acidity of the food, how new the pan is, and how the pan is seasoned

https://ift.onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2...

https://pubmed.ncbi.nlm.nih.gov/10073514/

killingtime74• 4 years ago

You can also use glass only if you use an oven

nayuki• 4 years ago

Even then, you have to worry about glass shattering due to thermal shock. https://www.youtube.com/watch?v=UyhdMa1ikKM

KolenCh• 4 years ago

The list is missing one common type of cookware—cast iron.

amluto• 4 years ago

Does anyone know why most stainless steel pots and pans contain large amounts of nickel? As I understand it, nickel is there to stabilize austenite, which has some potentially nice mechanical properties but is non-magnetic and not great at conducting heat. Nickel is also fairly expensive, so it seems to me that less than expensive alloys without nickel could be preferable.

So why doesn’t everyone use, say, 430 stainless steel pans?

adrian_b12• 4 years ago

The 400 series of steels (without nickel) are not ductile enough for certain kinds of manufacturing technologies.

So cutlery is made with the cheaper 400 series, but pots and other vessels are made from the more expensive 300 series, with nickel, because they need to survive a large deformation from a plane sheet of metal to a deep pot, without cracking during the deformation.

The fact that the nickel also ensures good corrosion resistance against hot acidic food juices is a bonus. The same corrosion resistance could be achieved without nickel, at higher chromium content (superferritic steels), but those steels are too fragile to be formed into vessels from sheets.

Shadonototra• 4 years ago

so back to steaming + glass, thanks

Litost• 4 years ago

For anyone wanting more details on stainless steel and teflon there's a short video on this from nutrition facts (so references the relevant research):

https://nutritionfacts.org/video/stainless-steel-or-cast-iro...

Part of a series of three which includes aluminium:

http://nutritionfacts.org/video/are-aluminum-pots-bottles-an...

and Melamine dishes and Polymide utensils:

http://nutritionfacts.org/video/are-melamine-dishes-and-poly...

Referencing what others have said, it also mentions the Dupont cover up over Teflon, so personally I'm always sceptical of whatever the current advice is, because how long will it be before something surfaces to contadict it etc.???

mark_l_watson• 4 years ago

Stainless steel is better than most alternatives. Slightly off topic, but I like lower temperature cooking. Instead of frying I like to simmer food in different vegetable broths with appropriate spices.

iandanforth• 4 years ago

Sibling discussions seem to contain a lot of hand-waving. I'd love to know the truth about the safety of stainless v plastic v glass etc but we seem to consistently run into two problems. 1. Chemistry is hard and 2. Biology is hard and slow.

The way we describe chemicals is usually component based and not functional. H2O and H2O2 look similar but water and hydrogen peroxide have radically different properties. One is good to drink regularly, the other deadly. Reading that something contains anionic chlorine might be bad, but then again it might be table salt. For more complex chemicals this gets even more confusing.

Then you take this extremely-hard-for-lay-people-to-parse language and try to use it to predict interactions with a human body. Moreover you really care about not just acute (strong, fast) effects but long term cumulative effects. The article is discussing acute effects for allergy sufferers, but what about 10 years of exposure to small amounts of leached nickle? 20? 30?

The possible number of variations on chemicals, the biological systems they can interact with, and the time/effort required to perform rigorous epidemiological studies for each seems like a herculean task we are ill equipped to tackle. I'd love to be told I'm wrong, but it just seems like any discussion of these topics is not just fruitless but genuinely dangerous as it's possible, given the lack of a credible causative structure, to convince ourselves of anything.

perlgeek• 4 years ago

The way we describe chemicals is usually component based and not functional. H2O and H2O2 look similar but water and hydrogen peroxide have radically different properties. One is good to drink regularly, the other deadly.

I don't think this is a fair characterization.

In inorganic chemistry, the ions do matter. Saying that something contains Fe ions is basically all you need to know; Fe 2+ and Fe 3+ can be easily converted into each other through redux reactions, so distinguishing them doesn't provide value.

If you are honest in your communication, you also distinguish between H20 and H2O2, precisely because they aren't equivalent.

Then you take this extremely-hard-for-lay-people-to-parse language and try to use it to predict interactions with a human body.

This part I agree with.

Remember the "free radicals" craze of the 90s (or was it early 00's?) Biologists talked about free radicals in the blood being a potential cause of some damage (was it cancer?), and people started to eat food that would bind free radicals, completely ignoring all the chemistry of the digestive system that stands between the food and the blood.

I'd love to be told I'm wrong, but it just seems like any discussion of these topics is not just fruitless but genuinely dangerous as it's possible, given the lack of a credible causative structure, to convince ourselves of anything.

Basically all research that is published, by its very nature, contributes a small piece of the puzzle. But it's the job of other researchers to interpret that and work towards a fuller understanding, until we have something that is ready for general consumption, both in terms of validating it, and putting it into context.

This is something that we as a society haven't figured out yet. Media loves to report on new science publications, and has a hard time putting the maturity (or lack thereof) and actual impact on daily life into context. But we cannot just blame "the media", we also have to blame ourselves for consuming it.

I'd love to know the truth about the safety of stainless v plastic v glass etc

I think the only thing we can say with certainty is that things that have been around long enough (like cast iron, clay cooking ware etc.) is most likely safe, otherwise we would have noticed it by now.

ampdepolymerase• 4 years ago

I won't put too much stock in unglazed clay cooking ware.

ufmace• 4 years ago

I think the only thing we can say with certainty is that things that have been around long enough (like cast iron, clay cooking ware etc.) is most likely safe, otherwise we would have noticed it by now.

Agree, I think this is the most important part. I think we obsess too much over things that might possibly have some small effect 1% of the time after 30 years or something after you apply a bunch of tricky statistics. Anything that has been used by millions of people for decades, centuries, would have been extremely obvious if it did anything bad.

vannevar2• 4 years ago

We're continuously ingesting plastics and various carcinogens from our food, air and water. I think the contribution from our stainless steel cookware is probably negligible by comparison.

deepsquirrelnet3• 4 years ago

Plants uptake nickel and chromium from soil in small amounts.

Stainless steel leaches nickel and chromium into foods during cooking (2013)

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