Many of us are in contact with stainless steel and aluminum daily, including everything from kitchen cookware and dinnerware to cutlery and food packaging. However, we are surrounded by a tone of diverse information about the safety of these materials so it is sometimes very hard to make any solid conclusions
In this article I have gathered, information from food safety authorities and scientific publications in one place, so you can go out of the post with a clearer idea about the safety of these metals
Moreover, the article will outline all of the important things related to the question: Is stainless steel safer than aluminum? Nevertheless, let’s start with a short answer
Stainless steel is generally safer than aluminum for food contact applications. It has been shown that overexposure to metal components of stainless steel is associated mainly with skin problems such as eczema. However, aluminum exposure has been linked softening of the bones, anemia, and pathological changes in the lungs.
If you want to find more details about this as well as clear references for presented information then further text can give you some important insights.
In addition, apart from just tackling the difference between stainless steel and aluminum safety, in general, the post will go deeper into the safety of stainless steel and aluminum alloys.
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Is stainless steel safer than aluminum?
*In the following text I will commonly use the abbreviations SS for stainless steel and Al for aluminum
First, I will present the comparison table after which I will give more in-depth information.
Stainless steel cookware |
Aluminum cookware |
|
|
Food grade alloys |
Commonly 304 and 316 alloys |
Commonly 1100, 3003, and 3004 alloys |
|
Main concerns |
Leaking of Nickel in the food |
Leaking of aluminum in the food |
|
Health effects |
Skin-related problems: Reference 2 |
More serious symptoms Reference 1 |
|
Tolerably weekly intake for humans(TWI) |
0.91mg of Ni per kg of the body mass* |
1 mg of Al per kg of body mass** |
|
Significance of exposure to concerning metal from cookware |
Bellow the set limitations |
Can overcome set intake limitations if aluminum utensils or packages are exposed to acidic food |
*Calculated based on the maximal daily allowance of 13µg/kg of the body set by the European food safety organization(EFSA)
**Also set by the EFSA
Reference 1– Scientific studies and references summarized in the comprehensive scientific paper about the Migration of aluminum from food contact materials to food
Reference 2– Comprehensive evaluation European Food Safety Authority of the risks of nickel exposure
Now I will present you with deeper insides into the information summarised in the table.
To compare the safety of food-grade Aluminum and Stainless steel alloys, it is first important to understand from which compounds they are made.
Metals like aluminum or stainless steel are not used as pure for most applications but they are alloyed(mixed) with other metals and minerals to get desired properties. However, these additional compounds can also have significant health impacts.
Food grade Aluminium alloy composition
Aluminum alloys used for the food contact application belong mainly to the 1000 series which are characterized by having Al purity >99%(1). From these series 1100 alloy is one of the most common ones(2).
In addition, aluminum alloys 3003 and 3004 can be also frequently found in cookware and cans. Unlike the 1000 series, they have a higher amount of added elements such as Manganese, Magnesium, Silicium, and Iron to adjust their physical properties.
Food-grade Stainless steel alloys composition
Stainless steel is mainly composed of iron. Moreover, nickel is added to steel to increase the overall ductility and steel-forming abilities. (8), while chromium is imputed to improve the stainless steel’s corrosion resistance by forming a chromium-oxide protective film on the metal surface. (9)
Main health concerns of Aluminium cookware
Main concerns about using aluminum come from Al leaking into food. Other elements are present in a very small percentage(less than 1.5% of mentioned alloys).
Main health concerns stainless steel cookware
In Stainless steel, the presence of chromium and nickel can be higher than 10% for each, so their percentage is quite significant. Unlike Chromium and Iron, Nickel is not essential for the human body and it is not used as a part of the enzymes or other molecules with function in normal metabolism(10).
Moreover, it has been found that 12-15% of women and 1-2% of men in the general population show an allergy to this metal(11)
Related to that, nickel is commonly addressed as one of the primary health concerns coming from stainless steel.
Health effects of Aluminum
The toxic effect of aluminum are affecting multiple organs in the body. However, many claims have been made on the topic of aluminum’s health impact, so it is important to distinguish which information is really relevant.
Even the Aluminum has been related to Alzheimer’s disease, some final judgments from Health and food safety authorities have concluded that there is no proven link between these two. A good example can be the latest statement of the German Federal Institute of Risk assessment (3.)
As it has been concluded in one of the big scientific reviews on Aluminium toxicity, coming from German scientists a few direct connections between aluminum and disease have been confirmed up to now including hemodialysis encephalopathy, softening of the bones, anemia, and pathological changes to the lungs (4.)
Health effects nickel from SS
Following the conclusions of the European Food Safety Authority, the main health effects of nickel are associated with elicitation eczematous flare-up reactions in the skin (SCD) in nickel-sensitized individuals(allergic individuals), following oral ingestion.
However, they concluded that there No clear signs of Nickel neurotoxicity have been reported in the few available studies. Additionally, No data linking cancer in humans with oral exposure to nickel are available (12).
Prescribed uptake Limitations of Aluminium
Because of the proven negative impact on health Europen Food Safety Authority(EFSA) seated the weekly limit for Al uptake at 1mg of Al per 1 kg of body weight(5). So, for a person of 70kg that will be a limitation of 70mg of Al weekly or 10mg daily. In this document, you will find an EFSA summary of research data and expert opinion regarding Al toxicity(5).
Prescribed uptake limitations of Nickel from SS
In 2013 the Council of Europe (CoE) published the latest limitations on metals that can be found in Stainless steel
These included specific release limits for iron, nickel, chromium, manganese, and molybdenum. CoE set the maximal daily Nickel intake of 0.14mg per kg of food also known as the specific release limit (SRL). Here you can find the CoE guidelines abstract in English. The full document can be downloaded for free only in Slovenian language(you can find more information about nickel leaking on page 77).
Significance of Aluminum leaking from cookware
Some of the previous studies have shown clear evidence of aluminum leaking from dishes in amounts significant for reaching Al intake limitations set by EFSA.
A comprehensive scientific study has been done on the leaking of AL from aluminum-based camping utensils. It has been shown that when they are exposed to oil or tap water, significant aluminum leaking hasn’t been observed(less than 5mg/L) (7).
However, in water with 0.5% citric acid (the simulant of acidic liquids) or preparing a fish with marinade have been cooked for 2h in mentioned utensils the leaking was respectively 638 mg/L of acidic liquid and 74mg/kg of marinated fish.
This means that by consuming just 10g of acidic liquids cooked in aluminum cookware for one week you will reach 63.8% of the Aluminum Tolearable Weekly intake for a person of 70kg.
By consuming the 250g of marinated fish daily on weekly bases you will reach 187% of the TWI.
Significance of Nickel leaking from cookware
So how significant the leaking of Ni(and other elements from SS) is? Can it impact health in a significant way?
This is exactly what the team of stainless commission of the internationally-renowned institute KTH(Royal Institute of Technology) in Sweden did.
They tested seven grades of stainless steel and demonstrated metal leaking amounts are below the Specific Release Limits (SRLs) settled by the CoE guidelines. This was information that I have get by reviewing the study. Similar conclusions based on mentioned KTH study and set Nickel intake limitations have been made by the experts from the Nickel institute dedicated to applications of this metal across different industries. You can find their conclusion here(Look on page 6.).
Food grade Aluminium alloy composition
Aluminum alloys used for the food contact application belong mainly to the 1000 series which are characterized by having Al purity >99%(1). From these series 1100 alloy is one of the most common ones(2).
In addition, aluminum alloys 3003 and 3004 can be also frequently found in cookware and cans. Unlike the 1000 series, they have a higher amount of added elements such as Manganese, Magnesium, Silicium, and Iron to adjust their physical properties.
Main health concerns of Aluminium cookware
Main concerns about using aluminum come from Al leaking into food. Other elements are present in a very small percentage(less than 1.5% of mentioned Alloys).
Health effects of Aluminum
The toxic effect of aluminum are affecting multiple organs in the body. However, many claims have been made on the topic of aluminum’s health impact, so it is important to distinguish which information is really relevant.
Even the Aluminum has been related to Alzheimer’s disease, some final judgments from Health and food safety authorities have concluded that there is no proven link between these two. A good example can be the latest statement of the German Federal Institute of Risk assessment (3.)
As it has been concluded in one of the big scientific reviews on Aluminium toxicity, coming from German scientists a few direct connections between aluminum and disease have been confirmed up to now including hemodialysis encephalopathy, softening of the bones, anemia, and pathological changes to the lungs (4.)
Prescribed uptake Limitations of Aluminium
Because of the proven negative impact on health Europen Food Safety Authority(EFSA) seated the weekly limit for Al uptake at 1mg of Al per 1 kg of body weight(5). So, for a person of 70kg that will be a limitation of 70mg of Al weekly or 10mg daily. In this document, you will find an EFSA summary of research data and expert opinion regarding Al toxicity(5).
Significance of Aluminum leaking from cookware
Some of the previous studies have shown clear evidence of aluminum leaking from dishes in amounts significant for reaching Al intake limitations set by EFSA.
A comprehensive scientific study has been done on the leaking of AL from aluminum-based camping utensils. It has been shown that when they are exposed to oil or tap water, significant aluminum leaking hasn’t been observed(less than 5mg/L) (7).
However, in water with 0.5% citric acid (the simulant of acidic liquids) or preparing a fish with marinade have been cooked for 2h in mentioned utensils the leaking was respectively 638 mg/L of acidic liquid and 74mg/kg of marinated fish.
This means that by consuming just 10g of acidic liquids cooked in aluminum cookware for one week you will reach 63.8% of the Aluminum Tolearable Weekly intake for a person of 70kg.
By consuming the 250g of marinated fish daily on weekly bases you will reach 187% of the TWI.
Food-grade Stainless steel alloys composition
Stainless steel is mainly composed of iron. Moreover, nickel is added to steel to increase the overall ductility and steel-forming abilities. (8), while chromium is imputed to improve the stainless steel’s corrosion resistance by forming a chromium-oxide protective film on the metal surface. (9)
Main health concerns stainless steel cookware
In Stainless steel, the presence of chromium and nickel can be higher than 10% for each, so their percentage is quite significant. Unlike Chromium and Iron, Nickel is not essential for the human body and it is not used as a part of the enzymes or other molecules with function in normal metabolism(10).
Moreover, it has been found that 12-15% of women and 1-2% of men in the general population show an allergy to this metal(11)
Related to that, nickel is commonly addressed as one of the primary health concerns coming from stainless steel.
Health effects nickel from SS
Following the conclusions of the European Food Safety Authority, the main health effects of nickel are associated with elicitation eczematous flare-up reactions in the skin (SCD) in nickel-sensitized individuals(allergic individuals), following oral ingestion.
However, they concluded that there No clear signs of Nickel neurotoxicity have been reported in the few available studies. Additionally, No data linking cancer in humans with oral exposure to nickel are available (12).
Prescribed uptake limitations of Nickel from SS
In 2013 the Council of Europe (CoE) published the latest limitations on metals that can be found in Stainless steel
These included specific release limits for iron, nickel, chromium, manganese, and molybdenum. CoE set the maximal daily Nickel intake of 0.14mg per kg of food also known as the specific release limit (SRL). Here you can find the CoE guidelines abstract in English. The full document can be downloaded for free only in Slovenian language(you can find more information about nickel leaking on page 77).
Significance of Nickel leaking from cookware
So how significant the leaking of Ni(and other elements from SS) is? Can it impact health in a significant way?
This is exactly what the team of stainless commission of the internationally-renowned institute KTH(Royal Institute of Technology) in Sweden did.
They tested seven grades of stainless steel and demonstrated metal leaking amounts are below the Specific Release Limits (SRLs) settled by the CoE guidelines. This was information that I have get by reviewing the study. Similar conclusions based on mentioned KTH study and set Nickel intake limitations have been made by the experts from the Nickel institute dedicated to applications of this metal across different industries. You can find their conclusion here(Look on page 6.).
Conclusions:
The presented information leads to the conclusion that aluminum cookware and utensils present a much higher risk to health compared to food-grade stainless steel. However, based on provided information you can make your own judgment.
In summary, it has been shown that the Leaking of Aluminum from utensils to food can be significant compared to the allowed weekly intake, set by food safety authorities.
Additionally, aluminum exposure in humans has been linked to some serious health (encephalopathy, softening of the bones, anemia, and pathological changes to the lungs).
On the other side, the stainless steel saint showed the leaking of the component metals in amounts that exceed the limitations set by the Council of Europe.
Moreover, the leaking of nickel, one of the SS component metals that have a bad reputation, has not been shown to be related to serious health problems(but mainly skin irritation issues).
*To find out more about nickel exposure and skin-related issues take a look at my post about stainless steel safety here.
But, since there are many Al and SS grades can we apply the presented conclusions in general? What about the Hard anodized Aluminum?
Does the grade of stainless steel or aluminum matter? Is hard anodized aluminum different?
Stainless steel grades used as food contact materials can have small variations in nickel, chromium, and iron amounts. The exception is the 18/0 Stainless steel which is made completely without nickel and can potentially be a good option for individuals that have problems with eczema and allergy to nickel.
Even such cookware is not common, there are a few brands available on amazon.
When it comes to aluminum, the question is, does the conclusion from the previous chapter about classic aluminum utensils apply to Hard anodized aluminum?
Hard anodization of aluminum is a process of making the material surface stronger. Basically, the process involves immersing the aluminum into the cold acid solution (electrolyte), and running a high-voltage electric current through the acid solution(1.). The result is the creation of a thick coating of aluminum oxide, through which the metal surface usually gets a dark brown or black surface.
However, there are not many studies that have tested the significance of aluminum leaking from hard anodized aluminum surfaces. Additionally, I haven’t found any available expert information about the safety of this material for food contact applications.
So, till a certain number of scientific publications will be available about this it will be hard to say more about does Hard anodized aluminum trigger fewer or more health concerns compared to conventional aluminum cookware.
Finally, let’s cover some practices that will help you to avoid exposure to metal leaking from your metal cookware. This can be very important in the case of bare aluminum utensils to reduce the ingestion of aluminum potentially significant to your health.
Additionally, In the context of stainless steel, these practices will help you to avoid exposure to nickel if you are having the described skin problems and if you use the stainless steel grades that contain this metal.
Which cooking practices to minimize metal leaking?
It has been shown that both Stainless steel and Aluminium cookware can leak certain amounts of metals into the food. In the case of aluminum, these amounts can be significant contributors to passing the limit of daily aluminum intake.
Additionally, as concluded, the leaking of metals from stainless steel is not sufficient to overcome the limits of allowed exposure of these metals (namely: chromium, nickel, and iron). However, in people sensitized to nickel it could be important to minimize nickel exposure in general, so avoiding certain practices with stainless steel utensils can be beneficial.
The leaking amounts of metals from cookware vary depending of course on the amount of the acidic ingredients(final Ph of the dish), the amount of the liquid in the dish, temperature and duration of cooking.
Finally, some studies show the amount of metal leaking in totally new stainless steel cookware drops significantly during the first several uses(13).
To explain more practically which rules I apply in my cooking to avoid excessive metal exposure I would highlight several cases:
-When I bought a new stainless steel piece, for the first few times I cook something that I would not eat(e.g. a bit of rice), that I would later use for making compost e.g.
-Personally, I consider that avoiding fruit-based sauces(e.g. blueberry sauce), tomato-based sauces, vinegar, lemon juice, and acidic marinades is a good practice. Mentioned ingredients have a low Ph(e.g. about Ph of 2 for lemon juice and vinegar) which can contribute to increasing metal leaking.
– I would consider using several ml of vinegar or 10 ml of lemon juice over 1L of a dish as not significant.
-Additionally, If I cook something very fast(5min or less) even if it is an acidic sauce I won’t consider it a problem. This commonly happens when I want to e.g. mix some acidic sauce with pasta base in the pan just before serving to plates.
-When preparing the tomato-based stew, or braising meat in red vine stock I would definitely go for pure ceramic cookware or enameled cast iron. I would avoid cooking with SS or Aluminium cookware with acidic food for such a long time
Such practices are based on considering available scientific publications, where most of the studies have investigated the significance of metal leaking from cookware after an hour or a few hours of exposure to food. Moreover, there have been no studies to the best of my knowledge that investigated or showed the significant metal leaking(from aluminum or stainless steel cookware) to food after 5 or 10 minutes of cooking.
Finally, in the case of aluminum, we are not only exposed to it significantly only through cookware and utensils. Moreover, there is a wide range of other sources like food, water, and drugs.
Find more about this in my in-depth review on aluminum foil safety. Because of this, it is important to limit any potential aluminum exposure sources, including aluminum cookware and dishes.
Here you can find some other steps that you can take to reduce your aluminum intake from different sources to which we are exposed.
Even Stainless steel is a great option for various kitchen applications in terms of safety and performance, many people question if its performance is comparable to some other conventional cookware like nonstick ceramic utensils. In order to find out more about that topic you will be able soon to take a look at my article here.
