Do not misunderstand the purpose of this article. There is no need to freak out, throw out all of your stainless steel, and spend a small fortune on new pots and pans! The purpose of this information is to inform you about how to choose the best stainless steel cookware, and further, how to use it wisely in your home. This article on silicone kitchenware offers similar guidelines.
The human body is an amazing thing. Complex defenses allow us to handle a wide range of toxins and troublesome compounds within reason. Making sure that you know how to use stainless steel cookware properly will keep you from testing Mother Nature’s limits!
Not all Stainless Steel is the Same
Stainless steel comes in a wide range of grades and types.
The grade of stainless steel is usually identified by three numbers such as 302 or 304. These digits are used to describe the overall quality, durability, and temperature resistance of the steel. The second number associated with stainless steel comes paired, such as 18/10 or 10/0. This indicates its composition, giving the percentage of chromium and nickel used in the alloy.
304 stainless steel is the same as 18/8. It is often called surgical stainless steel. It is also the minimum type one should purchase for cookware!
18/8 and 18/10 are the most common types used for stainless steel cookware and food applications. Many other grades and types of stainless steel abound, and you can learn more about them all here (1).
Because stainless steel is a poor conductor, many higher quality stainless steel cookware sets use stainless steel only as a cladding on an aluminum or copper core or a bottom plate of more superior conductive materials.
Why are Toxic Heavy Metals in Stainless Steel?
Steel is primarily comprised of iron, with a small amount of carbon. Iron has a few problems, such as easily succumbing to rust. Rust is a type of corrosion (2). If you have cast iron cookware, you are used to keeping it well “seasoned”. This means protecting the iron from moisture and air that combine to form rust. This is accomplished by creating an oil based coating/barrier.
Some metals are more resistant to rust and other forms of corrosion than others. Chromium and nickel happen to be two such elements. When combined with iron, the trio of metals create a far more corrosion resistant final product. So these heavy metals are added to stainless steel to make the final product more durable, reliable, functional, and beautiful.
The downside is that both of these heavy metals are well known health triggers for some individuals. Acute contact dermatitis (ACD), occurs in about 10% of people exposed to nickel, usually women. Cheap earrings are a common way a person becomes aware of a skin sensitivity to nickel.
Not a single cell in the human body requires nickel
It is important to note that there is currently no known biological need for nickel for humans!
While some species do require it for proper functioning, any nickel we are exposed to must be removed by and from our bodies. If this does not occur for whatever reason, heavy metal poisoning can be the result over time.
As a result, the addition of heavy metals to stainless steel may improve its practicality, but it also renders these products more dangerous to health when not used wisely.
Let’s examine how much chromium and nickel in our stainless steel cookware may actually end up in our culinary creations and ultimately, in our bodies.
The Science of Cooking with Stainless Steel
Using some types of cookware adds molecules of the cookware’s materials to our food. This can really add up as we prepare meals day in and day out.
A well known example of this is cast iron, which adds small amounts of iron to our food. While this is widely believed to be beneficial, for some people it is not. Adult men and menopausal women, for example, should carefully watch their iron levels if they cook with cast iron regularly. Too much iron is a little known but very real cardiovascular risk, especially for those that don’t donate blood or eat a lot of iron rich foods (4).
The more acidic the foods, the more we stir, and the longer we cook, the more of these molecules likely end up in our meals.
Stainless Steel Cookware: Not as Inert as Believed
Stainless steel is often touted as an inert, quality alternative to cookwares with questionable, dangerous non-stock coatings like teflon that easily up end in our air and our food. However, it is far from being immune to making additions to our dishes, especially of the heavy metal variety.
How much heavy metal leaching is actually happening when you cook with stainless steel? It appears under certain circumstances a substantial amount! According to the Journal of Agricultural and Food Chemistry:
After a simulated cooking process, samples were analyzed by ICP-MS for Ni and Cr. After six hours of cooking, Ni and Cr concentrations in tomato sauce increased up to 26- and 7-fold respectively, depending on the grade of stainless steel. Longer cooking durations resulted in additional increases in metal leaching, where Ni concentrations increased 34 fold and Cr increased approximately 35 fold from sauces cooked without stainless steel.
Cooking with new stainless steel resulted in the largest increases. Metal leaching decreases with sequential cooking cycles and stabilized after the sixth cooking cycle, though significant metal contributions to foods were still observed. The tenth cooking cycle, resulted in an average of 88 μg [micrograms] of Ni and 86 μg of Cr leached per 126 g serving of tomato sauce. Stainless steel cookware can be an overlooked source of nickel and chromium, where the contribution is dependent on stainless steel grade, cooking time, and cookware usage. (5)
Nickel and Dined
What are the risks of excessive chromium and nickel from cooking with stainless steel cookware? First of all, the health risks from the nickel are worse than from the chromium. For this reason, it is best to stick with higher chromium stainless steel cookware. Our body needs chromium albeit in small amounts. There are also many biological defenses against excess intake (6).
One word of caution. If you cook with stainless steel a lot and eat foods that are known to be high in chromium, it may be best to check your supplements and diet carefully. Excessive chromium in any supplements you take can move you toward dangerous intake levels. Foods high in chromium include brewers yeast, grassfed beef, free range eggs, oats, broccoli, and sweet potato.
Since we have no dietary or biological need for nickel, its presence in stainless steel is far more concerning. Extremely sensitive individuals may not be able to use stainless steel cookware at all.
Lower quality stainless steel cookwares increase these dangers dramatically. Cheaper stainless steel will possibly leach significantly more nickel and other metals into foods.
SS everywhere, including coffee to drink
Also note, stainless steel (SS) is used in a wide variety of food applications. This includes such common appliances as coffee machines, crockpots, and stockpots. These are another source of regular and possibly high exposure, especially since coffee is very acidic (7).
Long simmering bone broth enhanced with a bit of vinegar to improve mineral status in the stock can be risky to cook in stainless too.
Don’t assume because you skipped out on stainless steel cookware you are safe from exposure!
10 Tips for Safe Exposure to Stainless Steel Cookware
Below are some helpful rules are thumb and general guidelines for safely cooking with stainless steel.
- For acidic cooking, ceramic coated cast iron such as Le Creuset and Lodge are a good idea. Glass cookware is an excellent and very affordable option as well. Copper cookware is safe too, though it is quite pricey. Copper is something our bodies actually needs. In addition, the amounts produced even under acidic cooking conditions are well within our dietary requirements (4).
- For longer cooking and acidic foods, such as tomato based sauces or slow simmering of stocks, use alternate cookware. Safe options include certified toxin free clay pots (such as Vita-Clay), glass, or ceramic coated cast iron. While convenient, stainless steel pressure cookers are not ideal for cooking these items.
- After about a half dozen cooking cycles, the amount of nickel and chromium leached into food reaches a stable and far lower amount than at the start. As a result, it is recommended to thoroughly wash new stainless steel cookware and then put it through a number of cooking cycles with a weakly acidic solution. Half water and half white vinegar is a good mixture to use. Pasteurized or raw ACV may be used instead if you wish to avoid (GMO) corn derived products. This process will remove the excess surface and outer layer metals. After this is done, cooking neutral or alkaline foods in stainless steel presents little risk. If you are exceptionally heavy metal sensitive, however, you may still wish to opt for non-stainless steel cookware for all meals.
- For acidic foods, a significant amount of chromium and nickel continues to leach into food from stainless steel even after years of use. Hence, choose other kitchen equipment for these dishes!
- Purchase only 304 or higher surgical stainless steel products. Avoid 200 series stainless steel. If you can afford it, 400 series is generally the best, but often pricey.
- If you are nickel or chromium sensitive, or test high for either of these metals, you may need to switch to alternate cookware. Also consider other stainless steel items you expose yourself to, such as coffee makers and more. You may be getting more nickel exposure than you realize.
- If you can afford it, some stainless steel cookwares use a cladding of extremely high grade 430 stainless steel. This equipment contains a minimal amount of nickel, but still contains chromium. For those who are sensitive to nickel, this would be another alternative to take advantage of the positives and minimize the negatives of stainless steel cookware.
- Be aware that most restaurants cook almost exclusively in stainless steel. If you are sensitive to nickel or chromium or already have a diagnosed problem with excess heavy metals, it is best to avoid ordering tomato based dishes or other acidic foods when eating out.
- Bottled store kombucha, an acidic beverage, is typically brewed in large stainless steel vats. It is best to avoid commercial kombucha for this reason. Be sure to brew kombucha or Jun tea in glass or tested, toxin free ceramic when made at home. Store these beverages only in glass as well.
- Because aluminum is sometimes sandwiched in between stainless steel layers in SS cookware, if your cookware becomes scratched or damaged (say by rust), you may also be adding brain impairing aluminum into your meals as well. Make sure you take good care of your stainless steel and recycle it if it becomes damaged in any way!
Informed consumers are safe consumers especially when it comes to kitchen equipment made with stainless steel!
John Moody is an author, speaker, farmer, homesteader, and Real Food activist. Most importantly, he is husband to an amazing wife and five awesome kids. John speaks nationally at a wide range of events, along with writing for numerous publications and consulting for farmers, homesteaders, and food businesses.
He recently published his first book, The Frugal Homesteader: Living the Good Life on Less.