We live in a world that contributes to an increasingly high toxic burden, thanks to pollution, a growing dependence on chemicals, use of pesticides, and other potential environmental contaminants. Although the effect on human health may remain somewhat up for debate, more and more studies point to a link between an increased toxic burden and a variety of chronic diseases, such as heart disease, reproductive health problems such as PCOS, neurological disorders, and metabolic syndrome.
As I’ve discussed in previous blogs, there are ways to mitigate your exposure and support the body to detox and reduce your individual burden. Choosing what type of food can go a long way toward alleviating your toxic burden and improving your natural detox capabilities, but it may not be enough. Some cookware (e.g., pots, pans, skillets, baking sheets) leaches chemicals and heavy metals into the foods you cook, which you then consume, adding to your body burden and mitigating some of the cleaner choices you may have made in food selection.
You may have seen some things around the internet about which cookware to avoid and which to use. Let’s see whether this holds up to what the scientific evidence has to say.
Potential Toxins in Cookware
Heat can increase the chance of toxins leaching into food, making cookware an important place to start when trying to detox your kitchen. When you go shopping for new pots and pans or other cookware, you have a wide range of choices before you, including stainless steel, copper, nonstick pans like Teflon, cast iron, ceramic, glass, and more. Not only does each type have unique characteristics in terms of cooking and cleaning, but the cookware materials also have different risks in terms of potential toxic exposure.
First, let’s take a look at the potential toxins in certain cookware materials:
Aluminum is used in many different consumer products, including cookware, especially single-use cookware. Additionally, it is common to use aluminum foil during grilling and cooking to make cleanup easier. However, cooking with aluminum may increase the risk of aluminum exposure, as it might leach from the foil or cookware. One study found that cooking with aluminum pots could add to the aluminum burden and may even exceed the daily limit, especially when cooking acidic foods. In this study, cooking with oil and water did not lead to a level of aluminum in excess of the specific release limit.
Artisanal aluminum cookware, which is more often found in developing countries, may also leach lead and cadmium in addition to aluminum. One study did find that pre-treating the cookware though boiling water prior to using it to cook reduced the amount of aluminum leached into the food. If you plan to do this, just be sure to discard the water!
Why does it matter that aluminum may find its way into your food when you cook? For decades, there has been a hypothesis that aluminum increases the risk of the development of Alzheimer’s disease, and there is compelling evidence demonstrating a potential health impact of aluminum. Aluminum has also been linked to increased risks of osteomalacia, microcytic anemia, and contact allergy. Certain populations, such as infants and children, may be at a higher risk. Some of the health problems may occur more from chronic use, higher exposure levels, or compounded levels rather than a one-time, small-dose exposure.
Other Heavy Metals
In addition to aluminum, some cookware may also release other heavy metals, adding to the body’s burden. Some of the heavy metals come from the glazes or coatings, while others are related to leaching from stainless steel.
Cadmium is one heavy metal that may leach from certain glazes and coatings on pots and pans, including glass and ceramic. Cadmium is a known toxic byproduct of smoking, so many of the studies on the health impact of the heavy metal are in regards to tobacco use. The International Agency for Research on Cancer lists cadmium as a Group 1 human carcinogen. It is also associated with chronic inflammation and chronic disease associated with inflammation, including cardiovascular disease, peripheral arterial disease, diabetes, and psoriasis. It has also been associated with age-related macular degeneration.
One study found that even low levels of cadmium exposure could cause problems, with the highest quintile of serum cadmium levels having an association with a 0.18 ft/sec reduction in gait speed, which may correlate with reduced physical performance during aging that could be associated with vascular, musculoskeletal, and cognitive dysfunction. There is also an association between cadmium toxicity and Alzheimer’s disease mortality. Blood cadmium levels have also been found to be inversely associated with telomere length, which means higher cadmium levels may lead to shorter telomeres, which is associated with aging.
The knowledge of the potential health risks of lead toxicity has become more common knowledge, with many regulations in place to prevent exposure by governmental organizations such as the FDA. However, some cookware products, especially older ones (made pre-1970), may still have lead in them, especially decorative ceramic or glass. The origin of the ceramic or glass may impact the level of lead. For example, a study in 2014 found that even after government interventions, around 90% of glazed ceramic pots from Mexico not labeled lead-free still contained lead, although this study did not test them to see if they were leaching into the food.
Another study compared ceramics from within Chinatown in Philadelphia with those found outside of Chinatown and found those in Chinatown were more likely to have a positive result in a lead screening test (21 of 86 in Chinatown compared to 4 of 46 outside of Chinatown), although the majority of these were still within the FDA-approved levels. This difference was not statistically significant, but it does show the importance of knowing the origin of your cookware.
Perfluorooctanoic acid (PFOA)
Although Teflon was once the king in terms of cookware due to its nonstick properties, the discovery of potential health problems due to leaching of two chemicals (PTFE and PFOA) have led to some changes in the nonstick pan industry.
Exposure to PFOA is not from just Teflon and other nonstick pans; it is a chemical pretty ubiquitous in the environment, and most people have at least some levels of it in their blood. For example, a recent study using data from NHANES 2013 – 2014 found that in children aged 3 – 11 years, there was PFOA in all children with a geometric mean of 1.92 ng/mL, which was comparable to those of adolescents and adults. These levels were even in young children born after certain regulations were in place for PFOAs. PFOAs can also get into breast milk, which may also impact the health of infants. There is some data that women who use older Teflon pans have higher levels of PFOA in their breastmilk than those with newer pans.
Recent studies on animals have also pointed to the potential for PFOAs to act as endocrine disruptors, which could have an impact on reproductive health. There have been positive associations between PFOA and high cholesterol risk, elevated uric acid, cardiovascular disease, diabetes, cancer risk, thyroid disease, and allergic inflammation. A recent systematic review found associations between exposure in childhood and an increased risk for dyslipidemia, immune dysregulation, asthma, renal function, developmental and neurological problems, and more. PFOA is listed as a possible carcinogen in humans (Group 2B) by the International Agency for Research on Cancer (IARC).
Because of the extensive evidence demonstrating the potential hazards of PFOA, some Teflon and nonstick pans post-2015 have chosen to eliminate PFOA, but that doesn’t necessarily make the new pans safe, as will be discussed. It is worth it to check your kitchen for any Teflon or nonstick pots and pans that may contain PFOAs and replace them with a safer variety.
The other main chemical of concern in nonstick and Teflon pots and pans is polytetrafluorethylene (PTFE). Back in 2005, the Environmental Working Group conducted tests on Teflon and found that even in conventional uses, Teflon pans would reach temperatures that led to the release of hazardous chemicals, which could lead to something known as polymer fume fever.
The longer a PTFE-covered pan or pot is used, the more likely for chemical leaching. One study found that at normal use, the emissions of PFCAs from pans with PTFE surfaces were about 4.75 ng per hour, while pans that were overheated led to more, with cooking at a 370-degree temperature leaching 12,190 ng per hour. However, these still would most likely remain below the TDI, which is 1,500 ng PFOA per kg body weight.
What to Avoid
Based on this list, it is best to avoid Teflon and other nonstick pans, especially those made with either PTFE or PFOA, as well as aluminum pots and pans. Additionally, you want to pay special attention to any types of glazes and coatings to ensure they will not leach heavy metals, including cadmium, nickel, and lead. Knowing the age and source of the materials can also help you decide whether it may or may not be safe.
Potentially Risky Cookware:
There are some cookware options that fall in the middle, meaning they may be potentially risky, especially for some populations, but they are safer than those above. Some of these also do not yet have sufficient evidence to determine their safety.
- Copper – Copper cookware falls into the grey area because too much copper can be toxic, but any copper leached into food through the cookware may also be a good source of copper for those with a deficiency. Certain foods (such as acidic foods) may make it more susceptible to leaching, similar to other cookware. Thus, if you use copper cookware, you may want to check your copper levels from time to time or rotate this cookware with pots and pans made from other materials.
- Silicone – There is not as much research into silicone bakeware and cookware as some of the other materials. One study did find that certain foods leached some silicone into the food. Specifically, meatloaf had 177 mg kg of siloxane migrated from a silicone baking mold, while milk-based foods had less than 2.4 mg kg. Another study found that migration was dependent upon fat content, although in 10 different experiments, it never was higher than 21 mg kg, which is lower than the limit of 60 mg kg. Most of the research into the impact of silicone on health is in regard to silicone breast implants rather than ingesting small levels of silicone via leaching into food, so for now, we will just have to watch this space.
- “Green” Cookware – Many manufacturers have turned to other substances to create their nonstick cookware, but it is unknown whether some of these substitutions are actually safer than PFOA. We will just have to wait for more research before determining if they truly are safe.
Safer Cookware Options:
If you want to reduce your risk of toxic exposure as much as possible, then you want to focus your cookware purchase on the following materials, which do not have as much risk for leaching chemicals and heavy metals. However, as you will see, they also have some potential health hazards.
Ceramic and Glass
Ceramic and glass cookware have become increasingly popular as a safer option, and for good reason. They do not leach as many chemicals or heavy metals; however, some may still have some potential hazards. As discussed above, coatings or decoration may have lead or cadmium in them. Additionally, certain metals, specifically lead, nickel, and cadmium, may leach from ceramics in certain conditions, largely based on the techniques for decoration and manufacturing as well as the material composition. Glass may also have heavy metals in it, and in some conditions, it may be possible for it to leach.
As with the other cookware discussed above, leaching is more common with acidic foods than others. The source of the ceramics also may determine the risk of any metal leaching. One study found that the levels of nickel and chromium migrating from generally available decorative Polish glassware and ceramics was minimal with little risk for health. However, more sensitive individuals may still react, depending on the situation. Another study looking into 1,273 samples of ceramics and glassware meant to come into contact with food (although not many intended for cooking) in the EU found lead and cadmium leaching, but they were typically below permissible limits and usually below analytical detection limits.
Cast iron is generally considered one of the safe metals for cookware. Although the iron may leach into food, it is generally at small amounts that only add to the average person’s daily amount. Since iron is one of the nutrients of concern, cooking with cast iron can increase the iron content of food and actually help reduce the risk of anemia.
A systematic review found using cast iron a promising intervention for iron deficiency, but that additional research was necessary. However, one study found that after six months of using cast iron cookware, there was no significant difference in the hemoglobin levels of known anemic children and adolescents and women, although there was a significant difference in the serum ferritin levels. It is important to note that this study used a control group taking iron supplements.
Because iron does leach from the cast iron pots and pans, there is a risk of iron overload, especially in certain populations such as those with hemochromatosis. As with many nutrients, a balance is necessary, and excess levels of iron could cause issues including liver problems, heart disease, and other health problems.
Stainless steel is another generally safe option, but there are still potential risks. Stainless steel may have some heavy metals in it, such as nickel and chromium, that can leach, especially when cooking acidic foods. Additional factors that may impact the risk of heavy metal leaching include the quality of the steel, the type of foods being cooked, and the cooking time and temperature.
In one study, metal leaching (specifically nickel and chromium) was more likely with longer cooking times and newer stainless steel. This study tested three different grades of stainless steel and a commercially available stainless-steel saucepan and used acidic foods (tomato-based sauce) for the testing, which are known to lead to an increased risk of metal leaching. Cooking times between 2 and 6 hours had no significant increases in the metal leaching, but longer cooking hours, especially 20 hours, led to a 95-fold increase in nickel and a 9-fold increase in chromium levels. Another study using grade 316 stainless steel pots found that lower pH and unused pots led to more leaching of nickel and chromium. They did conclude that for the majority of subjects, the levels remained safe under common conditions. However, an individual may be more susceptible, such as those with a sensitive allergy.
Thus, when you choose your ceramic, stainless steel, or glass cookware, you need to ensure they are of high quality and do not have any coatings that may leach heavy metals or other toxins. Additionally, you want to avoid cooking with any acidic foods, as this could increase the chance of leaching, as well as avoid cleaning with abrasive sponges or other cleaning utensils so they do not get scratched, as this could lead to flaking and other damage that could lead to leaching.
Tips for Choosing Safe Cookware
Based on research, the safest cookware is that made of ceramic, glass, cast iron, or stainless steel, especially higher qualities without contaminated glazing. However, it is not always possible to do a complete kitchen detox, so there are a few ways to make your kitchen as clean as possible within your budget and other hurdles you may face:
- Look for cookware that does not have a note with a California Prop 65 warning, since it is a pretty rigorous law that requires posting a notice if an item has any chemicals or toxins known to cause cancer, reproductive harm, or birth defects.
- Use non-abrasive sponges to clean any metal or nonstick cookware to avoid hurting it and releasing the chemicals in flakes.
- Line bakeware with unbleached parchment paper—avoid using aluminum foil for this.
- If your budget does not allow you to replace everything at once, especially since many of the safer varieties also come with a hefty price tag, start with the pot or pan you use the most.
If you have additional concerns about the impact of any chemical or heavy metal leaching from your cookware or other kitchen items, talk with your doctor or another healthcare practitioner about the best course of action for your situation.