With inputs from Sujata Shukla and Mridula Varghese.
Quite a few of us question the use of non-stick cookware where the coating is peeling off. It is alright to use that cookware from the point of view of PTFE/non-stick coating consumption. As mentioned in “Is Teflon® Cookware Harmful?“, Teflon® is an inert substance that isn’t likely to be harmful to our health .
The other perspective is of the underlying metal and if the cookware is safe to from the point of view of metal consumption. The same perspective applies to all-metal cookware. Most cookware, non-stick and otherwise, use aluminium as the base metal. While there are other metals used, I’m going to go with Aluminium as an example for this article, it being the most commonly found in our kitchens.
Most adults consume between 1 to 10 mg of Aluminium each day  from different sources including food, water and utensils. As per the European Food Safety Authority (EFSA) the upper limit for weekly consumption or Tolerable Weekly Intake (TWI) is 1 mg per kilogram of body weight . This means, a person weighing 60 kilos mustn’t consume more than 60 mg per week or 8.5 mg per day.
Aluminium leaches into food at different rates depending on the type of vessel used. Assuming the average person consumes about 750 gm of cooked food per day, the table below lists the leached aluminium content. 
|Type||Leach||Total Leach / day|
|Old Aluminium Pots||314 mcg/gm||235 mg|
|New Steel Pots||241 mcg/gm||180 mg|
|New Clay Pots||132 mcg/gm||99 mg|
|Old Clay Pots||195 mcg/gm||146 mg|
|New Aluminium Pots||126 mcg/gm||94.5 mg|
The above table was calculated using findings from one source . As per other research papers:
- 150 mg Aluminium per meal = 450 mg per day 
- 5 mg Aluminium per 100 gm of food = 37.5 mg per day 
- Up to 945 times the amount of Aluminium found in liquid after boiling in an aluminium pot 
From what the numbers say, it appears most of us are likely to be consuming many times the recommended maximum intake of Aluminium each day, regardless of which research we choose to believe.
We tend to prize our old, metal utensils, which actually leach more metal into our food than newer utensils. 
What are the effects of excess aluminium in our systems? The accumulation of Aluminium in our bodies is thought to cause health issues . While some sources say that ill effects from short term exposure through dietary means have not been observed , the same sources agree that the tolerable weekly intake (TWI) can be reached through dietary means alone. Possible effects on our bodies include:
- Neurotoxicity effects (e.g. neuronal atrophy in the locus ceruleus, substantia nigra and striatum) 
- Linked to dementia and encephalopathy 
- Possible link with Alzheimer’s disease 
- Further studies needed to establish/rule-out link with breast cancer 
The solution to my mind is to change our cooking methods in addition to adopting Teflon® coated and hard anodised utensils and discarding them when they’re worn. Glass cookware may also be a viable option, though a deeper look is needed. Alternative cooking methods include stir-frying (to reduce cooking time), steaming (reduce contact with metals), grilling using wooden skewers and so on. I invite you to examine my views and share your own on this topic.
Mridula Varghese, who saw a preview of this article and its references, while agreeing with the conclusions drawn from looking at information from the various sources mentioned, thought there could be a variance in the quantity of leached aluminium based on materials used from different sources, brand and geographical locations, in addition to our conclusions changing based on the presence of more data. I agree with that line of thinking and while hoping she’s right, do not believe additional data or locations etc. will make much difference at the end of the day.
Keep in mind that both, cooking time and temperature matter. The higher the temperature and cooking time, the higher the leaching of aluminium into our food.
While the above values and health effects are startling, there are many more factors in play and these are numbers in theory. Additionally, more data is required. Nevertheless, making a change in our cooking methods and lifestyle will undoubtedly help in keeping us healthier.
- Is Teflon® Cookware Harmful?
- Dietary and other sources of aluminium intake
- EFSA Advises on the Safety of Aluminium in Food
- Comparative Study of Leaching of Aluminium from Aluminium, Clay, Stainless Steel, and Steel Cooking Pots
- Effect of Aluminum Leaching Process of Cooking Wares on Food
- Leaching of aluminium from cooking pans and food containers
- Aluminium dissolved from kitchen utensils
- Effect of pH, Salinity and Temperature on Aluminum Cookware Leaching During Food Preparation
- Toxicity, mechanism and health effects of some heavy metals
- The Health Effects of Aluminum Exposure