Hard anodised aluminium cookware is made of aluminium bathed in acid solution, then exposed to an electric current. A layer of aluminum oxide is deposited on the surface, thus anodization occurs. Cookware that is anodised has a very hard surface that is corrosion resistant and durable. Commonly referred to as hard anodised aluminium, Calphalon is a well-known brand of hard anodised cookware. Because anodised products contain aluminium, a few questions have been raised about health warnings of hard anodised aluminium cookware.
In 2007, Helen Suh MacIntosh, a professor in environmental health at Harvard, citing a study by Clemson University, states that while it is true that foods cooked at high temperature in aluminium can leach aluminium into acidic foods, "This leaching of aluminium with acidic foods does not happen with aluminium cookware that is anodised, or electrochemically processed to seal the aluminium in the cookware."
The misunderstanding about anodised aluminium cookware stems from the fact that simple aluminium cookware can indeed cause aluminium to leach into foods. As MacIntosh states, "Most exposures to aluminium occur through ingestion or eating and drinking, with daily intakes generally low, averaging between 30 to 50 mg. For the typical person, drinking water, medicines and other pharmaceuticals (such as antacids and antiperspirants) are the biggest contributors to aluminium exposures; however, aluminium cookware is also a potential source."
Research by Clemson University, and analysis by Harvard professor Helen Suh MacIntosh, conclude that anodised cookware does not create a health warning. By its very nature, anodised cookware is meant to prevent aluminium infiltration.