Aluminium foil is one of the most common items in the kitchen. Whether you’re wrapping leftovers, lining a baking tray or sealing a packet of fish and vegetables for the oven, it’s cheap, convenient and widely considered safe. But that shiny piece of metal may not be as inert as it appears.
A 2012 study published in the International Journal of Electrochemical Science found that aluminium foil can leach metal into food, particularly when it comes into contact with acidic ingredients such as tomatoes, vinegar and citrus, or heavily seasoned meals cooked at high temperatures.
What the researchers found: The study, titled Risk Assessment of Using Aluminium Foil in Food Preparation, was conducted by chemical engineers from the United Arab Emirates and Egypt.
Researchers prepared several meat sauces containing different combinations of tomato juice, citric acid, apple vinegar, salt and spices. Aluminium foil was then exposed to boiling sauces, steam and oven-cooked meals covered with foil. Using scanning electron microscopy and mass spectrometry, the team measured how much aluminium transferred from the foil into the food. Although the study was laboratory-based rather than a clinical trial, the researchers used well-established scientific methods to measure metal leaching.
The findings that should make you pause: In every test, the foil lost some weight, indicating that aluminium had leached into the food. Depending on the amount of foil covering the pan, a family-style meal prepared with a mild tomato and citric acid sauce added 22.8 to 75.4 milligrams of aluminium per serving. Increasing the citric acid level brought that up to the 40 to 132.4 milligram per person.
The researchers also found that tomato juice alone significantly increased aluminium release by lowering the acidity of the cooking liquid.
Water quality also influenced the results. The same recipe prepared with drinking water released roughly 132.4 milligrams of aluminium per serving, compared with about 65.2 milligrams when tap water was used.
Vinegar and spices were the biggest wild cards: Swapping citric acid for apple vinegar changed things dramatically. According to the study, a sauce made with apple vinegar leached about 465 milligrams of aluminium per serving, more than three times the amount measured from the citric acid sauce.
Adding only 3 grams of spice to the same citric acid and tomato sauce produced an even greater effect, increasing aluminium transfer to roughly 537.2 milligrams per serving.
The researchers believe certain organic acids and compounds found in spices accelerate the breakdown of aluminium’s protective oxide layer, allowing more metal to migrate into food.
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Heat speeds up the process: When researchers baked food covered with foil for 90 minutes, the combined contribution from the foil and aluminium pan reached about 361 milligrams per serving.
Microscopic images revealed that the foil surface became cracked, pitted and heavily damaged after prolonged heating. According to the researchers, higher temperatures weaken the protective oxide coating that normally helps prevent aluminium from dissolving into food.
How much aluminium is actually too much: According to the Joint FAO/WHO Expert Committee on Food Additives, adults can safely consume up to 2 milligrams of aluminium per kilogram of body weight each week. That’s about 136 milligrams a week for a 150-pound adult from all sources, including food, water and cookware combined.
Some meals prepared in the study, particularly those containing vinegar and large amounts of spices exceeded that weekly guideline in a single serving. While the body eliminates most dietary aluminium through the kidneys, researchers say regularly consuming high amounts is not advisable.
Does aluminium cause Alzheimer’s disease: Concerns about aluminium and Alzheimer’s disease have circulated for decades, but current scientific evidence does not support a direct link. Major health organizations, including the Alzheimer’s Society, say studies have not established aluminium exposure from food, cookware or drinking water as a cause of Alzheimer’s or other forms of dementia.
That does not mean excessive aluminium intake should be ignored. Health experts note that high exposure remains a concern, particularly for people whose kidneys cannot efficiently remove aluminium from the body.
Who should take extra precautions: People with chronic kidney disease are more vulnerable because their bodies remove aluminium less efficiently, allowing it to accumulate over time.
Infants and young children are also considered more sensitive to aluminium exposure relative to their body weight. For these groups, experts recommend avoiding direct contact between acidic foods and aluminium foil whenever possible.
This is not a one-off finding: A separate 2019 peer-reviewed study found that when researchers baked salmon, mackerel, duck breast, tomatoes, and other foods in foil, aluminium levels increased significantly after cooking, particularly in marinated dishes.
Together, the studies consistently show that acid, salt and heat are the main factors that increase aluminium migration into food.
How to minimize exposure: You don’t have to stop using aluminium foil altogether, but a few simple changes can significantly reduce the amount of aluminium that ends up in your meals.
You can take steps such as placing parchment paper between food and aluminium foil when baking. Avoid wrapping tomato, vinegar or citrus based dishes directly in foil. Reduce cooking temperatures and avoid unnecessarily long cooking times. Use glass, ceramic or stainless steel cookware for acidic recipes.
The bottom line: Aluminium foil remains a useful kitchen staple for storing leftovers, wrapping sandwiches and lining baking trays where food does not come into direct contact with the metal.
The greater concern arises when acidic, salty or heavily seasoned foods are cooked directly in foil at high temperatures for extended periods.
If dishes such as lemon marinated chicken, baked fish or tomato based recipes are regular features on your menu, switching to parchment paper, glass or stainless steel cookware is a simple step that can help reduce unnecessary aluminium exposure without changing the way you cook.
The Economic Times
