SHARJAH // Food cooked in aluminium foil can contain more than six times the safe level of the metal, a UAE study has found.
Dr Fathia Mohammed and Dr Essam Zubaidy, researchers at American University of Sharjah's chemical engineering department, found that one meal cooked in aluminium can have up to 400mg of the metal.
The safe maximum, according to the World Health Organisation, is about 60mg per person per day, although this varies according to a person's weight.
At high doses, the metal can accumulate in the bones and brain. Aluminium absorption into the body has been linked with Alzheimer's and osteoporosis.
The pair have investigated foil from China, India and Egypt, publishing four papers on their work. The most recent, in May's International Journal of Electrochemical Science, concluded that aluminium foil should be used only for packing, not cooking.
The researchers cooked meats such as mutton and chicken in a variety of ways, time periods and temperatures with a variety of other ingredients, such as tomato juice, citric acids, apple vinegar and salt, and with vegetables and water. Most recently, they focused on minced meat. Their aim was to find ways of reducing the amount of metal leached into the food.
"The body can tolerate 1mg of aluminium per 1kg of bone weight before it accumulates in the brain, in the bone and so on," said Dr Mohammed.
Using environmental scanning electron microscopy to analyse the quality of the foil before and after cooking, they found significant leaching.
"We tried to cover the food and also to put the food on the foil, to see the effect of contact," Dr Zubaidy explained.
A circular piece of foil 22cm across leached 100mg of aluminium into the food cooked on it - "too much for one family of three to ingest", said Dr Mohammed.
"To the naked eye, it looks fine, but under the microscope you see a big difference. The higher the temperature, the more the leaching. Foil is not suitable for cooking and is not suitable for using with vegetables like tomatoes, citrus juice or spices."
Oman banned restaurants from cooking with foil in 2010, deeming it harmful. Food authorities there stipulated that the shiny side of foil could be used for storage of hot food, and the matt side only for cold food.
One of the main dangers of long-term aluminium absorption is osteoporosis. Because aluminium has similar properties to calcium, it can be absorbed into the structure of bones. It can also be deposited in brain tissue, which is thought to be linked to Alzheimer's disease.
Dr Mohamed Yousef Baniyas, a toxicologist and provost at UAE University, noted that the use of salt, citric acid or vinegar in cooking increased the release of aluminium.
However, he doubts that for healthy individuals the amount released is likely to be hazardous. "It's important to look at the mechanism of aluminium in Alzheimer's," he said. "There is still some room for discovery."
Dr Zubaidy said they had found traces of aluminium in water, due to the water treatment process, and significant levels in foods such as processed cheese, as well as bakery goods cooked on aluminium trays and using baking powder, a derivative of aluminium sulphate.
Dr Mohammed said adding water reduced leaching when using aluminium for cooking, as it acted as a protective coating. But leaching was exacerbated when food is reheated or even cooled in the aluminium.
"Adding spices, salt, vinegar and any citrus juice should be done at the last stage of cooking to avoid major leaching," she said.
But alternatives, such as cooking vessels made of titanium or stainless steel, are costly or not such good conductors of heat.
"Many pots are even made using reused aluminium, which is even worse. But if any aluminium pots are scratched, the leaching process is even quicker," she said.
In their recent paper, the team concluded that "excessive consumption of food baked with aluminium foil may carry a serious health risk".