The effects of fluoride on the leaching of aluminium saucepans during cooking

Dietary and other sources of aluminium intake

Aluminium in the food supply comes from natural sources including water, food additives, and contamination by aluminium utensils and containers. Most unprocessed foods, except for certain herbs and tea leaves, contain low (< 5 micrograms Al/g) levels of aluminium. Thus most adults consume 1-10 mg aluminium daily from natural sources. Cooking in aluminium containers often results in statistically significant, but not practically important, increases in the aluminium content of foods. Intake of aluminium from food additives varies greatly (0 to 95 mg Al daily) among residents in North America, with the median intake for adults being about 24 mg daily. Generally, the intake of aluminium from foods is less than 1% of that consumed by individuals using aluminium-containing pharmaceuticals. Currently the real scientific question is not the amount of aluminium in foods but the availability of the aluminium in foods and the sensitivity of some population groups to aluminium. Several dietary factors, including citrate, may affect the absorption of aluminium. Aluminium contamination of soy-based formulae when fed to premature infants with impaired kidney function and aluminium contamination of components of parenteral solutions (i.e. albumin, calcium and phosphorus salts) are of concern.

Soapstone (steatite) cookware as a source of minerals

Steatite or soapstone, is a soft metamorphic rock composed mainly of talc, dolomite and actinolite, which is abundantly found and used for the manufacture of cookware in south-east Brazil. The study estimates its usage for cookware among dwellers of Ouro Preto, and assesses the possible toxicological or nutritional impact on food preparation. Pans made of steatite were purchased both in the crude (n = 6) and 'cured'forms (n = 6). Migration of Ca, Fe, Mg, Mn, Co, Al, Cr, Ni, Pb and Cd was determined for 20 sequential cooking trials, using 3 and 5% acetic acid as a food simulant. Analytical determinations were carried out by inductively coupled plasma atomic-emission spectrometry and the data treated by an individual model of random effects, simple linear regression and Pearson's correlation. About 81% of Ouro Preto's native population own soapstone cookware and, of these, 79% use the pans regularly. Mineral migration followed the general solubility of the crystalline components of the rock. Therefore, Ca, Mg, Fe and Mn were, in that order, the elements that exhibited highest migration, whereas the remaining were seen in negligible levels, except for Ni in the crude pans. The 5% solution favoured migration, whereas curing tended to restrict migration and extend durability of the pan. It is concluded that while cured soapstone pans do not offer mineral toxicity, they may contribute to the mineral nutrition of human beings.

Safety evaluation of dietary aluminum

Aluminum is a nonessential metal to which humans are frequently exposed. Aluminum in the food supply comes from natural sources, water used in food preparation, food ingredients, and utensils used during food preparations. The amount of aluminum in the diet is small, compared with the amount of aluminum in antacids and some buffered analgesics. The healthy human body has effective barriers (skin, lungs, gastrointestinal tract) to reduce the systemic absorption of aluminum ingested from water, foods, drugs, and air. The small amount of aluminum (<1%) that is systemically absorbed is excreted principally in the urine and, to a lesser extent, in the feces. No reports of dietary aluminum toxicity to healthy individuals exist in the literature. Aluminum can be neurotoxic, when injected directly into the brains of animals and when accidentally introduced into human brains (by dialysis or shrapnel). A study from Canada reports cognitive and other neurological deficits among groups of workers occupationally exposed to dust containing high levels of aluminum. While the precise pathogenic role of aluminum in Alzheimer's disease (AD) remains to be defined, present data do not support a causative role for aluminum in AD. High intake of aluminum from antacid for gastrointestinal ailments has not been reported to cause any adverse effects and has not been correlated with neurotoxicity or AD. Foods and food ingredients are generally the major dietary sources of aluminum in the United States. Cooking in aluminum utensils often results in statistically significant, but relatively small, increases in aluminum content of food. Common aluminum-containing food ingredients are used mainly as preservatives, coloring agents, leavening agents, anticaking agents, etc. Safety evaluation and approval of these ingredients by the Food and Drug Administration indicate that these aluminum-containing compounds are safe for use in foods.

Utensílios para alimentos e implicações nutricionais

Há grande variedade de materiais empregados na confecção de utensílios para os alimentos: barro, ferro, vidro, cerâmica, inox, pedra, alumínio e outros. Cerca de 43% de panelas vendidas atualmente nos Estados Unidos são de aço inoxidável. Outra parcela da população utiliza utensílios de alumínio. Este artigo visa especular a contribuição nutricional de utensílios usados na preparação de alimentos e feitos de três diferentes materiais (alumínio, ferro e aço inoxidável), através de revisão de literatura científica.

Studies on aluminium leaching from cookware in tea and coffee and estimation of aluminium content in toothpaste, baking powder and paan masala

Studies were conducted in order to assess the level of aluminium (Al) in samples of Indian tea, coffee, toothpaste, paan masala (mouth freshener) and baking powder. Leaching of Al from cookware while preparing tea and coffee was also studied. Experiments were also conducted to study the sequential leaching of Al from cookware by preparing tea and coffee in the presence of standard size Al sheets (coupons). A small amount of Al was found to have leached from coupons during preparation of tea. Tea leaves, were found to be a rich source of Al and a maximum of 2.2% Al is extracted in tea infusions. Coffee powder on the other hand was not found to be a rich source of Al. Baking powder was found to be a rich source of Al and 1 kg of cake prepared with 1-3 teaspoon of baking powder may contain 2-12.7 mg of Al in each serving (25 g). Toothpaste also contains a significant quantity of Al, more so, when packed in Al tubes. Ingestion pattern of Al from these items by humans is also discussed.

Leaching of aluminium from aluminium dishes and packages

A study was carried out of the leaching of aluminium from aluminium cooking vessels and packages. Very small or undetectable levels of aluminium leached from packaging materials into foodstuffs. In boiling tests with neutral porridge no migration of aluminium into the test matrix was observed from the pan. When boiling milk, the leaching of aluminium was 0.2-0.8 mg/kg. The aluminium content of tap water in aluminium pans when reaching boiling point was 0.54-4.3 mg/l and increased with increasing boiling time to 6.3-17 mg/l. Aluminium dissolved in foods based on acidic fruit juice rose to levels of 2.9-35 mg/kg when the foods were boiled in aluminium pans. Steaming of currant berries in an aluminium vessel gave aluminium concentrations of 19-77 mg/kg in the resulting juice. The highest aluminium concentration of 170 mg/kg was measured in rhubarb juice prepared in the steaming vessel. Aluminium dissolved in water to levels of 0.81-1.4 mg/l when heated for the first time in new coffee percolators. The aluminium concentration of water heated in older percolators was 0.09-0.78 mg/l.

Dietary intakes of some essential and non-essential trace elements, nitrate, nitrite and N-nitrosamines, by Dutch adults: estimated via a 24-hour duplicate portion study

Duplicate portions of 24-hour diets of 110 adults have been analyzed for aluminium, cadmium, copper, lead, manganese, mercury, zinc, nitrate, nitrite and volatile N-nitrosamines. The mean daily intake of copper (1.2 mg) is only about 50% of recommended values; mean daily intakes for manganese (3.3 mg) and zinc (8.4 mg) are adequate and marginal respectively with respect to recommended amounts. For the non-essential elements Al, Cd, Hg and Pb, mean daily intakes of 3.1 mg, 0.01 mg, 0.002 mg and 0.034 mg were found, respectively. For Cd this amounts to 17% of the acceptable daily amount, for Al, Hg and Pb 5%, 5% and 8%, respectively. Since 1976-1978 the dietary intake of lead has been reduced by a factor three; for the other six elements daily dietary intakes are almost the same as in 1976-1978. Average nitrate intake was 52 mg NO3-/day, about 25% of the ADI. Only 16 diets contained a measurable amount of nitrite. The highest daily intake (0.7 mg NO2-) is less than 10% of the ADI. Volatile N-nitrosamines were detectable in two duplicate diets (NDMA and NPIP). It is estimated that the daily dietary intake of volatile N-nitrosamines is around 0.1 microgram or less.

Effect of fluoride on the amount of aluminium dissolved by boiling fruit acids

Boiling citric and tartaric acids dissolved aluminium from sheets and pans made of this metal. Fluoride increased the amount of aluminium dissolved by both citric and tartaric acids at the sort of concentrations which might be used in normal cookery (0.2%, pH 2.6). Increasing the amount of fluoride increased the amount of dissolved aluminium. The proportional increase was greater at low fluoride levels. Acids varied in their individual effects; tartaric acid dissolved considerably more aluminium than citric acid under any given set of conditions. The longer an acid solution was boiled with aluminium, the more of the metal dissolved. Repeated boiling of aluminium in acid solutions did not necessarily alter its response to further boiling. Old pans were attacked more strongly by acid solutions when fluoride was present. The precise composition of the aluminium metal used did not affect any of these conclusions.