Acrylamide, a harmful chemical identified in baked and fried foods, does not increase the risk of breast cancer in women, say US and Swedish researchers, writes Lindsey Partos.
The food industry faced acrylamide concerns in April 2002 when scientists at the Swedish Food Administration first reported unexpectedly high levels in carbohydrate-rich foods heated to high temperatures, such as chips, roast potatoes, crisps and bread.
Since then, an international effort of more than 200 research projects has been initiated around the world with their findings co-ordinated by national governments, the European Union and the United Nations.
Acrylamide appears to form as a result of a reaction between specific amino acids and sugars found in foods reaching high temperatures in their cooking processes.
But following new findings, this week researchers at the Harvard School of Public Health and the Karolinska Institute in Stockholm, Sweden, claim the amount of acrylamide eaten in the diet does not pose an increased risk of breast cancer among the women in the study.
Although they caution that their findings only relate to breast cancer. Lorelei Mucci, lead author of the study, warns : "It is still important to examine the risk associated with other cancers as well as neurological conditions."
Animal and laboratory studies in the past have shown higher levels of certain types of tumours in rats, including mammary gland tumours, but according to the researchers they were exposed to levels 1,000 to 100,000 times greater than levels humans are exposed to through diet.
The Swedish and US scientists assessed acrylamide intake of more than 43,000 women, including 667 breast cancer cases, who were enrolled in the Swedish Women's Lifestyle and Health Cohort.
Acrylamide intake was determined from food frequency questionnaires reported by the women in 1991; the women's health status was tracked via national health registers until the end of 2002.
The average daily acrylamide intake among the participants was 25.9 micrograms per day. Less than 1.5 per cent of the women consumed more than 1 microgram of acrylamide per kilogram of body weight per day, a level used in risk assessment models.
The foods that contributed the most to acrylamide intake were coffee (54 per cent of acrylamide dose), fried potatoes (12 per cent of dose) and crisp bread, (9 per cent of dose).
"Comparing the women in the study who had the lowest daily acrylamide intake, the researchers found no significant increased risk of breast cancer among the women whose intake was higher," report the researchers in the 16 March, 2005 issue of the Journal of the American Medical Association.
Since the Swedish discovery in 2002, food players have been working on improving knowledge of this harmful chemical in foodstuffs, in particular, working on production methods to slice acrylamide out of formulations.
Scientists now know that the most important precursor is the free amino acid asparagine which reacts with reducing sugars in the Maillard reactions that also form colour and flavour.
Since 2002 research has shown that although trace amounts of acrylamide can be formed by boiling, significant formation generally requires a processing temperature of 120 oC or higher.
Most acrylamide is accumulated during the final stages of baking, grilling or frying processes as the moisture content of the food falls and the surface temperature rises, with the exception of coffee where levels fall considerably at later stages of the roasting process.
Since formation is dependent on the exact conditions of time and temperature used to cook or heat-process a food, there can be large variations between brands of the same product and between batches of the same brand. Large variations are also to be expected during cooking although this aspect has been less well documented.
The composition of the food also has an influence, crucially the content of free asparagine and reducing sugars. Varietal, storage and seasonal variations can occur. Within ranges of natural variation, the limiting precursor in cereals is asparagine while fructose and glucose are more important in potatoes. Other important factors are pH and water content.
In a review recently submitted to a UN working grou on acrylamide, Europe's €600 billion food and drink industry (CIAA) said that recent investigations have achieved a 30 to 40 per cent reduction in acrylamide levels of potato crisps by introducing several adjustments in the existing production procedures.
Significant reduction was also reported from process-optimisation for non-fermented crispbread, but little progress has so far been obtained in reducing levels in various other important intake sources, for example, roasted coffee and breakfast cereals.
Findings revealed at a meeting earlier this month under the aegis of JECFA, the UN's committee on food additives, showed the most efficient reduction has been achieved by using the enzyme asparaginase to selectively remove asparagine prior to heating.
"Although tested both in cereal and potato models, the use is probably limited to specific food products manufactured from liquidised or slurried materials," says the group.
Several other means of lowering the precursor levels can be applied at various stages of the food chain, for instance, by variety selection and plant breeding, controlling growth and storage factors affecting sugar concentrations in potatoes, pre-treatment of potato pieces by soaking or blanching, and prolonged yeast fermentation time in breadmaking.
Other mitigation possibilities include alteration of the product composition: addition of competing amino acids or acidic compounds, and alteration of process conditions - lowering the frying temperature.
But a key obstacle to this progress is the fact that the feasibility of adapting these methods to large-scale food processing has not been "completely studied" in most cases.