- Acrylamide, a compound that causes cancer symptoms in
animals, is formed during frying and baking, two studies now show.
- The discovery solves a mystery that had caused public
alarm. In April a Swedish study found the chemical in crisps and biscuits,
but not raw food, at levels higher than the World Health Organisation (WHO)
recommends for drinking water1.
- "I haven't known as much interest in a topic in
many years," says Don Mottram, who studies food chemistry at the University
of Reading, UK. Not knowing where the chemical was coming from was "a
very big problem", he explains.
- Baked bread tastes better than raw dough, and fried chips
are tastier than boiled, because of the Maillard reaction. As long as there's
sugar around, high temperature breaks proteins down to give food more flavour
and a golden brown colour.
- The Maillard reaction also produces acrylamide, Mottram
has found, as has Richard Stadler of the NestlÈ Research Centre
in Lausanne, Switzerland, in independent experiments2,3. Potatoes and some
cereals contain large amounts of the amino acid asparagine, which is similar
to acrylamide. In the lab, heating asparagine with sugar at 185 C turns
much of it into acrylamide, Motram and Stadler have found.
- "During cooking, many complex chemical reactions
take place," says Stadler: other amino acids change their form repeatedly,
also producing acrylamide. More tests are needed on different types of
food to see how acrylamide forms, he says, and to understand the effects
of different cooking techniques.
- Exposing more of a food to higher temperatures, as in
thin potato crisps, generates more acrylamide. So too does cooking food
for longer. No acrylamide has been found so far in boiled foods, probably
because of their lower cooking temperature.
- Hot topic
- In rats and fruitflies, acrylamide causes cancerous changes,
at concentrations 1,000 times higher than those found an average diet.
There is no direct evidence for acrylamide having a similar impact on humans,
but the International Agency for Research on Cancer nevertheless classified
it as "probably carcinogenic" in 19944.
- Rats don't eat heated food. But as humans have been doing
so for thousands of years, we may be more tolerant to acrylamide, Mottram
suggests. Obesity, diabetes and a lack of fruit and vegetables in Western
diets are more serious health threats than acrylamide, he adds.
- Finding the mechanism at work is important, but still
just "one of many missing points", says Jorgen Schleudt, head
of WHO's food-safety programme. He is calling for more research into the
effects of acrylamide on humans.
- Indeed, next week the United Nations Food and Agriculture
Organization and WHO are launching a web-based network to coordinate acrylamide
research. It should encourage a "global exchange of information",
- Tornquist, M. et al. Acrylamide: A cooking carcinogen?.
Chemical Research in Toxicology, 13, 517 - 522, (2002). |Homepage|
- Mottram, D.S., Bronislaw, L.W. & Dodson, A.T. Acrylamide
is formed in the Maillard reaction. Nature, 418, 448 - 449, (2002). |Homepage|
- Stadler, R.H. et al. Acrylamide from Maillard reaction
products. Nature, 418, 449, (2002). |Homepage|
- IARCAcrylamide. Monographs on the evaluation of carcinogenic
risks to humans, 60, 389, (1994). |Article|
- © Nature News Service
- Macmillan Magazines Ltd 2002