Are potatoes now a cancer risk? Here’s what you need to know

The UK Food Standards Agency (FSA) has launched a campaign warning of the cancer risk associated with cooking potatoes and other starchy foods at high temperatures. How worried should we be, and do we need to change the way we eat? New Scientist looks at the evidence

What’s the problem?

In a word, acrylamide. This chemical is used in lots of industrial processes, including water purification, and to separate DNA molecules in experiments. Acrylamide is also found in some foods.

Which foods contain acrylamide?

Acrylamide is made by something called the Maillard reaction, which browns cooked foods and gives them their pleasing flavour. As sugars and amino acids react together, they produce thousands of different chemicals. Particularly high levels of acrylamide are found in starchy foods, like potatoes and bread, when cooked at temperatures over 120 oC. The chemical can also be present in breakfast cereals, biscuits and coffee.

Is acrylamide dangerous?

In the body, acrylamide is converted into another compound, glycidamide, which can bind to DNA and cause mutations. Animal studies clearly show that acrylamide causes all sorts of cancers, but it’s hard to relate this to us.

“Although evidence from animal studies has shown that acrylamide in food could be linked to cancer, this link isn’t clear and consistent in humans,” says Emma Shields, at charity Cancer Research UK.

It’s much harder to study the effects of acrylamide in people, but there’s no reason to think that it couldn’t damage human DNA too. However, other lifestyle factors carry much more defined cancer risks. “It’s important to remember that there are many well-established factors like smoking, obesity and alcohol, which all have a big impact on the number of cancer cases in the UK,” said Shields. 

What should we do?

“To be on the safe side, people can reduce their exposure by following a normal healthy, balanced diet – which includes eating fewer high calorie foods like crisps, chips and biscuits, which are major sources of acrylamide,” says Shields.

And when frying, baking, toasting or roasting starchy foods, the FSA’s advice is to “go for gold”: aim for a golden yellow colour or lighter.

But I like my roast potatoes brown and crispy!

Then you might do well to eat them less often. “It’s those kinds of trade-offs we’re encouraging people to just think about,” says Steve Wearne of the FSA. “We’re not saying to people to worry about the occasional meal that’s a bit overcooked. This is about managing risk across your whole lifetime.”

How else can we reduce the risk?

Don’t keep raw potatoes in the fridge. At low temperatures, an enzyme called invertase breaks down the sugar sucrose into glucose and fructose, which can form acrylamide during cooking. Frozen food doesn’t carry this particular risk, as sucrose doesn’t get broken down at very low temperatures.

You can also try blanching potatoes before frying. This removes half the sugar, resulting in lower levels of acrylamide.

In the future, safer potatoes may be available. Restaurants and the food industry are already being encouraged to use potato varieties that naturally produce less acrylamide. Now growers are looking to develop varieties that contain less asparagine, an amino acid that seems to be important for making the chemical.