Can burnt toast and roasted potatoes cause cancer?
The Food Standards Agency in the UK launched a campaign Monday to warn about cancer risks linked to eating burnt toast, over-roasted potatoes and other starchy foods cooked at high temperatures.
The campaign is based on longstanding evidence from animal studies in 2002, but the link is yet to be proved in human studies. Some experts are highlighting that other lifestyle factors pose much greater cancer risks, such as smoking and obesity.
What exactly is the problem with these overcooked starchy foods? Earlier mouse studies identified that high levels of a compound called acrylamide led to an increased risk of cancer.
Acrylamide is what makes bread and potatoes turn golden in color when fried, baked, toasted or roasted. The compound is formed from simple sugars, such as glucose, reacting with an amino acid, known as asparagine, when these foods are cooked at temperatures above 120 degrees Celsius. Asparagine is found naturally in starchy foods.
If cooked for too long, these foods turn from golden to brown and eventually black. As they do, they produce higher levels of acrylamide, further increasing your cancer risk, as highlighted by the FSA campaign, called "Go for Gold."
The campaign asks people to keep their food golden and not let it cook to those darker colors.
The aim is to increase awareness among the public. Although the research is not new, the agency believes that people remain unaware.
"Our research indicates that the majority of people are not aware that acrylamide exists, or that they might be able to reduce their personal intake," Steve Wearne, director of policy at the Food Standards Agency, said in a statement. The government body analyzes and shows current research in food safety, nutrition and food-related disease of importance to public health.
Wearne added that his agency wants to "highlight the issue so that consumers know how to make the small changes that may reduce their acrylamide consumption whilst still eating plenty of starchy carbohydrates and vegetables as recommended in government healthy eating advice."
The advice given in the campaign is to:
- Aim for a yellow or golden brown color when frying, roasting or baking food.
- Follow cooking instructions on food packages to avoid overcooking.
- Eat a balanced diet.
- Avoid keeping potatoes in the fridge before cooking them, as this can further increase acrylamide levels.
How big is the cancer risk?
Evidence of cancer risk has not been proved in humans, but experts point out that this data may never become available, as teams cannot readily expose people to acrylamide to test the outcome.
"No one will willingly eat acrylamide ... (but) because it's carcinogenic in animals, it would be carcinogenic in humans," said Donald Mottram, emeritus professor of food chemistry at the University of Reading in the UK.
Mottram's team first identified how acrylamide was made in food when the links to cancer first emerged in 2002.
"(The FSA) have given this advice before, but not quite so clearly defined," he said, highlighting the third point included: to eat a balanced diet. The US Food and Drug Administration has also provided advice for some years on how best to reduce acrylamide exposure in your diet.
Boiling the foods brings no risk, as acrylamide is not formed, said Mottram.
"I still eat crisps and fries ... but what we want to do is prepare these foods so the risks are minimized," Mottram said. "Color is a good guide. It's the only guide you have in your home."
Nigel Halford, professor of plant genetics at Rothamsted Research in the UK, agrees.
"They're not saying don't eat roast potatoes or don't eat bread, but instead that people can do fairly simple things to reduce their exposure," Halford said. "It does make quite a difference."
Halford is developing new forms of potatoes with reduced levels of sugars and asparagine to limit their ability to produce acrylamide. "We're looking at ways to reduce the precursors," he said.
But rather than relying on these changes, Halford recommends following the FSA advice. "Consumers get weary of this advice, and you've seen the kick-back today," he said. "But they're just saying to cook to a lighter color."
Cancer Research UK commented that while recognizing the risk associated with over-browning these foods, people should remember that other lifestyle-related factors have a bigger impact on cancer risk.
"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 the major sources of acrylamide," said Emma Shields, Cancer Research UK's health information officer.
"It's also important to remember that there are many well-established risk factors like smoking, obesity and alcohol, which all have a big impact on the number of cancer cases in the UK."