Roasting and frying starchy foods could increase the risk of cancer, said the Food Standards Agency (FSA).
FSA has issued a public warning over the risks of acrylamide - a chemical compound that forms in some foods when they are cooked at high temperatures (above 120C).
A new campaign tells people how they can cut their risk, including opting for a gold colour - rather than darker brown - when frying, roasting, baking, grilling or toasting.
Acrylamide is found in high levels in a range of foods including breakfast cereals (not porridge), chips, potato products (such as waffles or children's potato shapes), biscuits, crackers, crisp bread and crisps.
It is also found in coffee, cooked pizza bases, black olives and cereal-based baby foods.
Root vegetables including potatoes, sweet potatoes, beetroot, turnip, swede and parsnips can all carry high levels of the compound once they have been roasted or fried until darker brown or crispy. As well as high temperatures, long cooking times can increase levels of acrylamide even further.
Foods such as skinny fries and crisps appear to have the highest levels.
Acrylamide forms due to a chemical reaction between certain sugars and an amino acid (asparagine) in the food.
However, boiling, steaming and microwaving appear far less likely to cause the reaction.
The US Environmental Protection Agency has said acrylamide is “likely to be carcinogenic to humans” and the International Agency for Research on Cancer (IARC), part of the World Health Organisation, says it is a “probable human carcinogen”.
In its new campaign, the FSA said people could take simple steps to reduce their consumption of acrylamide.
As a “rule of thumb”, people should aim for a golden yellow colour or lighter when frying, roasting, baking or toasting starchy foods.
For example, roast potatoes should not be “fluffed up” to maximise dark brown crispy bits and they should be roasted to the lightest colour that is acceptable. Toast should also be browned to a light brown colour.
The FSA said people should not keep potatoes in the fridge, which can increase overall levels of acrylamide. Instead, raw potatoes should be stored in a dark, cool place with temperatures above 6C.
Cutting potatoes into larger wedges reduces their surface area, thereby cutting down the level of acrylamide that can form. Crinkle-cut chips are worse than normal chips as they have a larger surface area.
The international expert scientific committee known as JEFCA has said acrylamide intake from food is a “human health concern” and levels should be as low as possible.