Question: Do the potential dangers to health resulting from eating roasted nuts also occur with roasted seeds? I am particularly concerned about roasted sesame seeds.
Answer: Nuts and seeds are small but mighty; packed with nutrients, fibre, protein and healthy fats that benefit our heart health and more. However, roasting and toasting processes can create an undesirable chemical contaminant called acrylamide in certain foods, including nuts and seeds.
Acrylamide is categorised as a potential human carcinogen by the World Health Organisation. It is formed during the cooking process in foods containing sugars and an amino acid called asparagine that produces desirable new flavours and aromas, as well as the chemical contaminant. Although acrylamide has not been linked directly to cancer in humans, in animal studies it has caused cancer, so it is recommended we take steps to reduce our acrylamide intake.
The concentration of acrylamide in carbohydrate-rich foods can be influenced at several points along the production chain, from selective plant breeding and fertilisation practices to altering recipes to include ingredients that inhibit acrylamide production.
A recent study involving researchers from AUT University found that extracts from green tea could reduce acrylamide formation during bread baking.
Processing ingredients can also alter acrylamide formation – washing and blanching foods can reduce acrylamide levels – and the cooking process, including temperature and duration, also alters concentrations.
A 2012 study found the greatest contributors of acrylamide to the typical New Zealand diet were potato products, bread, breakfast cereals and drinks.
New Zealand potato crisps and corn chips had a mean acrylamide level of 580-596 micrograms per kilogramme of chips. The mean acrylamide levels in toasted breads was 58-72mcg per kg of bread.
As well as potato products, breads, cereals, cakes and biscuits, acrylamide tends to accumulate in lower moisture foods, including roasted nuts and seeds.
Levels on average vary from 33-251mcg per kg of roasted nuts and seeds, depending on the variety. However, a 2019 study found high amounts of acrylamide (135-633mcg per kg) in roasted sesame seeds.
Although these levels in roasted sesame seeds are the same as potato products, what differs is the sheer quantity of each food we would normally eat. A typical serving of potato is about 135g and is often eaten several times a week. A typical serving of nuts or seeds is 30g. And unless you have a very specific use for sesame seeds, it’s hard to imagine eating more than 30g of sesame seeds a day.
On that basis, yes, roasted sesame seeds may have a higher concentration of acrylamide, but if they are eaten only occasionally, they will not contribute substantially to your overall acrylamide load.
Focus on eating a variety of different nuts and seeds in your daily diet, rather than just sesame seeds. And although raw nuts and seeds are the healthier option, the Heart Foundation recommends raw and roasted options (preferally free of flavourings and coatings).
You could arguably have a greater impact on reducing your acrylamide intake by focusing on your preparation and consumption of any potato products and breads, rather than sesame seeds, which, quantity-wise, typically contribute vastly smaller amounts of acrylamide to a diet.
Tips to reduce acrylamide formation
- Don’t store potatoes in the refrigerator or where exposed to light, because this can increase the components that promote acrylamide formation.
- Soak potatoes in water for 15-30 minutes or blanch in boiling water before frying or roasting because this reduces the components that promote acrylamide formation.
- Follow the manufacturer’s cooking instructions – many have adjusted their instructions to reduce acrylamide levels in their foods.
- Cook potato products such as oven fries, hash browns and roast potatoes in a moderate oven (180-190°C) to a light golden colour only. Deep-fried chips should be cooked at a maximum of 175°C. Chunkier-style chips are preferable.
- Toast bread or other foods to the lightest colour acceptable to your taste, while noting that the crust has higher acrylamide levels.
Source: Food Standards Australia New Zealand.
