Going nuts: Why raw is better than roasted for your health
As well as vitamins and minerals, nuts provide a concentrated source of unsaturated fat and fibre. Photo / Getty Images
Nuts are packed with nutrients and fats that benefit heart and gut health. But those roasted at high heat, while tasty, can be risky.
Question:
I was interested to read about the gut-health benefits of peanuts and wondered if this finding applies equally to raw and unsalted roasted peanuts?
Answer:
Eating just 3-4 small handfuls of nuts a week can decrease the risk of coronary heart disease by about 20 per cent, according to the Heart Foundation. Moreover, recent research affirms that regular nut consumption promotes a healthy gut microbiome, which is beneficial.
However, when nuts are roasted, undesirable compounds can form. So, from a health perspective, is it best to avoid all roasted nuts?
The biggest issue with roasted nuts (particularly almonds) is the potential presence of acrylamide, a possible human carcinogen that has been found in animal studies to cause cancer.
We love the distinctive flavours that occur when nuts are cooked by high heat, but this can also produce acrylamide, which can form during the browning Maillard reaction between reducing sugars (glucose) and amino acids (asparagine) at temperatures above 120°C. How much forms depends on the cooking time and temperature, with higher temperatures and longer cooking times generally creating more.
However, several other foods contribute more acrylamide to our diet than roasted nuts. For New Zealand adults, potato products (hot chips, roast potatoes, crisps) are the most significant contributor, followed by bread (fresh or toasted), breakfast cereals and then beverages (beer, tea and coffee). When it comes to children, biscuits take that fourth spot in place of drinks.
From a nutrient perspective, roasted nuts will have varying levels of vitamins compared with raw nuts. For example, roasted almonds had more folate but significantly less vitamin B1 (thiamine) when assessed for the New Zealand Food Composition tables. It makes sense that roasting could cause the loss of heat-sensitive vitamins such as thiamine (folate is less sensitive to heat). But the problem with much of the data is that raw and roasted nuts do not necessarily come from the same batch, so slight nutrient differences may exist before they go through roasting.