Eat Nuts Safely to Avoid Aflatoxins



Nuts are rich in nutrients such as protein, unsaturated fatty acids, dietary fibre, minerals and vitamins. They are one of the healthy high-fat food in the balanced diet recommended by the Health Bureau of Macao, and it is advisable to eat one tablespoon of nuts per day.


However, nuts may easily become mouldy due to improper storage conditions, such as high humidity and warm environment. The moulds may produce mycotoxins, like aflatoxins.


How to prevent aflatoxins in nuts?

In 2012 the International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) classified aflatoxins as Group 1 carcinogens, with sufficient data to ascertain that aflatoxins can cause cancer in humans. Hence, attention should be paid to the storage conditions of nuts. In this respect, the food sector should purchase nuts from reliable suppliers. They should be stored in a cool and dry place after purchase and avoid exposure to high temperatures and humidity or storage under unsealed conditions. Moreover, it is not advisable to buy large quantities of nuts at a time to reduce the chance of mould growth due to prolonged storage.


Besides the obligation of the food sector to adopt good practices to ensure food safety, the Administrative Regulation no. 13/2016 “Maximum Limits of Mycotoxins in Food” in Macao has established the maximum limits of aflatoxin B1 in “peanuts and peanut products” and “other cooked nuts and seeds and their products, with the exception of peanuts”. In addition, the Department of Food Safety of the Municipal Affairs Bureau (IAM) continuously conducts sampling tests of food products on the market through routine food surveillance programme to ensure food safety in Macao. In 2022 IAM and the Consumer Council conducted an investigation into pre-packaged nut products to test whether the nuts available on the market contain aflatoxins. No abnormalities were detected in the samples, but they were found to be high in calories, fat and sodium. Therefore, the public should refrain from eating excessive amounts of nuts. IAM continuously conducts Targeted Food Surveillance on food products on the market to ensure the food safety in Macao*.


The public are advised to buy nuts from general retailers and reputable shops in good hygiene condition. They should avoid buying food from abroad through online stores and surrogate shopping service, as it is hard to ensure that their storage and transport conditions comply with food safety and hygiene requirements. While it is not advisable to buy large quantities of nuts at a time, consumers should opt for nuts in small individual packages that are properly sealed. After purchasing nuts, consumers should always store nuts in a cool and dry place to inhibit mould growth and prevent the unstable unsaturated fatty acids in nuts from autoxidation which would render them an unpleasant rancid smell and destroy their nutritional contents. Once the package is opened, it is advisable to consume the nuts as soon as possible.


Are nuts a healthy snack?

Nuts are a type of food that contains healthy fats and the levels of fats in them vary across different types of nuts. The fats in nuts are mostly unsaturated fatty acids, including Omega-3 essential fatty acid (it is unable to be synthesised by the human body and only obtainable from the diet). Omega-3 fatty acid helps to reduce the risk of cardiovascular diseases, so nuts are good sources of healthy fats and moderate consumption of nuts is beneficial to health. Nevertheless, nuts generally have high fat content. The fat content in 5 pieces of almonds or cashews, or 10 pieces of peanuts, equates to a teaspoon of oil. Nuts are also rich in calories. Therefore, “moderate” consumption is one of the keys to determine if healthy food is truly healthy.


Besides paying attention to the consumption amounts, when purchasing nut products, consumers should note that some manufacturers may add various seasonings to nuts, or have them coated, battered or deep-fried during processing to make them more tasty and appealing to consumers. Consumption of these overly flavoured and processed nuts may cause excess intake of sodium, fats and sugars. They are also higher in calories than plain nuts, which runs in contrary to the intention of eating nuts to promote health. In this respect, we have to read carefully the ingredients listed on the food labels during shopping, and choose plain mixed nuts with less additives in them. It is preferable to eat a variety of nuts instead of a single type to ensure a varied and balanced nutritional intake.


In summary, the nutritional values of nuts can only be highlighted when eating them in moderate and appropriate amounts.


*For more information on Targeted Food Surveillance, please visit: