The real threat of aflatoxins in your food

Monday March 22 2021

The fungus can be recognised by a gray-green or yellow-green mould growing on corn kernels in the field or in storage PHOTO/COURTESY/IITA.ORG

Although Kenya has lifted the ban on Ugandan maize, the concern that the maize contains aflatoxins, remains. The National Cancer Institute, USA, defines aflatoxins as a family of toxins produced by certain fungi that are found on agricultural crops such as maize (corn), peanuts, cottonseed, and tree nuts. 

These types of fungi are abundant in warm and humid regions of the world and can contaminate crops in the field, at harvest, and during storage. Consumption of food contaminated with these mycotoxins poses a serious health threat to humans and livestock. 

An estimated 25 per cent or more of the world’s food crops are destroyed annually in the fight against aflatoxins, according to the World Health Organisation (WHO). 

WHO adds that more than 14 types of aflatoxins can be tolerable but B1, B2, G1, and G2 are particularly dangerous to humans and animals. 
Aflatoxin M1 may also be ingested through milk and milk products, including breast milk, especially in areas where the poorest quality grains are used to feed animals.

Studies show a higher dietary exposure to aflatoxins in developing countries than in developed countries, which is mainly due to the difference in standards of food storage and transportation. People in areas where maize is the staple food, are highly vulnerable to aflatoxins. 

Studies also show that pre-harvest contamination mainly occurs in maize, cottonseed, groundnuts, and tree nuts such as almonds and Brazil nuts, among others, while post-harvest contamination can affect a variety of crops such as coffee, rice, and spices. 


In Uganda, studies blame the maize contamination on unfavourable environmental conditions such as erratic rainfall, high temperatures and high humidity as well as poor harvesting and storage methods. 

Prevalence, risks 
Although low socioeconomic status, chronic diarrhoea, infections, and malnutrition, among others, can cause stunting among children, aflatoxins too have been linked to birth and growth defects. 

A pilot study published in 2014 by the Tropical Medicine & International Health, showed significant levels of aflatoxins in rural Ugandans of all ages, with the highest among those near trading centres. Those who consumed matooke had fewer aflatoxins than those who consumed posho. 

A recent study carried out in Uganda, found that aflatoxin exposure contributed to 16 per cent of stunting among children. And among those both stunted and underweight, the figure was 34 per cent. Consuming large doses of aflatoxins, for example 1mg/kg or higher, over a period of one to three weeks, is “acutely toxic and potentially lethal.” It causes aflatoxicosis, a condition associated with abdominal pain, diarrhoea, vomiting, jaundice and ascites and might lead to death. 
However, scientists say doses that trigger acute toxicity in humans vary depending on age, gender, health, nutritional status and factors such as chronic viral hepatitis, alcoholism, smoking and liver complications. 

Adults are more tolerant to acute exposure than children. Dr Paul Kasenene, a nutritionist, recently told NTV Health Focus that aflatoxins may weaken one’s immune system, thus lowering one’s ability to resist infections such as HIV and tuberculosis, among others. 
Long-term exposure to aflatoxins, scientists say, can affect the functioning of organs, especially the liver and kidneys. Dr Kasenene adds that the worst threat is causing liver cancer. Vulnerability is higher among those infected with hepatitis B. 

Published by ResearchGate, a European commercial social networking site for scientists and researchers, a study shows that 20 out of 68 people reported to have been exposed to “the unknown poison,” in an aflatoxicosis outbreak died in Dodoma, Tanzania in 2016. 

Majority of the fatalities were children below 15 years and were attributed to liver failure due to contamination after consuming home-grown maize with abnormally high levels of aflatoxins.

Another report showed a 15-year-old Ugandan child weighing 36kg who was eating aflatoxin-contaminated cassava daily until he died of liver failure. 

Prevention, treatment
Dr Kasenene says aflatoxins are hard to detect because they can exist in forms that cannot be seen by mere looking at the foods. Hence, to reduce the risk of exposure, he advises consumers to buy nuts in their pods, where possible, and store them for a short time. 

“Because the longer you keep them, the higher they are likely to be contaminated,” he says, adding that consumers can also try substituting maize with traditional grains such as millet, chia seeds, sorghum, amaranth, which are less risky. 

Among preventive measures the WHO listed are: carefully inspecting whole grains and nuts and discarding any that look mouldy, discoloured, or shrivelled; buying grains and nuts as fresh as possible and those which have not been transported over a long time—processing or roasting does not entirely kill aflatoxins; diversifying one’s diet to mitigate aflatoxin exposure and improve health and nutrition, among others. 

Kasenene suggests antibiotics, blood transfusion or intravenous fluids to flush out the toxins, as some of the treatments. Advanced interventions include light therapy and other liver-detoxifying procedures. 

*Additional information 

Control and removal of aflatoxins
● Guidelines for preventing mycotoxins in farm commodities have been suggested by the U.S. Department of Agriculture. Moisture is the single most important parameter and prompt drying to safe levels is essential for control of toxigenic molds. Foreign matter and damaged seed should be removed. 

● Provision of clean, dry, adequately cooled and ventilated storage is important and good sanitation is essential to minimise mold contamination during storage and processing. 

● Sorting or separation can concentrate the vast majority of aflatoxin-contaminated kernels into relatively small fractions and only a small loss is incurred as a result of their removal. 

● Heat is relatively ineffective for destruction of aflatoxin although normal roasting, as of peanuts for the preparation of peanut butter, results in considerable reduction in aflatoxin content. 

● Oxidising 
agents readily destroy aflatoxin, and treatment with hydrogen peroxide may be useful. Treatment of defatted oilseed meals with ammonia can reduce aflatoxin content to very low or undetectable levels with only moderate damage to protein quality.