The bitter truth about aflatoxins

Monday, 19 April 2021 00:00 -     - {{hitsCtrl.values.hits}}

 


By Dr. Prasanna J.P. Gunawardena


You have probably heard about the chilling effects of aflatoxins from the horrifying news headlines, but do you know what aflatoxins are? In this article, I will explain to you what aflatoxins are, which foods they affect, and describe how the health risks associated with the aflatoxins can be mitigated and avoided. 

 

So what are these dreaded aflatoxins?

Chemically speaking, aflatoxin is a type of ‘mycotoxin’. Aflatoxin is a common name for specific secondary metabolites produced by Aspergillus fungi, primarily Aspergillus flavus, Aspergillus parasiticus and Aspergillus nomius. These types of aflatoxigenic fungi produce various members of the aflatoxin group of chemicals – AFB1, AFB2, AFG1 and AFG2. 

There are natural moulds found around the world and concentrated mostly in the food supply in areas with wet and warm climates. Under favourable conditions typically found in tropical and subtropical regions, including high temperatures and high humidity, these moulds, normally found on dead and decaying vegetation, can invade food crops. Drought stress, insect damage can also contribute to higher occurrence of moulds. 

The aflatoxins were first discovered immediately after an outbreak of a disease which affected turkeys of unknown etiology in England in 1960. Since then, there are numerous scientific researchers who have conducted investigations in order to understand how exactly these toxins affect the mankind. Aflatoxins do not only pose significant health risks but also create a high economic burden, since approximately at least 25% of the world’s food crops are being destroyed due to the aflatoxins annually.

 

Zooming in on Sri Lanka

Recent media speculation about imported consignments of coconut oil, which were highly contaminated with aflatoxins, have made Sri Lankan society furious. Unfortunately, the media merely presents a distorted view of the situation, since most people who present arguments for and against aflatoxins are extremely far from scientific community and lack the understanding of basic biological concepts. The situation at hand has resulted in circulation of myths or half-truths about aflatoxins and the health risks associated with them. 

Most people believe that contaminated coconut oil is the only way in which aflatoxin can enter a human body. However, this is simply not true and there are plenty of alternative ways aflatoxins can sneak into our bodies. The bitter truth is that some goods which are regularly consumed by ordinary Sri Lankan citizens on daily basis are already contaminated with aflatoxin. Let’s have a closer look at some examples.

 

Coconut oil – the greatest threat? 

Coconut oil is the most widely used vegetable oil in Sri Lanka. There are handful of scientists, who have done research on the topic of ‘Aflatoxin contamination in edible vegetable oils in Sri Lankan market’ over the last decade and you can read their findings via open resources on the internet. Most of researchers have found out that nearly 20-30% of the coconut oil samples (locally produced as well as imported) were contaminated with aflatoxins. The total aflatoxin contamination in coconut oil ranged from 2.25 to 72.70 μg/kg and Aflatoxin B1 contamination in coconut oil ranged from 1.76 to 60.92 μg/kg. 

This is an alarming result because unlike other agricultural commodities that get contaminated with aflatoxins, consumers get exposed to greater and continuous health risks through using coconut oil on a daily basis. High levels of aflatoxin contamination in coconut oil may be a result of improper agricultural practices that facilitate toxigenic fungal growth on copra. The only solution to the problem lies in getting the market coconut oil tested (at accredited laboratories only) for the presence of aflatoxins and while introducing good manufacturing practices to the industry.

 

What about rice? 

In Sri Lanka, rice is the main staple which is mostly processed into parboiled rice. Among cereals, rice and corn are mostly contaminated by aflatoxins in natural conditions due to changes in agricultural practices. There are some interesting studies which analysed the levels of aflatoxin B1 and aflatoxin G1 in parboiled and raw milled rice collected from major rice producing areas and rice consuming townships in Sri Lanka. In almost all the samples of parboiled rice examined, the aflatoxin B1 and G1 contents were significantly higher than in raw milled rice.

 

The enemy in plain sight

 However, Aflatoxins do not only affect rice and coconut oil. Aflatoxins can invade the food supply at any time during production, processing, transport and storage. Improper storage under conditions that favour mould growth (warm and humid storage environments) can typically lead to levels of contamination much higher than those found in the field. Moulds that produce aflatoxins are regularly found in improperly stored staple commodities such as rice, maize, cassava, chili peppers, cottonseed, millet, peanuts, sesame seeds, sorghum, sunflower seeds, sweetcorn, tree nuts, wheat, palm kernel (copra), nuts and oil seeds especially peanuts, tree nuts and dried fruits and a variety of spices (ex. nutmeg, pepper and paprika). 

Pre-harvest contamination with aflatoxins is mainly limited to maize, cottonseed, peanuts and tree nuts. Post-harvest contamination can be found in a variety of other crops such as coffee, rice and spices. 

Food processing techniques are not sufficient to eliminate aflatoxins from contaminated food and feed due to their heat- resistant nature. When contaminated food is processed, aflatoxins enter the general food supply where they have been found in both pet and human foods, as well as in feedstocks for agricultural animals.

Milk and milk-based products contain another type of aflatoxin M1, which can be detected in dairy cattle that have ingested feed contaminated with aflatoxin B1. 

Animal fed contaminated food can pass aflatoxin transformation products into eggs, milk products, and meat. Subsequently, humans may be exposed to this aflatoxin through milk and milk products, especially in areas where the contaminated grain is used for animal feed. While infants could be in danger of intoxication through breastfeeding. 

 

Aflatoxins and their health consequences

Exposure to aflatoxins through diet can lead to serious health complications and consequences. These effects can be both acute and long-term, and their effects on the human body vary. They can be teratogenic (cause a birth defect in the child), mutagenic (cause a mutation or a change in the DNA of a cell), carcinogenic (promote carcinogenesis, the formation of cancer), immunotoxic (adversely affect immune system) and hepatotoxic (cause damage or destruction to liver cells). Aflatoxins predominately affect the liver and kidneys but can also negatively impact reproductive organs.

 

Regulatory limits for aflatoxins

Even a low concentration of aflatoxins is hazardous for humans and livestock. The identification and quantification of aflatoxins in food production is a major challenge to ensuring food safety today.

Most farmers do not know about the existence of aflatoxins, let alone the grave risks associated with their consumption, and therefore are not concerned about their mitigation. 

Quantitative analysis of aflatoxins is optional for locally consumed foods, but mandatory for crops designated for export in order to meet international regulatory standards. Therefore, different countries have implemented strict regulations for aflatoxins in food and feed to ensure that the health of individuals is not impaired.

The safe limit of aflatoxin lies in the range of 4–30 μg/kg for human consumption. The European Union has the strictest standard level with AFB1 and total aflatoxins not beyond 2 μg/kg and 4 μg/kg, respectively, in any product meant for direct consumption. Similarly, the maximum acceptable limit set for aflatoxins in the United States is 20 μg/kg. On the other hand, in Sri Lanka total aflatoxins levels is can reach 10 µg/ kg, while the maximum level of aflatoxins B1 is set at 5 µg/ kg. However, there is sufficient evidence that demonstrates that this amount does not do enough to protect everybody, especially people living in developing countries where these crops are consumed in high amounts and immunity is already low for other reasons.

 

Removal or inactivation of aflatoxin

Removal or inactivation of aflatoxin in food and feedstuffs is a major global concern. Aflatoxins can be detoxified or removed from contaminated foods and feeds through physical, chemical, and biological methods depending on the conditions. . However, the treatment has its own limitations, since the treated products should be safe for human health and essential nutritive value should not deteriorate during the process.

The following methods are often suggested for effective decontamination of some mycotoxins. Aflatoxins’ contamination of crops at pre- and post-harvest conditions can be controlled to some extent by the implementation of good agricultural practices (GAPs), good manufacturing practices (GMPs) and good storage practices (GSPs). 

Furthermore, the novel processing technologies involving a microwave, UV, pulsed light, electrolysed water, cold plasma, ozone, electron beam or gamma (γ) irradiation in combination with either biological, physical, chemical or genetic engineering methods have the potential to improve the efficiency of aflatoxins decontamination as well as to overcome the limitations of any specific technology. 

Therefore, utilisation of the novel technologies along with raising public awareness for implementing GAPs, GMPs and GSPs are crucial for controlling aflatoxins contamination in food and feed to ensure food safety and security for maintaining human and animal health.

 

Control strategies of aflatoxins which can be helped in Sri Lanka

Comprehensive, multi-sectoral approaches are required to control the complex aflatoxin problem and improve the health, income, and livelihoods of local farmers, farm households and consumers. A comprehensive aflatoxin control program could include a range of complementary components, for instance:

1. Effective policies, standards and regulations, policy-relevant information (from economic, food security and health assessments); campaigns to raise consumer demand for safe, high-quality food; 

2. Distribution and adoption of improved inputs and technology solutions, and improved quality of production;

3. Market mechanisms to inspect commodities, regulate quality, and ensure proper storage;

4. Access to safe and high-quality food ingredients;

5. Efficient withdrawal of and alternative uses for contaminated commodities.

Action is needed at all levels (local, regional, and national) to reduce aflatoxin prevalence and exposure in Sri Lanka. Although we do have sound standards on aflatoxin levels, the flaw of the current system lays at the implementation level. 

If there is a general awareness of aflatoxin in our country and there are supporting regulations and institutions, then the impact on humans stemming from the aflatoxin contamination will be low, but the positive market impact will be high.

            

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