Aflatoxin M1

Aflatoxins are a group of highly toxic and carcinogenic compounds produced by molds, primarily Aspergillus flavus and Aspergillus parasiticus, that contaminate foods like peanuts, corn, cottonseed, and tree nuts under favorable conditions. 

Among these, aflatoxin B1 (AFB1) is the most potent and carcinogenic.  Its metabolite, aflatoxin M1 (AFM1), is formed when AFB1 is ingested and metabolized by mammals.  High levels of aflatoxin B1 in animal feed that is then eaten by dairy cows leads to its excretion in milk and dairy products.  

Classified as a Group 2B carcinogen by the International Agency for Research on Cancer (IARC), AFM1 is of particular concern due to its presence in milk and dairy products, posing health risks, especially to infants and young children.  Regulatory agencies like the FDA have established maximum permissible limits for AFM1 in dairy products to mitigate exposure risks. 

Various strategies, including chemical treatments, adsorbents, and biological approaches, are being explored to reduce AFM1 levels and protect public health.

What are Aflatoxins?  [12.] 

Aflatoxins are a group of highly toxic and carcinogenic compounds produced as secondary metabolites by certain molds, primarily Aspergillus flavus and Aspergillus parasiticus.  [12., 26.]

They are one type of mycotoxin, which are a larger group of toxic chemical compounds produced by molds.  

These mycotoxins are formed when the molds colonize foods like peanuts, corn, cottonseed, tree nuts, and spices under favorable temperature and humidity conditions.   [12., 19.] 

The main aflatoxins are B1, B2, G1, and G2, with aflatoxin B1 (AFB1) being the most potent and carcinogenic.  [7.] 

Their production occurs when the mold's growth is stressed, such as during drought conditions or improper crop storage. 

Aflatoxins are among the most carcinogenic substances known - they can cause acute toxicity leading to liver failure, hemorrhaging, and even death in severe cases.   [12.]  Chronic exposure increases the risk of developing liver cancer, as aflatoxins can bind to DNA and cause mutations, particularly in the p53 tumor suppressor gene.  [12., 14.]

They can also suppress the immune system, and can cause stunted growth in children.  [13., 19., 20.] 

Worryingly, aflatoxins are highly stable and can persist in foods and animal feeds even after processing and cooking.  They bioaccumulate in the body over time, especially in the liver, due to their lipophilic nature and resistance to metabolic breakdown.  [4., 16., 18.]

Aflatoxin B1 is metabolized to the reactive aflatoxin-8,9-epoxide, which binds to DNA and proteins, initiating carcinogenesis.  [20.] 

Animals fed contaminated feed can pass aflatoxin metabolites into meat, milk, and eggs, posing risks to humans consuming these products.

Anti-Aflatoxin Biomarkers

Anti-aflatoxin biomarkers are a group of compounds or metabolites that can be measured in biological samples to assess exposure to aflatoxins, which are toxic and carcinogenic metabolites produced by certain molds. 

These biomarkers provide a direct measure of internal exposure and can help evaluate the associated health risks.

A variety of biomarkers have been used to identify the presence of aflatoxins in humans and animals.  

Aflatoxin M1 Sources

What is Aflatoxin M1?

Aflatoxin M1 (AFM1) is a major metabolite of aflatoxin B1 (AFB1), which is produced by the fungi Aspergillus flavus and Aspergillus parasiticus.  AFM1 is formed when AFB1 is ingested by mammals and undergoes hydroxylation in the liver, resulting in the addition of a hydroxyl group to the molecular structure.  [15.] 

AFM1 is classified as a Group 2B carcinogen (possibly carcinogenic to humans) by the International Agency for Research on Cancer (IARC).  [12.]  While less potent than its parent compound AFB1, AFM1 has been shown to cause liver cancer in certain animal studies.  [1.] 

Aflatoxin M1 in Milk and Dairy Products

The primary concern with AFM1 is its presence in milk and dairy products including cheese due to the carry-over from livestock consuming AFB1-contaminated feed.  [1., 2.]  When dairy cattle ingest AFB1-contaminated feed, a portion of the AFB1 is metabolized to AFM1, which can then be excreted in the milk.  [1.]

To mitigate the risk of AFM1 exposure, regulatory agencies like the U.S. Food and Drug Administration (FDA) have established action levels or maximum permissible limits for AFM1 in milk and dairy products.  The FDA has set an action level of 0.5 parts per billion (ppb) for AFM1 in fluid milk products.  [1.] 

Aflatoxin M1 Contamination of Food and Feed

In addition to its presence in milk and dairy products, aflatoxin M1 can contaminate various food and feed crops, such as corn, peanuts, cottonseed, and other grains during pre-harvest, harvest, and storage stages.  [17.] 

Aflatoxin M1 Laboratory Testing and Detection Methods

Test Information, Sample Collection and Preparation

Various biological samples can be employed to detect and quantify aflatoxin M1 biomarkers, particularly blood, urine and nasal secretions.

Blood samples are typically collected via venipuncture in a clinical setting, while urine and nasal secretion samples may be collected from the comfort of home.  

It is important to consult with the ordering provider prior to sample collection, as certain protocols may be recommended beforehand.  

Interpretation of Aflatoxin M1 Test Results

Optimal Levels of Aflatoxin M1 Test Results

Because of the high level of toxicity of aflatoxins, optimal test results indicate undetectable levels of aflatoxins, including aflatoxin M1.  

Clinical Significance of Elevated Aflatoxin M1

Elevated levels of aflatoxin M1 indicate recent or current exposure to aflatoxin B1, as aflatoxin M1 is a metabolite of aflatoxin B1.  It may also indicate a high level of dairy intake, as high levels of aflatoxin M1 may be present in dairy products.  [1., 2.]  

Because aflatoxins are known to bioaccumulate, testing positive for the presence of aflatoxins may indicate a persistent historical exposure.  [8., 9., 24.] 

Clinical Significance of Low Aflatoxin M1

Low or undetectable levels of aflatoxin M1 are considered ideal.  

Aflatoxin M1 Related Biomarkers

In addition to the direct measurement of aflatoxin M1 biomarkers, other biomarkers can provide complementary information about aflatoxin exposure and its potential health effects.

Aflatoxin B1 as a Precursor, along with Aflatoxins B2, G1, and G2

Aflatoxin B1 is the primary aflatoxin produced by Aspergillus fungi and is the precursor to aflatoxin M1.  Measuring aflatoxin B1 levels alongside the other major aflatoxins, aflatoxin B2, G1, and G2, provides a more in-depth picture of total aflatoxin exposure. 

Oxidative Stress Markers  [21., 27.]

Aflatoxin exposure is known to induce oxidative stress, which can lead to cellular damage and contribute to the development of various diseases. 

Biomarkers such as malondialdehyde (MDA) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) can be measured to assess oxidative stress levels and the associated risk of aflatoxin-related toxicity.  [21.] 

Liver Function Markers  [10.] 

Since the liver is a primary target organ for aflatoxin toxicity, monitoring liver function biomarkers like alanine aminotransferase (ALT), aspartate aminotransferase (AST), and bilirubin can provide insights into the extent of hepatic injury and potential liver damage caused by aflatoxin exposure.  

Inflammatory Biomarkers  [21.] 

Aflatoxin exposure can trigger inflammatory responses, and biomarkers such as C-reactive protein (CRP), interleukins (e.g., IL-6, IL-8), and tumor necrosis factor-alpha (TNF-α) can be measured to evaluate the inflammatory status and associated health risks.

Aflatoxin M1 Treatment and Mitigation Strategies

Aflatoxin M1 contamination in milk and dairy products poses a significant risk to human health, particularly for infants and young children.  Consequently, various strategies have been explored to mitigate and reduce aflatoxin M1 levels in these products.

Strategies to Reduce Aflatoxin Contamination in Food and Feed  [3.] 

Mitigating exposure to the carcinogenic mycotoxin aflatoxin M1 (AFM1) in contaminated milk and dairy products has been an area of active research.  Conventional thermal treatments like pasteurization and sterilization are generally ineffective at destroying AFM1.  

Several chemical treatments have shown promise, including ammoniation, which can reduce AFM1 content by 79-90% through molecular breakdown, and the use of hydrogen peroxide as a detoxifying agent. 

Adsorbents like bentonite clays have also demonstrated the ability to bind and reduce AFM1 levels. 

Biological approaches, such as the use of probiotics and plant extracts from sources like broccoli, garlic, and curcumin, have exhibited potential in decreasing or detoxifying AFM1 in milk.

Potential Treatments for Aflatoxin M1 Exposure

Supplementation with antioxidants like vitamins C and E, and selenium can aid the body's natural detoxification mechanisms against mycotoxins like AFM1.  [3.] 

Because aflatoxins and their carcinogenic aflatoxin epoxides are detoxified by glutathione, supporting the glutathione system with vitamin C, selenium and NAC may aid in detoxification.  [23.] 

Also, liver function must be maintained in the setting of aflatoxin exposure.  This includes ample hydration, as optimal liver cell function relies on appropriate hydration.  This becomes particularly important if liver damage and/or renal damage has occurred.  [11.]

BInders including activated charcoal, clays, or some strains of lactic acid bacteria have been used to bind aflatoxins in food.  [22.]  Few studies are available regarding the use of these binders in humans, although they are being increasingly recommended.  

Antifungal therapies are recommended by some specialists.  [5.] 

Additionally, mycotoxin exposure often co-occurs.  It is important to consider testing levels of mycotoxins beyond the aflatoxin family, including ochratoxins, fumonisins, and zearalenone, for a full assessment of an individual’s toxicity burden.  [22.] 

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