I had a fascinating conversation about aflatoxin in human food and animal feed with Dr. Tim Williams, a professor at the University of Georgia who specializes in research on peanuts. (ECHO featured aflatoxin in EDN 87. Aflatoxin is an extremely powerful carcinogen that comes from infection of stored crops with a certain mold.
Dr. Williams told me that in the developed world, government regulations keep aflatoxin in food so low that the only effect we normally see from it in people is a long-term effect—namely cancer, and especially liver cancer. On the other hand, animals often consume higher doses because animal feeds are not as heavily regulated. The U. S. government allows 30 ppb of aflatoxin in human food but ten times that amount, 300 ppb, in animal feed. Because of the higher exposure of animals to aflatoxin, one finds that articles published in veterinarian journals discuss many additional illnesses and nutritional problems caused by aflatoxin. These include lower nutritional status, lower birth weights, slower growth of the young, lower feed efficiency, suppressed immune system, increased rates of cancer and death.
In many developing countries, there is no or little governmental regulation of and inspection for aflatoxin in foods and feeds. Even if there is governmental control in food processing, there is no oversight of food sold in markets or consumed right on the farm. The result is that humans are exposed to levels of aflatoxin in food that are as high as or higher than that to which animals are exposed in feed. Dr. Williams’ important conclusion is that, for developing countries, we need to look at veterinarian literature instead of human medical literature when evaluating what effects we might expect to see from eating food contaminated by aflatoxin.
“This is important to know,” says Dr. Williams, “because not much attention has been paid to aflatoxin in severely malnourished populations. The reason is that other overwhelming problems in these situations seemed more important than a future risk of liver cancer. Now we are learning that there are additional immediate problems that need to be addressed.”
In this article, I share some of the surprising and disturbing effects of ingesting high levels of aflatoxin. I also share some good news about adding small amounts of a certain kind of clay (bentonite) to the diet, to protect against aflatoxin. Be sure to read through to the conclusion!
Effect of Aflatoxin on Birth Weight and Growth. Exposure to even very low doses of aflatoxin, both in the womb and after weaning, is harmful to infants. Reducing maternal exposure to aflatoxin during pregnancy can lead to a 0.8-kg increase in weight and 2-cm increase in height of children within the first year of life (Turner et al, 2008). A study in Benin and Togo showed that aflatoxin exposure increases markedly following weaning, and exposure early in life is also associated with reduced growth (Gong et al, 2003).
Modulating Effect of Aflatoxin Concentrations. Aflatoxin modulates (i.e. interacts with and has an effect on) certain existing health problems, such as being underweight, having infectious diseases (such as HIV), drinking unsafe water, being exposed to smoke from open fires, and having deficiencies of vitamin A and iron.
People Living with HIV/AIDS Face Increased Aflatoxin Exposure and Harm
Families of people living with HIV/AIDS are often less able to afford non-contaminated food. To make matters worse, the HIV virus reduces the availability of anti-oxidants that are needed to help detoxify aflatoxin. In addition, often people who have HIV/AIDS are also positive for hepatitis B. The hepatitis B virus decreases the process in the human body that normally detoxifies aflatoxin, while aflatoxin greatly increases the risk of developing liver cancer in people already at higher risk on account of their positive hepatitis B status.
Animal data and, where it exists, human data on immune suppression and nutritional interference show that aflatoxin symptoms are comparable to HIV infection symptoms. However, an important difference is that the symptoms of aflatoxin exposure (but not cancer, if it has developed) disappear if aflatoxin is removed from the diet.
The HIV Virus May be More Readily Spread To Individuals with High Exposure to Aflatoxin
Susceptibility to infection depends on how easily the viral particles may penetrate barriers to infection. An antibody called “secretory IgA” is the main immunoglobulin found in mucous secretions and also in small amounts in blood.
Secretory IgA resists degradation by enzymes, so it can survive in harsh environments such as the digestive and respiratory tracts, to provide protection against microbes that multiply in bodily secretions.
Human secretory IgA levels are decreased as a function of aflatoxin exposure. As a result, the integrity of membrane barriers is decreased and the person becomes more vulnerable to various infections, especially bacterial sexually transmitted diseases.
Dr. Williams said that people with HIV and aflatoxin are also more likely to infect another person.
Aflatoxin May Increase the Rate of Disease Progression in HIV/AIDS Patients. An investigation in the late 1980s looked into why there was an unusually rapid progression of HIV and AIDS in heroin addicts in the Netherlands and Scotland. The results revealed heroin that was contaminated with aflatoxin. The concentration of aflatoxin in urine of the patients was comparable to levels found in West Africans exposed through food (Henrickse et al, 1989).
It is “opportunistic infections” that usually debilitate and kill AIDS patients, rather than the actual virus directly. Aflatoxin exposure promotes opportunistic infections in animals and humans. Children with immune systems compromised by malnutrition and aflatoxin were found to be especially prone to infection.
Negative Synergy between Aflatoxin and Hepatitis Virus The word “synergy” refers to situations where two good things, when combined, end up being extremely good—at least more than the total of what their individual contributions would amount to separately. Sometimes people explain synergy by saying it is like a situation where suddenly two plus two equals five. Negative synergy, in contrast, is where two bad things together are extremely bad.
In people who test positive for having hepatitis B (HPB), “aflatoxin is up to 30 times more potent than in persons without the virus. The relative risk of cancer increased from 1 for the general population to five for HPB-infected individuals to 60 for individuals who are both infected with HPV and exposed to higher levels of aflatoxin. In some areas where both agents are common, [liver cancer is] the predominant cancer and the leading cause of death (64% of cancers)” (Williams et al, 2004). In these areas, the incidence of liver cancer is estimated to be 16 to 32 times higher than rates in USA and Europe. Worldwide in the year 2000, it is estimated that 8.8% of cancer mortalities were from liver cancer (Williams et al, 2004).
Aflatoxin is 30 times more potent to persons that are also positive for hepatitis B.
But there is Hope!!! There is some great news, though. Certain clays mixed in small concentrations with contaminated commodities bind the aflatoxin before it can be absorbed in the intestine. These clays are classified as “calcium bentonites.” This special kind of clay has a lattice layer structure that is able to trap and hold the aflatoxin inside the structure. Other clays only adsorb aflatoxin to their surface, but not powerfully enough to prevent the digestive system from reversing the binding and allowing uptake.
Adding a bentonite to food in amounts one-fourth to one-half of a percent by weight provides protection against aflatoxin for all animals. Such clays are used in animal feeds worldwide, in both developing and developed countries. For example, Novasil is a bentonite product which has been steam treated to increase the space between layers. Bentonite is approved by the Food and Drug Administration in the USA for including in human food for functional purposes, e.g. to make food go down the throat more easily.
When I first learned of the ability of clay to bind aflatoxin, I thought of the practice common in some countries of eating “clay cookies.” In Haiti this is especially common among pregnant women. I thought that this practice might be eliminating the absorption of aflatoxin from the gut. Unfortunately the bentonite clays are naturally found only in a few countries and at only a few places in those countries.
But where can calcium bentonite clays be found in the countries where aflatoxin is the greatest risk to the food supply? In countries where food or feed manufacturers use bentonite as a minor ingredient, it should be available in-country. Calcium bentonite clays are not expensive. Dr. Williams estimates that the ingredient cost in the USA is 66 cents per YEAR per person. In other countries, where these clays are available and mined, the cost might be less. It is likely that the cost would be somewhat higher if the bentonite was being imported, but not prohibitively so.
Calcium bentonite has a very wide range of industrial applications, so sources include producers or importers of bentonite. Would industrial-grade bentonite be suitable as a food or feed additive? I asked Dr. Williams. He had significant reservations. “Because these clays were mined without thought of being used in food or feeds, one could not be certain that they are free from contamination of heavy metals and other toxins such as PCBs. There is also the biological contamination risk to consider. We would really hesitate to recommend using clays without knowledge of their chemistry, and that they are within allowed levels of metals and other products.” (Personal communication, 2008)
Dr. Williams adds that the bentonite in food is also effective against rotaviruses. He suggests that bentonite in food/feed may thus have the added benefit of helping where this virus might be present in the water.
Gong, Y.Y. et al. 2003. Determinants of aflatoxin exposure in young children from Benin and Togo, West Africa: the critical role of weaning. International Journal of Epidemiology 32(4) 556-62.
Henrickse RG, SM Maxwell, and R. Young. 1989. Aflatoxins and heroin. Journal of Toxicology Toxic Reviews 8:88-94.
Turner, P.C. et al. 2008. Aflatoxin exposure in utero causes growth faltering in Gambian infants. International Journal of Epidemiology 36: 1119-1125. Williams, J.H. et al. 2004. Human aflatoxicosis in developing countries: a review of toxicology, exposure, potential health consequences, and interventions. American Journal of Clinical Nutrition 80(5): 1106-1122.
Price, M.L. 2009. Aflatoxin in the Diet Makes the Progression of HIV/AIDS and Hepatitis Much Worse. ECHO Development Notes no. 103