Ninja Tactics Against Toxins

What if there were dangerous toxins that had the potential to contaminate our food, but, much like the Teenage Mutant Ninja Turtles’ secret protection of the citizens of New York and because our food system does a great job of protecting us from that threat, they don’t pose a risk to you? In this episode, Steve talks about mycotoxins and how protection from them varies around the world.

Here is a question for you: what if there were some super dangerous toxins that had the potential to be in your food, but they don’t actually pose a risk for you because our food system does a great job of protecting us from that threat? Would you want to know more about this?

My granddaughter doing her "Ninja pose" when she was three.

I’m talking here about a real thing – something that could be seriously scary, but which fortunately isn’t among the problems we face, at least those of us in the “rich world.” The toxic chemicals I’m talking about are called mycotoxins. These are natural chemicals that can form in various foods when those foods are infected with certain fungi or molds. This sort of infection often happens because a crop is damaged by insects, but there are some cases where the infection can happen without those sorts of injuries.

There are quite a few different kinds of mycotoxins, and several are seriously nasty things. The fact that our food system protects us is great news, but sadly, lots of people in the poorer parts of the world don’t enjoy the same degree of protection that we do. In fact, mycotoxins are among the major causes of cancer and of premature death in parts of Asia and in sub-Saharan Africa. So, back to my question: do you want to know more about this topic?

I think that one thing that makes this a tricky question is that we are used to the idea that the news or the focus of social dialog tends to be about the bad things, the negatives. This kind of “good news” doesn’t tend to get much attention.

As I thought about doing an episode on this topic, a random line came to mind from the 1990s kid’s show, “Veggie Tales”. In one of the cartoon’s famous “silly songs with Larry” segments about “The Pirates Who Don’t Do Anything,” one of the characters says, “Why even bring it up?” That captures my quandary about venturing into an episode about mycotoxins – should I even bring it up?

Another pop culture reference could be the classic line from Mad Magazine’s Alfred E. Neuman: “What, me worry?” Of course, that was satire, and the real goal of the magazine was to get a new generation to worry about the things their elders were telling them were just fine. But perhaps a better pop culture reference for this mycotoxin issue would be the Teenage Mutant Ninja Turtles. They were “good guys” out there protecting the people of New York, but doing so secretly, because, well - they were mutant Ninja turtles and didn’t want to draw attention to themselves.

The Ninja Turtles: William Tung from USA [CC BY-SA 2.0 (https://creativecommons.org/licenses/by-sa/2.0)].

So, with this mycotoxin thing, the protection that we are getting is through the efforts and attention of real people who farm or play important roles in how foods make their way through the system to us as consumers.

After thinking about this for a while I’ve concluded that it would be a good thing for people to know about this good news and engage in the thinking about how to extend this sort of protection to the less fortunate around the world.

Mycotoxins, these dangerous chemicals made by plant infecting molds and fungi, are not at all new. One early record of this problem comes from the first century “parable of the wheat and the tares” attributed to Jesus. The story opens with a land owner’s workers coming to him with the urgent question, “Didn’t you plant good seed?” The reason for their alarm was that as the wheat field was maturing, they could see that it was infested with a particular weed in the genus of grass we now call Lolium. Back in Jesus’ time they called it, “darnel.” Now like any modern or ancient field, there are always various weeds that have to be managed. But this wasn’t just any weed; it was a grass that was well-known to people of the time as a problem, and animals or people who ate wheat contaminated with this grain would get sick. This was because of a mycotoxin formed in the grain by a fungal “endophyte” that tended to grow there. Early in the growing season, darnel looked a lot like wheat, but once the heads were formed, they were recognizable, as was their dangerous potential. Of course, these ancient farmers didn’t know about mycotoxins as such, but they knew that this was a consequential contaminant of their food supply and one that farmers would normally have tried to avoid by planting seed that was free of this weed.

Drawing of the "heads" of various British grasses, Pratt, Anne, 1806-1893 [No restrictions, Wikimedia commons).

The farmer’s response is perhaps the earliest record of bioterrorism. He says, “Some enemy must have done this,” meaning that someone must have sneaked into the field and intentionally spread darnel seed at the beginning of the growing season.

The farmer’s solution also makes sense. He says to wait until the wheat crop finishes its grain development and drying process, then selectively gather the darnel seed heads to burn them. It would have been a labor-intensive thing to do, but obviously something he considered necessary so the wheat would be safe to eat and so grain saved for seed for the next year wouldn’t be contaminated again with the darnel.

Another historical example of a mycotoxin in the human food supply comes from medieval Europe when there was a malady known as “Saint Anthony’s Fire.” People would develop intense pain in their feet and hands, mental disturbances, and even miscarriages among pregnant women. People eventually figured out that it came from eating bread or other things made with rye. They named this issue with the grain Ergot, which we now know to be caused by an infection of the rye by a fungus called Claviceps purpurea that makes mycotoxins called “ergot alkaloids.” It is believed that some of the mental effects of this mycotoxin poisoning was behind the strange behaviors that led to the Salem Witch Trials. Throughout history, thousands of people have died from the effects of this toxin, but eventually people learned how to reduce the potential of infection and how to recognize and sort away the toxic infected grain. Interestingly, the various chemical compounds made by this fungus and their derivatives have led to the development of over 100 pharmaceutical drugs and also the hallucinogen, LSD. As an earlier POPagriculture episode says, “Mother Nature is a pretty amazing chemist,” but frequently we don’t want some of what she makes!

So, mycotoxins have been a potential threat in our food supply for a long time, and so have efforts to mitigate the risk. Flash forward to 1960 when there was a mysterious die-off of turkeys on poultry farms in England. It was termed “Turkey X Disease,” but it also happened with flocks of ducklings or young pheasants. It turned out that the problem traced back to moldy peanut meal that had been imported from Brazil as feed. The contaminated nuts were analyzed and what scientists found was a family of four chemical toxins that are made by some strains of several species on the fungus Aspergillus. They are now known as Aflatoxins and they can kill animals or people at high dosages. The more sinister aspect of these toxins is that they can cause cancer among people who get some regularly in their diet. Worldwide, aflatoxins could well be the biggest single cause of death through liver cancer, because so many people in the poorer parts of the world depend on maize (corn) and ground nuts (peanuts) as the base for their diet, and those crops can get contaminated with aflatoxin. Aflatoxins can occur in many other crops as well, including cottonseed; nuts like almonds, pistachios and walnuts; figs; and spices. They can be passed along through milk and cheese if the cows are fed aflatoxin-containing grain.

So, how are you and I protected from this dangerous side of nature? Well, as is often the case with pest-related challenges, what really helps is to have a diverse set of tactics – a set of what we might call “Food Safety Ninja Strategies.”

In many cases the key “bad guys” are insects, because the damage they cause through their feeding opens the door for infection by the mycotoxin-producing molds. Particularly with corn and tree nuts, there are caterpillars who chomp away at the developing ears of corn or the hulls of the nuts, opening the door for the mold. A similar thing can happen with fruits like apples when insect feeding leads to growth of a Penicillium mold that makes a different mycotoxin called patulin. Patulin isn’t as scary as aflatoxin, but still something to be avoided if possible.

In an earlier POPagriculture episode titled “There’s More Than One Way to Kill a Bug,” I talked about how farmers deal with insects using insecticides, biocontrol agents, natural enemies of the bugs, and with chemicals that repel, disorient, or otherwise confuse the bugs. Those are all good options for our “food-supply-protecting ninjas.” In the case of field corn, the genetically engineered hybrids that produce the super safe and selective Bt protein suffer much less insect damage, and thus the risk from mycotoxins, like aflatoxin, or another nasty one called Fumonisin, is much reduced.

The next Ninja strategy has to do with crop protection products that directly target the molds or other fungi. This approach usually requires using the right fungicide at the right point in time. There is a mycotoxin known by the common name “vomitoxin” that can form from infections of a fungus called Fusarium if it rains while wheat or barley crops are in the middle of their bloom period. A fungicide spray made at that time can prevent infection.

It also helps if farmers combine that tool with the choice of wheat varieties that are at least partially resistant to the fungus. It’s also important to choose the right order for crops in the rotation and to pay attention to which crops are in the adjoining fields. Corn can be a problem for wheat in both those cases because the Fusarium can grow on the corn stubble. Leaving corn fields un-tilled is the most environmentally sound option for farmers in terms of soil health and minimized carbon footprint but not tilling in the corn stubble increases the risk of vomitoxin in an adjoining wheat field. But if farmers combine the ninja tactics of plant resistance and careful use of a fungicide it is possible to keep our food safe.

Another interesting strategy is the use of an “atoxigenic strain” of the mycotoxin-forming fungi which is biologically very similar but doesn’t make the toxin(s). If the farmer can provide a big supply of those spores of the “good guy” strains, they can outcompete the strains that do make the toxins. This Ninja strategy is widely used, particularly in the peanut, almond and cotton industries. It is also one option that is starting to be used as a sort of home-grown remedy in less affluent countries.

So, fighting back against the pests in the field is the beginning of our mycotoxin defense, but a lot also happens after harvest. It is important for things like grains to be harvested and then stored under conditions that are dry enough to prevent further growth of the molds. Not having the ability to create and maintain good storage conditions is one of the biggest reasons that mycotoxins are such a dangerous issue in less affluent countries. A nationwide campaign has recently been pursued in Ghana to make farmers more aware of this risk during storage so they can at least try to avoid infected grain.

Back to our apple example, in the process of harvesting and handling, the apples can get little injuries. That Penicillium fungus can get into those wounds and grow while the apples are in cold storage. Chemical fungicides and biological control agents like yeasts can be applied during the step in the process when the fruit when the fruit is being cleaned and sorted on its way into storage. That’s another Ninja strategy to prevent formation of the patulin toxin.

There is another really cool tactic used to protect us from mycotoxins. In the places where things like almonds or peanuts are stored, there is equipment to send the individual, shelled nuts single file down a fast-moving conveyer belt. As the nuts go past a source of UV light, they will give off a specific color of light by fluorescence if Aspergillus fungus is in or on the nut. A machine detects that color of light and a little puff of air knocks the potentially contaminated nut off the line and out of the final food products that consumers will buy, such as snacks, peanut butter, and almond milk. Recently the Swiss company Bühler collaborated with Microsoft to develop a high-throughput grain inspection system that can do this with wheat and corn. Now, this approach can’t really succeed if there is a lot of contamination, but if several of the other Ninja strategies have been implemented, this sort of final clean-up is feasible. That high degree of protection is quite standard for things like nuts and peanuts produced in the U.S., but not from all places around the world where those are grown. I like to make sure that my nut products come from the U.S.

Now, there is one recent addition to our Ninja arsenal for mycotoxin prevention, and it involves enlisting the help of the crop plants themselves. It is also something that could help farmers in the poorest parts of the world. Scientists in the U.S. and India collaborated on an anti-mycotoxin strategy using a biotech approach called “RNAi.” They armed plants with the ability to make RNA sequences that exactly match a part of genes in the bad guy molds. That “RNAi” very specifically binds to the RNA that the mold produces when it is making a key enzyme necessary in creating its mycotoxin. A nearly universal defense mechanism in plant or animal cells detects those double-stranded RNAs and sends out an enzyme called “dicer” to chop them up. Therefore, the fungus can’t make its enzyme, so it can’t make the toxin. If this defense mechanism could be put into the genes for the corn and peanut varieties that poor farmers grow, they could have a much better level of protection than they do today. The RNAi strategy is an example of what is called a “scale neutral” solution that, like the atoxigenic strain biocontrol tactic, could help all farmers around the world, regardless of their access to resources. Sadly, the biggest barrier to that scenario is likely to be from anti-GMO activist groups, who have largely prevented any kind of biotech solutions from being offered for free to farmers in Africa and Asia. Hopefully, international organizations grounded in science will persevere on this front. They might also be able to fund better storage facilities and maybe even grain-sorting technologies to further diversify the Ninja capabilities for the benefit of those who still suffer the most because of mycotoxins.

So, I hope this discussion gives you some encouragement and some appreciation for the things that go on behind the scenes for our benefit when it comes to this challenge of mycotoxins. I believe that a benefit recognized is better than one that is just an untold story.