Sunday, May 8, 2011

Food Fears: Toxins

During my recent detox (recap here), I spent a lot of time thinking about what exactly I was removing from my body.

I mean, detox implies toxins, right? You are removing toxins from your body. That seems obvious...but how did those toxins get into my body? And what exactly do I need to do to remove them?

As many of you know, I am a trained biochemist. I understand many aspects of how organisms work at the chemical level, and I dabble in immunology and food science, but I'm by no means an expert. So, when it doubt, I looked up some info.

First, I looked up the definition of toxin:

toxin: a poisonous substance that is a specific product of the metabolic activities of a living organism and is usually very unstable, notably toxic when introduced into the tissues...

(Thank you Merriam-Webster). 
So, when we're talking about toxins, we're talking about something produced by an organism that is somehow harmful to my body. I have to ingest, be infected by, or somehow come in contact with such things to have a toxin in my body to remove. 
Some really common toxins: 
  Botulinum Toxin: 
Clostridium botulinum is the bacteria responsible for making the botulinum toxin, which has recently re-emerged as a popular chemical for cosmetic manipulation (Commercial name Botox). 

Besides its use as a popular cosmetic injectable, botulinum toxin is a rare, but deadly food poisoning agent. Early in the development of commercial methods for preservation, it would contaminate canned goods. This is because Clostridium botulinum grows anaerobically (i.e. an = without, aerobic = air; anaerobic = without air) and can grow easily in sealed cans provided that the contents provide enough nutrients and are at the right pH. During its growth, the bacteria produces botulinum toxin, which remains in the food even after the bacteria is killed. 

Botulinum toxin is a toxin that effects your nerves and brain, which is defined as a neurotoxin. It causes your muscles to fail by blocking the release of specific chemicals that signal movement to your muscles. It binds irreversibly, which means that the damage is done permanently - or until your body recycles that machinery and builds new machinery. Botulinum toxin is also extremely toxic. There are several forms of it, and the most potent form is lethal to a 200 lb human in concentrations of 0.0000001 gram. Try to imagine that tiny, tiny amount!

While much of canning technology has improved and contamination by botulinum toxin is now rare, a serious outbreak occurred a few years ago in Bolthouse Farms carrot juice. Because Clostridium botulinum is an environmental bacteria that exists in a lot of soils, consuming improperly stored raw foods can lead to poisoning. In our community of healthy living, I am consistenly worried about people who cold press and store juices, especially root veggies like ginger, carrot, and beet. Be very careful, and I would encourage you to not store juices for more than a couple days, and always in the fridge! 


Lets switch gears and talk about another kind of common poisoning - more classical food poisoning - which can be caused by a variety of bacteria, but basically uses the same mechanism. This mechanism is dependent on enterotoxins, which are usually bacterial proteins that are released to wreck havoc on your intestines. 

The common causes of enterotoxin-based food poisoning are the following: 

Escherichia coli 
Clostridium perfringens
Salmonella sp. (variety of species)

Other non-food based diseases with similar mechanisms include: 
Dysentery (Shigella dysenteriae)
Cholera (Vibrio cholerae)
Montezuma's revenge (variety of bacteria causes, sometimes parasites like Giardia lamblia)

Each of these bacteria have slightly different toxins, but they all have similar mechanisms and symptoms. Classical food poisoning manifests as diarrhea and abdominal cramps, and this is due to the toxin produced by the bacteria. 

To understand how it works, we have to go back to some basic biology and talk about tonicity. 

In, our bodies, every organ and tissue is made from cells. 

Those cells have water and electrolytes (like sodium and potassium) on the inside of the cell and on the outside of the cell: (raindrops = water, green dots = electrolytes). 

In a normal cell, there is a balance between the inside and the outside of the cell. This keeps the cell hydrated and round. However, if there is a lot of electrolytes outside the cell (or too little water), water will flow from inside to outside: 

This make the cell collapse (it's called being hypertonic).

Alternately, if the cell has too many electrolytes inside (or too little water), water flows into the cell from outside. 

This makes the cells enlarge (called hypotonic):
Having this happen all the time would be really annoying. Our bodies would have to be very elastic, as we get hydrated and dehydrated many times over the course of the day. Instead, our bodies have mechanisms to minimize this activity. 

Cells have ion channels. These proteins allow for ions like electrolytes to move into and out of the cell in a controlled manner. Often, they are energy dependent, and that makes them tightly controlled by our bodies. In our intestines, we have very highly controlled ion channels that have a regulating protein that is controlled by another chemical. 

If the ions (in this case, Chlorine (Cl-)) needs to be moved outside the cell to balance the water, the purple signalling molecule binds to the orange regulatory molecule, and the channel opens to move the ions out. If they need to be moved in, ion channels can also do that.

As you can imagine, this is a really a complex and highly regulated operation that happens everyday in our bodies. 

When we have food poisoning via a toxin mediated infection (like E.coli, V.cholerae, or S.dysenteriae), the bacteria makes a toxin that binds to a protein that produces the purple regulatory molecule. The purple regulatory molecule (cAMP for all of you super-nerds out there) then turns on the ion channel and won't let it turn off. The ions go outside the cell. Then there is the kicker: The water in your intestines follows them outside the cell. You become dehydrated as your body freaks out trying to get your intestines to balance their tonicity. 

The danger with these enterotoxins comes from dehydration and the stress caused by diarrhea to your body (i.e. tears and blood). Sometimes ruptures occur and then the bacteria spread outside the gut and into the blood. This is incredibly dangerous and should be treated immediately. 

Shellfish poisoning
Let's switch gears one last time. Let's talk about these guys: 

Shellfish from contaminated environments can be very dangerous to humans, in that it causes a variety of paralytic, diarrheal, and neuronal symptoms. 

Bivalves like mussels, clams, scallops, etc feed by filtering through smaller organisms and using their nutrients. However, these smaller organisms are very susceptible to environmental toxins and stresses that cause the production of small molecules for defense. It turns out that paralytic shellfish poisoning isn't actually caused by the shellfish, but algal blooms (sidenote: Jill, maybe you should've seen if certain committee members had a softspot for bivalves and pitched your bloom-reducing research with that in mind ;)). These algal blooms contaminate the water with saxitoxin, which is then filtered into the small organisms that the oysters eat. The oysters and clams can clear the toxin from their bodies, but it takes anywhere from weeks to years. 

How does it work? For those of you who were wondering about the science lesson associated with enterotoxins (above), yes, it is useful again. 

So, enterotoxins cause our ion channels to be more overactive by causing overproduction of cAMP, the small molecule that activates the ion channels. Saxitoxin, the toxin responsible for paralytic shellfish poisoning ALSO uses our ion channels, but in a different way. 

Saxitoxin causes paralysis by blocking our sodium/potassium ion channels, which are really important for our neurons. Blocking neuron function effectively blocks movement at a very global scale. This results in the paralysis in the name.


Normal neuronal synapses can send signals to eachother using either chemical or electrical means. They can release chemicals from one neuron, which can then be received by receptors at another neuron, or they can build up an electrical charge and then 'zap' the next neuron and create a signal. 

In order to build up that electrical current, the ion channels need to be involved. Much like in cellular tonicity, the ions want to balance across the membrane. Instead of allowing the ions to balance across the membrane, the ion channels block their exit from the neuron. This causes an electrical potential to build up across the membrane, since one side will have a lot of positive charges of sodium and potassium, and the other will have much fewer positive charges because the sodium and potassium aren't being released. This occurs until a critical charge, when the electrical potential is released: ZAP!

In order to get ready for the next signal, the ions have to be controlled. Saxitoxin prevents control of the ions by blocking the ion channels, and preventing them from recycling to a neutral state post-electrical output. This makes the synapse unable to carry the next signal that comes along.

Paralytic shellfish poisoning is controlled by monitoring the waters that the fish are grown in. Since much of our shellfish is farmed, those waters are treated to prevent algal blooms. Fishermen try to use responsible harvesting techniques to prevent such events in wild populations, but as the climate changes and the ocean environment changes over time, this may turn out to be a huge problem in the future.

Obviously, I wasn't suffering from these types of toxins during my recent detox. So what was I removing from my body? Stay tuned for another science overview in the near future that highlights toxic chemicals and minerals in our daily diets and how they can be removed from our bodies!

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