How Do We Know Which Food Chemicals Are Dangerous?

Posted by Eric Troy on 16 Aug 2015 03:55

Large amounts of arsenic will kill you. Large amounts of mercury can damage the brain and nervous system, and eventually lead to death if exposure continues. Large amounts of radiation can damage your organs, cause various cancers, and kill you if the amount is high enough. Large amounts of Vitamin A are toxic, and can kill you in a high enough dose or with continued ingestion of large doses. Did you know that the same is true of other vitamins, especially fat soluble ones? In fact, you will find that many nutritious and healthful substances can be harmful in large doses.

Not all potentially harmful chemicals are as obvious as say, snake venom, shellfish toxins, or botulinum (causing botulism poisoning, discussed later). Sometimes the effects are cumulative, happening over time as the chemical builds up in the body, for example. In fact, the body's ability to get rid of a substance has a lot to do with its potential for harm. How harmful a chemical is, and how ubiquitous it is in the environment and our food, effects its discovery. As well, when it comes to nutrients, the amount of the nutrient the body routinely needs affects how easy it is to discover this nutrient.

Note on the Word 'Discovery'

Before I continue, I want to acknowledge that I am being quite loose with the word discovery. Rarely can one single event be deemed "the discovery" of a vitamin or other nutrient. Often, this discovery is the result of cumulative steps, carried on through years of work, with later scientists building on the work of others. Do not assume that by the use of this word that I mean to suggest that a substance was discovered as a single event by one person. This may or may not be true.


Discovery of Substances That Affect the Body

There are many ways a substance that affects the body can be discovered. For example, sometimes a disease state leads to the discovery of an important nutrient. Scurvy is one such example. First, did you know that we human beings are one of the few animals that cannot make our own vitamin C? That's right, your dog can make his or her own vitamin C. It could be that vitamin C is still a conditionally essential nutrient for a dog, as for instance, during times of stress or pregnancy. But for the most part, dogs do not need to "eat vitamin C containing foods."

Obviously, we would have never discovered the importance of dietary vitamin C by studying dogs, or most other species. What we did discover, though, is that certain foods present in the diet tended to prevent scurvy. This led to the theory that there was some vital nutrient present in these particular foods, and eventually this led to the discovery of ascorbic acid. The story is, of course, more involved, and more interesting than this truncated version.

So, a lack of certain substances in the diet can lead to disease states and these can lead to the discovery of the substance. This is how some nutrients have been discovered. We discover them through the effects of "too little." The idea that a lack of a certain food substance could cause a familiar illness did not always go unquestioned. For example, today, it is taken for granted that thiamine, or vitamin B1 is the anti-beriberi vitamin. But when Christiaan Eijkman first suggested, in 1896, that the skin of brown rice contained an 'anti-beriberi factor' that was not present in polished white rice, and that therefore, the consumption of white rice instead of brown rice caused the disease, he was ridiculed. Now, it is true that his initial conclusions were a bit spurious. He thought that the actual starch in the white rice must be poisonous, and that some compound in the outer husk must protect [chickens] from the poison. Obviously, white rice is not poison. However, it wasn't just this belief, but the entire notion that a single dietary compound, present or missing, could be the source of a devastating disease, which was not easy to accept.

You can read more about Eijkman and the discovery of thiamine, the anti-berrberri vitamin, at For further reading about many other vitamin discoveries, without the usual dry biochemical recitations, I recommend Vitamin Discoveries and Disasters: History, Science, and Controversies, by Frances Rachel Frankenburg.

Noticing that the lack of a certain substance causes a disease is not the only way we can discover such a substance. We can also discover a substance, or at least discover its activities in the body, due to the effects of too much.

Toxic Vitamin A

Now, remember that I said that too much Vitamin A is toxic? Today, it is possible to develop acute vitamin A toxicity. This would be more likely in a child who ingested a large amount of a vitamin A supplement. But another chronic possibility is chronic toxicity due to the routine taking of over-dosed supplements, or a surplus of vitamin A-containing foods in the diet (rare). This can cause may symptoms, including changes in skin, hair, nails, and the liver. It can cause birth defects if pregnant women take in too much vitamin A. Headache and rash may occur, and the skin may even begin to peel. Here are some other specific symptoms:

Early Symptoms of Vitamin A Toxicity

  • coarse hair
  • loss of eyebrow hair
  • dry and rough skin
  • cracked lips

Later Symptoms of Vitamin A Toxicity

  • severe headache
  • increased intracranial pressure (pseudotumor cerebri)
  • weakness
  • cortical hyperostosis (especially in infants or children)
  • susceptibility to fractures (especially in elderly)
  • itchy skin (children)
  • anorexia (children)
  • failure to thrive (children)

Now imagine that we originally discovered vitamin A through this toxicity syndrome? What would we then have thought about vitamin A? Would we have leaped to the conclusion that this was a vital nutrient? Of course not. We would, as is usually the case, theorized that a large amount of vitamin A is toxic, and that the toxic effects are proportional to the dose, with more or less harmful effects corresponding to the size of the dose. In other words, vitamin A (of course it wouldn't have been named that) is bad for you, and the more you get, the worse off you'll be. Pretty much the same way we think of any toxic substance.

But we did not discover vitamin A this way. We discovered its important and vital physiological roles in the body. We discovered that vitamin A was 'good for you.' What do we tend to assume about substances that are good for you? We assume that more is even better for you! So, it took a while for us to learn that more and more vitamin A was not better and better for your body. And, there are still people who haven't learned.

Now, if you are really thinking about this, you might have noticed something. If large amounts of vitamin A are bad for you (we of course have to set a standard for what is a large dose) but small to moderate amounts are good for you, might this be true of all sorts of other things that are toxic in large amounts? And, does it matter whether we discovered the toxic effects first?

Is Arsenic Always A Poison?

You're on to something. Let's go back to arsenic. It is a classic poisoning agent. Arsenic causes generalized symptoms that would look like a bad stomach bug. Hard to detect. Builds up in the body and eventually kills if the exposure is not stopped. Usually, it is given to victims in daily doses over time, to make it look more like a naturally occurring illness. However, a large enough one-time does of arsenic could kill as well.

Arsenic is a mineral, much like many other minerals in the body. And, did you know there is arsenic in your body right now? YES! Because it is in the environment, and therefore ends up in the in the plants we eat just like other minerals. Certain soils might have more arsenic and therefore lead to certain crops having more arsenic. Reliance on these crops to the exclusion of other foods could be bad for us. Brown rice is often named as a bad arsenic crop, because of this.

You may have heard Dr. Oz telling you about the dangers of arsenic in brown rice. The message is that arsenic is toxic and no amount of arsenic is okay for the body. However, the truth is we do not yet know if trace amounts of arsenic have a role in the body. This may come as a surprise, given it is such a notorious poison, but the same that is true of vitamin A could be true of arsenic. There are other minerals that our body needs in "trace" amounts. It could turn out that arsenic is one of them. It may not. The point is that you cannot assume that because arsenic is so toxic in large amounts, that it is always toxic and never useful.

Ultratrace Minerals

Now, to be fair, arsenic may be more of an "ultratrace" mineral, than a trace mineral. There are are several other unusual suspects that may also be utratrace minerals: nickel, silicon, tin, vanadium, and boron, to name a few. There have already been essential roles discovered for these in animals. We have yet to determine whether they are essential for humans, and if so, what their roles are. It is quite possible that discrete roles will be discovered for any or all of these minerals, albeit at extremely small amounts. I want you to understand the point here: It doesn't matter whether any of this turns out to be true. The point is that just because something is toxic in large enough amounts does not exclude it from being useful in small, or tiny amounts.

So, you see, the assumption that something that is toxic in large amounts must be avoided at any and all amounts is erroneous.

With trace minerals, especially ultratrace minerals such as these, study becomes more difficult. Vitamin C deficiency is common. So is vitamin D defficiency, and other vitamin deficiencies. The same is true of some of the macrominerals. But there are no trace mineral deficiencies! These minerals are everywhere in the environment and it is not a problem to get more than enough, assuming that you need them at all. Although with certain of these minerals, our intakes may just be a tiny bit higher than what we need, as you can see, we can't easily look at the effects of "not enough" of these minerals, like we can for Vitamin C and other micronutrients.

Unfortunately, to learn about these, animals must be used. Due to animal studies, we now know, for example, that nickel is important to the health of many body tissues and that a nickel deficiency can damage the liver and other organs. Tin seems to be necessary for normal growth. Vanadium as well seems to be necessary for growth, but also for normal bone development and reproduction. Boron also seems to have an important role in bone health.

Vegetarians are often told to supplement vitamin B12, a very important nutrient. Guess what the most important mineral is in a molecule of vitamin B12. Cobalt. That's right, cobalt!

Arsenic, Mercury, and Lead as Trace Minerals?

Given arsenic's reputation as a poison, and even a carcinogen, you might find it hard to believe that it could ever be deemed essential to your health. But, it may well be.

Mercury is all over the news, especially due to the high levels of this heavy-metal in fish (and some fish oils and other supplements). No way mercury could be good for you in any amount! Think again. It might be.

You know about all the serious harm that lead has done. We took it out of paint and out of gasoline because of its poisonous effects on the body, especially to children. Well, lead may be essential at very small amounts. We just don't know yet. There may be other heavy-metals that also turn out to be essential trace minerals.

So, how do we know what substances are harmful? As you can see, it is not a simple question of what is harmful and what is not. Often, things that are vital in small or moderate amounts are toxic in large amounts, and vice versa. The casual assumption that many of today's food zealots make about "toxic chemicals" is completely erroneous. They tell us that we must avoid these chemicals at all costs! Otherwise, the results will be catastrophic. This is not always the case, and not even often the case.

The Body Can Deal With Many Toxins

Some substances that are harmful in large amounts may not have a corresponding useful intake, but this does not mean that they are harmful in proportion to their intake. It is possible that a substance may be quite neutral to the body in small amounts, due to the body's easily being able to metabolize the substance and render it harmless. The liver is the primary organ responsible for this, and it does a bang-up job, but it has help from the kidneys and even the digestive tract.

People often assume that all it takes to determine the "toxicity" of a food is to determine what chemicals it contains, and then decide if one or more of these chemicals are toxic. However a food can contain toxic chemicals and still not cause poisoning in humans or animals. First, the toxin must be present in large enough amounts. Second, it must be present in a form that can be taken up by the body and assimilated in some way. Some of the "toxic chemicals" that we are told to fear pass right through the gut unchanged, for example. Or, our body is able to safely detoxify small amounts of these chemicals. It is also important to realize that the body metabolizes these compounds continuously, meaning that as doses of chemical enter into circulation, previous doses have already been rendered harmless. Whether a compound is water-soluble or fat-soluble has an effect, and of course, so do many other complex things.

We often talk about toxins or poisons in terms of the amounts they are generally seen in. Lead has been used in such various ways and in amounts sufficient to cause harm to tissues, that lead becomes "poison" not because of its actual degree of toxicity, but because of the amounts seen in both industrial and common exposure.

Ironically, the most toxic organic substances are those with which we very rarely come into contact. See, a substances that is only toxic in huge amounts is not very toxic at all. If we regularly came into contact with serious toxins, we wouldn't have the luxury of fearing our food!

On the other hand, even the most innocuous chemicals can become toxic if we concentrate them enough. We should, perhaps, be more fearful of huge unnecessary doses of vitamins and minerals in popular supplements than we should be of inadvertent toxins in the food supply. On the other hand, we should perhaps be fearful of rendering innocuous substances more "harmless" by trying to purify them. For example, you might think that the ultimate water is pure distilled water. You'd be wrong. Many unqualified "health gurus" assert, without justification that "pure water" is essential for the body, without a trace of evidence to support their assertion. Pure water is so very hard to achieve, and in fact, we do not really know the effects of drinking large amounts of perfectly pure water, as opposed to large amounts of common water, which has various minerals and other substances in it. It has been proposed that drinking purified water might leach minerals from the cells. While this may be stretching things, it does not mean that pure water is therefore more virtuous than impure water.

Arsenic as Medicine

Did that heading throw you? I started out talking about arsenic as a poison. Then I revealed that arsenic may be an essential nutrient in trace amounts. Now I am associating it with medicine. It's true. Arsenic has been used both as a poison and a medicine for thousands of years. You can read more about this here.

As revealed over there at Nostrumopia (yes, one of my little blogs), arsenic was used openly as a medicine even while it was known to be a poison at large doses. The answer that the patent-medicine makers would give was "the dose makes the poison." Although these patent medicines were ridiculous and made claims that nobody would be tempted to believe today, arsenic has been used in conventional medicine for quite legitimate means! Before I go on, let me remind you that there are other poisons that are also medicines. The dose really does make the poison. The difference is that, as I also pointed out in the patent-medicine article, the nostrum makers were making assumptions based on inferences, with no evidence that arsenic was a medicine, and and often had no other justification than this adage about doses.

The thinking involved in using arsenic as a patent-medicine was based on its being a known preservative for woods and other materials. It stopped microbes from causing these things to rot. Therefore, maybe it would have the same effect on us. This would make it great as a anti-parasite, or to treat infected wounds. Heck, maybe it would simply "preserve" you. Sounds like a ridiculous and illogical leap, doesn't it? But as a theory, it isn't really that ridiculous at all. Arsenic may well be a great antimicrobial. The problem is in not testing this theory and discovering whether it was a great antimicrobial for actual use in humans.

At the same time, just because the patent-medicine sellers had little justification for their claims, their opponents had little justification to assume that any amount of arsenic was harmful, and that it could never have medicinal (or physiological) properties. You cannot exactly blame someone for thinking that human beings are large animals and it takes a large amount of arsenic to harm them. Yet, they play host to small harmful parasites. Might a small does of arsenic, taken by mouth, harm or kill these small parasites? Indeed, today's anti-parasite medicines would make us sick if we took more than the recommended dose, and perhaps kill us if we took it all at once.

But once you understand how arsenic poisoning works, and how other heavy-metal poisoning works, you see the error. Even if arsenic could kill the parasite, by the time the parasite was gone the arsenic would have built up in your body and made you quite ill. Depending on the actual dose you had been taking, who knows what might happen. Is it worth "poisoning yourself" to control a parasite, especially if there are safer treatments?

Now, take that logic a bit further. It may not be worth poisoning yourself to control a parasite, when drugs are available that will handily dispatch the organism without undue side-effects (as they are today). But, what about other illnesses? What if you've been handed a death sentence and there are no harmless medicines to cure it? That is what chemotherapy for cancer is. Those undergoing chemotherapy treatment certainly can feel that their body is being harmed by the treatment. They suffer a great deal from debilitating side effects. They are, in fact, ingesting what would be viewed a poison under different circumstances. Arsenic has been used as a chemo-therapy agent. It has also been used to treat syphilis, malaria, and other diseases. Given in controlled doses, the benefits often outweigh the harm, and a person who might have died from a disease could benefit from a "controlled poisoning" from arsenic, and then recover from this poison afterwards. Arsenic has been replaced by safer alternatives for most of these illnesses, but it is still used in chemotherapy today.

We often expect things to be harmful or not harmful. We likewise expect all drugs to be like penicillin (even penicillin derivatives can cause problems). I.E. do nothing but good. Rarely does nature work this conveniently for us. Substances can be both harmful and useful, depending on the amount and on the risks versus benefits.

Useful Toxins in Medicine

Arsenic is not the only useful toxin in medicine. As far back as 1822, Jusitius Kerner realized that botulinum toxin, the cause of 'botulism poisoning (see link above)' might have therapeutic value. He actually called the substance he was working with "wirkenden stoffes" or "bad sausages" and did not know the true nature of the toxin he was considering, or its origin. Botulinum toxins are among the most toxic of all substances. They are produced by the bacterium Clostridium botulinum and exist in seven neurotoxic forms. In 1978, the FDA approved the first test of a botulinum toxin type A in human subjects.

You may think that botulinum treatments are nothing more than a vanity aesthetic treatment used to lessen the appearance of wrinkles. However, the toxins ability to temporarily paralyze muscle by inhibiting the release of acetylcholine and other neurotransmitters has caused researchers to investigate its use for a large number of different uses and benefits.

Medical Uses of Botulinum Toxin

Botulinum toxin has been used for chronic headaches, swallowing difficulties, vision properties, back pain, urinary problems, gastrointestinal problems, muscle spasticity of cerebral palsy and multiple sclerosis, dystonia, and other complaints. It is truly a very useful toxin! Yet, it is thought that one gram of botulinum toxin could kill 20 people.

Other Useful Medical Toxins

Other useful toxins are quinine, an antimalarial and the active ingredient in tonic water, which was invented as a malaria preventative in the first place (today's tonic water has much less quinine), salycates, digitalis, curare and many other plant toxins that are useful at small doses. Increasingly, animal toxins, such as venom, are being studied for their potential to produce useful compounds, including exciting work on eristostatin, a protein in the venom of the Asian sand viper, which may help fight malignant melanomas.

Indeed, what we call a toxin, versus a medicine, has everything to do with the amount administered. Many common and invaluable drugs are, in fact, toxins. These toxins, when used in appropriate amounts under controlled conditions, are called drugs.

Not all toxins used widely used for medicinal purposes were effective. If you are old enough, you may remember when a toxin was kept on hand in many households, to be used internally. Commonly called ipecac, ipecac syrup, or syrup of ipecac, it started out as a cough syrup but became more widely used to induce vomiting. Derived from the rhizome and roots of the ipecacuanha, it contains alkaloids that act as an emetic, irritating the stomach lining and stimulating vomiting. It was especially used for children, who might be prone to accidentally ingesting poisonous substances. Therefore, its primary use is to rid the body of accidentally ingested poisons. Unfortunately, ipecac had more potential to be misused than it did to rid the body of unwanted substances. Although it is still sometimes used, it is not as widely manufactured, and its use is not recommended.

No Amount of Chemical Is Okay?

The popular food blogger Vani "The FoodBabe" Hari, has been quoted as saying that "no amount of chemical is okay to ingest" or something to that effect. As I and other authors have pointed out many times, food is made of chemicals! Now, I hope I have made it more clear that whether a chemical present in food is harmful, not harmful, or even essential to our body is not so clear-cut. Many of the nutrients that we need to survive can harm us in large amounts, and many of the chemicals that are famous for being harmful in large amounts, are useful in small amounts! Food-alarmist prey on our need for simple and easy-to-digest information. Often, they label entire categories as 'good' or 'bad' in order to get us to believe that we can achieve perfect health by simply avoiding "boogey-men." Words like chemical, toxin, etc. are used with abandon and without any understanding of the terms whatsoever.

Recall my comments about arsenic in brown rice. Is all brown rice high in arsenic? No. Should a person who eats a varied diet be worried about the arsenic in brown rice? No. Do you need to completely avoid brown rice? No, again. The same food-zealot that tells you about the dangers of brown rice, will probably also tell you to never eat white rice. In truth, however, white rice is fine as part of a varied diet! You see, all that these toxic evangelists really accomplish is to make you unsure and fearful of EVERYTHING. For people who make use of a rich variety of foods, there is absolutely no need to fear any one of them. In fact, it is this variation and freedom to eat all kinds of different foods which protect you from ingesting large amounts of any potentially harmful chemical.

I explained some of the aspects of vitamin A toxicity. Although it is rare to see vitamin A toxicity from food, it has been noted in arctic explorers who at large amounts of bear and whale liver, both of which contain thousands of units of vitamin A. So, you see, it was the dependence on this ONE food source that caused the problem. Limiting your food choices does not protect you from danger, it runs you right into it! Recently, Australian Chef "Paleo Pete Evans" came under fire for his new family food book which featured a recipe for baby-formula made with chicken livers. Health experts in Australia, learning of this in advance of publication, issued warnings about the potential for infant deaths from this formula, due to vitamin A toxicity. As a result, the publishing of the book was delayed. Instead of heeding the warnings, Pete Evans ignored them and has gone ahead with private publishing. What is striking is that not even an adult should rely on liver for the majority of their food intake, let alone an infant! The sodium content of his formula has also been questioned.

Do not fear your food. Fear those who tell you to fear your food. They show a complete lack of critical thinking. It is not helpful to conclude that a substance is harmful or beneficial until you ask how much of the substance is used. As I've explained, a substance that is poisonous at high concentrations, can be an essential nutrient at low concentrations. The reverse, then, is also true, and a substance that is needed in small amounts may be toxic at large amounts.

Sometimes, more of a nutrient is better, but only up to a certain point. I am not aware of any nutrient that continues to exert better effects at higher and higher concentrations with no end. It is possible for the effects of a nutrient, with higher and higher intake, to reach a plateau in its beneficial effects, and then level off with no additional benefit with higher intake past this plateau point. More often, a higher intake is better up to a certain point, reaching an optimum intake level, and then becomes harmful past this intake level. Since all food sources have higher or lower levels of certain substances, the best way to achieve an optimal, but not harmful, intake of nutrients is to eat a wide variety of foods, and to not limit your food choices due to unfounded fears of any one chemical substance.

I'll leave you with a quote from researcher Brian Wansink, found here:

To overcome food ingredient fears, learn the science, history, and the process of how the ingredient is made, and you’ll be a smarter, savvier consumer.

See also the related article Are Most Diseases Caused by Poor Nutrition, and The Poisonous Apple: A Chemical Cocktail.

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