What makes a substance toxic? Consumers are led to believe that anything deemed “toxic” is bad for your health— whether it be household cleaning products or the food you eat. Alternatively, any food or product that is completely non-toxic and free of chemicals can do no harm. Is this always the case?
Fear of chemicals and ‘toxins’ in your food and our surrounding environment has fueled many misinformed opinions and left consumers confused. (The Dirt-to-Dinner team has discussed this misplaced fear in previous posts about GMOs, pesticide use, and rBST.) But, there is no need to panic. In reality, whether or not something is toxic depends on numerous factors, such as the substance’s form, the amount you are exposed to, how you are exposed, and your genetic make-up.
It is not as simple as “this is good, that is bad”
Answer the following…
- Do you buy products that are labeled as “natural” or “no added chemicals”?
- Do you think products labeled as “natural” are better for you than those not labeled “natural”?
- If products had “made with chemicals” splashed across their labels in red letters would you avoid them?
If you answered yes to all three, marketing tactics might be getting the best of you. Unfortunately, it’s just not that simple! Making choices that affect our health would certainly be easier if everything was as easy as “that is bad for you, and this is good for you.” Yes, some things, like habitually smoking cigarettes, are obviously not good for your health, but most things do not fit neatly into that “good” or “bad” category. Scientists were so intrigued by this fact that they created a discipline, toxicology, to study what effect chemicals have on our health.
There are two terms that people— even many non-toxicologist scientists and medical doctors— commonly get confused. Those two terms are toxicant and toxin. The term most frequently used incorrectly is toxin.
Toxins are naturally-occurring poisons produced by living organisms such as bacteria, fungi, plants, insects, and algae. Toxin is frequently misused when people are really referring to “toxicants” or toxic substances resulting from human activities.
Toxicants are manufactured and extracted chemicals such as pesticides, cleaning agents, industrial emissions or by-products, mining by-products, etc. that are in our environment.
Our bodies are equipped to protect us
Our bodies are ready to protect us from toxic levels of chemical compounds. In order to best protect our health, our bodies respond either by
1). Metabolizing chemical compounds using specialized proteins called enzymes that catalyze chemical reactions to produce less harmful chemicals, called metabolites. Occasionally the metabolite is more harmful than the original chemical, but most often it is harmless or less harmful than the original compound.
2). Attaching molecules to the harmful compound leading to either excretion or directing it to an enzyme for further processing.
Where we get in trouble, however, is when our bodies’ systems are overwhelmed. In these instances, there is too much for our systems to process and substances can become toxic. This all depends on the dose.
Too much of anything can be a bad thing
Dose is the amount of a chemical (i.e., in the form of food, beverage, nutritional supplement, medicine, etc.) administered at one time; the total dose is the amount times the frequency times the duration. If the dose is too high, your body’s ability to eliminate may be overpowered causing adverse effects. So, the dose makes the poison.
And too much of even a good thing can be damaging. Take, for example, water: on occasion, the news blasts a headline such as “Georgia teen dies from drinking too much water, Gatorade” or “Woman dies after water drinking contest”. Consuming large volumes of water faster than your body can eliminate the excess causes an imbalance of your body’s electrolytes, which damages your organ systems and can result in death.
Another example is polyphenols. Polyphenols are chemicals with antioxidant properties found in plant-based foods such as fruits, vegetables, and nuts that have been shown to protect DNA from damage at low doses but also damage DNA at high doses. We’ve discussed the properties of polyphenols in previous articles that discussed turmeric, red wine, and matcha, as polyphenols are naturally occurring in these foods. These days, there are many companies marketing polyphenol-containing products to boost your antioxidant levels, but rarely do those marketing campaigns ever mention what happens if you consume too much of their products. If you are taking over the counter supplements containing polyphenols and eating a diet rich in naturally occurring antioxidants you might actually be damaging your DNA. And this is where our genetics and other personal characteristics come into the picture…
What’s good for you may not be good for me…
Our genetic makeup (or genotype) has a major impact on how we respond to a chemical. For example, we all have varying levels of enzymes in our bodies and some of us do not produce certain enzymes at all. This is why some people will have an adverse reaction or get sick when they are exposed to particular chemicals while others do not, or one person may experience adverse health effects at a very small dose while others will not feel any effects until they are exposed to a much higher dose.
Alcohol metabolism is an example of a genetic variation that is very well studied. In some sectors of the human population, particular enzyme variants involved in alcohol metabolism are genetically modified so that aldehyde, a toxic alcohol metabolite, builds up in the person’s system making them feel sick after consuming only small amounts of alcohol.
In addition to our genetics, we also differ in our responses to chemicals because of our gender, age, life stage, race, and health. Children and adolescents are often more susceptible to chemicals because their systems are still developing and are more vulnerable to damage. And older people or people who are immune-compromised are more susceptible because their systems are weakened.
Advancements in genetic sequencing methodologies may soon help to determine an individual’s sensitivity to chemicals. Emerging technologies coupled with the sheer amount and availability of data is making it easier for scientists to study population and individual genomes to determine chemical susceptibility. (See our post about CRISPR for more information on emerging technologies related to our genomes.) With the decreasing cost of genetic sequencing methodologies and increasing computing capacity, it is quite conceivable that in the near future, there will be rapid tests to determine the chemicals, if any, to which you are more sensitive.
Since there are thousands of chemicals in our environment (remember, everything is made of chemicals), outside of a select, well-defined group of “bad apples”, very little is actually known about subpopulation or individual genetic susceptibility to specific chemicals.
Of course, chemicals often vary in how dangerous they are to humans, which is why you will see a warning on some products (e.g., a jug of household bleach) and not on others (e.g., a jug of spring water). Some chemicals are toxic to humans at such a small dose that it is best to avoid any exposure. An example of a particularly deadly chemical is methyl mercury, an organic mercury compound that can cause death in very small doses. In 1996, a scientist accidentally spilled a couple drops of organic mercury on her gloved hand during an experiment. Three months later she was feeling confused and off-balance and went to the hospital. Less than a year later, she was dead.
Pay attention to warning labels.
Routes of Exposure
If you ever had a big multicolored bruise on your arm or leg, you may have been asked, “How did you get that?”. But in toxicology, when toxicologists ask how someone gets a disease or is exposed to a toxic substance, they are really asking – “By which route is a person exposed?”
- Dermal (through our skin)
Route of exposure is an important factor in determining toxicity because, just like dose, it has bearing on what happens to the person who is exposed (the response). Mercury is a great example of different forms causing different health outcomes. Mercury is present in the environment in several forms – metallic or elemental mercury is the chemical found in thermometers. It’s not toxic if you touch or eat it, but beware if you inhale it as the vapors are toxic to your nervous system.
On the other hand, when mercury combines with carbon to form organic mercury it is extremely toxic in very small quantities, and exposure through your skin or ingestion can kill you as it happened to the scientist who accidentally dropped some on her gloved hand.
You may have heard warnings about mercury contamination in fish. Mercury in fish is in the form of inorganic mercury – that is, mercury combined with other elements such as oxygen and sulfur to form salts. Inorganic mercury occurs naturally in our environment or can be emitted through industrial processes and when consumed, has a tendency to concentrate in and cause damage to kidney tissues.
So as you can see by this mercury example, in addition to a chemical’s form, the way you are exposed to a chemical also influences how or if it will affect your health.
How long have you been exposed?
Also of interest to toxicologists is whether the exposure is acute or chronic. Acute exposures are of short duration and chronic exposures are repeated or occur over an extended period of time. If we think of alcohol consumption, acute exposure to a large dose may make us sick or leave us feeling ill the next morning, but chronic exposure to one 5 oz. glass of wine with dinner every night may actually be good for your health.
The Bottom Line:
The truth is, most chemicals in our food, water, surrounding environment, and even those made by our own bodies are not completely good or bad for us. They are determined to be good or bad depending on different factors, such as dose, form, and route of exposure. Our personal characteristics, such as our age, gender, health, and genetics also play a significant role in how we respond to chemicals. Our bodies are equipped to handle chemicals, but when our systems are not functioning properly or overwhelmed by the chemical dose, we may experience adverse health effects, become ill, or worse.