Chemicals and Food: A Little Perspective

What do formaldehyde, hydrogen peroxide, and acetaldehyde have in common? They are all chemicals that we perceive as dangerous and known carcinogens or mutagens. They are also all likely to be found in your Thanksgiving dinner. No – they are not additives, preservatives, or contaminants – rather compounds found naturally in food. It is not uncommon to hear an argument that “artificial” chemicals added to food are dangerous. However, natural vs unnatural is not a good indicator of risk, and it helps to put that risk into perspective.

Let’s take a class of compounds widely present in foods – pesticides. It may be surprising to most that we consume many fold more natural pesticides than synthetic – regardless of whether you eat organic food. Ames, Profet, and Gold estimated in 1990 that the average synthetic pesticide intake was 0.09 mg per day, whereas that of natural pesticides was about 1.5 grams per day. In other words, 99.99% of pesticide consumption is from “natural” sources – or 10,000 times that of synthetic pesticide residues. This is because there are literally thousands of chemicals in plants that are produced in an effort to ward off pests. In addition, Gold, Ames, and Slone (2008) showed that in research through the 1990’s, the proportion of these natural chemicals found in plants that cause cancer in rodents at high doses is not much different than commercial pesticides.

Percent cancer-causing in rodents

Total tested

Natural pesticides



Commercial pesticides



Natural chemicals in roasted coffee



Table reproduced from: Gold, Ames, and Slone. 2008. Animal Cancer Tests and Human Cancer Risk: A Broad Perspective.


These researchers also produced a large table of how the average consumption of many natural food chemicals, food additives, and pesticides compares to the dose known to cause tumors in rodents. The accompanying graphic is a powerful visualization of how much closer to the cancer-causing dose most natural food chemical exposure is than food additives or pesticide residues are.

Of course, fruits and vegetables do not cause cancer (at least the vast majority of them). In fact, many probably reduce the risk of various cancers, and confer other health benefits. But plants can contain some other nasty chemicals that are harmful to us in other ways. In a recent paper on this topic, Gribble (2013) reminds us how toxic some fruits and vegetables can be. For example, aflatoxins, or mold metabolites found on peanuts and corn, are known to cause liver cancer. Other types of mycotoxins found on corn and cereals have led to esophageal cancer in humans, probable fatal birth defects, and pet deaths from contamination. Potatoes contain chaconine and solanine and there are documented cases of toxicity and death. Dioxins and furans, which are well studied in their potential for toxicity, can both be found in nature as well, and the latter are present in coffee, bread, and olives. Gribble reminds us that even though many obsess about whether food safety and security is accomplished in a natural or artificial manner, this debate is rather irrelevant when considering that the chemical risk of foods is generally of low concern in a diversified diet. However, pathogens, bacteria, and fungi are natural risks that exceed the threshold for concern. In fact, the CDC estimated that in 2011, about 48 million illnesses were caused by foodborne pathogens in the US alone, causing over 3,000 deaths.

As another matter of perspective, it is helpful to consider what we know is risky. The International Agency for Research on Cancer (IARC) of the WHO classified alcoholic beverages in the highest category: “carcinogenic to humans” – back in 1988. Alcohol is widely consumed yet this fact does not dominate public discourse. Arsenic and aflatoxins also make this group. “Emissions from high-temperature frying” and nitrate or nitrite (in conditions that promote nitrosation) make the “probably carcinogenic to humans” group, and coffee makes the “possibly carcinogenic to humans” list with an association with urinary bladder cancer. Meanwhile, it is sometimes incorrectly claimed around the internet that artificial sweeteners or GMOs cause cancer. It’s also quite easy to find single studies associating with cancer for almost any food ingredient, but most of these are found not to be consistent when multiple studies are analyzed. It becomes easy to see why novice research readers can make erroneous conclusions about ingredient safety.

Everything we consume is a complex mixture of chemicals. The chemicals added on and to foods undergo risk assessment, and we try to study the acute and long-term risks of both natural and non-natural chemicals as best we can. Any system cannot reduce risk to zero, and there may be good reasons to conclude that certain pesticides or food additives – synthetic or natural – are not 100% safe. However, any argument using naturality as a safety measure is not good science. The dose determines toxicity for all chemicals, and it would be rather silly to be concerned with the small amount of formaldehyde in your apple.

  • StellaBarbone

    One of the ironies about GMO panic is that GMO corn has a bacillus thuringiensis gene spliced in which both decreases its level of insect damage and its subsequent level of aflatoxin contamination. “Organic” corn is usually sprayed with Bt anyway. GMO sweet corn is the safer choice,

    Another interesting factoid I read just yesterday is that bananas naturally have a measurable level of a radioactive isotope of potassium. If I liked bananas, I wouldn’t let it worry me, but happily I could spend the rest of my life banana free.

  • Jayme Crandall

    Recent studies show artificial sweeteners to be incredibly toxic, and increase risk for type 2 diabetes, possibly MORE than any other reason. They also change the entire gut microbiota, in turn destroying the immune system, possibly causing autoimmune and other problems. Being skeptical is good, Being ignorant of our toxic lifestyle is only cute when you do not have a platform to convince others that its “healthy”