Do Pesticides affect Gut Bacteria?

The definition of a pesticide is a substance used to destroy insects or other organisms that are harmful to cultivated plants or animals. Pesticides are widely used and can cause an improved agricultural product and contribute dramatically to increased yields for most grains and seeds, fruits, and vegetable crops. From an economic perspective, this is amazing, but what is the cost to our health?

Why are pesticides used?

Farmers use a variety of pesticides to:

• Protect crops from pests, weeds, and disease
• Prevent rats, mice, flies, and other insects from consuming and contaminating crops
• Prevent crops from being contaminated by harmful microbes and molds when being stored

Even frequently buying organic produce does not exempt you from pesticide residue. Only a select number of pesticides are used with organic crops. The country’s organic crop standards specify the type that is used. Often these pesticides are naturally occurring (like copper sulfate), but this fact may not make them any less dangerous. Just because something is natural does not make it safe. After all, arsenic is natural, but definitely not safe!

Every country has set a standard, called the acceptable daily intake (ADI) regarding how much pesticide may remain in the food. This level evaluates the maximum amount of pesticide that a person can consume over their lifetime without an appreciable impact on their health. 

There are a few factors that are considered when determining this value, such as

• Rate of pesticide application
• Pesticide degradation
• Number of applications
• Pre-harvest intervals
• Additional ingredients that enhance product useability (e.g. sprays)

They only approve a pesticide for use when the amount of residue left on food items is below the levels that might cause an adverse effect. Different organizations evaluate these ‘maximum residue levels’ (MRL) frequently. Plus, new research is being conducted every day to ensure that these levels remain correct.

They evaluate both short- and long-term effects, including cancer risk, gene damage, and harm to an unborn child. We consider the ADI to be safe for all humans, including pregnant women, infants, and children. To be even more certain of the safety of these pesticides, they’ve set the ADI 100-1000 times lower than potential harmful effects in test animals. With all these safety checks in place, it is highly unlikely that pesticides will cause harm when used appropriately. 

Researchers set MRL once they know the risk levels. MRLs are established for all foods, including fruits and vegetables (and their juices), meat, dairy products, grains, and all processed foods. Depending on the type of pesticide and the type of food in question, residue levels can range from a fraction of a part per million or several parts per million. 

Each country tests its own food for both domestic and imported foods. As an additional layer of safety, some countries may opt to sample foods that are commonly eaten by infants and children more frequently. 

Dirty Dozen

The Dirty Dozen is an annual list that is developed by the Environmental Working Group or EWG that shows the average amount of all pesticides found on popular fruits and vegetables prior to washing. 

The 2021 ‘dirty’ dozen list includes: 

The problem with this list is that it incorrectly combines hazard with risk. 

Hazard vs risk

Hazard: Something that can cause harm 

Risk: Represents the probability that harm will occur at any exposure

To understand this, let’s use a shark as a metaphor for the difference between hazard and risk. Sharks have very sharp teeth and powerful jaws. They can be harmful and considered a hazard. However, if you were viewing a shark in an aquarium, it poses a much smaller risk compared to if you were perhaps swimming in shark-infested waters because there is a lower probability for exposure. 

Effectively, the EWG equates any pesticide residue as a risk, rather than relating detected pesticide residues to known safety standards. The EWG publicizes these results annually even though the actual levels are almost always below established tolerances, their presence represents a hazard but not a risk. Once again, the dose certainly makes the poison!

How do pesticides affect the gut?

Whilst the substances in approved pesticides don’t target human cells (and are thus deemed to be safe in small quantities), what kind of effect can these substances have on the microorganisms that live in your gut? There are over 100 trillion microorganisms in and on you at all times, so definitely something we need to take into consideration!

One of the most hotly debated pesticides is glyphosate, let’s explore it in more detail…

What is glyphosate?

Glyphosate is a non-selective herbicide that specifically targets broadleaf plants and grasses. It does this by interfering in a specific enzymatic pathway (the shikimic acid pathway), thus preventing the plant from making certain proteins needed for growth. This pathway is not found in humans, only in plants and some microorganisms (for example your gut microbiome).  

Glyphosate first started being used in 1974 and is currently one of the most widely used herbicides worldwide. It’s found in a variety of products since it’s used both commercially and domestically. Roundup is one of the most popular and well-known brands.

In recent years, weeds have become somewhat resistant to the effects of glyphosate, which has made it necessary to spray it more frequently at higher concentrations. Previously you would need to spray glyphosate before the plants germinated, so it would kill the entire plants, including the crop. But in recent years glyphosate-resistant crops have developed. 

Signs and symptoms of glyphosate exposure

Acute side effects: Glyphosate may cause eye and skin irritation and if you breathe it in, the lining of your nose and throat may also become irritated. Swallowing larger quantities of glyphosate may cause increased saliva, burns in the mouth and throat, nausea, vomiting, and diarrhea. Sometimes, people have died by purposefully drinking large quantities of glyphosate-containing products. 

Long-term side effects: The United States Environmental Protection Agency (U.S. EPA) as well as the World Health Organization (WHO) have both concluded that glyphosate is unlikely to cause cancer through dietary exposure. However, the International Agency for Research on Cancer (IARC), classified glyphosate as probably carcinogenic (i.e. it probably causes cancer) in 2015. Non-Hodgkin’s lymphoma is one type of cancer associated with glyphosate exposure. 

Glyphosate is available in several chemical forms in different products. Often, these substances are more toxic than technical, pure, glyphosate. This may be one reason there is a disparity between the long-term health effects reported by the U.S. EPA and the IARC. 

The conflicting information linking glyphosate to cancer has led several countries around the world to ban the use of glyphosate. 

Countries that have banned/ restricted the sale of glyphosate

The countries that have banned or restricted the sale of glyphosate include Argentina, Australia, Austria, Bahrain, Barbados, Belgium, Bermuda, Brazil, Canada, Colombia, Costa Rica, Czech Republic, Denmark, El Salvador, Fiji, France, Germany, Greece, India, Italy, Kuwait, Luxembourg, Malawi, Malta, Mexico, Netherlands, New Zealand, Oman, Portugal, Qatar, St. Vincent and The Grenadines, Saudi Arabia, Scotland, Slovenia, Spain, Sri Lanka, Sweden, Switzerland, Thailand, United Arab Emirates, United Kingdom, and Vietnam. 

How do you reduce pesticide residues?

People who are at the highest risk of being exposed to pesticides include agricultural workers who apply the pesticides to crops and other people who are in the immediate area during and right after pesticides are spread. It is very important that people spreading pesticides (on crops, in homes, or in gardens) should be adequately protected. People not directly involved in the spread of pesticides should stay away from the area during and just after a spread.

The general population is exposed to significantly lower levels through residue on the food we eat. You can reduce the amount of pesticide you consume by peeling or washing your fruit and vegetables. There is no need to wash your fresh produce with soap. Clean running water is sufficient. One study found that washing fruits (like apples) in a bicarbonate of soda and water solution helped to reduce the amount of pesticide residue found on the skin (but not pesticides that penetrated below the skin). However, it was less effective than peeling the fruit. If you are worried about pesticide residue, then this may be a viable, inexpensive option for you.

Top 5 tips to protect your gut from pesticide exposure

1. Drink enough water to prevent dehydration-related constipation. Regular bowel movements help you maintain a healthy gut. 
2. Make sure you have a healthy gut by eating a varied diet with sufficient amounts of fruits and vegetables, whole grains, and high-fiber foods.
3. Add naturally occurring fermented foods like yogurt, kefir, kimchi, sauerkraut and tempeh to your meals and snacks. These add to the biodiversity of the microorganisms that live in your gut. 
4. If you are concerned you have an imbalance of microorganisms in your gut, consider taking a general probiotic supplement. They are a safe and easy way to restore balance.  
5. Wash all fresh produce thoroughly under fresh running water, even if you don’t intend to eat the peel. Some residue and bacteria can get inside your produce when you cut into it. Use a vegetable scrubbing brush where necessary to brush away stubborn dirt and make sure that produce with multiple nooks and crannies (like broccoli or cauliflower) have been soaked in water for 1-2 minutes. Then rinsed until no more dirt residues.

References

• Ams.usda.gov. 2018. [online] Available at: <https://www.ams.usda.gov/sites/default/files/media/2017PDPAnnualSummary.pdf> [Accessed 22 June 2021].
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• Canada.ca. n.d. [online] Available at: <https://www.canada.ca/content/dam/hc-sc/migration/hc-sc/cps-spc/alt_formats/pdf/pubs/pest/_fact-fiche/pesticide-food-alim-eng.pdf> [Accessed 22 June 2021].
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• Pesticide Facts. n.d. Importance & Benefits of Pesticides | Pesticide Facts. [online] Available at: <https://pesticidefacts.org/topics/necessity-of-pesticides/> [Accessed 22 June 2021].
• Centers for Disease Control and Prevention. 2021. Steps to Safe and Healthy Fruits & Vegetables. [online] Available at: <https://www.cdc.gov/foodsafety/communication/steps-healthy-fruits-veggies.html#:~:text=Clean%20fruits%20and%20vegetables%20before,vegetables%20when%20you%20cut%20them.> [Accessed 22 June 2021].
• Yang, T., Doherty, J., Zhao, B., Kinchla, A., Clark, J. and He, L., 2017. Effectiveness of Commercial and Homemade Washing Agents in Removing Pesticide Residues on and in Apples. Journal of Agricultural and Food Chemistry, 65(44), pp.9744-9752.
• Who.int. 2021. Pesticide residues in food. [online] Available at: <https://www.who.int/news-room/fact-sheets/detail/pesticide-residues-in-food> [Accessed 22 June 2021].
• Baum Hedlund Aristei & Goldman. 2021. Where is Glyphosate Banned? | Baum Hedlund Aristei & Goldman. [online] Available at: <https://www.baumhedlundlaw.com/toxic-tort-law/monsanto-roundup-lawsuit/where-is-glyphosate-banned-/> [Accessed 22 June 2021].
• Wric.ucdavis.edu. 2016. [online] Available at: <https://wric.ucdavis.edu/ucd-access/pdf/2016_WWG_38a_Wilen.pdf> [Accessed 22 June 2021].
• Henderson, A. M.; Gervais, J. A.; Luukinen, B.; Buhl, K.; Stone, D.; Cross, A.; Jenkins, J. 2010. Glyphosate General Fact Sheet; National Pesticide Information Center, Oregon State University Extension Services. http://npic.orst.edu/factsheets/glyphogen.html.

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