The Link between Insecticides and Diabetes

on February 13, 2018 by Chris Kresser

Statistics from the EPA indicate that more than one billion pounds of insecticides are used per year in the United States in agricultural, lawn, garden, and home applications. (1) Alarmingly, emerging research indicates that our overzealous use of insecticides may be contributing to rising rates of diabetes. Read on to learn about the link between insecticides and diabetes and how avoiding these toxins can help protect your metabolic health.

Insecticides are diabetogenic

A wide variety of insecticides are currently used for agricultural, residential landscaping, and home applications. While many people do not think about the health repercussions of insecticides, a growing body of research indicates that these synthetic chemicals are diabetogenic, meaning they promote the development of diabetes. Three specific classes of insecticides have been identified as diabetogenic: organophosphate insecticides, organochlorine insecticides, and carbamates.

Organophosphate insecticides (OPs) are the most widely applied insecticides worldwide. They account for more than 40 percent of the pesticide market and are used in agriculture, in mosquito abatement programs in public spaces, and as pest control in residential landscaping. Due to their frequent use in agriculture, they contaminate fruits, vegetables, grains, and drinking water. Organophosphates are also brought into the home as dust on clothing and shoes.

Malathion, a type of organophosphate insecticide, has been found to reduce pancreatic insulin secretion and induce fasting hyperglycemia, a hallmark of diabetes. (2) A significant positive correlation has also been found between plasma organophosphate residues and HbA1c, an important biomarker for diabetes. Concerningly, animal research suggests that the adverse effects of organophosphates on glucose control may begin early in life during the neonatal period, which is a critical developmental window for glucose regulatory pathways. (3)

Forty percent of all pesticides used worldwide are from the organochlorine class of chemicals, including the now-banned pesticide DDT, made infamous in Rachel Carson’s seminal work Silent Spring. While many organochlorine insecticides have been banned due to their neurotoxicity, many are still applied in agricultural settings. Organochlorine residues are present on non-organic fruits and vegetables and contaminate animal products. They have also been implicated in pesticide drift, the unintentional diffusion of pesticides due to spray drift. Organochlorine insecticides are persistent environmental pollutants that break down slowly in the environment and, once in the human body, stick around for a long time due to their affinity for fat tissue. Research has found that pesticide applicators exposed to heptachlor, an organochlorine insecticide, have 94 percent increased odds of developing diabetes. (4) Exposure to DDE, a breakdown product of the organochlorine insecticide DDT, is also associated with an increased risk of diabetes. (5, 6)

A billion pounds of insecticides are used per year in the U.S., and it may be causing your diabetes. Know how to reduce your exposure

Carbamate insecticides are widely used in homes, gardens, and agriculture. They are used as surface sprays and baits for controlling household pests, widely applied as lawn insecticides, and sprayed in public areas as mosquito control. While we don’t have research establishing a definitive link between carbamates and diabetes, there is evidence suggesting that exposure to these pesticides alters endocrine function as well as carbohydrate, lipid, and protein metabolism; these two effects may impair glucose regulation and increase the risk of diabetes. (7, 8)

How do insecticides promote diabetes?

A handful of mechanisms have been discovered that explain the link between insecticide exposure and diabetes. Insecticides promote diabetes by increasing gluconeogenesis, inhibiting acetylcholinesterase, stimulating oxidative stress and inflammation, interacting with the gut microbiota, and disrupting circadian rhythms.

Increased gluconeogenesis

Gluconeogenesis is the metabolic pathway that produces glucose from non-carbohydrate substrates such as lactate, glycerol, and amino acids. Excessive gluconeogenesis impairs blood sugar regulation, and increased gluconeogenesis is a key characteristic of diabetes. (9)

Exposure to the organophosphate insecticide malathion stimulates gluconeogenesis, thus raising blood glucose levels and promoting insulin resistance. Increased gluconeogenesis in the presence of malathion could either be a compensatory mechanism or the result of tissue damage. (10)

Inhibition of acetylcholinesterase (AChE)

Organophosphates are well known for their ability to inhibit acetylcholinesterase (AChE), an enzyme that catalyzes the breakdown of the neurotransmitter acetylcholine. Inhibition of acetylcholinesterase causes an accumulation of the neurotransmitter acetylcholine in the body. High acetylcholine, in turn, stimulates the HPA axis and promotes the release of hormones that activate glycogenolysis and gluconeogenesis; uninhibited stimulation of these pathways promotes hyperglycemia and insulin resistance. (11)

Oxidative stress and inflammation

A large body of evidence indicates that oxidative stress and inflammation are key underlying factors in the development of diabetes. (12) Insecticides are potent stimulators of oxidative stress and inflammation. Malathion induces oxidative stress and inflammation in the liver, increasing gluconeogenesis and hepatic insulin resistance. (13) Malathion also raises levels of TNF-α, a pro-inflammatory cytokine that dysregulates glucose homeostasis. Organophosphate insecticide exposure is also associated with elevated 8-deoxyguanosine, a biomarker of oxidative damage to protein, lipids, and DNA. Oxidative damage-induced changes in the structure and function of these molecules alter biochemical signaling pathways that regulate blood glucose levels.

Interactions with gut microbes

The gut microbiota plays many crucial roles in the regulation of metabolism. However, exposure to organophosphates not only promotes gut microbial dysbiosis—it also causes our gut bacteria to turn against us and become diabetogenic. (14) New research has found that the degradation of organophosphate insecticides by gut bacteria produces short-chain fatty acids, like acetic acid, that induce gluconeogenesis and glucose intolerance.

Circadian rhythm disruption

Circadian rhythms are the set of biochemical processes in the body that follow an approximately 24-hour cycle and control many aspects of behavior and physiology. Disruptions of human circadian rhythms are known to increase the risk of diabetes and other metabolic diseases. Recent research indicates that carbamate insecticides structurally resemble melatonin, a hormone that regulates circadian rhythms and targets its receptors in various organs and tissues. In the pancreas, melatonin receptor signaling regulates insulin release and glucose metabolism. By inhibiting the binding of melatonin to its receptors, carbamates disrupt the circadian control of glucose homeostasis. These effects suggest that carbamate exposure may increase a person’s risk of diabetes. (15)

Steps for reducing exposure to insecticides

There are several steps our patients can take to reduce their exposure to insecticides and protect their metabolic health.

Advise your patients to avoid the use of insecticides on their lawns and gardens and in their homes. This is especially important for families who have young children that play in the yard and on the floor and are in close contact with lawn and household dust, two potentially significant sources of insecticide exposure. 

Tell your patients that organic really is better! Non-organic produce is a significant source of insecticide residues. By choosing organically grown fruits and vegetables, your patients can reduce their exposure to insecticides. (16) In fact, frequent consumption of organic produce is associated with lower levels of DAP (dialkylphosphate), a biomarker of organophosphate insecticide exposure. (17) Higher organic food consumption is also associated with a reduced risk of metabolic syndrome, a condition that shares many features with type 2 diabetes. (18)

Recommend that your patients filter their drinking water. Significant levels of insecticides have been detected in tap water. (19) By investing in a high-quality water filter, your patients can further reduce their exposure to insecticides.

Use probiotics for prevention. Supplementation with probiotics may protect the body from the harmful effects of insecticide exposure. In animal studies, Lactobacillus rhamnosus has been found to reduce the intestinal absorption and toxicity of organophosphate insecticides. (20) This probiotic can be found in both probiotic supplements and fermented foods.

Now I want to hear from you. Have you found any relationship between insecticide exposure and diabetes in your patients? Have you counseled your patients about ways in which they can reduce their exposure? Let me know in the comments below.

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