The Impact of Insecticides on Circadian Rhythms

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Lately, there’s been an awful lot of talk about circadian rhythms, which exist in every living thing and refer to the body’s 24-hour cycle of biological processes, often called the sleep/wake cycle. In other words, we’re talking about your internal body clock, and there’s a good reason why circadian rhythms are garnering so much attention.  

Circadian rhythms are vital to our health, and disruption of your daily timekeeping enhances the risk of metabolic complications (including diabetes), obesity, neurodegenerative issues, mood disorders, and more.1–3   

There are multiple factors, like shift work, travel across time zones, sleep restriction, limited daytime light exposure, and excessive light exposure at night, that can “desynchronize” our internal body clocks.  

And according to new research out of the University of Buffalo, synthetic chemicals commonly found in insecticides and garden products can disrupt circadian rhythms by binding to melatonin receptors, adversely affecting signaling of this key clock-controlling hormone.4 

Melatonin Function 

Melatonin is a naturally occurring hormone that is rhythmically released by the pineal gland, reaching peak levels at night. Melatonin helps regulate the sleep/wake cycle, and along these lines, melatonin facilitates feelings of sleepiness. 

Melatonin production is governed by light. When it’s dark, you produce melatonin; on the other hand, light inhibits melatonin synthesis. This is why excess exposure to light in the evening can disrupt circadian rhythms, and it’s also why inadequate sunlight exposure can lead to feelings of fatigue and poor mood states. You know, the ol’ winter blues, which are likely related to inadequate sunlight and disrupted circadian rhythms. 

Melatonin has other important functions, such as regulating metabolism. For instance, melatonin helps prevent hypoglycemia by inhibiting insulin secretion, which suggests that the body may not be particularly well-suited for nighttime eating (especially carbs). This is perhaps one reason why it’s a good idea to consume most of your food during daylight hours, and it may also be why disrupted circadian rhythms are tied to type 2 diabetes.5 

Insecticides and Melatonin 

According to this new research, a class of chemicals known as carbamates, which are found in insecticides and garden chemicals, interfere with melatonin’s function by binding to the MT2 receptor site. In other words, these synthetic chemicals are taking melatonin’s seat, which is where the hormone needs to be to exert its action.   

Specifically, the study cites two carbamates:  

  1. Carabaryl, which is illegal in several countries but is the third most widely used insecticide in the U.S. 
  2. Carbofuran, which is the most toxic carbamate insecticide  

Although carbofuran has been banned for use on food crops for human consumption since 2009, it is still used in many countries, including Mexico, and traces of this compound can be found in food, plants, and wildlife. 

Effects of Melatonin Interference 

Interfering with melatonin may have several negative consequences, with the most obvious being disrupted circadian rhythms and disturbed sleep. Poor sleep quality and quantity are closely linked to an increased risk for type 2 diabetes and metabolic syndrome. 

Melatonin is also a potent antioxidant, and along those lines, it may help protect against excessive oxidative stress and inflammation. Melatonin interference, in turn, may accelerate aging and impair immunity.  

It’s also important to point out that the endocrine system (the system of the body that regulates hormones) is intricately interwoven. In other words, interfering with one hormone impact many others. Thus, impairment of melatonin may have deleterious effects on other hormones throughout the body.  

For instance, melatonin helps regulate the release of reproductive hormones like progesterone, estrogen, and testosterone. Along these lines, disturbances in melatonin function may negatively affect reproductive function in women, including the frequency and duration of menstrual cycles. And long-term disruptions of circadian rhythms could potentially accelerate menopause. 

Take-Home Points 

Properly synced circadian rhythms are very important to our overall health. Considering that circadian rhythms are already extremely vulnerable to various insults in modern-day society, you’d be wise to limit your exposure to these insecticides as much as possible. 

Along those lines, opting for organic fruits and vegetables and thoroughly washing all produce are pragmatic take-home points. If you grow your own fruits, vegetables, and herbs, pay close attention to the garden products you use, and obviously, avoid direct exposure to these insecticides and choose organic options whenever possible. 

References: 

  1. Shi S, Ansari T, McGuinness OP, Wasserman DH, Johnson CH. Circadian disruption leads to insulin resistance and obesity.Curr Biol CB. 2013;23(5):372-381. doi:10.1016/j.cub.2013.01.048. 
  2. Schroeder AM, Colwell CS. How to fix a broken clock.Trends Pharmacol Sci. 2013;34(11). doi:10.1016/j.tips.2013.09.002. 
  3. Potter GDM, Skene DJ, Arendt J, Cade JE, Grant PJ, Hardie LJ. Circadian Rhythm and Sleep Disruption: Causes, Metabolic Consequences, and Countermeasures.Endocr Rev. 2016;37(6):584-608. doi:10.1210/er.2016-1083. 
  4. Popovska-Gorevski M, Dubocovich ML, Rajnarayanan RV. Carbamate Insecticides Target Human Melatonin Receptors.Chem Res Toxicol. 2017;30(2):574-582. doi:10.1021/acs.chemrestox.6b00301. 
  5. Tuomi T, Nagorny CLF, Singh P, et al. Increased Melatonin Signaling Is a Risk Factor for Type 2 Diabetes.Cell Metab. 2016;23(6):1067-1077. doi:10.1016/j.cmet.2016.04.009. 

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