Where Are the Roots of Addiction?

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From profiling the microbiomes of many people, science has learned that only about one-third of each person’s internal bacteria are like other people’s. As Honor Whiteman explains for MedicalNewsToday.com:

…two thirds of the gut microbiome is unique to each person, and what makes this unique is the food we eat, the air we breathe and other environmental factors. Some studies have even suggested the makeup of the gut microbiome is influenced by genes.

Wency Leung of The Globe and Mail summarizes another astonishing fact about the tens of thousands of species that live inside us—there are no “good guys” or “bad guys.”

Rather, the microbiome is now understood to be a complex and bustling community, where even potentially disease-causing strains can be useful neighbours and friendly ones can turn against us.

Individual microbiomes are like fingerprints! They are all different, and even organisms of the same kind can act in different ways and have varying effects on the metabolisms of their hosts. By taking antibiotics, we can cause a mass extinction event among the microbiota, but aside from killing them, we can’t really control what they do—not consciously, anyway. But one theory holds that our genes can say Yea or Nay to quite a few questions. Consider the Enteric Nervous System:

The ENS and its connection to the brain also causes foods to affect your mood. For example, fatty foods can make you feel good because they contain fatty acids that are detected by the gut wall, which then sends out feelings of comfort to the brain.

Research has suggested possibilities to explain how the microbes get their way. Julie Beck wrote for The Atlantic about potential mechanisms that the critters might use to induce in us the sensations that we describe as cravings:

They may change the expression of taste receptors, making certain foods taste better; they may release hunger-inducing hormones; or they may manipulate the vagus nerve (which connects the stomach to the brain) to control their hosts’ eating behavior.

In a piece titled “Your Gut Bacteria Want You to Eat a Cupcake,” Beck mentions how individuals who are “chocolate desiring” and those who are “chocolate indifferent” may eat identical diets and yet have different microbial metabolites in their urine, and what that appears to mean.

Psychologist and evolutionary biologist Athena Aktipis teaches at Arizona State University, where she studies how the gut, with its links to the nervous system, endocrine system, and immune system, could be sending out signals that influence our physiologic and behavioral responses. These, presumably, would include addictive behavior, whether the behavior involves hard drugs, alcohol, or food. How could this happen? Maybe through the vagus nerve, “which connects 100 million nerve cells from the digestive tract to the base of the brain.” Aktipis writes:

Microbes have the capacity to manipulate behavior and mood through altering the neural signals in the vagus nerve, changing taste receptors, producing toxins to make us feel bad, and releasing chemical rewards to make us feel good.

Given all this, is it possible that the particular arrangement of intestinal fauna in each individual could be responsible for the development of addictive behaviors? Can the little critters make a person shoot heroin into his or her own antecubital vein? Can they make a person eat a pound of cheese for a bedtime snack?

Your responses and feedback are welcome!

Source: “The gut microbiome: how does it affect our health?,” MedicalNewsToday,com 03/11/15
Source: “Say hello to your little friends: Making sense of gut bacteria,” TheGlobeandMail.com, 06/07/15
Source: “Get to Know Your Microbiome for Health & Wellness,” CarpeVitaInc.com, 06/05/15
Source: “Your Gut Bacteria Want You to Eat a Cupcake,” TheAltantic.com, 08/19/14
Source: “Do gut bacteria rule our minds?,” UniversityofCalifornia.edu, 08/15/14
Image by Tim Pierce

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About Dr. Robert A. Pretlow

Dr. Robert A. Pretlow is a pediatrician and childhood obesity specialist. He has been researching and spreading awareness on the childhood obesity epidemic in the US for more than a decade.
You can contact Dr. Pretlow at:


Dr. Pretlow’s invited presentation at the American Society of Animal Science 2020 Conference
What’s Causing Obesity in Companion Animals and What Can We Do About It

Dr. Pretlow’s invited presentation at the World Obesity Federation 2019 Conference:
Food/Eating Addiction and the Displacement Mechanism

Dr. Pretlow’s Multi-Center Clinical Trial Kick-off Speech 2018:
Obesity: Tackling the Root Cause

Dr. Pretlow’s 2017 Workshop on
Treatment of Obesity Using the Addiction Model

Dr. Pretlow’s invited presentation for
TEC and UNC 2016

Dr. Pretlow’s invited presentation at the 2015 Obesity Summit in London, UK.

Dr. Pretlow’s invited keynote at the 2014 European Childhood Obesity Group Congress in Salzburg, Austria.

Dr. Pretlow’s presentation at the 2013 European Congress on Obesity in Liverpool, UK.

Dr. Pretlow’s presentation at the 2011 International Conference on Childhood Obesity in Lisbon, Portugal.

Dr. Pretlow’s presentation at the 2010 Uniting Against Childhood Obesity Conference in Houston, TX.

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