Summary: A high-fat diet can disrupt gut bacteria, change behavior, and influence brain chemicals in ways that increase anxiety. The study found that rats fed a high-fat diet had less diversity in gut bacteria and higher expression of genes associated with stress and anxiety. This suggests that poor eating habits can not only lead to weight gain but also negatively impact mental health.
Highlights:
- A high-fat diet can disrupt the gut microbiome, leading to an imbalance in gut bacteria.
- An altered gut microbiome may influence brain chemicals, potentially increasing anxiety-like behaviors.
- Healthy fats, such as those found in fish, olive oil and nuts, are beneficial for the brain and can counteract the negative effects of a high-fat diet.
Source: University of Colorado
When stressed, many of us turn to junk food for comfort. But new research from the University of Colorado Boulder suggests this strategy could backfire.
The study found that in animals, a high-fat diet disrupts resident gut bacteria, alters behavior and, through a complex pathway from the gut to the brain, influences brain chemicals in ways that fuel anxiety.
“Everyone knows these are not healthy foods, but we tend to think of them strictly in terms of mild weight gain,” said lead author Christopher Lowry, a professor of integrative physiology at CU Boulder.
“If you understand that they also impact your brain in ways that can promote anxiety, the stakes are even higher.”
Lowry’s team divided the adolescent rats into two groups: half received a standard diet of about 11 percent fat for nine weeks; the remainder followed a high-fat diet, consisting of 45% fat, consisting mainly of saturated fats from animal products.
The typical American diet is about 36 percent fat, according to the Centers for Disease Control and Prevention.
Throughout the study, researchers collected fecal samples and assessed the animals’ microbiome, or gut bacteria. After nine weeks, the animals underwent behavioral tests.
Compared to the control group, the high-fat diet group, unsurprisingly, gained weight. But the animals also had significantly lower diversity of gut bacteria. Generally speaking, greater bacterial diversity is associated with better health, Lowry explained.
They also harbored significantly more of a category of bacteria called Firmicutes and less of a category called Bacteroidetes. A higher Firmicutes/Bacteroidetes ratio has been associated with diet typical of industrialized countries and obesity.
The high-fat diet group also showed higher expression of three genes (tph2, htr1a and slc6a4) involved in the production and signaling of the neurotransmitter serotonin, particularly in a region of the brainstem known as the core. of the dorsal raphe, cDRD, which is associated with stress and anxiety.
While serotonin is often touted as a “feel-good brain chemical,” Lowry notes that certain subsets of serotonergic neurons can, when activated, cause anxiety-like responses in animals. Notably, increased expression of tph2, or tryptophan hydroxylase, in cDRD has been associated with mood disorders and suicide risk in humans.
“To think that a simple high-fat diet could change the expression of these genes in the brain is extraordinary,” Lowry said. “The high-fat group essentially had the molecular signature of a high anxiety state in their brains.”
Lowry suspects that an unhealthy microbiome compromises the gut lining, allowing bacteria to slip into the body’s circulation and communicate with the brain via the vagus nerve, a pathway from the gastrointestinal tract to the brain.
“If you think about human evolution, it makes sense,” Lowry said. “We are wired to really notice the things that make us sick so we can avoid them in the future.”
Lowry points out that not all fats are bad and that healthy fats like those found in fish, olive oil, nuts and seeds can be anti-inflammatory and good for the brain.
Her advice: Eat as many kinds of fruits and vegetables as possible, add fermented foods to your diet to support a healthy microbiome, and ditch the pizza and fries. Also, if you’re eating a hamburger, add a slice of avocado. Some research shows that good fats can counteract some of the bad ones.
About this research news on eating and anxiety
Author: Lisa Marshall
Source: University of Colorado
Contact: Lisa Marshall – University of Colorado
Picture: Image is credited to Neuroscience News
Original research: Free access.
“High-fat diet, microbiome-gut-brain axis signaling, and anxiety-like behavior in male rats” by Christopher Lowry et al. Biological research
Abstract
High-fat diet, microbiome-gut-brain axis signaling, and anxiety-like behavior in male rats
Obesity, associated with a high-fat diet (HFD), and anxiety are common among people living in modern urban societies. Recent studies suggest a role for microbiome-gut-brain axis signaling, including a role for brain serotonergic systems in the relationship between HFD and anxiety.
Evidence suggests that the gut microbiome and the brain serotonergic system may together play an important role in this response.
Here, we conducted a nine-week HFD protocol in male rats, followed by analysis of gut microbiome diversity and community composition, brainstem serotonergic gene expression (tph2, htr1aAnd slc6a4) and defensive behavioral responses related to anxiety.
We show that HFD consumption decreases alpha diversity and alters community composition of the gut microbiome in association with obesity, increases brainstem. tph2, htr1a And slc6a4 mRNA expression, including in the caudal portion of the dorsomedial dorsal raphe nucleus (cDRD), a subregion previously associated with behavioral responses related to stress and anxiety, and, ultimately, increased behavioral responses defensiveness linked to anxiety.
HFD increased the Firmicutes/Bacteroidetes ratio compared to the control diet, as well as higher relative abundances of wetand decreases in Prévotelle. We found that tph2, htr1a And slc6a4 mRNA expression increased in subregions of the dorsal raphe core in the HFD, compared to the control diet. Specific bacterial taxa were associated with increased expression of serotonergic genes in cDRD.
Thus, we propose that HFD-induced obesity is associated with impaired brain microbiome-gut-serotonergic axis signaling, leading to increased anxiety-related defensive behavioral responses in rats.