When we’re stressed, many of us turn to junk food for comfort. But new research from CU Boulder suggests this strategy could backfire. The study found that in animals, a diet high in fat destroys resident gut bacteria, alters behavior, and, through a complex pathway that connects the gut to the brain, influences brain chemicals in ways that fuel theanxiety.
Fueling anxiety with the wrong diet
The study found that in animals, a high-fat diet destroys resident gut bacteria, alters behavior and, through a complex pathway connecting the gut to the brain, affects 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 a little 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 a way that can promote anxiety, the stakes become even higher.”
For the study, published in the journal Biological Research Lowry worked with first author Sylvana Rendeiro de Noronha, a doctoral candidate at the Federal University of Ouro Preto in Brazil.
In a previous study, the team found that rats fed a high-fat diet composed primarily of saturated fats showed increases in neuroinflammation and anxiety-like behaviors.
Although the evidence is mixed, some human studies have also shown that replacing a high-fat, high-sugar, ultra-processed diet with a healthier one can reduce depression and anxiety.
To better understand what might be driving the fat-anxiety connection, Lowry’s team divided male adolescent rats into two groups: Half received a standard diet with about 11% fat for nine weeks; the others ate a 45% high-fat diet, composed primarily of saturated fats from animal products.
According to the Centers for Disease Control and Prevention, the typical American diet is made up of 36 percent fat.
During the study, the 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, it’s not surprising that the high-fat diet group gained weight. But the animals also showed significantly lower diversity of gut bacteria. In general, greater bacterial diversity is associated with better health, Lowry explained. They also hosted much more of a category of bacteria called Firmicutes and less of a category called Bacteroidetes. A higher ratio of Firmicutes to Bacteroidetes has been associated with the typical industrialized diet and obesity.
The high-fat diet group also showed increased expression of three genes (tph2, htr1a and slc6a4) involved in the production and signaling of the neurotransmitter serotonin, particularly in a brainstem region known as the dorsal raphe nucleus cDRD, which is associated with stress and anxiety.
While serotonin is often called a “feel-good brain chemical,” Lowry notes that certain subsets of serotonin 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 just a high-fat diet could alter the expression of these genes in the brain is extraordinary,” Lowry said. “The high-fat group essentially had the molecular signature of a heightened state of anxiety in the brain.”
It is not yet clear how a disturbed gut can change chemicals in the brain. But Lowry suspects that an unhealthy microbiome compromises the lining of the gut, allowing bacteria to enter 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 all makes sense,” Lowry said. “We are hardwired to actually 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.
But his animal research suggests that exposure to an ultra-high-fat diet composed mostly of saturated fats, especially at a young age, could both increase short-term anxiety and prime the brain to be more prone to it later. future.
Her advice: Eat as many different types of fruits and vegetables as possible, add fermented foods to your diet to support a healthy microbiome, and give up pizza and French fries. Also, if you eat a burger, add a slice of avocado. Research shows that good fats can counteract some of the bad ones.
A poor-quality diet can lead to brain changes associated with depression and anxiety
A first-of-its-kind study of the brain chemistry, structure and diet quality of 30 volunteers shows that eating a poor-quality diet could lead to brain changes associated with depression and anxiety.
Brain scans show changes in neurotransmitters and gray matter volume in people who eat a poor diet, compared to those who adhere to a Mediterranean-style diet, which is considered very healthy. The researchers also found that these changes are associated with rumination, a part of the diagnostic criteria for conditions that affect mental health, such as depression and anxiety.
This research was conducted by the University of Reading, Roehampton University, FrieslandCampina (the Netherlands) and Kings College London, and is published in Nutritional Neuroscience.
When someone eats a poor-quality diet, there is a reduction in gamma aminobutyric acid (GABA) and an increase in glutamate – both neurotransmitters, along with a reduced volume of gray matter – in the frontal area of the brain. This could explain the association between what we eat and how we feel.
Dr Piril Hepsomali, from the University of Reading, said: “We can eat well! Ultimately, we see that people who eat an unhealthy diet, high in sugar and saturated fat, have imbalanced excitatory and inhibitory neurotransmission, as well as a reduced volume of gray matter in the frontal part of the brain. This part of the brain is involved in problems of mental health such as depression and anxiety.
Exactly why diet affects the brain in this way is still being studied. It is possible that obesity and dietary habits high in saturated fat cause changes in glutamate and GABA metabolism and neurotransmission, as has been shown in animal studies.
Distinct alterations to the gut microbiome, due to dietary patterns high in saturated fat, are thought to impact the cellular machinery that drives both GABA and glutamate production.
A diet high in saturated fats and sugars has also been shown to reduce the number of parvalbumin interneurons, which play the role of transporting GABA to where it is needed.
Unhealthy diets also impact glucose, increasing blood sugar and insulin. This increases glutamate in the brain and plasma, thus reducing the production and release of GABA. A diet high in fat and cholesterol can cause changes in cell membranes that also alter the release of neurotransmitters.
These changes in brain chemistry could lead to changes in the volume of the brain’s gray matter, as observed in this study.
Dr. Hepsomali continued: “I would like to point out that GABA and glutamate are also intimately involved in appetite and food intake. A reduction in GABA and/or an increase in glutamate could also be a driving factor in making unhealthy food choices. So, there may be a circular relationship between eating well, having a healthier brain and better mental well-being, and making better food choices to eat well.”
A Mediterranean diet can relieve symptoms of stress and anxiety, study says
It’s no secret that the Mediterranean diet is good for your health. Already recommended for reducing the risks of bowel cancer, heart disease and dementia, new research from the University of South Australia published in the journal Nutrients shows that the Mediterranean diet can also reduce symptoms of stress and anxiety.
Conducted in collaboration with the University of the Sunshine Coast, researchers assessed the impact of the Mediterranean diet on mental health among 294 older Australians (aged over 60), finding that it reduced the severity of anxiety and stress, regardless of age, gender, sleep, and BMI.
Furthermore, they identified that specific elements of the diet – fruits, nuts, legumes and low consumption of sugary drinks (less than 250 ml per day) – reduced the severity of anxiety and stress.
Globally, anxiety is the most common mental health disorder affecting more than 301 million people. In Australia, 1 in 4 people experience anxiety in their lifetime.
Dr. Evangeline Mantzioris, dietician and UniSA researcher, says the Mediterranean diet can play a significant role in improving mental health and quality of life.
“Globally, we are facing an unprecedented aging population, but despite this longevity, many people continue to struggle with their health and well-being,” says Dr. Mantzioris.
“Lifestyle behaviors, including diet quality, are increasingly gaining attention as modifiable risk factors for poor mental health, with the Mediterranean diet endorsed to reduce the risk of chronic disease and support healthy aging.
“In this study we showed that when older people followed a Mediterranean diet, their symptoms of stress and anxiety decreased, and that this occurred regardless of their age, gender, BMI, or the amount of sleep and exercise they got. .
“It’s a big step forward for the Mediterranean diet: through a relatively simple lifestyle change, people can dramatically improve their stress and anxiety levels, and who wouldn’t want to try.”
A Mediterranean diet includes lots of fresh fruits and vegetables, whole grains and seeds, nuts, legumes and olive oil. Fish and seafood should be incorporated at least twice a week, while dairy and lean proteins can be consumed daily in smaller portions. The diet encourages infrequent consumption of red meats and processed foods.
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