• Comfort foods may be linked to increased stress and anxiety, new research shows.
  • A high-fat diet may lead to an imbalance in gut bacteria, which could influence brain chemicals, potentially increasing anxiety-like behaviours.
  • Experts explain the findings.

It’s normal to opt for comfort foods when you’re feeling stressed. The type of dishes help you to feel, well, comforted. However, new research shows that the high-fat foods you may go to for support could actually be adding fuel to your anxiety and stress fire.

A study published in Biological Research looked into how a diet high in saturated fats impacts gut bacteria, behaviour, and brain chemistry in rats. The research team divided adolescent rats into two groups: half got a standard diet of about 11% fat for nine weeks; the others got a high-fat diet of 45% fat, consisting mostly of saturated fat from animal products.

Throughout the study, researchers collected faecal samples and assessed the animals’ microbiome, or gut bacteria. After nine weeks, the animals underwent behavioural tests. When compared to the control group, those eating a high-fat diet gained weight.

They also displayed a significantly reduced diversity of gut bacteria. More bacterial diversity is generally associated with better health, explained lead author Christopher Lowry, a professor of integrative physiology at CU Boulder, in a statement.

The high-fat diet group also showed higher expression levels of three genes involved in the production and signalling of serotonin, a neurotransmitter commonly referred to as a “feel-good” brain chemical. This was especially evident in a region of the brain stem associated with stress and anxiety.

While serotonin may boost positive feelings, certain subsets of serotonin neurons can trigger anxiety-like responses when activated. In particular, one of the three genes that were found to have elevated expression in the brain stem region linked to stress and anxiety has also been associated with mood disorders and a higher risk of suicide in humans, Lowry noted in the statement.

The average Australian's intake of saturated fat is about 15% of total energy intake, despite recommendations that it should not be above 10%, according to the Australian Institute of Health & Welfare. Saturated fats increase our risk of heart disease. The Australian Dietary Guidelines recommend that we "replace foods containing saturated fats with foods that contain unsaturated fats, that is, either monounsaturated or polyunsaturated fats."

We get trans and saturated fats from foods like

  • coconut oil
  • butter and cream
  • pastries and pies
  • processed meats and sausages
  • cheese
  • potato chips

We get unsaturated fat, or "healthy fats" from

  • nuts and seeds
  • legumes 
  • avocado
  • fish
  • eggs
  • poultry

The results of the study show that this excess fat consumption may not only lead to weight gain but could also potentially worsen stress and anxiety.

So, how can a high-fat diet lead to higher levels of stress and anxiety? Well, when you consistently eat more fat than your body needs, it can change the composition of your microbiome, mainly by reducing the diverse makeup and number of “good” bacteria in your gut, says Newgent. “But keep in mind that eating an overabundance of protein or carbs can disrupt gut health too… it’s not just limited to too much fat,” she adds.

Because of the gut-brain connection, research has shown that anxiety symptoms may worsen in those who have an imbalanced gut microbiome, says dietitian Melissa Prest. “Likewise, when a healthy gut bacteria is restored through diet and supplementation, anxiety symptoms may improve,” she explains.

The bottom line

This study confirms what other studies have reported with changes to the gut microbiome when fat is the predominant nutrient, says Prest. Still, more research is needed in human studies to confirm these results, she notes. Newgent agrees, saying that “this study was conducted on male rats, so the results may not be the same in humans, especially females.”

If you’re concerned your diet has thrown off your gut microbiome, Prest says high-fibre diets will help restore and promote it.

“Fibre is rich in plant foods like beans, legumes, fruits, vegetables, and whole grains,” she notes. Newgent agrees and recommends following a Mediterranean-style diet, which provides anti-inflammatory benefits. “By reducing inflammation, you can reduce your body’s cortisol [the body’s stress hormone] levels which in turn may help to relieve stress,” she explains.

So, if you already experience anxiety, it may be a good idea to choose a high-fibre, whole-food diet that includes less added sugars and unsaturated fat, says Prest. But keep in mind that you likely don’t need to change course based on this study alone, as “more research is needed to suggest an optimal diet pattern for people with anxiety,” she clarifies.

Whether or not you have an anxiety disorder, it’s always best to get personalised diet advice from a dietitian as part of the healthcare team, Newgent advises.

© prevention.com
First published:
Tags:  anxietycomfort fooddietfatfoodhealthmental healthnutritionsaturated fatstress