Adding “scream” emojis to your texts lately? You are not alone.

Wait — you are alone, isolating — and that’s when anxiety and depression may move in. Exercise, yoga, and meditation are all documented methods to cope with the mental stress of coronavirus constraints. Diet is also powerful, and not just because gaining the “COVID 15- pounds” would make anyone sob.

So even if your chosen comfort foods are generally healthy and not of the chips, cookies and ice cream ilk, consider probiotics and prebiotics to boost your mood.

These beneficial organisms and the fibers that feed them are crucial to mental health.

Quick review

Gut microbes harvest your food, protect against pathogens, boost immunity and perform other vital functions. Your unique collection of bacteria, viruses and fungi are generally stable. But stress (new workplace, isolation, fear of illness) can disrupt the balance, leading to dysbiosis, which messes with health.

Gut-brain axis

Chatter between your brain and gut goes far beyond the “stomach grumbling” heard by your head when you’re hungry. The recently discovered “gut-brain axis” is a highly sophisticated bi-directional pathway: microbes impact the mental response to stress and its expression as anxiety, mood disorders or depression. And on the flip side, your mix of gut microbes responds to stressors such as anxiety.

Animal research offers some evidence of the network. In one study, social stressors reduced the relative abundance of Bacteroides, while increasing that of bacteria from the more pathogenic genus Clostridium.

And In one classic example, mice fed broth laced with Lactobacillus rhamnosus were less likely to be anxious or stressed and produced less of the stress hormone corticosterone than control mice that drank a bacteria-free broth. In another, a bifidobacterium strain normalized anxiety-like behavior in mice with colitis and showed some success in humans with irritable bowel syndrome linked depression.

Humans are also less anxious when given probiotics, according to some studies. In one, adults given both Lactobacillus helveticus and Bifidobacterium longum for 30 days reported beneficial psychological effects. And compared to controls, a small sample of women given a fermented probiotic cocktail for four weeks displayed changes in activity of brain regions that control central processing of emotion and sensation.

How probiotics may work their mental magic

One recent review revealed robust evidence in tested rodents:

  • Chronic stress hormones reduced
  • Brain-derived neurotrophic factor (BDNF), crucial for brain plasticity, memory, and neuronal health, increased.
  • Increased tryptophan (serotonin precursor) levels,  a prime actor implicated in stress and emotions across the gut-brain axis.
  • Reduced inflammatory biomarkers, which shows biomarkers aligning with depression.
  • Improved antioxidant abilities
  • Behavioral changes: improved memory and reduced anxiety and depressive symptoms.

And in humans:

The authors also assessed mood symptoms, anxiety symptoms or cognition in humans treated with probiotics (most frequently used probiotic strain was Lactobacillus casei, and duration of treatment period ranged from 3 weeks to 6 months.)

  • Stress and anxiety: Improvement seen in five of seven studies
  • Cognition: Three studies showed some improvement in coping and memory skills.
  • Mood: Three of the five trials assessing mood reported improvement with probiotic treatment.

Thus, most found encouraging results however the strain of probiotic, dosing, and duration of treatment varied widely.


Given the mounting evidence for probiotics as Prozac, researchers have created a new term for these beneficial bacteria: psychobiotics.

A team in Cork, Ireland defined a psychobiotic this way:

”…a live organism that, when ingested in adequate amounts, produces a health benefit in patients suffering from psychiatric illness.”


As the stress of remote work and confinement continue, take special care of your microbes. Pinpointing which probiotics work best is difficult as much of the research has been in animals.

However, here are a few general tips:

  • Eat fermented foods daily (yogurt, kefir, kimchi.)
  • Consider a multi-strain probiotic daily.
  • Feed your microbes well with high-fiber fruits, vegetables and grains. These prebiotic fibers are absolutely needed for a healthy microbiota.

Think of them as comfort foods for your brain.

Clare Fleishman RDN, MS