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The Nutrition Examination Research Digest (NERD) aims to provide rigorous, unbiased analysis of the latest and most important nutrition and supplementation studies. Click here to subscribe or login if already a subscriber .

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Dampening exam anxiety with probiotics

When you're stressed out for an exam, you probably don't instinctively reach for probiotics. Your microbiome may impact anxiety though, and this trial tested a probiotic for anxiety-lessening around exam time.

Study under review: Fermented Milk Containing Lactobacillus casei Strain Shirota Preserves the Diversity of the Gut Microbiota and Relieves Abdominal Dysfunction in Healthy Medical Students Exposed to Academic Stress

Introduction

If you’re down in the dumps, in some cases you may be able to use your microbiome as a scapegoat. The links between the bugs in your gut and mood are slowly and ploddingly becoming better understood[1] in recent years. NERD #16, Volume 2, “Little Bugs For Big Depression,” discussed a study[2] that showed mood improvements can be achieved by people with major depressive disorder with the help of a mix of three probiotic strains: Lactobacillus acidophilus, Lactobacillus casei, and Bifidobacterium bifidum.

The pathway through which microbes in your gut may influence mood is called the microbiota–gut–brain axis[3] (or more colloquially as the “gut-brain axis”). The bi-directional communication that occurs between the gut and the brain[4] is mediated through various endocrine, neural, and immune pathways. Trying to figure out which strains of probiotics produce favorable outcomes can be an onerous task, with a lot of trial and error involved. Many effects of probiotics are strain-specific[5] (as shown in Figure 1), so swapping out one for another may produce an altogether different effect.

Figure 1: Recommendations for probiotic use

Source: Floch et al. J Clin Gastroenterol. 2015 Nov-Dec.

Lactobacillus casei strain Shirota (LcS), the probiotic strain used in the study under review, has been previously researched for its effects on cancer[6], immune modulation[7], and intestinal health[8]. LcS is one of the more well-known probiotics (commonly sold under the brand name Yakult) and has passed through the rigorous process of being approved as Generally Recognized As Safe (GRAS) by the Food and Drug Administration of the United States. Preliminary evidence has indicated that LcS may be able to ameliorate mood disturbances[9] in elderly people with initially poor mood and decrease anxiety in people with chronic fatigue syndrome[10]. In the paper under review, researchers looked to primarily investigate LcS’s effect on stress-induced abdominal dysfunction. This can include symptoms like cramping, bloating, and general gastrointestinal discomfort. In addition, they examined secondary outcomes such as psychological state, salivary stress markers, and genetic expression changes related to stress response.
The microbiome has the ability to modulate certain aspects of mood through pathways in the gut-brain axis. Lactobacillus casei strain Shirota (LcS) has been shown to reduce symptoms of anxiety and mood disturbances in select populations. This study expands that line of research and investigates LcS’s effects on stress-induced abdominal dysfunction, psychological state, salivary stress markers, and genetic expression patterns responsible for immune system activity.

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Other Articles in Issue #21 (July 2016)

  • Interview: Norm Robillard, PhD
    Gut health is extremely variable and complex, so learning from experts is important. Norm is a microbiologist whose expertise lies in the effect of diet on gut conditions.
  • Let the sun shine in! (to your retinal ganglion cells)
    We've covered the detriments of night-time blue light before, but how important is getting blue light during the work day? This controlled trial looked at its effect on working memory.
  • Heritable bacteria
    How can researchers figure out the role of your genetics in determining the kinds of bacteria you have in your gut? Get over a thousand sets of twins and do some fancy testing. We describe the results here.
  • Probiotics and prebiotics for atopic dermatitis
    This meta-analysis looked at all the existing trials on the common type of eczema called "atopic dermatitis", to see if combining pro- and prebiotics helps reduce symptoms.
  • Potential relief for IBS through vitamin D
    Vitamin D isn’t just for bone health. Its role in dampening inflammation and regulating immune responses suggest that it may help in treating IBS, which is directly tested in this randomized trial.
  • Interview: Elle Penner, MPH, RD
    Elle is the senior dietitian at the nutrition and fitness tracking juggernaut MyFitnessPal. We discuss some tips for new moms thinking about diet considerations.
  • Fish oil showdown: anti-inflammatory effects of EPA vs. DHA
    Chronic inflammation is a driver of many health conditions, and plays a key role in heart disease. Fish oil is a popular supplement partly due to its potential anti-inflammatory actions. But which omega-3 has a greater impact, EPA or DHA?
  • Heavy menstrual bleeding in athletes
    An increasing proportion of athletes are female, yet the persistent issue of menstruation is rarely researched in the context of athletics. This study gets the ball rolling.
  • Could fasting help treat MS symptoms?
    Multiple sclerosis involves immune attacks on the nervous system. Current treatments address symptoms, but may have substantial side effects. Fasting diets may both help symptoms and regeneration of existing damage.