What if your psychiatrist prescribed yogurt and vegetables as    an antidepressant?  
    It may sound like alternative medicine, but researchers at the    intersection of psychiatry and biochemistry think that adding    certain beneficial bacteriato a persons    intestinescouldbethe future fortreating    anxiety and depression.  
    Diet and Depression  
    Studies have found thata diet high in vegetables    and low in processed foods correlates with lower rates of    depression.But showing that what you eat    actually affects your mental health has been more    complicated, because people who are depressed may be less    likely to eat healthier, as opposed tothe other way    around.  
    But now, in a recentstudy out of Australias    Deakin University,    scientistssay they have    used food to effectively treat depression.  
    Its the first controlled experiment, to our knowledge,    to show that dietary intervention can curb mood disorders,    says Dr. Felice Jacka, a psychiatrist    at Deakin and the studys lead researcher.  
    Deakin and colleagues recruited 56 people, all of whom met two    criteria: They wereclinically diagnosed with moderate to    severe depression, and they had consumed a lot of sweets and    processed meats at the expense ofhealthier    foodslike fruit, vegetables and fish.  
    The participants were then randomly assigned to one of two    treatments: diet counseling or befriending.  
    Over the course of the 12-week study, subjects in the diet    intervention group regularly met with nutritionists who    counseled them to increase their consumption of vegetables,    whole grains and fish, and to decrease their intake of junk    food.  
    The patients who were subject to befriending met with    trained research assistants to discuss topics like hobbies or    board games; they did not receive any psychological    therapy.This group served as a control to    ensure that any improvement in the diet intervention group    wouldnot be due to positive social interaction with the    nutritionist.  
    At the end of the 12 weeks, all of the participants were    re-evaluated, using the same depression measures asat the    studys start. The results? While both groups showed fewer    symptoms of depression, thosewho had received the diet    intervention were significantly less depressed than those in    the control group.  
    Furthermore, the more healthy changes that the subjects made to    their diet, the less depressed they were at the end of the    study.  
    It was pretty remarkable, Jackasays. Their level    of improvement correlated closely with the level of improvement    to their diet.  
    How Can Food Affect Our Mood?  
    At the end of the study, the researchers found similar    levels of biomarkers like glucose and cholesterol in the diet    and control groups. The groups did not differ in the overall    amount of exercise they had engaged in.  
    So what happened to the group with the improved diet to    make them less depressed?  
    While many people intuit that they are what they eat when    it comes to mental health, Jacka and other researchers believe    there is another factor at work: our    intestines, and    thesignals they send to our brains.  
    We are still only starting to tease all of this out,    saysMelanie Gareau,a    physiologist at UC Davis who specializes in understanding    interactions between ourbrain and our gut. Given all that    we know about thatlink, the Australian study results make    sense, she says.  
    Weve known for quite a while that over 95 percent of    the serotonin in our bodies is produced in the intestines,    says Gareau. As serotonin is one of the primary    neurotransmitters mediating depression, she thinks itsno    surprise that what goes into our intestines can affect our    emotions.  
    But its not just about the food we are eating, she says.    Its how that food interacts with the trillions of bacterial    cells that live in our guts, collectively calledour    microbiome.  
    Gareau points to a small study out ofUCLA    that showsthe effect of probiotics    micro-organisms believed to be beneficial to humans on    brain activity.   
    In the study, 12 women over the course of a month were    given yogurt containing Bifidobacteria and    Lactobacillus.Both of these have been    associated with decreased depression in    rodents, and there have been suggestive    links between those types of bacteria and mood    inhuman studiesas    well.Although its not clear whether taking    probiotics with these particular bacteria changes the overall    profile of our microbiome for any extended length of time,    ingesting them does increasetheir levels for shorter    periods.  
    In the UCLA study, after four weeks of consuming these    probiotics, the women completed an emotional response task in    which they viewed pictures of angry and fearful faces, while    their brain activity was recorded through functional magnetic    resonance imaging, or fMRI. The procedure, which measures    changes in blood flow within the brain, showed which areas were    activated while the subjects viewed    theimages.  
    The faces [we used] can trigger threat responses in    people, explains Dr. Kirsten    Tillisch, the studys lead researcher and a    gastroenterologist at UCLA. And we know that people with    anxiety show increased responses to them.  
    As it turnedout,the women who took the    probiotics showed lessbrain activity when    viewingthe emotional images than women who took a    placebo. Dr. Emeran Mayer, a    co-researcher in the study and the author of The    Mind-Gut Connection, explains that this kind of    dampened response resembles the pattern you might expect to see    in someone who isnt hyper-reactive to the environment.  
    The brains reactivity to threatening stimuli is    reduced. So you could speculate that these people might be less    prone to anxiety, Mayersays.  
    Is it the Food or the Bacteria?  
    But if our microbiome affects our mood, how so? Researchers    think the processmightoccur through metabolites,a byproduct    released bybacteria that feedson food our bodies    cannot fully break down.  
    These metabolites can enter into the bloodstream or    nervous system, travel up to our brain, and influence how    neurons talk to one another. Metabolites may also serve as    messengers, signaling cells in the intestines to increase or    decrease compounds like serotonin.  
    Carlito Lebrilla,    a professor of biochemistry and molecular medicineat UC    Davis, says you have to look at both the bacteria    and the food to understand whats    happening.  
    Although there has been an increase in the marketing of    probiotic supplements in recent years, especially for    improvingphysical health, probiotics are not doing all    of the work here, Lebrillaexplains. Ingesting    probiotics, whether through supplements or a food like yogurt,    lays down some of that good intestinal bacteria, so that they    are poised and ready to give off the right kind    ofmetabolites. However, whether or not your gut bacteria    produce those metabolites depends on thefood you eat    afterward.  
    So you can eat a probiotic food like yogurtall day and    still not experiencethe potentially positive effects,    Lebrillasays. Thats because we still dont know which    metabolites make our brains feel better, which bacteria give    off those metabolites, and which kinds of foods feed    those bacteria.  
    Thats what we are trying to do right now, Lebrilla says. He    says that while scientists have identifieda few types of    bacteria that are likely to give off good metabolites, there    are hundreds and possibly thousandsof bacterial strains    in our intestines. If we could map out the specific    bacteria-metabolite combinations that reduce anxiety and    depression, we would be a step closer to creating customized    diets for our brains. Its something that could take a couple    of decades to accomplish, Lebrillasays, but its not    that far-fetched.  
  In the meantime, both Jacka and Mayer point out that over tens of  thousands of years, our bodies have evolved in concert with the  microbiota in our intestines to function optimally with the foods  we have been eating.For millennia we fed off  of a mostly plant-based and lean-meat diet. Butin recent  years there have been profound changes to the kinds of foods we  eat, Jacka says, particularly in the reduced amount of  vegetables and increased amount of sugar.  
    Its wildly different from what we were eating even a    generation ago.  
    Taking that into consideration, what the findings from    her study might really show is not a    new diet to curb mood disorders, but    rather how we might look back to the foods our ancestors ate in    order to restore balance to our bodies and brains.  
Link:
Can Probiotics Help Your Depression? What We Know, What We Don't - KQED