You are what you eat

Anyone who’s ever tried to cure the blues with Ben and Jerry’s knows that there is a link between our stomachs and our moods. Foods high in fat and sugar release pleasure chemicals like dopamine and opioids into our brains in much the same way that drugs do, and I’d certainly argue that french fries and a chocolate milkshake can perk up even the lousiest of days.

This brain-belly connection works in the opposite direction, too. Ever felt nauseous before giving a big presentation? Or had butterflies in your stomach on a first date? It’s this system relating feedback from your brain to your gut causing those sensations and giving you physical signals that something big is about to happen.

However, instead of trying to suppress those feelings (or running to the bathroom every five minutes) it now appears that we can use this brain-body loop to our advantage. Formally referred to as the microbiome-gut-brain axis, bacteria that live in our stomach and intestines can affect our responses to stress and anxiety, and research in recent years has shown that probiotic bacteria – like those found in many strains of yogurt – can help to reduce anxiety and elevate mood in addition to helping us “stay regular”.

Previous research has shown reduced fear and stress responses during anxiety-inducing tests in mice who were fed broth with an added probiotic. This included less freezing in the face of fear, greater exploration of new environments, and fewer indicators of depression during a behavioral despair test (cheerful, huh?). These chilled out mice also had lower levels of corticosterone – a major stress hormone – after being tested, corroborating these behavioral findings.

Now, recent research from a team of doctors at UCLA’s School of Medicine and *CONFLICT OF INTEREST ALERT* funded by Danone, the yogurt company, has for the first time provided support for this brain-stomach connection in humans. These researchers looked at the effect eating yogurt (or as they like to call it, a “fermented milk product with probiotic”) every day for four weeks had on neural responses to pictures of negative faces. This type of task usually causes an increase in activity in emotion and somatosensory regions of the brain, like the amygdala and the insula, indicating an unpleasant or stressful reaction to the images. Compared to control individuals who had eaten just a normal fermented milk product, those who had eaten the probiotics had decreased activity in these brain areas, suggesting they were not as affected by the pictures.

Curiously though, there was no difference between the groups in probiotic levels found in stool samples taken (yes, they tested their poop), and none of the participants reported feeling any changes in their levels of stress, anxiety or depression during the study. However, there were significant differences in brain activity between the groups while they were resting, including in the areas identified during the task. Altogether, it looks like even small amounts of probiotics (i.e., not enough to change your gut levels) can still have a significant affect on our brain activity, even without noticeably changing our moods.

This interaction between our guts and our gray matter is thought to be facilitated by the vagus nerve traveling down the base of the brain into the stomach, transmitting sensory information and chemical signals from internal organs back up to the brain. Supporting this theory, when this nerve was cut in the first study the positive effects of the probiotics disappeared, and the test mice were back to their normally anxious selves.

It doesn’t appear that non-fermented milk products have the same positive effects on the brain, so it looks like I’ll be switching my usual Ben and Jerry’s to frozen yogurt for the next few weeks while I finish writing up my PhD thesis. Maybe it’ll help with my growing “thes-ass” too!

(Originally posted on Mind Read)

(“Thes-ass” coinage credit to Anna Bachmann)

The healing power of the brain-gut connection

Anyone who’s ever tried to cure the blues with Ben and Jerry’s knows that there is a link between our stomachs and our moods. Foods high in fat or sugar release pleasure chemicals into the brain in much the same way that drugs do, and chocolate in particular is frequently touted as a mood-elevating treat. Now research from a team of pharmacologists in Ireland provides new support for this brain-gut connection, showing that probiotic bacteria, like those found in many strains of yogurt, can elevate mood and reduce anxiety.

Formally referred to as the microbiome-gut-brain axis, this system has been implicated in stress responding, with gut microflora affecting the HPA (hypothalamic-pituitary-adrenal) axis and altering stress and anxiety responses. In the current study, researchers gave mice Lactobacillus rhamnosus and then subjected them to various stress-inducing tests. Mice who had been fed the probiotic solution demonstrated less freezing or fear-response behaviors compared to those who were given plain broth. They were also more likely to explore exposed novel environments in an elevated maze, an indication of security and lack of anxiety. Finally, on a depression assessment, mice were placed in a forced swim test (also called the behavioral despair test), where they were submerged in water and had to struggle to stay afloat. Lack of effort and time not spent attempting to swim are seen as indicators of depression and hopelessness, and probiotic-fed mice had less immobility time than broth-fed mice. Corroborating these behavioral results, test mice also had lower levels of corticosterone after being stressed than control mice.

This interaction between the brain and the gut is facilitated by the vagus nerve, a cranial nerve that transmits sensory information from internal organs to the brain. When this nerve was cut the effects of the probiotics disappeared, and test mice had decreased exploratory behavior and greater periods of immobility, similar to the broth-fed mice.

The anxiolytic effects of L. rhamnosus seem to be tied to GABA, an inhibitory neurotransmitter involved in anxiety. Probiotic administration altered levels of GABA mRNA expression in regions of the brain, including the amygdala, hippocampus, and prefrontal cortex. In depressed individuals, GABA levels in the frontal cortex are shown to be reduced, but in the probiotic-fed animals, cortical GABA levels were elevated. This led the researchers to theorize that L. rhamnosus might help to protect against stressful or anxiety-producing events. GABA levels in the amygdala are also commonly elevated in depressed individuals, and GABA antagonists (which reduce the levels of the neurotransmitter in the brain) are sometimes used as antidepressants. In the current study, lower levels of GABA were found in the hippocampus and amygdala after probiotic consumption, suggesting an interaction between L. rhamnosus and the memory and emotional centers of the brain, potentially increasing associative learning and memory consolidation and decreasing fear responding to stressful events.

The connection between diet and behavior doesn’t just apply to stress. Certain highly specified restrictive diets have also been used to help treat and control a variety of neurological disorders, most notably epilepsy. First pioneered in the 1920s at John’s Hopkins Children’s Hospital, extreme high-fat/low-carbohydrate diets are gaining support as a possible alternative for drug-resistant epilepsy, though some physicians are still skeptical. The diet works by invoking ketosis, a process in which the body burns fat stores rather than carbohydrates for fuel. This typically occurs when the body is in a starvation state and is the premise on which low-carb diets are based. However, ketogenic diets also appear to have an antiepileptic effect, particularly in cases of severe pediatric epilepsy. Doctors are not sure why the treatment works, but one theory is that the ketone bodies produced by the liver when the body burns fat protect neurons from damage, though how or why this happens is still unknown.

A keystone paper from University College London published in 2008 was the first to empirically report the efficacy of the ketogenic diet, and a recent provocative profile in the New York Times of a family dealing with epilepsy, “keto,” and the trials it brings has brought this treatment to national attention. The diet itself is strictly regimented and incredibly difficult to follow. It requires exact caloric measurements and proportions of protein, carbohydrates, and fats, with roughly a 3-to-1 fat to carb/protein ratio. This relates to a diet of roughly 90% fat, which can be dangerous, potentially triggering kidney problems and malnutrition. However, the effectiveness of the treatment is gaining recognition, and patients who are on the ketogenic diet (mostly children) are carefully monitored for cholesterol levels and cardiovascular health.

The ketogenic diet is now being looked at to potentially treat other serious medical disorders, such as Parkinson’s disease and cancerous tumors. It is important to note, though, that individuals being treated with a prescribed diet are also frequently on concomitant medication. Diet alone will not be able to cure all ailments, but the connection between diet and mental and physical health cannot be denied, and in the very least it is a good place to start keeping yourself well and taking preventative action.