Scientific Links Between Processed Foods and Depression Keep Getting Stronger
July 16, 2015
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By Dr. Mercola
Research shows that the food you eat can have a profound effect on your mental health. So, regardless of your mental health problem, the importance of addressing your diet simply cannot be overstated.
In a very real sense, you have two brains — one in your head, and one in your gut. Both are created from the same tissue during fetal development, and they’re connected via your vagus nerve, the tenth cranial nerve that runs from your brain stem to your abdomen.
It is now well established that the vagus nerve is the primary route your gut bacteria use to transmit information to your brain, which helps explain why mental health appears to so intricately connected to your gut microbiome1 — the bacteria and other microbes living in your gut.
For example, researchers recently found that fermented foods helped curb social anxiety disorder in young adults.2,3 Another study4 found that mice engaged in obsessive-compulsive repetitive behaviors were pacified when given a strain of the bacterium Bacteroides fragilis.
Gut bacteria also produce mood-boosting neurotransmitters like serotonin, dopamine, and gamma-aminobutyric acid (GABA). In fact, the greatest concentration of serotonin is found in your intestines, not your brain.
At the end of the day, if you’re trying to address your mental state, optimizing your gut health should be toward the very top of your list.
The Strong Link Between Sugar and Depression
A number of food ingredients can cause or aggravate depression, but the number one culprit is refined sugar and processed fructose, which feed pathogens in your gut, allowing them to overtake more beneficial bacteria.
Sugar also suppresses the activity of a key growth hormone in your brain called brain-derived neurotrophic factor (BDNF). BDNF levels are critically low in both depression and schizophrenia.
Diets high in sugar also triggers a cascade of chemical reactions in your body that promote chronic inflammation, which over the long term disrupts the normal functioning of your immune system and wreaks havoc on your brain.
Last but not least, refined sugar and processed fructose and grains are key contributors to insulin and leptin resistance, which also plays a significant role in your mental health.
One recent study5,6 found that high-glycemic foods (including those high in refined grains and added sugar) were associated with higher odds of depression.
Added sugar in particular was strongly associated with depression, reconfirming what William Dufty said in his classic best-selling book, Sugar Blues, first published in 1975. Sometimes it takes a while for science to catch up — in this case 40 years!
Other Processed Food Ingredients That Promote Depression
Other processed food ingredients that can contribute to depression and/or other mental health problems include:
- Genetically engineered (GE) ingredients can significantly alter your gut flora, thereby promoting pathogens while decimating the beneficial microbes necessary for optimal mental and physical health.
- Glyphosate— the most widely used herbicide on food crops in the world with nearly 1 BILLION pounds applied every year — has been shown to cause nutritional deficiencies, especially minerals, which are critical for brain function and mood control.
It also causes systemic toxicity, and was recently declared a Class 2A probable human carcinogen. Roundup, in which glyphosate is the active ingredient, has also been shown to increase the antibiotic-resistance of E. coli and Salmonella.
- Artificial food additives, especially the artificial sweetener aspartame, can wreak havoc with your brain function. Both depression and panic attacks are known potential side effects of aspartame consumption. Other additives, such as artificial colorings, are also known to impact mood.
- Gluten, a protein found in grains such as wheat, rye, and barley, may negatively impact mood and brain health.
In fact, a number of studies indicate that wheat can have a detrimental effect on mood, promoting depression and even more serious mental health problems such as schizophrenia.
Most non-organic wheat is also treated with glyphosate in a pre-harvest processed called desiccation, which adds to its problematic effects (see glyphosate above).
To Heal Depression, Heal Your Gut
As noted by The Epoch Times:7 “In the last 20 years or so, scientists have developed a new respect for bacteria, and the paradigm is turning from a strategy of war, to one of co-existence. Science now considers a robust, diverse bacterial colony to be essential to good health.”
Indeed, the bacteria residing on and in your body outnumber your cells 10 to 1, and viruses in turn outnumber bacteria 10 to 1. In many respects, you are your microbiome.
As Tom Insel, director of the National Institute of Mental Health, told The New York Times:8
“We are, at least from the standpoint of DNA, more microbial than human. That’s a phenomenal insight and one that we have to take seriously when we think about human development.’’Rapidly mounting research reveals that many of these little microbes have very specific functions, and as a whole play a profound role in your biological processes and overall health — including your brain health.
“According to Dr. Raphael Kellman, a New York City-based physician who specializes in treating the microbiome...the microbiome not only influences our mood, but it also has a lot to do with how the brain functions and develops over time,” The Epoch Times9 notes.The fact that improving your microbiome can affect your cognitive function means it’s also important to nourish your gut to stand a better chance against neurodegenerative disorders such as Alzheimer’s. Interestingly, researchers have also found that recurring depression is associated with shrinkage of the hippocampus, the area of your brain associated with memory formation,10 and depression itself appears to be a risk factor for dementia.
‘By improving the microbiome we can actually see positive changes in mood, cognitive function, and executive function,’ Kellman said...
‘The microbiome communicates with the brain through a number of mechanisms... These pathways include direct neurotransmitters that the microbiome produces.
It communicates with the brain via the vagus nerve, and also via the endocrine system in the stress pathway — the hypothalamus, pituitary, and adrenal axis.’
Current treatment for neurological disorders focus on direct changes to brain chemistry, tweaking levels of neurotransmitter chemicals in hopes of tuning in the right balance. But the future of mental health treatment may focus much more on the gut than the brain, and more on food than drugs.”
Here, it’s important to take your vitamin D levels into account, as both depression and Alzheimer’s disease are associated with vitamin D deficiency.
The Birth Of A More Holistic Model For Mental Health
Depression and anxiety are typically treated with antidepressants, despite the fact studies have shown them to only be on par with placebos in terms of effectiveness. They’re also associated with a slew of side effects, including the progression into more severe and/or chronic mental health problems. Recent research may in part explain why antidepressants can worsen the situation rather than making it better.
The ‘chemical imbalance’ theory states that depression and anxiety disorders are due to low serotonin levels. Selective serotonin reuptake inhibitors (SSRIs) work by making more serotonin available for use in your brain, which is thought to improve your mood. Alas, recent research reveals that people with social anxiety do not have low serotonin; they have higher than normal levels. So further boosting serotonin with an SSRI will only make the anxiety worse...
The new focus on gut health is a welcome departure from the synthetic drug model. As discussed in The New York Times,11 researchers are listing and investigating psychoactive compounds found in feces, and are experimenting with fecal transplants in animals to assess its effect on neurodevelopment:
“Anxiety, depression, and several pediatric disorders, including autism and hyperactivity, have been linked with gastrointestinal abnormalities. Microbial transplants were not invasive brain surgery, and that was the point: Changing a patient’s bacteria might be difficult but it still seemed more straightforward than altering his genes. When Lyte began his work on the link between microbes and the brain three decades ago, it was dismissed as a curiosity.
By contrast, last September, the National Institute of Mental Health awarded four grants worth up to $1 million each to spur new research on the gut microbiome’s role in mental disorders, affirming the legitimacy of a field that had long struggled to attract serious scientific credibility... It seems plausible, if not yet proved, that we might one day use microbes to diagnose neurodevelopmental disorders, treat mental illnesses and perhaps even fix them in the brain.”
Abnormal Gut Flora Fosters Abnormal Brain Development
Researchers have also begun experimenting with fecal transplants in autistic children,12 and while such investigations are still in its infancy, there’s plenty of cause for optimism. There does in fact appear to be a close connection between abnormal gut flora in infancy and abnormal brain development — a condition Dr. Campbell-McBride calls Gut and Psychology Syndrome (GAPS). GAPS is the result of poorly developed or imbalanced gut flora and may manifest as a conglomerate of symptoms that can fit the diagnosis of autism, attention deficit hyperactivity disorder (ADHD), attention deficit disorder (ADD) without hyperactivity, dyslexia, dyspraxia, or obsessive-compulsive disorder, just to name a few possibilities.
Dr. Campbell believes autistic children are born with perfectly normal brains and sensory organs, but once their digestive system becomes a major source of toxicity instead of being a source of nourishment, they start to develop autistic symptoms. This theory fits in well with more recent research13 published by the American Society for Microbiology, which identified a bacteria (Sutterella) that is unique to the intestines of children with autism. According to the authors:
"Many children with autism have gastrointestinal (GI) disturbances that can complicate clinical management and contribute to behavioral problems. Understanding the molecular and microbial underpinnings of these GI issues is of paramount importance for elucidating pathogenesis, rendering diagnosis, and administering informed treatment.
Here we describe an association between high levels of intestinal, ucoepithelial-associated Sutterella species, and GI disturbances in children with autism. These findings elevate this little-recognized bacterium to the forefront by demonstrating that Sutterella is a major component of the microbiota in over half of children with autism and gastrointestinal dysfunction (AUT-GI) and is absent in children with only gastrointestinal dysfunction (Control-GI) evaluated in this study."
Nourishing Your Gut Flora May Boost Your Mood and Protect Your Mental Health
All things considered, it seems quite clear that nourishing your gut flora is extremely important to support a positive mood and stable mental health. To do so, I recommend the following strategies:
In summary, foods have an immense impact on both your body and your brain, and eating whole foods as described in my nutrition plan is the best way to support your mental and physical health. Whether you need a quick pick-me-up or you’ve been struggling with poor mood for a while, the best remedy is likely not found in your medicine cabinet but right in your pantry or refrigerator.
- Avoid sugar and processed, refined foods in your diet. Remember eating real food is one of the most powerful and simple strategies you can implement to take control of your health. If you need help doing this, read through my nutrition plan for a simple, whole-food based diet. There is simply no question that eliminating refined sugars is the most powerful intervention the average person can make to improve their gut flora.
- Eat traditionally fermented, unpasteurized foods. Fermented foods are the best route to optimal digestive health, as long as you eat the traditionally made, unpasteurized versions. Ideally, you want to eat a variety of fermented foods to maximize the variety of bacteria you’re consuming. Healthy choices include fermented vegetables, lassi (an Indian yoghurt drink, traditionally enjoyed before dinner), fermented milk like kefir, kimchee, and natto (fermented soy).
- Take a high-quality probiotic supplement. If you don’t eat fermented foods on a regular basis, do consider taking a broad-spectrum probiotic. Research has shown that certain probiotics may help alleviate anxiety by modulating the vagal pathways within the gut-brain, affecting GABA levels, and lowering the stress-induced hormone corticosterone.
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