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Gut flora & your health

by Dr. Mercola


Eating unpasteurized sauerkraut is one of the best ways to establish beneficial lactobacilli cultures in the digestive tract.

• While many think of their brain as the organ in charge of their mental health, your gut may actually play a far more significant role. The big picture many of us understand is one of a microbial world that we just happen to be living in. Our actions interfere with these microbes and they in turn respond having more effects to our individual health as well as the entire environment.

There is some truth to the old expression, having “dirt for brains.” The microbes in our soil, on our plants and in our stomachs are all a result of our actions. Antibiotics, herbicides, vaccines, pesticides and the tens of thousands of synthetic chemicals we’ve created all have impacts and result in reactions from these microbes.

Mounting research indicates that problems in your gut can directly impact your mental health, leading to issues like anxiety and depression. The gut-brain connection is well recognized as a basic tenet of physiology and medicine so this isn’t all that surprising even though it’s often overlooked. There’s also a wealth of evidence showing intestinal involvement in a variety of neurological diseases.

Portrait of Dr. Mercola

Dr. Mercola

With this in mind, it should also be crystal clear that nourishing your gut flora is extremely important because in a very real sense you have two brains: one inside your skull and one in your gut and each needs its own vital nourishment.

The featured proof-of-concept study, conducted by researchers at UCLA, found that probiotics (beneficial bacteria) actually altered participants’ brain function. The study enlisted 36 women between the ages of 18 and 55 who were divided into three groups: 1) The treatment group ate yogurt containing several probiotics thought to have a beneficial impact on intestinal health, twice a day for one month. 2) Another group ate a “sham” product that looked and tasted like the yogurt but contained no probiotics. 3) The control group ate no product at all.

Compared to the controls, the women who consumed probiotic yogurt had decreased activity in two brain regions that control central processing of emotion and sensation. During the resting brain scan, the treatment group also showed greater connectivity between a region known as the “periaqueductal grey” and areas of the prefrontal cortex associated with cognition. In contrast, the control group showed greater connectivity of the periaqueductal grey to emotion and sensation-related regions.

Your diet affects your mood and mental health

According to lead author Dr. Kirsten Tillisch, “Time and time again, we hear from patients that they never felt depressed or anxious until they started experiencing problems with their gut. Our study shows that the gut-brain connection is a two-way street… When we consider the implications of this work, the old sayings ‘you are what you eat’ and ‘gut feelings’ take on new meaning.”

The implications are particularly significant in our current era of rampant depression and emotional “malaise.” And the drug treatments available today are no better than they were 50 years ago. Clearly, we need a new approach, and diet is an obvious place to start.

Previous studies have confirmed that what you eat can alter the composition of your gut flora. Specifically, eating a high-vegetable, fibre-based diet produces a profoundly different composition of microbiota than a more typical western diet high in carbs and processed fats.

It’s important to realize you have neurons both in your brain and your gut – including neurons that produce neurotransmitters like serotonin. In fact, the greatest concentration of serotonin, which is involved in mood control, depression and aggression, is found in your intestines, not your brain! Perhaps this is one reason why antidepressants, which raise serotonin levels in your brain, are often ineffective in treating depression, whereas proper dietary changes often help.

Gut bacteria are vulnerable to diet and lifestyle

Processed, refined foods in general will destroy healthy microflora and feed bad bacteria and yeast so limiting or eliminating these from your diet should be at the top of your list. Processed foods wreak havoc on your gut in a number of different ways. First, they are typically loaded with sugar and avoiding sugar (particularly fructose) is, in my view, based on the evidence, a critical aspect of preventing and/or treating depression. Not only will sugar compromise your beneficial gut bacteria by providing the preferred fuel for pathogenic bacteria, it also contributes to chronic inflammation throughout your body, including your brain.

Many contain artificial sweeteners and other synthetic additives that can wreak havoc with brain health. In fact, depression and panic attacks are two of the reported side effects of aspartame. Preliminary findings presented at the 65th annual meeting of the American Academy of Neurology also report that drinking sweetened beverages – whether they’re sweetened with sugar or artificial sweeteners – is associated with an increased risk of depression.

Processed foods are also typically loaded with refined grains, which turn into sugar in your body. Wheat, in particular, has also been implicated in psychiatric problems, from depression to schizophrenia, due to wheat germ agglutinin (WGA), which has neurotoxic activity.

The majority of processed foods also contain genetically engineered (GE) ingredients (primarily corn and soy), which have been shown to be particularly detrimental to beneficial bacteria.

Your gut bacteria are also very sensitive to and can be harmed by: 1) Antibiotics, unless absolutely necessary and when you do, make sure to reseed your gut with fermented foods and/or a probiotics supplement. 2) Conventionally-raised meats and other animal products as CAFO animals are routinely fed low-dose antibiotics. 3) Plus genetically engineered grains, which have also been implicated in the destruction of gut flora. 4) Chlorinated and/or fluoridated water. 5) Antibacterial soap.

Reseed your gut flora

Considering the fact that an estimated 80% of your immune system is located in your gut, reseeding your gut with healthy bacteria is important for the prevention of virtually all disease, both physical and mental. The first step is to clean up your diet and lifestyle by avoiding the items listed above. Then, to actively reseed your gut with beneficial bacteria, you’ll want to:

Radically reduce your sugar intake

I’m being repetitive here to drive home the point that you can take the best fermented foods and/or probiotic supplements, but if you fail to reduce your sugar intake you will sabotage your efforts to rebuild your gut flora. When you consume sugar at the level of the typical American, you are virtually guaranteed to have a preponderance of pathogenic bacteria, yeast and fungi, no matter what supplements you are taking.

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. Some of the beneficial bacteria found in fermented foods are also excellent chelators of heavy metals and pesticides, which will also have a beneficial health effect by reducing your toxic load.

Healthy choices include fermented vegetables, Lassi, an Indian yoghurt drink, traditionally enjoyed before dinner; fermented milk, such as kefir and Natto (fermented soy). Ideally, you want to eat a variety of fermented foods to maximize the variety of bacteria you’re consuming. Fermented vegetables, which are one of my new passions, are an excellent way to supply beneficial bacteria back into our gut. And, unlike some other fermented foods, they tend to be palatable, if not downright delicious, to most people. As an added bonus, they can also be a great source of vitamin K2 if you ferment your own using the proper starter culture. Most high-quality probiotics supplements will only supply you with a fraction of the beneficial bacteria found in such homemade fermented veggies so it’s your most economical route to optimal gut health as well.

Take a high-quality probiotic supplement

Although I’m not a major proponent of taking many supplements (as I believe the majority of your nutrients need to come from food), probiotics are an exception if you don’t eat fermented foods on a regular basis.

Cultured foods like raw milk yogurt and kefir, some cheeses, and fermented vegetables are good sources of natural, healthy bacteria. So my strong recommendation would be to make cultured or fermented foods a regular part of your diet; this can be your primary strategy to optimize your body’s good bacteria.

If you do not eat fermented foods on a regular basis, taking a high-quality probiotic supplement is definitely recommended. A probiotic supplement can be incredibly useful to help maintain a well-functioning digestive system when you stray from your healthy diet and consume excess grains or sugar or if you have to take antibiotics.

© Dr. Mercola, founder of the world’s #1 natural health site,

photo © Daniel Vincek

One comment

  1. Patricia /

    “The majority of processed foods also contain genetically engineered (GE) ingredients (primarily corn and soy), which have been shown to be particularly detrimental to beneficial bacteria.”


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