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What are you feeding your gut bacteria?

Updated: May 9

Snack food

I am sure you realize that you have a personal bacteria collection that live all over you and inside you.  On your skin, up your nose, in your ears, in your mouth but mostly in your gut. “yuck”. (just joking as these are mostly the good guys).

There are more bacteria in you, than you have cells of your own body and these bacteria have their own DNA.  The numbers are staggering.  Estimated number of micro-organisms per person is 10 with 14 zeros on the end of it, comprising over 500 different species.

These bacteria are different in different people for many reasons, such as the types of food you eat, the soil bacteria where you live, the animals and people you associate with, the bacteria in the air and water.  They initially established following your birth, from the air, the bacteria on the hands of the attending people, your mothers health, bacteria in the birth canal and the bacteria in the colostrum from your initial breast feeding.  Some people were not exposed to all of these of course.

However if you have taken antibiotics, then it is possible that your carefully constructed microbiome (the name given to this bacteria) could have been seriously damaged with many bacteria killed off.  The good news is that if you have an appendix then, it is believed, this is your body’s lifeline store of good bacteria from which your gut can be re-populated.

In your gut, there must be a balance of good bacteria and bad bacteria, known as Firmicutes (the good guys - Bacillota) and Bacteroidetes (the not so good guys - Bacteroidota).   I am sure it is not as black and white as this, but one recommendation is that a balance of about 85% good guys and 15% bad guys provides for optimum health.

Your overall health is totally dependent on these bacteria.  They help us to digest food, they produce B vitamins and produce most of our neurotransmitters.  Neurotransmitters are critical for nerve and brain function.  These are chemical substances which are released at the end of a nerve fibre by the arrival of a nerve impulse and, by diffusing across the synapse or junction, effects the transfer of the signal to another nerve fibre, a muscle fibre, or some other structure

For example, the neurotransmitter Serotonin, which is sometimes referred to as the “happiness” hormone is produced in your gut from tryptophan which is one of the essential amino acids we get when we are eating complete protein.  GABA, glutamate and about 50% of your dopamine is also made in the gut.  70% of your immune system is also located in your gut.

If you eat yoghurt, you have probably heard of the bacterium Lactobacillus which is one of the Firmicutes and is famous for helping produce Butyrate.  This has benefits for the gut lining, stimulates the production of Glutathione which is your bodies master antioxidant, helps prevent cancer cells from developing, helps minimize inflammation and supports hormone production.

The condition of your personal gut bacteria is always changing and this change is in response to many things particularly what you eat and how often.  If you eat food that nourishes good bacteria then they will reproduce and build up the army of good guys.  However if you eat food that nourishes the bad bacteria then they will proliferate and can cause poor health.  Examples of the impact of excess bad bacteria include: Intestinal putrefaction, production of bacterial toxins, production of cancer causing substances, and bloating with excess gas production.

You can also starve out bacteria by choosing to ignore their food,  so by eating the bad guys food, you are in effect starving out the good bacteria.

How do you get food to your gut bacteria?  It has to bypass all the other digestion processes on the way.  You digestion process begins as soon as food arrives in your mouth and then continues down through your gut.  For example proteins start to be broken down with chewing and the action of saliva and then move on to the stomach where the hydrochloric acid completes the breakdown into amino acids.  Incidentally the natural and healthy acidic level in humans (pH around 1.5-2 ) is stronger than carnivores such as cats (pH 2-2.5) and is actually similar to scavenger animals, suggesting that early humans were also scavengers.  Plant eating animals have a very much lower acidic level (pH around 6.5-7).

Food that directly feeds bacteria is known as a prebiotic.  This soluble and insoluble fiber plus resistant starch can pass directly through the digestion system to reach your gut bacteria.  A live culture that is eaten for the purpose of re-populating your gut is known as a probiotic, and by eating these it can be possible to help rebuild a damaged microbiome, however that acid environment of your stomach can make this difficult.

The best approach is to look after your existing microbiome by feeding the good bacteria and ensuring that you do not accidentally starve them out by providing food that nourishes only the bad bacteria.  What you may not be aware of is that these bacteria actually drive your eating behavior’s.  If you are craving the wrong foods, then it is the bad bacteria that are in control and by signaling the brain they “demand” the food they prefer.

If this sounds unlikely, remember that your gut is directly linked to your brain via the vagus nerve and most of your neurotransmitters are manufactured in the gut.  Gut bacteria can also influence the nervous system by altering the activity of the stress-associated hypothalamic–pituitary–adrenal (HPA) axis.  Both the hypothalamus and pituitary gland are located in the brain.

Let’s take a quick moment to recap what we are learning here:

  • Your gut microbiome is critical to your health

  • The makeup of your microbiome can be changed by what you eat

  • The resulting changes in your microbiome can impact your brain

  • What you crave to eat is driven by your microbiome

  • You can choose what to eat and by doing so can improve your gut health.

So what foods should you be eating and what foods should you be avoiding?

My brief summary is to:

Avoid ultra processed food, sugars, grains, milk and lectins, vegetable oils and instead

Eat more vegetables, dairy (not milk), meat, fish and eggs, animal fats, olive oil, coconut oil.

One of the major differences between our diet today and the diet of people a few hundred years ago is that today we have access to refrigerators.  This has made a huge difference, by keeping food fresh for longer, allowing transport and reducing spoilage.  However it comes with a dark downside.

When there were no refrigerators, we had to treat food differently in order to prevent waste and spoilage, and one of these ways was by fermenting, another was sprouting.  Vegetables would be fermented, milk would be fermented, grains would be sprouted or fermented and as a result many of our traditional methods of food preparation involved fermentation.  This is carried out by adding bacteria to the food, then leaving it to ferment by using up and therefore reducing the natural sugars and, in effect, creating a different product that does not spoil the same and often can be stored for longer without refrigeration.

For example, traditional bread making involved fermenting the flour and grains for 24 hours or more, with the result that the sugars in the bread are mostly consumed leaving a much more healthy loaf for eating.  The closest bread to this today is sourdough bread although do your research as some sourdough is fake.  In the interests of speed, convenience and profitably most modern breads do not go through the fermenting stage for sufficient time for the sugars to be consumed.  In addition the speed of processing does not allow the yeasts to break down the plants natural defenses releasing the nutrients and minerals and reducing the impact of anti-nutrients such as phytates, lectins, oxalates and gluten.  The result is a much less healthy product, but it rises well, is soft and has a longer shelf life.

Another regular food staple which has suffered a similar fate is milk.  Traditional milk storage required fermenting to make yoghurt or cheese.  While we can still buy yoghurt, for convenience and profit, the product is made in a very short time, again this does not allow for the true time taken for the lactose (sugar) in the milk to be used up feeding the bacteria and the result is often additionally sweetened creating a sugar heavy, unhealthy product from what could be a gut-healthy product.  But children like it better and with refrigeration it has a relatively long shelf life.

This loss of traditional practice also exists with corn.  Traditionally societies soaked corn in an alkaline solution, possibly wood ash and water, to break down the anti-nutrients and release the vitamin B3 (niacin) for them to absorb.  Thousands of people have died from the disease Pellegra, and many still die today when corn is dominant in the diet because this ancient technique is overlooked.

There is a danger that these traditional practices that can change foods from being unhealthy and hard to digest to easy on the gut, will be lost as people forget about the ancient customs.  More insidious is that without applying these practices we are creating a health problem for many people who remain susceptible to these modern convenience changes.

Animals that eat plants have the ability to ferment the food within their digestive system, but humans are not built like that. These animals have huge abdomens and often multiple stomachs where the fermentation can occur.  Look at the large abdomen on a gorilla, or the multiple stomachs of a cow.  However we have learned over many years that we can solve this problem by fermenting the food before we eat it as described above.  Unfortunately this knowledge and the understanding of the need for it is rapidly being lost.

What we are buying as “food” today is in many cases, not food as our bodies expect.

A suggestion is to get a book on fermentation and have a go at producing gut healthy versions of the FODMAP foods mentioned above.  These foods will help feed the gut and ensure plenty of healthy good bacteria.

For support, check out my book on Amazon here or contact me at “”.

Seek professional medical advice before making dietary changes, particularly if you have underlying health problems.  Good health,  George Elder, Diet Research Reviewer, Dip. Nutrition.

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