Digestion is a word use a lot but do we really know what it means?

Having a healthy digestion really sets the scene for health and wellbeing and when problems occur it can cause havoc – low energy, bloating, hormone imbalances, skin problems, headaches, aches and pains, allergies, constipation and diarrhoea are just a few signs that something isn’t right. So lets go on a journey from the mouth to the anus to find out what really happens…

Digestion is basically the process of breaking down the food we eat into nutrients that are small enough to be absorbed across the gut barrier into the bloodstream.

Our ‘gut’ is where this process takes place and is basically one big tube that runs from our mouth to our anus (changes in size, changes in pH, changes in length and the lining changes according to where it is in the gut). There are also organs along the way such as the liver, gallbladder and pancreas that have specific roles in digestion. 

In order for food to move down the gut we have valves along the way (bit like doors) that stop food or bacteria from going backwards and we have muscles to push it down which is what is known as peristalsis.   We also have another process – similar to peristalsis in that involves muscles and nerves and that is called the Migrating Motor Complex (MMC) – bit like a mexican wave that runs every 90 minutes and basically clears everything though – very important part of our digestive system. It is very active at night but it requires an empty stomach to work (constantly grazing and night shifts are not so good).  Problems with the MMC = problems with digestion. 


Our Senses

Digestion starts in the mouth technically -it really starts even before – when we smell food, when we see food, when we think about food, our circadian clock also kicks in  (time of day our brain tells our gut to get ready).  Our brain is telling our stomach  to produce chemicals that will digest the food we are about to eat.  This is why eating at the same time, having good routines and mindful eating is so important – preparation to eat is key



We then start to salivate. Saliva contains enzymes that start to break down carbohydrates this is known as ‘chemical digestion’.  We have 2 little glands at the back of our mouth inside our cheeks which squirt saliva when we eat and then we have 2 little glands where our tongue joins the floor of the mouth and that secretes saliva continuously. We secrete up to 1L of saliva a day give or take. 

Saliva itself is important. Its unique to each of us and made from filtered blood but has other things added such :

  • Calcium to make sure our teeth stay strong
  • Hormones
  • Painkiller – only a tiny amount and some studies suggest it could be an antidepressant and may be linked to comfort eating but the jury is out…
  • Mucins  (which form mucus) and its job is to catch any bacteria
  • Anti-bacterial substance to kill off that bacteria (again a very small amount)  
  • Good bacteria 

Sometimes there is also substances that can be used to analyse disease and sometimes there can be ‘bad bacteria’ which may or maynot be responsble for conditions such as SIBO (small intestinal bacterial overgrowth).  

We have powerful muscles in our jaw which, with our teeth allow us to crunch and pound.  Our tongue is another amazing muscle that helps us digest our food by rounding up stray food and bringing it back to be pounded.  Chewing is extremely important – as it makes it easier to break down our food in stomach and intestines – we don’t have teeth anywhere else for a reason. Hence the adage ‘chew your drink and drink your food’. 

Sometimes being bloated is because we didn’t chew our food properly or ate too fast.  Its really important to not add any more mouthfuls until what you have is fully chewed and swallowed. 

As I said above there is some thought now that the bacteria in our mouth and our tonsils may be responsible for IBS/SIBO (and even psoriasis) so I will be sharing more about this in the future as oral health and the oral microbiome are very important to a healthy digestive system. 



When you swallow your ‘liquid food’ travels down your food pipe (oesophagus) into your stomach .  

Your stomach is only the size of your fist but has room to expand to about 2 fistfuls.  It’s very high up (higher than most people realise) and finishes just below the rib cage- so any bloating or pain under the rib cage is going to be the small intestine or large intestine. 

It’s also a weird shape, almost like the letter J,  when we drink fluid or eat more water based foods (fruit and non-starchy veggies) they generally move down to the lower part of the stomach and are digested first. 

The top part of the stomach can hold food before pushing it to the bottom part for digestion. Stomach acid and enzymes are produced which break down the food further and the muscles churn it.   

Carbohydrates are broken down quickly as they have already been partially digested in the mouth. Proteins are specifically broken down into the stomach and take a bit of time as the acid and enzymes unfold the protein and snip away to make smaller bits (amino acids) so they can be broken down even more in the intestines.  

Fats take the longest time to break down in the stomach. 

pH is very important in digestion – the stomach is about 1.9 and 2.1 (very acidic) anything out of that range and you can experience bloating. If the stomach isn’t acidic enough it can actually affect the pH in the intestines and mean food doesn’t get broken down as well later on down the digestive tract.

The biggest issues with the stomach are not enough hydrochloric acid or too much  – both can cause reflux. Plus too much air in the stomach, not chewing food properly and eating too much in one go can also cause bloating.


Small intestine

From the stomach, the mush (chyme) is passed into a small tube known as the small intestine.  Which looks like a bunch of sausages all coiled up. The Small Intestine is actually about 3-7 metres long.  However, because it is the ‘digestion factory’ in order to work properly it has to be longer than that so it folds – every mm2 has finger like projections called villi, these villi also have finger like projections called microvilli and these have further projections that look like mini-antlers – all to increase the surface area. If you ironed out all these projections the small intestine would actually be about 30-40m2 (1).

As soon as food enters the small intestine, our liver and pancreas start to produce digestive juices and enzymes that get squirted into the chyme (similar to washing up powder) which further breaks down our food into tiny pieces. 

Each of those little finger like projections have blood vessels and further enzymes for the last bit of break down before those tiny molecules pass through a barrier into the bloodstream and travel to the liver. 

Some people don’t have enough specific enzymes (known as brush border enzymes which live in the microvilli) which break down carbohydrates causing intolerance such as lactose intolerance.  


Liver & Gall Bladder

The liver then screens them for any poisons or anything harmful – anything dangerous is destroyed or ‘detoxified’ .  

If we eat too much then our liver will store some of the excess. Too much ‘storage’ can cause the liver to not function properly. Fatty liver is an example of this dysfunction and can be caused by too much carbohydrate, fat and alcohol.  The liver sends out the safe nutrients back into the blood where they are taken to the heart and then pumped around the body to our cells. 

The liver is also responsible for fat digestion as it makes a substance called bile which is stored in the gallbladder and also squirted into the small intestine.  However fat is absorbed and dealt with very differently via our lymphatic system (that is a whole different topic for another time). 

The liver and gall bladder are really important organs for healthy digestion and when they don’t work properly it can cause digestive symptoms.

Large intestine (aka the colon)

The colon looks like a giant, plump sausage. This is the main house of our gut bacteria.  The appendix which is attached to the colon monitors all foreign microbes and attacks anything it considers ‘bad’ – leaving all the good bacteria alone. After a bout of diarrhoea (which can flush away the good bacteria) the appendix steps in and provides ‘back up’ quickly. 

Any food residue that is left such as fibre is then fed on and substances called short chain fatty acids are produced which are extremely important for our heath. 

The gut bacteria also produce vitamin K, small amount of vitamin B12, vitamin B1 and vitamin B2.   

Some extra substances are absorbed here including calcium and water and salt are balanced here too.  Those substances still go to the liver for checking and detoxification. 

The final few centimetres are the only place where anything absorbed goes straight into the blood stream hence why some medicines are suppositories as they are absorbed quickly and don’t go via the liver for checking and detoxification. 

The waste then moves into the rectum where it is eventually passed out as poo! 


How fascinating is that!!   Remember you really are what you eat – that snickers bar will be broken down and absorbed and end up in a skin cell on your right buttock. 


How do you know if you have poor digestion? 

If you are aware you are digesting then something is wrong.  You should not experience any discomfort anywhere in your gut, bloating, pain, cramping, hardness, loss of appetite, nausea, diarrhoea or constipation.  If you do it needs assessing. 


Top 10 Tips for a healthy digestion system

  1. Mindful Eating – use your senses – Slow Eating – Chew, chew, chew!
  2. Brush your teeth – see your dentist if you have any problems – get your tonsils checked
  3. Eat small portions or smaller meals – don’t over eat if you have bloating in your stomach.  Make sure you leave at the  absolute minimum 2 hour gaps between eating so that your MMC works properly
  4. Eat at the same times every day – try not to eat at night
  5. Make sure you are relaxed when you eat – stress is #1 reason behind digestion issues
  6. Consider aperitifs before you eat – swedish bitters or bush bitters
  7. Eat plants – this is the only place where you will get fibre which is the fuel for your healthy gut bacteria.  Eat fermented foods (if you react to them then this is a sign of an unhappy digestive system).  
  8. Drink enough water
  9. Remove any aggravating foods particularly if you think you might have a carbohydrate intolerance – try an elimination and challenge diet (watch out for Sarah’s new course on this)
  10. Get tested if you have any problems (and contact Sarah for an appointment)

There is a YouTube video of this blog. Head over to Sarah’s You Tube Channel if you are interested in watching rather than reading.

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Email me at sarahb@sarahbrenchleynaturopathy.com 

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