Smorgasbord Health Column – The Digestive System Part One – It begins in the mouth by Sally Cronin

I have received a number of emails regarding the digestive system and its many different functions and also related health issues…I am therefore going to feature a post a day for the next couple of weeks, taking you through the various organs involved and how our food is digested to ensure we receive the nutrients that we require.  Also some of the health issues that can be experienced when the system is not working efficiently.

The Digestive System – It begins in the mouth.

As the purpose of these blogs is to offer you an overview of the body, I am not going to attempt to give you all the specifics about this complex and fascinating process. However, it does serve to illustrate the knock-on effect on our overall health if one part of the operating system, or chemical process, is damaged and off-line for a period of time.

Actually the digestive process starts in the nasal passages – remember how it feels to smell fresh baked bread, the BBQ or a curry. The saliva starts to build up in your mouth – which is why we call it ‘mouth-watering’. As soon as that process begins – we are ready to eat and digest the food. Interestingly enough, people who have a reduced or non-existent ability to smell rarely become obese!

The mouth

The mouth is much larger than we would imagine from an external view and it contains the tongue and the teeth behind the entrance, which is guarded by the lips and mouth. At the rear of the mouth are the various tubes leading to the lungs or the rest of the digestive tract.

There are two palates within the mouth, the hard and soft palates. The hard palate to the front of the roof of the mouth is used by the tongue to mix and soften food whilst the soft palate (velum) can expand to allow food to pass back into the oesophagus without being forced up into the nasal passages.

The cheeks and soft tissues of the mouth are covered in a mucous membrane that keeps the mouth moist helped by the salivary glands. This membrane is one of the most vulnerable to wear and tear in the body and has remarkable powers of regeneration.

The tongue

The tongue is triangular, wider at the base than at the tip. It is attached at the base to the lower jaw and to the hyoid bone of the skull. At the sides of the base it is attached to the pharynx which is the cavity at the back of the mouth. The top of the tongue is curved and is home to our taste buds, the front is called the apex and the back of the tongue is called the dorsum.

The tongue is very flexible and is controlled by a complex set of muscles both in the tongue itself and also in the jaw and neck. The styloglossus muscle in the neck is responsible for the upward and backward movement of the tongue and the hyoglossus also in the neck brings it back down into the normal resting position.

Of course one of the main functions of the tongue is its involvement in our speech and its health is therefore vital. Without it our ability to process food in the mouth and to talk would be virtually non-existent.

Food has to be chewed before it is presented to the rest of the digestive tract. The tongue will roll the food around the mouth so that the teeth can begin the process of breaking it down into manageable pieces.

The teeth

The teeth are very necessary to our digestive process as food needs to be in small enough pieces to pass through the oesophagus into the stomach and also to allow enzymes adequate access to the last crumb. If it is a large chunk of food it will not be processed efficiently and we will lose much of the benefit.

We have two sets of teeth in our lifetime and how we look after the first set can have an effect on the health of the second and adult teeth. I was a dental nurse and in the 60’s we began to see the effect of increased sugars particularly in soft drinks on children’s teeth. My boss who was then in his 60’s was horrified in the difference that had taken place in only 20 or 30 years. As children we have 20 milk teeth that develop from small root structures under the gum at birth appearing around 9 months old to around 6 years old when they are pushed out by the 32 adult teeth as they begin to erupt. The second teeth can be affected by diet when they are still beneath the gums and this can lead to a lifetime of fillings and extractions.

All our teeth have specific roles in digestion and we are given enough so that as we age and lose a few we can still have the ability to process food. Of course in the last hundred years or so we have got very clever and can now replace teeth with dentures or better still implant new artificial teeth into the jaw that last around 15 to 20 years depending on the material used.

The incisors are designed to cut and the pointed canines are perfect for tearing foods such as meat and plant food apart. Our premolars and molars towards the back of the mouth can grind and crush other foods such as nuts, seeds and if necessary even bone.

Teeth are firmly fixed in sockets in the upper and lower jaw by a root system that may have one or two roots depending on tooth type and its role. Gum surrounds the tooth to help protect from decay and act as a buffer while the teeth work on food several times a day for our lifetime. The outer surface is enamel, which is one of the hardest substances in the human body and beneath this is dentine a pulp that protects the sensitive nerve and blood system in the middle of the tooth.

One of the key elements of efficient digestion is how we chew our food. Most of us eat far too quickly, not allowing the teeth to produce small enough pieces of food or our saliva and enzymes to carry out their part in the process.

Chewing slowly has the added benefit of allowing a message to get through from the stomach to the brain to tell it that you are full and to stop eating. This not only helps us maintain a healthy weight but it also reduces the stress and pressure on the digestive system.

N.B – If you have elderly relatives it is important to make sure that they have regular dental care and if they have dentures they fit properly. The inability to chew food means that they will tend to drop certain foods from their diet and begin to suffer from nutrient deficiencies, particular B vitamins that are in whole grains and meats.

The salivary glands –

The salivary glands at the base of the tongue produce an enzyme called ptyalin that digests starch and a chemical called Lysozyme that sanitises the food to prevent infection both in the mouth and the digestive tract. It is hard to believe but the human adult will produce in the region of 1½ litres of saliva per day consisting of mucous and fluid. It is important that the mouth is kept very moist not only for comfort but to enable us to deal with dry foods allowing it to be chewed more easily. It is also essential once food has been chewed, to ease the next stage of the digestive process when food is swallowed.

There are a number of salivary glands positioned in the mouth the largest being the parotids, in the neck, just in front of the ears. The glands that excrete the most saliva are under the jaw. These are the submandibular glands. And finally, under the tongue in the floor of the mouth are the sublinguals. The amylase enzyme produced by these glands converts the carbohydrate we eat into disaccharide sugars for further processing later in the stomach and intestines. (If you want to witness this in action, wave a cooked sausage in front of a dog’s nose and place their jaw over a basin!)

The pharynx

I looked at the respiratory role of the pharynx in the blogs on lungs, but it also is a channel for food. Its upper parts are connected to the nose and the mouth and lower part is connected to the voice box or larynx and leads to the oesophagus for swallowing.

We have all choked on food at one time or another and the reason for this natural and instinctive action is the epiglottis, the flap that prevents food and foreign particles from entering the lungs.

When we swallow this flap tilts backward and the larynx rises up. The cartilage bands around the larynx called the vocal cords come together and close the flap to seal off the entrance to the trachea. As soon as the food has passed safely into the oesophagus on its way to the stomach the epiglottis re-opens to allow air into the windpipe again.

Next time we will move into the oesophagus and the stomach.

©sallycronin Just Food for Health 1998 – 2018

A little bit about me nutritionally.

A little about me from a nutritional perspective. Although I write a lot of fiction, I actually wrote my first two books on health, the first one, Size Matters, a weight loss programme 20 years ago. I qualified as a nutritional therapist and practiced in Ireland and the UK as well as being a consultant for radio. My first centre was in Ireland, the Cronin Diet Advisory Centre and my second book, Just Food for Health was written as my client’s workbook. Here are my health books including a men’s health manual and my anti-aging book.

All available in Ebook from

And Amazon UK:

Comprehensive guide to the body, and the major organs and the nutrients needed to be healthy 360 pages, A4:

Thank you for dropping in and if you have any questions fire away.. If you would like to as a private question then my email is I am only too pleased to help in any way I can. thanks Sally


The Digestive and Immune Sytems – Short Story – What happens to a chicken sandwich as it digests!

The immune system- The Digestive process.

In my book, Just Food for Health, the chapter on the digestive system is nine A4 pages long (there are a few illustrations). You are used to seeing long posts from me which is why I split the topic over several posts last week. About this time last year I wrote this short story to describe the passage of a very common and tasty snack that many of us enjoy. Usually with only one thing in mind. The taste.. However, perhaps after following this chicken sandwich through your digestive tract you might think about it in a different way. For those who read this last year.. apologies but I wanted to link last week’s digestive system series and the previous immune system together.


Firstly, though a little about antibiotics. Most of the stories in the media are about the concerns of scientists and doctors that we are fast running out of effective antibiotics to kill the many strains of bacteria that threaten our health.

If human DNA only mutates every 10,000 years or so, they are outstripped by ‘Formula 1‘ bacteria. They are mutating in a heartbeat to survive and this is where the problem lies with antibiotics. We have over prescribed them in the last 50 years or so, pumped them through the food chain resulting in damage to our immune systems and we have created a group of superbugs that don’t care what you throw at them.

Our immune system is our own personal health insurance and we need to make sure that it is boosted so that it can handle the minor bacterial infections we will all have from time to time and only have antibiotics if our system cannot overcome the problem itself.

The purpose of this post is to illustrate how the food that we put in our mouths is critical to the efficiency of our Immune System. Without the right ingredients that have to be processed at every stage of digestion, there would be no defence mechanism in place and we would die. Therefore you really need to think of these two major operating systems of the body as working in tandem.

Our body is pretty amazing but it is not a magician. You do not eat a meal and are suddenly flooded with vitamins and minerals. It is necessary for the food to go through a complex process before its nutrients can be utilised to combat bacteria and provide us with energy.

For that task we need enzymes and other ingredients produced by our organs. For the purpose of this post I am going to use a sandwich that many of us might eat and then forget about. What happens to it after the juicy chicken and tangy mayo has left our mouth is not our concern surely?  But it is!

One of the most complex systems in our body is already at work having begun the process the moment you started to chew the first mouthful of the sandwich.

chicken sandwich

You take your first bite of a wholegrain sandwich with chicken and salad, a bit of butter and a smidgen salt and mayonnaise (lovely)- in the meantime your teeth, tongue and salivary glands that produce the first phase of enzymes begin the digestive process before passing the food (properly chewed is helpful) into the pharynx at the back of the throat. For example amylase produced by the salivary glands converts the bread in the sandwich into pairs of sugars, or dissacharides.

Salivary Glands

The food then passes into the oesophagus through to the stomach where hydrochloric acid modifies pepsinogen, secreted by the stomach lining to form an enzyme called pepsin. Pepsin breaks down the chicken into smaller units called polypeptides and lipase will break down any fatty globules into glycerol and fatty acids. The acid in the stomach will also kill as much harmful bacteria as possible (not only in the food itself but passed on from the hands that made it and the board it was made on). The end result is a highly acidic liquid that is passed into the duodenum.

Stomach and Pancreas

The duodenum will secrete a mucus in response to two hormones (secretin and pancreozymin) that are released to neutralise the acidic liquid that was your chicken sandwich. Bile is also passed into the duodenum either directly from the liver or from the gallbladder where it has been stored.

Acid Alkali scale-01

Bile is a complex fluid containing water, electrolytes and organic molecules including bile acids, cholesterol, phospholipids and bilirubin essential for the digestion of fats and their absorption along with fat-soluble vitamins as they pass through the small intestine. The bile has also picked up the waste products that have been accumulating in the liver so that they can be passed through the colon for elimination.

Referring back to my cholesterol blogs – –  this is when total levels are affected by the efficiency of the bile process. Cholesterol not only comes from food but is also manufactured in the liver. It is virtually insoluble in most fluids except for bile where the acids and fats such as lecithin do the job. If this process is not effective cholesterol can collect into stones that block the ducts and cause problems with the digestion of fat. Bile levels in the body are lowest after fasting which is why you have a cholesterol test at least 12 hours after your last meal.


By the time the liquid sandwich reaches the duodenum the particles within it are already very small, however they need to be smaller still before they pass into the ileum, where the final chemical processing will take place. The enzymes that have joined the mix from the pancreas and amylase will break down the food even further into peptides and maltose which is a disaccharide sugar.7. The small intestine is lined by millions of villi, tiny hair like projections which each contain a capillary and a tiny branch of the lymphatic system called a lacteal (yesterday’s blog). More enzymes maltase, sucrase and lactase are produced to facilitate the absorption of the smaller particles through the villi – including breaking down the sugar pairs into single sugars called monosaccharides which pass through easily.

Intestinal villi

Villi in the intestines

The glycerol, fatty acids and the now dissolved vitamins are sucked up into the lymphatic system through the lacteal and into the bloodstream. Other nutrients such as amino acids, sugars and minerals are absorbed into the capillary in the villi which connects directly to the hepatic portal vein and the liver. It is here, in the liver that certain nutrients will be extracted and stored for later use whilst others are passed onto the body.

Single villus

Single Villus with its complex absorption system

The carbohydrate in the sandwich we have eaten has been broken down into first pairs of sugars and then into single sugar molecules and have passed through the villi into the liver. Glucose provides our energy and the liver will determine current levels in our system, how much glucose to convert to glycogen to store and how much to release directly into the bloodstream as long term imbalance can cause diabetes.

Once all the nutrients have been extracted and passed into the bloodstream, lymphatic system or liver, any insoluble and undigested food moves into the large intestine. Any water and salt remaining in the mixture is absorbed into the lining of the intestine and the remainder mixes with all the other waste products produced by the body such as bacteria and dead cells – it is then pack and pressed and stored for excretion.

So there goes the last of your chicken sandwich. I hope it puts a different perspective on the food that you are putting into your mouth – it also is important to remember that if you have a white diet, white grains, fats and sugars, you are giving your body a great deal less to work with and your body and immune system will struggle to get what it needs to be healthy.

The only foods that provide our digestive system with the raw ingredients to maintain and boost our immune systems are natural, unprocessed vegetables, fruit, protein, wholegrain carbohydrates and healty fats.

If 80% of the time you are consuming these foods cooked from scratch then 20% of the time eating foods that have are not as healthy is not a problem.

Most of us have access to an amazing variety of fresh foods but stay firmly fixed on a handful. We need a really wide variety of food to obtain all the nutrients we need for our immune system and this shopping list might help you out.

©sallygeorginacronin Just Food For Health 2008

Thanks for dropping by and please feel free to share.. your feedback is always very welcome.. Sally

Smorgasbord Health – Digestive System – Are you contributing to the multi-billion pound Indigestion pill business!

smorgasbord health

I have already covered the most important of our survival mechanisms which was the respiratory system since the most urgent requirement that we have as humans is for oxygen. Fluids and food are the next priority so in this series of blogs it is the turn of the digestive system.

There is much evidence to suggest that the indigestion pills that millions of people consume daily because their digestive systems are in overload, are causing more harm than good.  When I went to the US in 1985 – the first advert I saw on TV was for a preparation to consume before you went out to eat to prevent later acid problems.  Take a good look at the adverts today – most are implying that they are a preventative measure so that you can eat exactly what you like and to hell with the consequences.  Not true.

Honestly, it was not until I studied nutrition and the human body that I had any interest in what happened to lunch after I had eaten it.  I expected that it would pass through my body and really only thought about it when it gave me indigestion.  The fact that these foods on a plate were vital to my survival was far less pressing than extinguishing my hunger pangs.

The process is fascinating – well for some of us!  However, it is I believe this lack of connection with the food we put in our mouths, and the magnificent processing power of out bodies to turn this hotchpotch of foods into energy, nutrients to feed a fetus, boost our immune system, repair cells, keep our brain alive, that is fuelling our obesity crisis.  So I hope you will enjoy this journey that we will follow along with your breakfast this morning.  It is a couple of thousand words but about 24 hours in real time.  Perhaps not as exciting as 24 hours with Jack Bauer but the digestive system’s mission is just as vital to our survival as is his.

This system is sophisticated and complex, with a combination of organs, glands and chemicals involved in the process that turns raw materials into the specific nutrients that the body needs to survive. In this first blog I will take a quick trip down the digestive system as far as the intestines.  Buckle your seat belt!


The Digestive system

Our bodies are not designed to take a piece of meat, apple or carrot and use it immediately in that form. So, it is necessary for the body to make enzymes that are capable of converting the original food into the optimum fuel for energy, growth, health and repair.

Enzymes are produced at various stages along the digestive tract by organs and glands such as salivary glands in the mouth, the stomach and the intestines. Enzymes are protein molecules that speed up the chemical processes in the body and they also work with, and alter, molecules of other chemical substances to ensure that the body is nourished, energised and healed.

The chemical process

The alimentary canal is over 30 feet long and starts in the mouth and ends at the anus and it is divided into two operating systems; the digestive system and the excretory system, both of which are vital to our health. The food is kept moving through the alimentary canal by smooth muscular contractions called peristalsis

The first stop for food is the mouth, where our tongues, teeth and salivary glands (that produce enzymes like amylase) begin the digestive process before passing the food into the pharynx at the back of the throat.

Amylase, for example, converts our carbohydrates into pairs of sugars, or dissacharides.

From here food passes into the oesophagus through to the stomach where stomach acid will continue the digestive process. Hydrochloric acid in the stomach modifies pepsinogen secreted by the stomach lining to form an enzyme called pepsin. Pepsin breaks down the protein in food into smaller units called polypeptides and lipase will break the fatty globules present in the food into glycerol and fatty acids. The acid in the stomach will also kill as much harmful bacteria as possible before it moves further into the body. The end result of this part of the process is a highly acidic liquid that is then passed into the duodenum.

Here it will be mixed with mucous secreted by the duodenum in response to two hormones that are released to neutralise the acid. One of the hormones, secretin, stimulates the release of alkaline juices and pancreatic enzymes are released in response to the second hormone pancreozymin. Bile is also passed into the duodenum either directly from the liver or from the gallbladder, where it has been stored.


Bile is a complex fluid containing water, electrolytes and organic molecules. These molecules include bile acids, cholesterol, phospholipids and bilirubin all essential in the digestive process. Bile acids help digest fats and allow for the absorption of fats, and fat soluble vitamins, as they pass through the small intestine. Bile also collects waste products that have accumulated in the liver and need to be passed through to the colon for elimination.

Cholesterol levels are affected by the efficiency of this bile process. Cholesterol comes not only from ingested food; it is also manufactured in the liver. It is virtually insoluble in most fluids – except for bile – where the acids and fats such as lecithin do the job. If these components are not effective cholesterol can collect into stones that block the ducts and cause problems with the digestion of fats.

Levels of bile in the body are lowest when we are fasting, which is why cholesterol tests are carried out at least 12 hours after your last meal. Most of the bile that is secreted during this period is diverted into the gallbladder, to be concentrated until it is needed when you have your next meal. As bile is not passing into the ileum, less passes into the bloodstream and the blood levels of cholesterol are stabilised and can be measured.

Only 5% of bile is eliminated from the body on a daily basis whilst the remainder is absorbed back into the bloodstream – during the passage through the ileum in the second part of the small intestine

The enzymes

By the time the liquid reaches the duodenum the particles in the liquid, whilst minute are still too large to be absorbed efficiently and the role of the enzymes is not just to process carbohydrates, proteins and fats but to also break them down into even smaller particles. For example, one of the pancreatic enzymes is trypsin which breaks down peptones, the particles at this stage, into peptides. Amylase will go to work on carbohydrates breaking them down into maltose, which is a disaccharide sugar.

This now digested food is passed down further, into the ileum, where the final chemical processing will take place.

More enzymes called maltase, sucrase and lactase are produced to facilitate the absorption of the food through the villi, which are millions of tiny hair like projections lining the walls of the small intestine. At this point the disaccharide sugars, or pairs, need to be converted into single sugars called monosaccharides for easy absorption by the villi.

Each one of these tiny hairs contains a capillary and a tiny branch of the lymphatic system called a lacteal. When the digestive mix comes in contact with the villi all the glycerol, fatty acids and dissolved vitamins are sucked up into the lymphatic system and then transported into the bloodstream. Other nutrients such as amino acids, sugars and minerals are absorbed directly into the villi capillaries, which connect directly with the hepatic portal vein and into the liver.

In the liver certain nutrients will be extracted and stored for later use whilst the other nutrients are passed on into the body. This is just one role that this vital organ plays in the digestive system and I will cover the liver in more detail later in the book.

How our energy is produced.

Starch based carbohydrates that we eat such as potatoes and bread are broken down into pairs of sugar molecules by the enzyme amylase in saliva in the mouth and further down in the digestive tract. These sugar molecules are broken down even further by other enzymes in the small intestine into single sugar molecules, which are absorbed by the villi capillaries and taken to the liver.

We need glucose to provide energy but it is very important that this is kept in balance. Too much glucose in the system and we can become diabetic and too little and our brain function ceases and we lose consciousness. Once the glucose reaches the liver it will determine if there is too much or too little in the bloodstream and either convert the glucose into glycogen and store it or release it directly into the bloodstream to be used as energy within each individual cell. Energy cannot be used directly by the cell so it is stored in a high energy chemical bond which links to a molecule of ADP (adenosine diphosphate) to a phosphate group, forming ATP (adenosine triphosphate). When this bond is broken energy is released as the ATP converts back to ADP, which begins the process all over again. Carbon dioxide is released as a waste product and is removed in the bloodstream through the lungs and out of the body.

Our glycogen stores in the liver and muscles is not huge and should the body be deprived of glucose producing foods for even short periods of time the body will have to make adjustments to maintain some form of balance. If glucose providing foods such as carbohydrates are not readily available in the diet the body will switch over to emergency power using either fat reserves (not too bad) or failing that, proteins in our muscles and tissues. This is why rapid weight loss is not advisable. Whilst we should burn fat reserves to a normal level it is dangerous to force the body into eating muscle which is extremely difficult to replace.

Insulin is produced by the pancreas and is secreted in response to high levels of glucose in the blood and other hormones such as adrenaline and cortisone can also be released if levels drop too far. In this way we maintain a healthy balance in the bloodstream and we do not develop diabetes. However it puts enormous stress on these organs and glands if we are constantly yo-yo dieting and restricting and bingeing alternately on various foods. The body prefers to receive a regular and staple diet combining the carbohydrates, proteins and fats in exactly the right amounts for its needs. The problem that we have with recent dieting fads is that we were all told twenty years ago to remove all fat from our diet and simply take in carbohydrates. This created excessive amounts of glucose in our bloodstream which if not used by the body is stored as fat. Add in the reduction in physical activity and none of this excess fat has then been used to provide energy but has instead accumulated over a period of time.

The current rates of obesity are the result of too many carbohydrates in the form of sugars and too little exercise.

Unless we all change our lifestyle and diet radically in the next twenty years the current figures for obesity will go from 65% to 85% and our children will be dying before us.

It normally takes ten thousand years for an evolutionary change to take place but humans have managed one in only 300 years since the introduction of excessive refined sugars and carbohydrates entered the food chain.

The second half of the journey – into the excretory system

Once all the nutrients have been extracted and passed into the bloodstream, or liver, any insoluble and undigested food moves into the large intestine. Any water and salt remaining in the mixture is absorbed into the lining of the intestine and the remainder mixes with all the other waste products produced by the body – such as bacteria and dead cells. It is packed and pressed into stool and stored for excretion at periodic times during the day.

 Next time – our mouth is so much more than a talking point.

©sallycronin Just Food For Health 2007

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