Until the introduction of agriculture, roughly 10,000 years ago, grains were virtually non-existent in the human diet. Since that time, the cultivation of wheat has literally served as an anchor for the expansion of civilisation as we know it. In Roman times, wheat was the primary fuel used to power the Roman army and every man in the republic was entitled to a wheat dole equivalent to 3,000-3,500 calories a day.(1) Bread has been considered “the staff of life” since biblical times (“give us this day our daily bread”) and today it is one of the most widely consumed staple foods in the world. So can something so pivotal to human civilisation actually be bad for us?
As hunter-gatherers, the human gut evolved over 2 million years on a diet of fruits, nuts, certain leaves, roots, fish and occasionally, meat. When grains started to be consumed, quite recently from an evolutionary perspective, some were not able to adapt to this evolutionary challenge and Celiac Disease was born.
Celiac disease (CD) is a condition that occurs in genetically susceptible individuals whereby gluten, a protein component found in wheat, barley and rye, triggers an autoimmune reaction that can damage the lining of the small intestine leading to symptoms such as abdominal pain, vomiting, diarrhoea, weight loss and eventually malnutrition. Prior to the millennium the prevailing medical opinion was that CD was a very rare disorder but studies since have demonstrated that CD is in fact one of the most common genetic diseases of humankind affecting almost 1% (1:133) of the population.(2)
Individuals diagnosed with CD have only one treatment option - the total exclusion of gluten from their diet. But as CD sufferers will attest, that’s easier said than done since today, on top of the obvious culprits like cereals, pasta and bread, gluten can be found in everything from sausages and beer to soy sauce, salad dressings and even some cosmetics,(3) not to mention foods that inherently do not contain gluten but may have been contaminated by factory processing. This can be a real problem as it only takes trace amounts of gluten to cause harm to these individuals.(4)
But it still begs the question, if only 1% of the population test positive for celiac disease, a figure that appears to be holding steady,(5) then why is going ‘gluten-free’ such a popular diet trend today? It’s estimated that 8% of the current UK population avoid gluten6 as part of a healthy lifestyle and this new mega-trend has caught the attention of food manufacturers. In 2015, 12% of new food products launched in the UK carried a GF claim(6) and GF breakfast cereals are leading the charge with sales growing by 79% a year since 2010.(7) In fact, the GF label is now appearing on products that are naturally gluten-free anyway in an effort to attract the health-conscious consumer(8) despite some products being unhealthy in the first place. This is akin to placing a “fat-free” label on a bag of sugar to appeal to those following a low-fat diet?
What is gluten and why all the fuss?
Grains are the seeds from cereal grasses, which evolved to survive from season to season. As such, grains can be easily transported and stored for considerable periods without spoiling which is why humanity has grown so dependent on this commodity for the majority of its food supply.(9) Wheat was the earliest recorded grain to be cultivated and is a staple food for more than a third of world’s population. The wheat kernel is mostly starchy carbohydrate with roughly 10-12% being protein.(10) Although there are hundreds of different proteins found in wheat, 80% of the protein content is made up of two specific protein molecules (also found in Barley and Rye), Gliadin and Glutenin, that combine to form what we call gluten. As the name implies, gluten has “glue-like” properties that give dough its stretchy consistency and enables bread to rise, by trapping the carbon dioxide gases produced by the yeasts feeding on the sugars, creating its spongey texture.
In order to digest protein, stomach acid and enzymes released from the pancreas go to work to break down the protein in our food into peptides and individual amino acids that are then absorbed into the bloodstream and utilised by our cells. Gluten, however, is a difficult protein for humans to digest. Gliadin, a large component of gluten, is resistant to digestive enzymes(11) and humans are unable to digest it completely so it can remain largely intact as it moves through the gut.
The small intestine is where we absorb nutrients from our food, the lining of which is only one cell thick. This layer of cells, known as the epithelial barrier, maintain tight junctions between themselves in order to absorb individual nutrients while preventing whole food particles and other toxins from entering the blood stream. Studies have shown that in both celiac and non-celiac individuals, gliadin triggers the release of a compound called Zonulin from these cells which acts on the tight junctions and opens them up slightly causing intestinal permeability, commonly known as ‘leaky gut’.(12) The problem begins when undigested gliadin, and potentially other molecules and toxins, leak into the bloodstream, activating a protective response from our immune system in the form of inflammation and the production of gluten-associated antibodies whose job it is to seek out any gluten molecules in the blood and tag them for destruction by other cells from our immune system.
Gluten and its role in autoimmune diseases
Amino acids are the fundamental building blocks of all proteins in our body. The ordered sequence of amino acids determines the type of protein. Gluten is a protein that has a very similar amino acid sequence to certain proteins found in the human body and as a result it can trigger the production of auto-antibodies that can cause injury to our own tissues leading to autoimmune diseases such as CD and numerous others(13). In fact, there are over 160 diseases that have now been linked to gluten in the scientific research(14) and while we used to believe that celiac disease only affected the gut, we now know that CD is actually a systemic disease that can manifest anywhere in the body.(15) In fact, for every CD-sufferer with gut-related symptoms, there are 8 who have related symptoms outside the gut.(16)
One major organ that can be affected by gluten is the brain. There are studies as far back as the 1960’s connecting gluten and CD with neurodegenerative diseases and disorders of the brain.(17) A more recent example is a 6-month study that looked at 132 school children diagnosed with both CD and Attention Deficit Hyperactivity Disorder (ADHD) which found that every child experienced a significant improvement in all markers of behaviour and function when following a GF diet.(18)
Scientists have confirmed that there is indeed a spectrum of gluten-related disorders beyond CD referred to as Non-Celiac Gluten Sensitivity (GS).(19) The symptoms of GS can mimic those of CD but without the autoimmune response and subsequent tissue damage to the gut lining and potentially other tissues in the body, making its clinical diagnosis challenging. In fact, today the only diagnostic criteria of GS is the reported improvement of symptoms when gluten is excluded from the diet. A recent trial found that GS is the cause of Irritable Bowel Syndrome (IBS) in 20% of IBS sufferers.(20) However, while gut issues are a factor in GS, most symptoms seem to predominate outside of the gut, with things such as; eczema, joint pain, muscle cramps, fatigue, headaches, behaviour changes and even depression,(19) all of which typically show improvement following a GF diet. And considering these symptoms can often be subtle, many people remain undiagnosed but have somehow figured out that they simply feel better when they don’t eat gluten and worse when they do. But those are the lucky ones. An extreme example is Felicia Kwaku, a nurse within the NHS, who, after many years of having a very sensitive gut and being given the ‘all clear’ from celiac disease, eventually ended up with gastritis and a bleeding duodenal ulcer. A nutritional therapist in London helped her to make the connection with gluten and since going GF her gut problems have all but gone away. But she attests, “Vigilance is key! I can’t take anything for granted as Gluten winds up in places that I would never have expected”.
So has this always been a problem or is it a more recent phenomenon?
Over the past 100 years, agricultural advances in cross-breeding have resulted in thousands of varieties of wheat being developed that are more disease-resistant and deliver higher yields. This has led to significant increases in both production and consumption globally. In fact, today the world produces 440% more wheat per acre than than it did 100 years.(21) These more recent varieties also contain a higher protein/gluten content than the varieties that were grown prior to the last century such as Spelt, Einkorn and Kamut wheat. What’s more, some of these newer breeds have been shown to trigger a greater immune response(22) which may explain why some with GS can better tolerate these more ancient grains. Add to that government-backed nutrition guidelines that promote grains and cereals as the bedrock of a nutritious diet(23) and one can start to wonder whether all these factors may be connected to the rise in gluten-related issues across the population.
The role of the microbiome and the importance of breastfeeding
The human gut is home to approximately 10 trillion bacterium (10 times the number of cells in the human body). Much attention is now being devoted to the role that these commensal organisms play in human health and disease. We have identified thousands of different species of beneficial bacteria (probiotics) that inhabit the gut, many of which play an important role in digestion. Bifidobacteria is a dominant species, certain strains of which have been shown to protect the gut lining by reducing the inflammation that can occur when gluten is consumed(24) limiting the release of zonulin and potentially reducing leaky gut and minimising the subsequent response from the immune system.
Breastfeeding has been shown to be an important aspect of establishing healthy gut bacteria and conferring immunity to the infant.(25) Babies that are breastfed have a microbiota dominated by bifidobacterium which is found in human breastmilk.(26) In the UK, breastfeeding rates are some of the lowest in the developed world with 19% of babies never having breastfed and only 34% of babies continuing to be breastfed at 6 months, dropping to less than 1% at 12 months.(27) Could this be yet another factor playing a hand in the world of gluten sensitivity?
With continued research linking gluten to an increasing number of health problems and governments around the world embracing a more preventative approach to wellness in the face of escalating healthcare costs, perhaps one day we’ll see policies introduced to reduce gluten consumption. Meanwhile, with public awareness on the rise, it’s not hard to envisage a future where gluten-free is the norm; where food producers, restaurants and supermarkets create a ‘Contains Gluten’ category as the exception. Until then, the number of GF options are multiplying each year and the GF trend is showing no signs of slowing down anytime soon.
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References
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