Over the last few years, we have seen a dramatic increase in the number of people following a gluten-free diet. While some need to avoid foods containing gluten or wheat due to medical reasons, there has also been a surge of otherwise healthy people choosing to follow a gluten-free diet for general health benefits. But is gluten-free eating always healthier? And what does the current research say about the inclusion of gluten in our diet in terms of gut health?
First and foremost, I think it’s important to state that there are some conditions where strict adherence to a gluten-free diet is required. For anyone with Coeliac disease, a wheat allergy or Non-Coeliac Gluten/Wheat Sensitivity, eating gluten-free is non-negotiable.
But what about the rest of the population?
To start investigation this question, a group of researchers recently conducted a randomized, controlled, cross-over trial involving 60 middle-aged healthy Danish adults with two eight-week interventions comparing a low-gluten diet (2g gluten per day) and a high-gluten diet (18g gluten per day). The two diets were balanced in the number of calories and nutrients including the same amount of dietary fibres. However, the composition of fibres differed was different between the two diets. The purpose of the study was to look at the effects of low gluten vs a high gluten diet on the microbiome, and see if any alterations were noticed in either of the groups in terms of gut health and patient-reported symptoms.
The study observed that following a low-gluten diet positively altered the participants' gut microbiome, reduced their gastrointestinal discomfort, and resulted in a small weight loss.
Based on the studies findings, the researchers concluded that the beneficial effects of low-gluten diet in healthy people may not be primarily due to reduced intake of gluten itself, but instead due to a change in dietary fibre composition. By reducing fibres from wheat sources and replacing them with fibres from vegetables, brown rice, corn, oat, and quinoa the people in the gluten-free group were consuming a much greater diversity of fibres. We know that this has a beneficial impact on the gut microbiome, and this was likely to be the reason they noticed less bloating and an improvement in general gut symptoms.
What this study demonstrates is the importance of a diet high in plant-based, fibre-rich foods for the health of our microbiome. We know that the more diverse our diet is, the better the health outcomes. We know that for every 8g increase in dietary fibre eaten per day, there is a decrease in total deaths and incidences of coronary heart disease, type 2 diabetes and colorectal cancer by 5-27%. Additionally, increased rates of dietary fibre have also been found to be protective against stroke and breast cancer. So here we see that it may not necessarily be the removal of gluten that improves health, but the inclusion of other dietary sources of fibre.
This study also highlights the importance of choosing gluten-free products wisely. Most gluten-free products available in the supermarkets are void of dietary fibres and natural, nutritious ingredients. Just because something states it is ‘gluten-free’, doesn’t mean it’s healthier. It's important to understand that gluten-free junk food is still junk food. In many cases, foods containing gluten may actually be healthier as they are less processed and contain fewer added ingredients than the foods marketed as ‘gluten-free’. This is because it is generally harder to make gluten-free foods taste good, especially if it's designed to be sat on a shelf before being sold. To try and replicate the taste and texture of gluten-containing products, many manufacturers add in sugars, vegetable oils, fillers, gums and preservatives. For someone who doesn’t have a medical condition where gluten needs to be avoided, you’d be better off having a gluten-containing sourdough bread made from 2 natural ingredients than having a gluten-free replica containing 20 processed ones.
Having said that, not all gluten-containing grains are created equal either. While the darker grains such as spelt, rye, durum, bulgar and barley are high in fibre and some vitamins and minerals, the majority of people aren’t opting for products made with these ingredients. Instead, they are purchasing packaged and processed foods containing highly refined white flour. The more refined the grain, the lower the nutrients and the fibre content, which isn’t great for our gut health or overall health.
Additionally, it's also important to consider the growing conditions for many of the highly refined grains. Glyphosphate is the core ingredient in a well-known herbicide and despite being declared a possible carcinogen (cancer-causing agent) in 2015 by, is still being used on many crops today. The possible effects of Glyphosphate on human health are currently the subject of intense public debate, but the research we do have indicates Glyphosphate has the potential to disrupt the microbiome and leave us more susceptible to negative health outcomes. With this in mind, it is worth considering not only which grains we are considering, but also how they were grown.
It’s also important to note that what the study classes as high gluten are 18g of gluten per day. This is equivalent to approximately 8 slices of bread, but if you think about the standard Australian diet, lots of people are consuming more gluten than that. For many, their day looks like wheat cereal 2 slices of bread for breakfast, biscuits for morning tea, a sandwich for lunch, a muffin or cake for an afternoon snack and a large bowl of pasta for dinner. Which far exceeds 18g of gluten. There is some evidence to suggest excessive gluten consumption may have negative effects on the gut lining and contribute to intestinal permeability (also referred to as leaky gut). Studies have found that diets high in gluten can up regulate the production of zonulin, which is a protein that regulates the tight junctions in the intestines. When zonulin is released into the intestines, these tight junctions open and result in intestinal permeability. So while it can be a part of a diet in moderate amounts, the excessive consumption of gluten and consequently low consumption of other plant-based fibre sources may have negative health consequences in the long-term.
So what’s the solution? We know that both gluten-free and non-gluten-free diets can be healthy and unhealthy. It’s about the quality of the food product you are consuming in each food category, the quantity you have and the general diversity of your diet.
The Take Home
If you suspect you may have a condition where you cannot tolerate gluten, make sure you go and get it investigated.
If you find out you do need to be on a gluten-free diet, make sure go for foods that are naturally-gluten free and choose products that are not highly processed. You’ll also need to be aware of making sure you are getting enough fibre from gluten-free grains, nuts, seeds, fruit and vegetables. If you have recently been told you need to be on a gluten-free diet but aren’t sure about what you should be eating or how to balance your meals, reach out and seek advice from a practitioner.
If you can tolerate gluten, by all means include it in your diet in moderation but prioritise the high fibre wholegrain and darker flours, avoid highly processed and sprayed grains, and make sure you are having plenty of other plant based fibre sources in your diet.
Drago, S., El Asmar, R., Di Pierro, M., Grazia Clemente, M., Sapone, A. T., Thakar, M., … Fasano, A. (2006). Gliadin, zonulin and gut permeability: Effects on celiac and non-celiac intestinal mucosa and intestinal cell lines. Scandinavian Journal of Gastroenterology, 41(4), 408-419. doi:10.1080/00365520500235334
Fasano A. (2012). Zonulin, regulation of tight junctions, and autoimmune diseases. Annals of the New York Academy of Sciences, 1258(1), 25–33. doi:10.1111/j.1749-6632.2012.06538.x
Hansen, L., Roager, H., Søndertoft, N., Gøbel, R., Kristensen, M., & Vallès-Colomer, M. et al. (2018). A low-gluten diet induces changes in the intestinal microbiome of healthy Danish adults. Nature Communications, 9(1). doi: 10.1038/s41467-018-07019-x
Mao, Q., Manservisi, F., Panzacchi, S., Mandrioli, D., Menghetti, I., Vornoli, A., … Hu, J. (2018). The Ramazzini Institute 13-week pilot study on glyphosate and Roundup administered at human-equivalent dose to Sprague Dawley rats: effects on the microbiome. Environmental health : a global access science source, 17(1), 50. doi:10.1186/s12940-018-0394-x
Reynolds, A., Mann, J., Cummings, J., Winter, N., Mete, E., & Te Morenga, L. (2019). Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. The Lancet, 393(10170), 434-445. doi: 10.1016/s0140-6736(18)31809-9
Valdes, A., Walter, J., Segal, E., & Spector, T. (2018). Role of the gut microbiota in nutrition and health. BMJ, k2179. doi: 10.1136/bmj.k2179