Fibre Obsessed

Fibre is often described as the ‘fourth’ macronutrient (Protein, Carbohydrates, Fats, Fibre), or as (Trowell, 1972) describes as the skeletal remains of plant cells, a.k.a ‘unavailable carbohydrates’.  It is riddled with research backing benefits of longevity, well being and a preventative measure to chronic diseases. Yet, why are we so deficient in it? 

What is fibre? 

Dietary fibre is basically a non digestible carbohydrate and lignin not degraded in the upper gut, but focuses on the replenishment of the lower gut. There are two types of fibre, soluble and insoluble. To put it plainly, insoluble fibre helps food pass seamlessly through the stomach and intestine. Common foods include, wholegrains such as couscous, brown rice, root vegetables, fruit with seeds, beans, pulses and lentils, as well as nuts and seeds. Whereas soluble fibre slows down digestion rate and pulls water during the process. Common foods with insoluble fibre include oats, peas, beans, apples, citrus fruit, barley, and psyllium. These two types of fibre work together to maintain a healthy, happy gut. 

How does fibre contribute to a healthy gut and well being?

You may hear from time to time, about the importance of a healthy gut , also known as a healthy microbiome. Microbiome refers to the collective genomes of the micro-organisms in a particular environment, and microbiota is the community of micro-organisms themselves (Valdes, 2008). We have approximately 100 trillion micro-organisms  within our human gastrointestinal tract, so you can begin to fathom how important our microbiome is. I often express to my clients that “it all starts with your gut”, we can heal most common daily health symptoms, such as some PMS, fatigue, sleep and mood, all from just supporting a healthy microbiome through nutrition. Some of the benefits gained from a healthy gut microbiota include increased immunity, appropriate hunger and appetite cues, metabolism and a healthy weight maintenance.

Furthermore, the best correlation to a healthy microbiome, is a high fibre intake with a high diversity in plant foods. It has a huge impact on weight , as (Valdes, 2008) discusses a well known study done in mice, in which the (germ-free and healthy) mice were split into two groups. One group were given microbes from healthy weight humans, and the other from obese or overweight humans. The group with the overweight microbes progressively gained weight over the next ten years. Whilst we cannot rely on studies done on rodents, it does, however, back up several other research produced around the health benefits of a healthy gut. Other evidence shows us that a diet deficient in fibre shows a lower bacterial diversity and has been reported to be observed in people with inflammatory bowel disease, arthritis, type 1 diabetes, atopic eczema (Valdes, 2008 & Singh, 2017) and even recent studies showing a positive effect on insulin resistance, with a reduction in type 2 diabetes risks by 20-30% (Weickert & Pfeiffer, 2018) . Additionally, a recent massive study done by (Reynolds, 2019) investigated several systematic reviews and meta analyses explaining the relationship between carbohydrates quality and health. With 58 clinical trials of 4635 adult participants, the data showed a 15-30% decrease in all-cause and cardiovascular related mortality, including coronary heart disease, stroke, type 2 diabetes and colorectal cancer when comparing the highest dietary fibre consumers with the lowest.  

When comparing eating habits, plant based has shown to be superior (whether you include minimal meat or not) plants should always be of high priority. However, our modern eating habits have our countries' meat eaters consuming so much more animal products and less and less plants. A study comparing vegans and omnivores found striking differences in digestion and metabolism generated by the gut microbes (Valdes, 2008). And whilst we cannot scientifically prove whether a healthy gut can influence healthier food choices or behaviours, we can acknowledge that research shows it will help define microbiome composition in its response to glucose, and this alone can impact our desire to over indulge, or experience regular bouts of fatigue. 

The burden of processed foods

David Burkitt conducted a well known study in fibre in 1969 when he was working un Uganda, he noted that middle aged people (from 40-60 years old) had significantly lower incidences of diseases such as colon cancer, diverticulitis, appendicitis, hernias, varicose veins, diabetes, atherosclerosis and asthma. All of which were very prevalent (and still are) in high income, well developed countries. Based on cleaves “common cause hypothesis” - suggesting that where a group of diseases occur together in the same population or area, usually suggests that there is a common cause. In which case, Burkitt noted the difference in fibre intake. For instance in the countries where these diseases were very low to non-existent, their fibre intake was as high as 100g p/day. Whereas these higher income areas, their fibre was 15g or less p/day. It is presumed that this is due to the accessibility to highly processed low fibre foods. It was also observed that the lifestyles behind the low fibre cohort were higher in red meats and animal fats (which also has correlation to these diseases). Moving 50+ years onwards, several epidemiologists have used this study to further the investigation in fibre intake, in which case has built an array of supporting evidence to suggest the health outcomes associated with fibre. Yet progress has been slow, with the average intake being 15-18g p/day depending on countries. This is highly due to the production and advertising on tasty, low cost, fibre deficient fast foods the food industry is doing a better job at influencing attitudes and behaviours, than health care professionals are. 

How much fibre to we really need

Our MOH national guidelines suggest that 50% of our daily energy intake should come from carbohydrates, with 15g of fibre p/ 1000 calories, or 25g p/day for females and 30g p/day for males. So on average a person consuming 2000 calories, should be having 25-30g of fibre and 250g of carbohydrates. But yet, with the growing trend of low carb and keto, alongside a high meat intake and processed foods, many are not meeting this. Or alternatively, they are meeting it, but it isn't sourced from wholegrains, so their fibre isn't being met. Infact Burkitt, in his research, recommends we need 50g of fibre p/day in order to optimise health outcomes.

You may be thinking, why are our fibre recommendations that much higher than protein? When all we hear constantly, is protein, protein, protein? Well firstly, carbohydrates are our first point of energy, so to sustain our busy lifestyles and to produce quality movement, carbohydrates are essential. Carbohydrates also offer an array of nutrients that fat and protein often don’t. Our recommendations are 50%, but with the intention that they are sourced from whole foods, meaning fruits, vegetables and whole grains. If we are meeting the target with whole foods then we can better access the likes of, vitamin C, E, K, B’s, A and iron to name a few. Which in turn correlates to a healthier operating body. 

Don’t get me wrong, protein is very important and women tend to require more of it than males. However, it often gets praised more so than the other macronutrients and we forget about poor fibre which is absolutely essential. Protein is praised for the way it metabolises, where we actually need to use energy to break it down , thus a sense of, ‘more bang for your buck’. However, as we cannot metabolise fibre and use it for other bodily functions, when sticking to high fibre whole grains, this can be argued as a similar point. 

Should you increase your fibre straight off the bat? Potentially not. It is best practice to ease your gut into the acceptance of more fibre as our bodies are smart and learn to work without it. For instance, recent observations have shown that a dramatic increase can temporarily reduce diversity, as the microbes that digest fibre become specifically enriched, from a change in composition via competitive interactions (Valdes, 2008). 

Plant based intake optimises fibre

Singh, (2017) discusses the array of diet styles in modern times including, omnivores, vegan, vegetarian, gluten free and mediterranean and their ability to modulate the intestinal microbiota. Several studies have shown that a diet high in animal protein and fat, and low in fibre led to a marked decrease in numbers of total bacteria and beneficial bifidobacterium and eubacterium. Another study with 10 participants who went gluten free for 30 days, showed a decrease in healthy bacteria as well, and furthermore, unhealthy bacteria actually increased (singh, 2017). Vegan and vegetarian diets within these studies were also not noted as an optimal host of bacteria, as vegan and vegetarian doesn't necessarily mean one is consuming proper quantities of whole foods. However, the mediterranean intake, as it has a higher focus on plant based foods with a variety of legumes, lentils, beans, fruits, vegetables, nuts and seeds, showed the best outcome for a healthy gut. Therefore suggesting that minimal animal intake and heightened wholefood diversity is superior when it comes to reaching your fibre intake and optimising gut health.

Conclusion

I make sure my clients work towards a high fibre diet, filled with an array of wholefoods, we do this slowly as the gut adjusts, working our way up to 35-45g p/day. As a collective, we require education, food security, and a move towards a more plant based diet in order to increase the amount of natural fibre consumed, and thus, improve our health outcomes. 

References / Further reading

Burkitt, D. P. (1983). Don’t Forget Fibre in Your Diet: To help avoid many of our commonest diseases. 4th edition. Dunitz, London.

Trowell, H. (1972). Ischemic heart disease and dietary fiber. American Journal of Clinical Nutrition, 25(9), 926–32.

Quagliani, D. and Felt-Gunderson, P. (2017). Closing America’s fiber intake gap: Communication strategies from a food and fiber summit. American Journal of Lifestyle Medicine, 11(1), 80–5.

DeVries, J. W. (2003). On defining dietary fibre. Proceedings of the Nutrition Society, 62(1), 37–43.

Australian Government National Health and Medical Research Council and New Zealand Ministry of Health. (2019). Dietary fibre. Nutrient Reference Values for Australia and New Zealand.

Weickert, M. O. and Pfeiffer, A. F. (2018). Impact of dietary fiber consumption on insulin resistance and the prevention of type 2 diabetes. Journal of Nutrition, 148(1), 7–12.

Slavin, J. (2013). Fiber and prebiotics: Mechanisms and health benefits. Nutrients, 5(4), 1417–35.

Valdes, A. M., Walter, J., Segal, E. and Spector, T. D. (2018). Role of the gut microbiota in nutrition and health. BMJ, 361, k2179.

Singh, R. K. et al. (2017). Influence of diet on the gut microbiome and implications for human health. Journal of Translational Medicine, 15(1), 73.

Reynolds, A., Mann, J., Cummings, J., Winter, N., Mete, E. and Te Morenga, L. (2019). Carbohydrate quality and human health: A series of systematic reviews and meta-analyses. The Lancet, 393(10170), 434–45.

O’Keefe, S. J. (2019). The association between dietary fibre deficiency and high-income lifestyle-associated diseases: Burkitt’s hypothesis revisited. The Lancet Gastroenterology & Hepatology, 4(12), 984–96.