The public health rationale for increasing dietary fibre: Health benefits with a focus on gut microbiota

Dietary fibre can be considered an essential macronutrient which feeds our gut microbiota, thus enabling the optimal functioning of this ‘virtual organ’. Recommended daily intakes range from 25 to 38 g/day. However, most individuals fail to reach this target and may consume <50% of the recommended amount. Poor dietary fibre intake is associated with an imbalanced gut microbiota leading to reduced diversity and increased abundance of non-beneficial microorganisms at the expense of beneficial ones. Inflammation is a recognised physiological effect of such a microbiome structure and is a common denominator in several non-communicable diseases associated with the Western lifestyle/developed world including obesity, cardiovascular disease, type 2 diabetes and colorectal cancer. Yet increasing dietary fibre intake can reduce risk factors associated with these diseases and may even improve prognosis. Several food manufacturers have now developed strategies to increase the fibre content of foods. However, research gaps still remain. In particular, dietary fibre is composed of various non-digestible carbohydrates and the exact effect of each of these on the gut microbiota is currently unknown. The links between dietary fibre and disease risk are generally associative. Understanding the biological mechanisms will require deeper insight into the impact of the gut microbiota on health. Furthermore, gut microbiota research has shown significant inter-individual variation meaning that some individuals may not respond to certain dietary fibres owing to the absence of specific microorganisms. Understanding how the different fibre types influence the microbiota, combined with knowledge of an individual’s microbiota, should lead to fibre-led, microbiota-based dietary advice.