The researchers say fiber should sit alongside nutrients already considered essential for humans, such as certain amino acids and vitamins.
Co-author Associate Professor Andrew Reynolds says increasing our dietary fiber intakes would deliver greater health benefits in Aotearoa New Zealand than increasing any other essential nutrient, given that our current fiber intakes are below World Health Organization (WHO) recommendations.
"The disease burden associated with diabetes, heart disease and colorectal cancer would be expected to be appreciably reduced by such a dietary change."
In a paper published in Nature Food, Associate Professor Reynolds and Professor Sir Jim Mann, both from the Otago Edgar Diabetes and Obesity Research Centre, along with Emeritus Professors Gerald Tannock (Otago) and John Cummings (University of Dundee) argue that recent advances in our understanding of dietary fiber mean that it now meets the criteria required for essentiality.
Their argument is supported by more than 100 years of research into its chemistry, physical properties, physiology, and metabolic effects as well as more recent meta-analyses and clinical trials – many of which were conducted at Otago.
Associate Professor Reynolds says the research team examined if there were any causal associations between dietary fiber intake and health outcomes and found overwhelming evidence of benefit.
"Looking across multiple studies, we see that when people increase fiber intakes, their body weight, cholesterol, blood sugars and blood pressure all improve. When following people over decades, we see those with higher fiber intakes get less heart disease, less type 2 diabetes, less colorectal cancer, and are less likely to die prematurely," he says.
"Focusing on increasing intakes of high-fiber foods such as whole grains, legumes, vegetables and whole fruit is likely to deliver substantial health benefits.
"The more that fiber is recognized and prioritized, the better. If people focus on increasing fiber in their diet then food producers are more likely to reformulate products to have more fiber, making it even easier to increase your fiber intake. There are a lot of potential benefits, should fiber be recognised as essential."
To be recognized as essential the nutrient must be beneficial to human health, not be produced by the body itself, and absence of the nutrient would result in a measurable deficiency state.
To date it has been the lack of a deficiency state that has prevented fiber from being recognised as essential. The answer to this previous limitation, the authors propose, happens to be one of the most exciting fields of health research at present.
Co-author Professor Mann says, "in some ways, it's quite simple".
"The gut microbiome exists almost exclusively on the dietary fiber we eat. A healthy gut microbiome is linked to all sorts of health benefits, with more discovered and understood each day."
Previous work of co-author Professor Tannock has shown that low fiber intakes result in a relatively unfunctional gut microbiome, with increasing fiber intakes restoring microbiome function and its relationship with the human host.
Currently, New Zealanders eat an average 20g of fiber a day, while the WHO guideline recommends at least 25g per day.
Associate Professor Reynolds says just 5 grams more per day on average would meet that minimum healthy intake of fiber for people.
Elevating dietary fiber to the status of an "essential nutrient" is far from mere semantics. It will prompt adjustments in dietary guidelines, food labeling, nutrition education, and even food industry formulations, placing fiber intake at a higher priority. The World Health Organization has already issued a global recommendation in 2023 for a daily intake of at least 25 grams of fiber. Officially recognizing its "essential" nature will significantly motivate various stakeholders to help people increase their consumption of whole grains, legumes, vegetables, and fruits through policy incentives and public education.
Confirming the essentiality of dietary fiber may be a simple yet effective strategy to address the global burden of disease at its root. It requires us to view fiber not merely as a "beneficial" component, but as an indispensable cornerstone for maintaining health. Future research needs to delve deeper into the precise relationship between fiber deficiency and gut microbiome dysfunction to ultimately complete this necessary update to the nutritional paradigm.
