By Associate Professor Eleanor Beck, Expert on Fibre, Advanced APD, PhD, University of Wollongong
The sixth International Dietary Fibre Conference was held in Paris from June 1-3, 2015. As a parent, how could I want anything more than a few days escape from my children in Paris? Interestingly though, the key message of the conference is that fibre is just like children. Fibre, like a child, is not one thing, but many things; all fibres (and all kids) are different; they behave differently and affect us in many different ways. While we might not always want to choose to have fibre or fibre rich foods (like we choose sometimes to seek a little rest from our children), the evidence consistently shows that fibre is important for health and increasingly the research, as discussed at the conference, is showing that variety in the fibres we eat is essential, because as Kaisa Poutanen of VTT Technical Research Centre, Finland quoted at the conference – “fibre is not fibre but rather fibre is a many splendored thing”.
The sixth International Dietary Fibre Conference was held in Paris from June 1-3, 2015. As a parent, how could I want anything more than a few days escape from my children in Paris? Interestingly though, the key message of the conference is that fibre is just like children. Fibre, like a child, is not one thing, but many things; all fibres (and all kids) are different; they behave differently and affect us in many different ways. While we might not always want to choose to have fibre or fibre rich foods (like we choose sometimes to seek a little rest from our children), the evidence consistently shows that fibre is important for health and increasingly the research, as discussed at the conference, is showing that variety in the fibres we eat is essential, because as Kaisa Poutanen of VTT Technical Research Centre, Finland quoted at the conference – “fibre is not fibre but rather fibre is a many splendored thing”.
The
conference featured a variety of scientists presenting engaging summaries of
the latest meta-analyses on the link between fibre intake and health. Data from
large cohorts, with over 1 million participants (in some cases) were
investigated and identify that for every 10g of total fibre intake, there is approximately
a 10% reduction in all-cause mortality (you are just less likely to die!).(1) Interestingly, when researchers
looked at the source of the fibres, it appears that fibre from grain foods ,
and to a lesser extent vegetable fibre is associated with significantly lower
mortality and that no significant association was found with fibre from fruit.(2) Research also suggests that
higher fibre intakes decreases risk of obesity, coronary heart disease,
hypertension, diabetes and certain types of cancers, however identifying the
mechanisms by which fibre protects against these diseases is difficult because
any one food may have many different fibres within the food, we eat a variety
of foods and we often process or cook our food in a variety of ways.
For
researchers, like myself, to explore the complex ways in which fibres promote
health, it is important to consider the chemical structure of the fibre,
including the structure and length of the carbohydrate polymers (essentially
fibres are long chains of carbohydrate molecules), the cell wall structure and
what other compounds are associated with the fibre within the food and how they
interact. Given all of these things impact the functionality of the fibre, it
is not surprising that fibre has been attributed to such a wide varied range of
positive health outcomes such as improved laxation (keeps you regular),
decreased cholesterol levels, improved blood glucose responses and satiating effects
(increased feeling of fullness). These health benefits are likely related to
the mechanisms by which fibres alter the rate of digestion and the way our food
moves through our digestive system. However as was discussed at the recent
conference there are a number of other effects such as anti-inflammatory
actions and immunomodulatory effects which are also likely to account for the
health benefits of fibres and these effects are now increasingly under
investigation. In particular, we know that fibres alter the human gut
microbiome (the community of bacteria living in our digestive systems) and often
stimulate the growth of beneficial bacteria. The presence of fibre in the large
bowel also feeds our gut microbiota in varied ways such that the bacteria will
also produce different metabolites, starting a cascade of reactions as varied
as modifying gut permeability to increasing release of satiating hormones. This
emerging area of research reminds us that we need to understand the complexity
of dietary fibre structures and how these variations impact on the physiology
and evolution of microbes (bacteria) living in our gut. The amount of varied bacteria
in our gut outnumbers the genetic variation in the human genome almost 10 fold
and so the scientists investigating their impact on health certainly have their
work cut out for them, but this will be
essential to advance our understanding of how fibres affect health via changes
to the gut microbiome
So, as a researcher and as a parent I have some varied jobs
to do. I know that to be diligent I need to not just look at how fibre affects
individuals (in clinical trials) but I need to ensure the fibre (and the food
overall) is well characterised to identify possible mechanisms of action. One
of the reasons it is hard to identify individual fibre effects is that we have
not been good at reporting all the details. It’s like having a toddler where
you cannot possibly identify every hazard without serious investigation because
they can find a mechanism to create havoc anywhere. As a parent, I need to
ensure that my family and I eat fibre from all different sources to ensure that
I can maximise the myriad of health effects possible with a healthy diet, but
as a researcher, I need to remember that fibre is not just fibre, but rather a
variety of complex molecules each with a variety of mechanisms which may
influence health.
While there is still so much to learn, there is one positive
outcome that everyone can agree on, and that is there are not negative studies
on fibre. As our dietary guidelines advise: “enjoy a wide variety of nutritious foods …..every day: plenty of
vegetables of different types and colours, and legumes/beans; fruit; grain
(cereal) foods, mostly wholegrain and/or high cereal fibre varieties…”. The
fifth fibre conference was in Rome, this one in Paris and the next scheduled
for the Netherlands in 2018. Who knows what could happen there, away from my
kids!
References:
1. Liu L, Wang S, Liu J. Fiber
consumption and all-cause, cardiovascular, and cancer mortalities: A systematic
review and meta-analysis of cohort studies. Molecular Nutrition & Food Research.
2015;59(1):139-46.
2. Kim Y, Je Y. Dietary Fiber Intake and Total Mortality: A
Meta-Analysis of Prospective Cohort Studies. American Journal of Epidemiology.
2014;180(6):565-73.
