Tuesday, February 3, 2015

Add years to life with fibre

Ask anyone why they should eat fibre and they’ll likely tell you to ‘help keep me regular’. But there are many more reasons to eat a high fibre diet including new evidence of it promoting longer life.

In recent months, with three independent meta-analyses of cohort studies being published in close succession, the academic flood gates have opened on the relationship between dietary fibre and longevity.

Two meta-analyses, published in the American Journal of Epidemiology in 2014, each pooling the data from approximately 1 million people found that compared to people eating the lowest amounts of fibre each day (15 grams per day), those eating the highest intakes (27 grams per day) had a significantly lower risk of  early death from any cause.(1, 2)  Researchers of one of these studies translated the effect as a 23% reduction in risk of a premature death for people eating the highest fibre intakes.(1)

Uniquely, the researchers of the first paper (Kim, et al) also analysed the data from these high quality studies to investigate whether different fibres (e.g. fibre from grains, vegetables or fruits) offered greater protection against an early death. They found fibre from grain foods and vegetables were significantly linked with a reduced risk of death and in comparison grains offered the greatest protection.(1) The researchers also found favourable effects on longevity with higher intakes of fibre from legumes such as beans; however this was only based on one study which reported the relationship between fibre from legumes and risk of death. 

This supports findings from the European Prospective Investigation Into Cancer and Nutrition cohort (EPIC)(3) that some fibre rich foods may be more protective than others. Within the European countries included in the EPIC cohort study the main source of total fibre varies within each population, however the countries with the strongest associations linking fibre intake with reduced risk of death were observed in the Danish and Greek cohorts, which had the highest percentages of fibre from grain foods and vegetables (56% and 16%, respectively, in Denmark and 29% and 36%, respectively, in Greece). As a comparison, Australia’s most recent National Nutrition Survey showed grains foods were the leading source of dietary fibre followed by vegetable and fruits contributed (44%, 19% and 15% respectively).(4)

Most recently, a further meta-analysis published in Molecular Nutrition Food Research in January took this comprehensive investigation a step further and looked not only at fibre intake and risk of death, but also the risk of death from specific diseases such as cancers and heart disease. This paper pooled data from over 1.7 million people from around the world and found that compared with the lowest fibre consumers, the highest consumers had a 23% reduced risk of death from heart disease and a 17% lower risk of death from cancer.(5)

How does fibre protect health?
As higher fibre intakes have been linked with a reduced risk of weight gain, type 2 diabetes, some cancers and heart disease it makes sense that that a higher fibre diet also translates to a longer life. Some potential mechanisms for the protective nature of higher fibre diets include:(1, 2, 5):
  • Promoting a healthy weight, through reduced energy intake and increased satiety
  • Improving blood glucose responses after eating a meal  
  • Decreasing cholesterol levels
  • Lowering levels of inflammation  
  • Promoting a healthy bacteria population in the digestive system, which in turn produce health promoting components (i.e. short-chain fatty acids)
  • Lowering blood pressure
Despite the ability to add years to life and life to years with higher fibre intakes, most Australians are falling short of fibre recommendations; females (19 years and  over) eating an average of 21 grams each day (25 gram recommendation) and males eating 25 grams each day (30 grams recommendation). As such, the majority of Australian fibre intakes are nowhere near the targets for people to reduce risk of chronic disease (28 grams each day for women and 38 grams for men).

In addition to inadequate fibre intakes, a survey commissioned by the Grains & Legumes Nutrition Council (GLNC) in 2014 found that on average two in three people did not identify grain foods such as rolled oats, wholemeal breads, wholemeal pasta, brown rice or muesli as being a source of fibre.(6) On the other hand, three out of four respondents to GLNC’s survey identified fruit and vegetables as a source of dietary fibre however only one in three people identify legumes foods such as kidney beans, baked beans, chickpeas, split peas, soy beans and lentils as containing dietary fibre.(6) Given grains are Australia’s leading source of dietary fibre, this apparent lack of awareness of the important nutrition contribution of grain foods is concerning. In light of the recent ‘anti-grain’ messages which flooded the media via proponents of low carbohydrate diets, people may be inadvertently cutting out fibre rich grain foods and legumes to the detriment of their health and longevity.  In respect to legumes specifically, with less than 5% of Australians reporting they ate legumes on the day before the most recent National Nutrition Survey these fibre rich foods such as beans, lentils, chickpeas and peas; which deliver around 5 grams per serve (75g or half a cup cooked) have huge potential to help Australians achieve a higher fibre diet and improve health.

Boosting fibre intakes
When it comes to fibre, the evidence is clear that small changes can make a huge difference over the life span. In fact each of the recent studies concluded that every 10 gram increase in total daily fibre intake is linked with a reduced risk of an early death by at least 10%.(1, 2, 5) These findings add to the already compelling body of evidence which supports dietary guidelines for people to enjoy a wide range of fibre rich plant foods each day and to reduce low fibre nutrient poor choices such as cakes, biscuits, confectionery, sweetened beverages and takeaway meals.

As the leading source of dietary fibre, GLNC encourages Australians to make smart grain choices such as enjoying grain foods 3 – 4 times per day with at least half as whole grain or high fibre options. This is an easy first step for Australians to boost their fibre intakes. To further assist Australians in achieving a higher fibre diet GLNC also recommends people eat legumes at least 2 - 3 times each week which is an achievable goal for people to start this healthy habit.

For a range of fibre rich recipes, cooking tips and snack ideas with grains and legumes visit the GLNC website.

  1. 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.
  2. Yang Y, Zhao L, Wu Q, Ma X, Xiang Y. Association Between Dietary Fiber and Lower Risk of All-Cause Mortality: A Meta-Analysis of Cohort Studies. American Journal of Epidemiology. 2014.
  3. Chuang S-C, Norat T, Murphy N, Olsen A, Tjønneland A, Overvad K, et al. Fiber intake and total and cause-specific mortality in the European Prospective Investigation into Cancer and Nutrition cohort. The American Journal of Clinical Nutrition. 2012;96(1):164-74.
  4.  ABS. Australian Health Survey: Nutrition First Results - Foods and Nutrients, 2011-12. Australian Bureau of Statistics, 2014.
  5. 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.
  6. GLNC. 2014 Australian Grains and Legumes Consumption and Attitudinal Report. Unpublished: 2014.