A summary of recent research on the health benefits of
fibre and whole grains
Fibre and Whole Grains
Executive Summary
Whole grains are an excellent dietary choice however the role of dietary fibre
seems to have been largely forgotten. The positive health impacts of cereal
fibre have been well documented1-7 and mounting evidence indicates that fibre
is an important contributor to the health benefits associated with whole grain
consumption. An independent literature review of the scientific evidence
behind a claim for whole grain intake and cardiovascular disease (CVD) risk
reduction concluded that there is insufficient evidence to support the claim10.
However, when the definition of whole grain was broadened to include the
presence of added bran, germ or fibre, the claim could be supported. The
evidence to date suggests that both whole grain and fibre content should be
considered when selecting grain-based foods for their health benefits.
Introduction
Whole grains contain all three parts of the grain - the endosperm,
the germ and the bran - whereas fibre is specific to the outer bran
layer of the grain. Both fibre and whole grains make a significant
contribution to a healthy diet;
however, new evidence indicates
...many of the
many of the health benefits
associated with whole grains may be
health benefits
more accurately attributable to their
associated with
fibre content.
whole grains
may be more
accurately
attributable to
their fibre
content.
The benefits of dietary fibre have
been well documented. Eating a diet
rich in cereal fibre has been shown
to reduce the risk of developing
coronary heart disease1 and type 2
diabetes2, support good digestive
health3, help protect against lower
digestive tract cancers4, promote
satiety5 and help manage weight6,7.
page 2
The nutritional robustness of whole
grains is well established. They are
packed with essential nutrients,
including B-vitamins, antioxidants
and fibre-rich bran, which are all
known to play a role in maintaining
health. Consumption of 2-3 serves
of whole grain foods a day is
reported to reduce the risk of
developing chronic disease,
including CVD8, type 2 diabetes2 and
certain cancers9. However, there is
often confusion surrounding the
definition of whole grains, which
creates complexity in interpreting
the research.
Whole grain characteristics
Whole grains contain all parts of the grain - the bran (fibre-rich
outer layer), the germ (nutrient-rich inner core) and the
endosperm (middle starch and protein layer), which comprises
approximately 80-90 percent of the grain. In the grain-refining
process, the bran is removed, resulting in loss of dietary fibre,
vitamins, minerals, phytoestrogens, phenolic compounds and
phytic acid. Examples of whole grains include wheat, rice, barley,
corn, rye, oats and triticale.
One striking finding
of the review was
that the majority of
studies applied the
definition of whole
grain inconsistently,
thus confounding
their results.
relationship between whole grain
consumption and reduced risk of
CVD and diabetes10. One striking
finding of the review was that the
majority of studies applied the
definition of whole grain
inconsistently, thus confounding
results. In many cases, constituents
of whole grains such as isolated
bran or germ were used to evaluate
health outcomes, but were classified
as whole grains in the findings.
Source: Slavin J., Why whole grains are protective: biological mechanisms.Proc Nutr
Soc. 2003 Feb;62(1):129-34. Review.
In many cases,
constituents of
whole grains
such as isolated
bran or germ
were classified
as wholegrains in
the findings.
Definitions of
whole grains are
inconsistent
Using the US Food and Drug
Administration’s (FDA) definition* of
whole grain, which is consistent with
the definition prescribed by Food
Standards Australia New Zealand
(FSANZ)**, the Life Sciences Research
Office (LSRO) conducted an
independent literature review of the
In the review, only studies that
measured a validated endpoint for
CVD and/or diabetes in a healthy US
population and populations
representative of the US were
considered. Studies were excluded if
they did not specifically describe or
define whole grains according to the
FDA definition. Based on these
criteria, four studies were included
in the analysis and no CVD health
benefit could be determined.
When expanding the analysis to
include a broader definition of
whole grains, a total of 29 human
* F
DA definition of whole grains: “whole grains consist of intact, ground cracked or flaked caryopsis, whose principal anatomical components – the
starchy endosperm, germ and bran – are present in the same relative proportions as they exist in the intact caryopsis.”
**FSANZ definition of whole grains: “whole grain means the intact grain or the dehulled, ground, milled, cracked or flaked grain where the constituents
– endosperm, germ and bran – are present in such proportions that represent the typical ratio of those fractions occurring in the whole cereal, and
includes wholemeal.”
page 3
studies (15 intervention and 14 observational) were reviewed
for the association between whole grain intake and CVD risk
and 21 studies for the association between whole grain intake
and diabetes risk. These included studies that considered
added bran and germ as whole grains or studies that did not
explicitly use the term “whole grains” but were in fact
conducted with individual whole grains.Thirty-eight studies
were excluded for not meeting one or more of the inclusion
criteria.
The nutrient
profile of whole
grains differs Whole grain
doesn’t always
mean high fibre.
Whole grains, CVD and diabetes
risk reduction
A key finding of the review was that there is inconsistent
scientific evidence to support a whole grain and CVD risk
reduction health claim if only whole grain studies that conform
to the FDA whole grain definition (using native proportion of
endosperm, bran and germ) are considered. However, when
the broader definition of whole grain was applied, which
included added bran and germ or studies that did not
explicitly use the term “whole grains” but were, in fact,
conducted with whole grains, a whole grain and CVD risk
reduction health claim could be supported. These findings
suggest that cereal fibre content is an important consideration
when choosing grain-based foods for their health benefits. The
link between whole grains and diabetes risk reduction was
found to be suggestive but inconclusive, whether or not fibre
was considered.
Additional new research was conducted by Brownlee et al
(2010) on the effect of whole grain consumption on markers of
CVD risk. The four-month, randomised, controlled dietary
intervention (n=316), which investigated the impact of replacing
refined grains with whole grains on CVD risk markers in the
diets of non-whole grain consumers, showed no significant
change in CVD risk after increased consumption of whole grain
foods. Participants were assigned to one of three groups:
control (no dietary change), intervention 1 (60g of whole grains
a day for 16 weeks) and intervention 2 (60g of whole grains a
day for 8 weeks followed by 120g of whole grains a day for 8
page 4
weeks.) The markers of CVD risk
(measured at 0, 8 weeks and 16 weeks)
were BMI, percent body fat, waist
circumference, fasting plasma lipid
profile, glucose and insulin; and
indicators of inflammatory, coagulation
and endothelial function. Although
whole grain consumption was
significantly increased among the
intervention groups, there were no
significant differences in any markers
of CVD risk between the groups.
Commenting on the link between whole
grain consumption and functional
health benefits, Brownlee et al stated
that, “although there are strong
observational data to support the
health benefits of increased whole
grain consumption, data from smallscale interventions are conflicting and
direct evidence from intervention
studies carried out in large numbers is
not available.”
Whole grain doesn’t always mean
high fibre
The nutrient profile of whole grains differs. Although whole grains
contain all three anatomical parts, the health benefits observed
from consumption of one grain do not necessarily apply to other
types. This is due to great variability among various whole grains
in their content of macronutrients, micronutrients and bioactive
components.
The nutritional variation between whole grains is particularly
relevant for fibre content. While the energy content is similar
across the various grains, the fibre content differs significantly.
For example, brown rice has 3.4 g of fibre per 100g compared with
whole wheat, which contains 12.2 g per 100g.
A key finding of the
review was that there is
no consistent scientific
evidence to support a
whole grain and CVD
risk reduction health
claim if only whole
grain studies that
conform to the FDA
whole grain definition
(using native proportion
of endosperm, bran and
germ) are considered.
Nutrient concentrations of a variety of whole grains
Barley
Brown
Rice
Energy, kJ
1481
1548
1527
1628
1402
1389
1494
Protein, g
12.48
7.50
9.42
16.89
14.76
12.61
14.73
2.3
2.68
4.74
6.9
2.50
1.54
1.08
73.48
76.17
74.6
66.27
69.76
71.18
74.90
17.3
3.4
7.3
10.6
14.6
12.2
6.2
Nutrient/100g
Fat, g
Carbohydrate, g
Total Fibre, g
Corn
(Yellow)
Oats
Rye
Wheat
Wild
Rice
Source: USDA. Composition of foods raw, processed, prepared USDA national nutrient database for standard reference, release 20. 2008
[cited 2008 Jun 2]. Available from: http://www.nal.usda.gov/fnic/foodcomp/Data/ SR20/SR20_doc.pdf
Conclusion
Fibre and whole grains are both important elements of a healthy diet. Based
on new evidence, there is a need for consistency in the definition of whole
grains. While whole grains are commonly recommended, the important role of
cereal fibre should not be overlooked.
page 5
Fibre and Whole Grains
Processed bran is the richest
source of fibre
Isolating the bran layer of the whole grain provides a
concentrated source of fibre. The table below compares the
fibre content of various whole grains and their processed
bran counterparts per 100 grams.
Fibre in
100g
whole grain
Fibre in
100g
processed bran
Wheat
12.2g
45.4g
Oats
10.6g
15.9g
Brown Rice
3.4g
25.5g
Type of
cereal
Source: Nuttab 2006 online version. www.foodstandards.gov.au/
consumerinformation/nuttab2006/onlineversionintroduction/onlineversion.
cfm?&action=default
Whole grain and fibre
recommendations
The Australian Dietary Guidelines recommend adults
consume nine serves of cereals each day, with the emphasis
on whole grains.
The NH&MRC recommended daily intakes for fibre are
30g for men and 25g for women. Suggested daily targets to
reduce the risk of chronic disease are 38g for men and
28g for women.
Go Grains Health & Nutrition Limited recommends
adults consume 48g of whole grains each day
® Registered trade mark. Kellogg (Aust.) Pty. Ltd. authorised user. April 2010.
page 6
...cereal fibre content
is an important
consideration when
choosing grain-based
foods for their health
benefits.
1 Pereira et al (2004) Dietary Fibre and Risk of
Coronary Heart Disease. Arch Int Med 164:
370-376
2 Priebe M et al (2009) Whole grain foods for
the prevention of type 2 diabetes mellitus
(Review) The Cochrane Library, Issue 1
3Vuksan V et al (2008) Using cereal to increase
dietary fiber intake to the recommended level
and the effect of fiber on bowel function in
healthy persons consuming North American
diets. Am J Clin Nutr. 88(5):1256-1262
4Bingham et al (2003) Dietary fiber in food and
protection against colorectal cancer in the
European Prospective Investigation into
Cancer and Nutrition (EPIC): an observational
study. The Lancet 361: 1496-1501
5Slavin et al (2007) Dietary fiber and satiety.
Nutrition Bulletin 32:S32-S42
6Liu et al (2003) Relation between changes in
intakes of dietary fiber and grain products and
changes in weight and development of obesity
among middle-aged women. Am J Clin. Nutr.
78: 920-927
7Koh-Banerjee et al (2004) Changes in wholegrain, bran and cereal fiber consumption in
relation to 8-y weight gain among men.
Am J Clin. Nutr. 80: 1237-1245
8Mellen P et al (2008) Wholegrain intake and
cardiovascular disease; A meta-analysis.
Nutr. Met. Cardio Dis. 18: 283-290
9Jacobs D et al (1998) Wholegrain intake and
cancer: an expanded meta-analysis. Nutr. and
Cancer 30(2): 85-96
10De Moura F et al (2009) Applying the FDA
Definition of Whole Grains to the Evidence for
Cardiovascular Disease Health Claims. J.
Nutr. 139: 2220S-2226
11Brownlee I et al (2010) Markers of
cardiovascular risk are not changed by
increased whole-grain intake: the WHOLEheart
study, a randomised, controlled dietary
intervention. Br J Nutr. Mar 23:1-10