Scientific Literature
A
number of studies have reviewed the toxicity of oats in individuals with
Coeliac disease. In a recent review of
studies published since 1995, Thompson (2003) concluded that the body of
research on oats supports the conclusion that most adults with Coeliac disease
can consume moderate amounts of uncontaminated oats without causing damage to
the intestinal mucosa. However, it is
not known whether this is due to oats lacking in harmful amino acid sequences
or due to those sequences occurring in small enough quantities so as to not
cause a problem.
Thompson (2003) also
noted some concerns with the methodologic limitations of some of these
studies. One issue that was noted
relates to the differences in the protein composition of oats versus that of
wheat, rye and barley. Wheat, rye and
barley prolamins account for 30% to 50% of total protein, whereas oat prolamins
account for only 10% to 15% of total protein.
Therefore, it has been suggested that a far greater quantity of oats
would have to be consumed to cause the same adverse effects as wheat, rye or
barley.
In one of the most
recent of such studies, Picarelli (2001) aimed to
define the role of oats in Coeliac disease to determine whether oats can be
safely included in a gluten free diet. The study design involved an in vitro
model to test whether oats induced antiendomysial antibodies production in
supernatant fluid from cultured duodenal mucosa specimens collected from 13
treated Coeliac disease patients. Antiendomysial antibodies are produced by
intestinal mucosa and are highly sensitive and specific for Coeliac disease.
The biopsy specimens were cultured with and without peptic-tryptic (PT) digest
of gliadin and avenin (from oats) and in medium alone. Samples from 5 of the 13
patients were cultured with the C fraction of PT-avenin. Antiendomysial
antibodies were detected in specimens from all 13 patients after the challenge
with gliadin but not after culture with medium alone. By contrast, no
antiendomysial antibodies were detected in any of the specimens cultured with
PT-avenin and its C fraction. Given this, it was concluded that oats can be safely included in the gluten free diet of
people with Coeliac disease.
In agreement,
Janatuinen et al. (2002) aimed to assess the safety of
long term ingestion of oats in the diet of Coeliac patients. In an initial
study, the effects of a gluten free diet and a gluten free diet including oats
were compared in a randomised trial involving 92 adult patients with Coeliac
disease, with 45 in the oats group and 47 in the normal group. After 6-12
months, patients in the oats group were able to eat oats freely with an otherwise
gluten free diet. After 5 years, 35 patients in the original oats group (23
still on an oats diet) and 28 in the control group on a conventional gluten
free diet were examined (Janatuinen, 2002). Clinical and nutritional
assessments were undertaken, duodenal biopsies for conventional histopathology
and histomorphometry were examined and a number of antibodies were measured.
The study found that there was no significant difference between the normal
group and those people consuming oats with respect to duodenal villous
architecture, inflammatory cell infiltration of the duodenal mucosa, or
antibody titres after five years of follow up. In both groups histological and
histomorphometric indexes improved over time. It was concluded that both adults and children with Coeliac disease can
use oats as part of an otherwise gluten free diet and that even long term use
of moderate amounts of oats included in a gluten free diet in adult patients
with Coeliac disease is safe.
Janatuinen (2002)
suggests that the reason why individuals with Coeliac disease can tolerate oats
is based on structural differences of proteins among oats, wheat, barley and
rye. It is recognised that the injurious agent in wheat is the gliadins and it is possible
that the absence of certain amino acid sequences from oat avenin that are found
in wheat gliadin, make oats tolerable to people with Coeliac disease.
In addition,
Janatuinen et al. (2002) recognises that recent guidelines from the Finnish and
the UK Coeliac Societies conclude that moderate amounts of oats can be consumed
by most individuals with Coeliac disease without risk. The guidelines also
suggest that removal of oats from the list of forbidden cereals in the diet for
people with Coeliac disease could increase compliance with a gluten free diet
by giving more choices and reducing the cost of gluten free foods.
Views of the External Advisory Group
Consultations
with the Dietary Management EAG on the issue of the toxicity of oats in
individuals with Coeliac disease revealed that opinion was divided. Although it was acknowledged that a number of
studies have been published indicating that oats can be tolerated by many
people with Coeliac disease, there was no overall agreement amongst members
that this information is conclusive.
Representative health professionals in New Zealand were of the view that
the majority of Coeliac patients can tolerate some oats in the diet. However,
representative Australian health professionals indicated that not all Coeliacs
can tolerate oats, therefore the prohibition on oats in gluten free
claims should be retained.
Submissions
Views were mixed amongst submitters to the
P264 IAR in relation to the toxicity of oats, particularly in relation to
whether there should be a specific prohibition of gluten free and low
gluten claims on foods containing oats. Many submitters referred to recent
studies indicating that the majority of people with Coeliac disease can
tolerate oats, and that therefore there should not be a specific prohibition of
gluten claims on foods containing oats in the Code. Others however, felt that
while evidence is not absolutely conclusive, caution should be applied within
the regulatory setting. The rationale provided for this approach included the
following points:
-
although studies found that the majority of people could tolerate oats, it was noted that the studies have limitations and that more work is required to resolve the issue;
- it was suggested that approximately 15% of Coeliac sufferers who ate oats reacted symptomatically and if the prevalence of Coeliac disease in Australia and New Zealand is 1:250-300, this represents a significant number of people who may react symptomatically to the presence of oats in gluten free foods; and
- the
potential contamination of oats with barley or wheat presents a problem for
people with Coeliac disease. Although studies have shown a certain degree of
tolerance to oats amongst people with Coeliac disease, in many cases
uncontaminated oats were used which do not necessarily represent the food supply
where uncontaminated oats are less freely available.
In relation to the issue of contamination,
the question was raised in the IAR as to whether the risk of contamination with
protein from other sources is an appropriate basis for excluding a significant
cereal source from carrying a gluten claim? Further to this, one submitter made
the point that there are no other provisions in the Code that regulate for
cross-contamination during processing.
Excerpt from www.foodstandards.gov.au/
