Gluten is a protein that is commonly
found in wheat, rye and barley, which gives bread and other baked
goods elasticity and a chewy texture. It is avoided in a small
percentage of the population that cannot tolerate gluten due to
Celiac disease or gluten sensitivity. Gluten-free foods often
contain less dietary fiber and other micronutrients, such as,
vitamins and minerals, thus making them less nutritious and they also
tend to cost more. However, recent popularity of gluten-free diets
has been trending even among people without any health problems.
A ‘Gluten-free’ diet has been
interchangeably used to represent a ‘healthy diet.’ On the
contrary, researchers have shown concern that it may actually lead to
the development of type 2 diabetes (T2D) over a period of few
decades. Although there is no scientific evidence that low-gluten
will contribute to diabetes, the scientists are concerned about the
long-term health benefits with the reduction in gluten consumption.
An analysis of a large study of U.S. health professionals observed
the effects of food on health in nearly 200,000 subjects. The study
suggested that gluten intake might not exert significant adverse
effects on the incidence of T2D or excess weight gain. Thus,
limiting gluten from the diet is unlikely to facilitate T2D
prevention and may lead to reduced consumption of cereal fiber or
whole grains that help reduce diabetes risk. The purpose of the
study was to determine if gluten consumption would affect health in
people with no apparent medical reasons to avoid gluten.
A long-term observational study looked
at the data from three big previously held studies that started 40
years ago with the Nurses’ Health Study (NHS) and continued with
Nurses’ Health Study II (NHS II) and the Health Professionals
Follow Up Study (HPFS) to observe the effect of nutrition on
long-term health. The studies, NHS (n=69,276), NHSII (n=88,610), and
the HPFS (n=41,908), estimated the gluten intake using a validated
food-frequency questionnaire collected every 2 to 4 years and the T2D
incident was defined as physician-diagnosed and confirmed diabetes
with supplementary information. The major dietary sources were
pastas, cereals, pizza, muffins, pretzels, and bread. The average
daily gluten intake was 5.8 grams per day for NHS, 6.8 grams per day
for NHSII, and 7.1 grams per day for HPFS.
The researchers found that most
subjects consumed less than 12 grams gluten per day and surprisingly,
within this range, the subjects who ate the most gluten had lower
risk of T2D during 30 years of follow-up. However, subjects who ate
less gluten consumed less cereal fiber that is a protective factor
from progression of T2D. Moreover, participants in the highest 20%
of gluten consumption had a 13% lower risk of developing T2D versus
subjects with the lowest daily gluten consumption less than or equal
to 4 grams per day. The mean gluten intake (± standard deviation)
was 5.83±2.23, 6.77±2.50, and 7.06±2.76 grams/day in NHS, NHSII,
and HPFS respectively, and strongly correlated with intakes of
carbohydrate sources, especially refined grains, starch, and cereal
fiber (Spearman correlation coefficients greater than 0.6).
During the prolonged 4.24 million years
of follow-up from 1984-1990 to 2010-2013, 15,947 T2D cases were
confirmed. An inverse association between gluten intake and T2D risk
was observed in all three cohorts after multivariate adjustment and
hazard ratio (HR) comparing extreme quintiles was 0.80 (0.76, 0.84; P
less than 0.001). Further adjusting for cereal fiber resulted in
slight attenuation in the association (HR [95%CI]= 0.87[0.81, 0.93]),
but not other carbohydrate components. There was no significant
association with weight gain in participants without major chronic
diseases and aged less than 65 years with changes in gluten intake in
multivariate adjusted model: 4-year weight change (95%CI, lb) was
0.08 (-0.06, 0.22; P=0.25) in NHS, -0.05(-0.18, 0.08; P=0.43) in
NHSII, and 0.36 (-0.24, 0.96; P=0.24) HPFS for each 5-gram increase
in gluten intake.
In conclusion, the study suggested that
gluten intake might not exert significant adverse effects on the
incidence of T2D or excess weight gain. In the conference media
release, the author acknowledged that the study does not conclude the
effects of gluten in the prevention of T2D, but limiting gluten from
the diet may lead to reduced consumption of cereal fiber or whole
grains that help reduce diabetes risk. The study suggested that if
avoiding gluten is not clinically deemed necessary, then avoiding
foods that have other benefits could be harmful unless replaced with
healthy, naturally gluten-free grains, such as quinoa or buckwheat.
Overall, although gluten-free diets have grown in popularity,
evidence is lacking regarding gluten intake and long-term health,
thus it is crucial to have a comprehensive understanding of diet and
nutrition prior to making dramatic changes in the diet.
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