A new study led by scientists at
King's College London shows that preserving the natural structure
of dietary fibre during food production can help to slow the rise
in blood sugar levels after a meal.
This finding may lead the way for
the development of a new generation of food products that contain
similar ingredients to existing products, but with a more natural,
enzyme resistant structure around the starch that enables it to be
digested more slowly. Such products would be particularly
beneficial in the prevention and management of obesity and type 2
diabetes which affects more than one in 17 people in the UK.
Starch is one of the largest
sources of calories and an important component of a healthy diet.
Understanding how starch is digested and metabolised is highly
relevant to weight management, as well as prevention of other
related conditions such as type 2 diabetes and heart disease.
Wheat is a good source of starch
and the predominant source of starch in the UK diet. It also
contains dietary fibre, which forms a complex protective network of
cell walls around the starch. Milling wheat grains to produce flour
damages these cell walls, allowing the starch to be digested more
quickly.
The research, funded by the
Biotechnology and Biological Sciences Research Council, found that
when participants ate wheat porridge made from coarser, larger
particles this gave rise to significantly lower blood sugar levels
than when they consumed a 'smooth' porridge made of finer wheat
flour. Both meals were made of the same ingredients and had the
same nutrient contents, but starch was digested more slowly in the
coarse porridge.
Within two hours of eating, the
blood sugar responses were 33 per cent lower and insulin responses
43 per cent lower when participants ate the coarser particles. They
also found that participants were less likely to experience an
undesirable 'sugar low' following the earlier peak in blood sugar
than when they ate the smooth porridge.
Researchers studied nine healthy
volunteers with pre-existing stomas, allowing access to the
contents of the small bowel without the use of surgery. When
researchers examined the contents of the intestinal fluid, they
identified a number of large pieces of food material containing
unabsorbed nutrients. Larger food particles were found to contain
more of the natural structure of the cell walls, which encloses
starch and other nutrients and delays or prevents their
release.
The results could have a
significant impact on the food production industry and suggest that
the development of new milling techniques which maintain the
microstructure of wheat might in the future give consumers a
greater choice of 'diabetic-friendly' foods or healthier versions
of wheat based products such as white bread, breakfast cereals, or
biscuits.
Dr Cathrina Edwards, lead
researcher from King's College London said: "Our research has shown
that there is a relatively easy way to limit the availability of
starch/calories from food simply by preserving more of the natural
structure of plant-based ingredients.
"The way in which foods are
processed clearly has a big impact on how much of the
nutrients/calories are absorbed from that food, but this important
information is not reflected on food labels. Greater understanding
of the structure of food and its effect on the body provides an
opportunity to transform ingredients and products such as bread,
pasta, breakfast cereals and other wheat based products, into meals
which provide slower energy release and prolonged fullness."
The
paper, Manipulation of starch bioaccessibility in wheat endosperm to
regulate starch digestion, postprandial glycemia, insulinemia, and
gut hormone responses: a randomized controlled trial in healthy
ileostomy participants, is published
in the American Journal of Clinical
Nutrition.