November 2010, Week 3


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Mon, 15 Nov 2010 10:57:45 -0500
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Enzyme in Saliva Shapes How We Sense Food Texture
Perception and digestion of starchy foods varies from
person to person
Abigail L. Mandel et al.
Monell Chemical Senses Center
October 13, 2010

PHILADELPHIA (October 13, 2010) - Creamy. Gritty.
Crunchy. Slimy. Oral texture perception is a major
factor contributing to each person's food preferences.
Now, a new study from the Monell Center reports that
individuals' perception of starch texture is shaped by
variability in the activity of an oral enzyme known as
salivary amylase.

"Differences in starch perception likely affect people's
nutritional status by influencing their liking for and
intake of starchy and starch-thickened foods," said
study lead author Abigail Mandel, a nutritional
scientist at Monell.

Starch, such as from wheat, potatoes, corn, and rice, is
a major component of the modern diet, comprising 40 to
60 percent of our calories. Amylase enzymes secreted in
saliva help break down starches into simpler sugar
molecules that are ultimately absorbed into the
bloodstream, thus influencing blood glucose levels.

In the study, reported in the journal PLoS ONE, analyses
revealed that changes of starch consistency in the mouth
were directly related to salivary amylase activity.

Enzyme levels and activity were measured in several
ways, using saliva collected from 73 subjects. First,
each person's saliva was mixed with a standardized
starch sample and a sensor measured the enzymatic break-
down of the starch's consistency. Next, enzyme and
protein assays directly measured the amount and activity
of salivary amylase in the saliva samples.

Finally, subjects completed continuous evaluations over
a 60-second interval to rate the perceived breakdown of
a starch sample while in the mouth.

"Taken together, this means that foods with different
starch levels will be perceived very differently by
people as a function of how much salivary amylase they
produce. What may seem like a thick and resistant
pudding or starchy food to some may seem noticeably thin
in the mouths of others," said senior author Paul A. S.
Breslin, a Monell sensory geneticist.

The findings may also extend to starch digestion and
metabolism, ultimately lending insight into why some
people develop metabolic diseases while others don't.
Individuals who have more salivary amylase may break
starchy foods down more quickly, leading to a more rapid
increase of post-meal blood glucose levels.

"In today's state of food excess and refined starch
ingestion, it is possible that high levels of salivary
amylase contribute to the risk of insulin resistance and
non-insulin dependent diabetes," said Mandel.

The study went on to demonstrate a genetic influence on
salivary amylase activity. Previous research had
revealed that an individual can have anywhere from 2 to
15 copies of AMY1, the gene that codes for salivary
amylase. Mandel and collaborators analyzed DNA samples
from 62 subjects and found that the number of AMY1
copies a person has is directly related to the amount
and activity of their salivary amylase.

Combining the findings, the study demonstrated a series
of relationships extending from variation in genes to
individual differences in nutrient perception in the
mouth. "A link from genetic variation to enzymatic
proteins to altered physiology to oral perception of
textures is quite novel and provides a complete story,"
said Breslin.

Additional studies will explore relationships between
the AMY1 gene copy number and liking for and consumption
of starchy foods, as well as whether salivary amylase
levels affect carbohydrate digestion and absorption.

Also contributing to the study were Catherine Peyrot des
Gachons, Kim Plank, and Suzie Alarcon, all from Monell.
Breslin also holds an appointment as Professor in the
Department of Nutritional Sciences at Rutgers
University. Funding was provided by the National
Institute on Deafness and Other Communication Disorders
and National Starch LLC.


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