The physiological response of the vagus nerve can dictate taste
and digestive reactions to food. A study suggests that gender is a
major factor in how the nerve functions.
PITTSBURGH, Pa. – The National Institute of Nutrition, Canada, recently
reported that men and women see nutrition differently. For example,
nearly three quarters of women now consider nutrition to be extremely
or very important, compared with little over half of men. Forty-four
percent of women, versus 33 percent of men, describe their eating
habits as excellent or very good. Women express more concern than men
about specific nutrition issues, such as calcium (80 percent vs. 54
percent) and iron (65 percent vs. 41 percent), as well as fat (87
percent vs. 69 percent). Forty percent of women and 25 percent of men
consider themselves to be extremely or very knowledgeable about
Maybe the survey is correct — women probably eat more
nutritious foods in a healthier manner. But they might not be able to
attribute their superior dietary habits to willpower. New research from
the University of Pennsylvania now claims that physiology — expressed
through gender differences in the vagus nerve’s gastric and hormonal
responses to food ingestion — might have a strong influence in women
preferring a Caesar salad to a cheeseburger.
Background and Study
The vagus is a nerve that passes from
the brain to the pharynx, larynx, trachea, lungs, heart, pancreas,
liver, and gastrointestinal tract as far as the left colic (splenic)
flexure. This nerve is essential to digestive and is activated at the
onset of, and during food ingestion.
One study examined how stimulation of the vagus nerve
contributed to emptying of the stomach in lean men and women. The
activity of the vagus nerve was greater in men compared to women. In
another study, secretion of hormones under the influence of vagal
innervation were studied. The release of the hormones were greater in
men compared to women after a high fat meal.
The author of the study, "Gender Differences in Vagally Mediated
Hormonal and Gastric Responses," is Karen L. Teff, Ph.D., from the
Monell Chemical Senses Center and University of Pennsylvania Health
System, Philadelphia, Pa. Her findings will be presented at the
upcoming conference, Genomes and Hormones: An Integrative Approach to
Gender Differences in Physiology. The program is being sponsored by the
American Physiological Society (APS), beginning October 17, 2001, at
the Westin Convention Center, Pittsburgh, Pa.
Methodology and Results
The vagal contribution to gastric
emptying was evaluated by determining the difference in gastric
emptying rate under normal ingestive conditions and during inhibition
of vagal activity with atropine.
Gastric emptying was measured using a dual-radio labeled method
(technetium and indium) in lean men and women. In that group, blockade
of vagal activity significantly delayed the gastric emptying in men (78
percent maximum counts at 90 minutes post-ingestion, atropine as
compared against 35 percent maximum counts with saline) but had no
effect in women.
The vagally mediated responses to taste in food were determined
by monitoring release of two hormones under vagal control, insulin and
pancreatic polypeptide. Normal weight men and women were fed a high fat
and low fat foods.
- Men exhibited significant increases in release of insulin (key to
protein synthesis and glucose utilization) and pancreatic polypeptide
- Women did not display any increase in insulin and their release of pancreatic polypeptide was reduced.
These data suggest that vagal responses to the taste of food differ between men and women.
The data in Dr. Teff’s study reveal that women exhibited diminished
vagally-mediated hormonal and gastric responses to food than men. This
finding could be a key indicator of why men and women differ in their
rate of digestion and their taste in foods.
American Physiological Society