This observation, plus the results of a study done in Sweden,22 led myself and
my colleagues to some theories about mechanisms that might explain the
touch/weight-gain relationship. The investigators in Sweden reported that
stimulating the mouths of the newborn, as well as the breasts of the breastfeeding
mothers, led to an increase in food absorption hormones, such as gastrin and
insulin.22 Schanberg and I argued that massage therapy delivered to several parts
of the body would lead to an even greater increase in food absorption hormones,
which could itself explain the weight gain.23 Assays on the insulin levels before,
during and after massage therapy suggested that insulin levels were elevated in
those preterm infants who received massage therapy versus those who did not
(a 61% increase versus a 4% decrease, respectively, in insulin levels).23 Of course,
future studies could assess the relative changes caused by several food absorption
hormones and other vagal stimulated changes, such as an increase in gastric
motility.