Food Structure for Nutrition - Food Colloids: Self-Assembly and Material Science - page 7

the body, ultimately contributing to the survival of neonatal mammals. 22 It
should be emphasized that research on these compounds and their functions is
proving to be more difficult than traditional nutritional investigations on
essential nutrients. Because these compounds and their functions are not
essential, they have discernible value only to infants under certain circum-
stances. Hence, their functions, actions, and overall benefits have proven
exceedingly difficult to recognize, and much less to study, and it is generally
agreed that only a very small subset of the total biological value of milk's
components is known. 23 Nonetheless, in study after study, the identification of
component after component is revealing the evolution of milk as a highly
functional food with properties that may find multiple applications to the
structure manipulation of other foods. The evolution of the mammary gland
was under constant Darwinian selection for the successful survival of
offspring. 24 Milk is indeed a genomic model for the multidimensional aspects
of nourishment. 25
The evolutionary origins of milk proteins and mammary regulation define
the key functions of milk and the mammary gland. The emergence during
evolution of the mammary gland likely involved adaptive recruitment of
existing precursor genes through alteration of regulatory sequences to allow
expression in primitive mammary glands, and duplication and mutation of
structural sequences to acquire new functions from pre-existing primitive
proteins. Evidence is consistent with early precursors to lactation being derived
from an ancestral apocrine-like gland that was associated with hair follicles that
led to secretions designed to nourish and protect the soft, rubbery shells of egg-
laying monotrenes. 26 The earliest mammary function after provision of nutri-
tion was possibly the passing of protective advantages onto offspring via
immunoglobulins, and thus aiding selection for survival. This would have
paved the way for the elaboration of myriad protective functions that are only
now beginning to be appreciated.
The functions of milk generally can be considered supportive of both
mammalian mothers and infants through several mechanisms. Milk provides
nourishment to infant offspring; disease defence for the infant; disease defence
for the mother; regulation or stimulation of infant development, growth, or
function; regulation or stimulation of maternal mammary tissue development,
growth, or function; inoculation, colonization, nourishment, regulation, and
elimination of infant microflora; and inoculation, colonization, nourishment,
regulation, and elimination of maternal mammary microflora.
Nourishing the mammalian neonate is the most obvious role of milk, and the
success of mammals attests to the value of milk as an initial food source for the
young of these species. The demands on milk as a sole source of nutrition are
remarkable. All of the essential macronutrients - water, vitamins, minerals,
amino acids, and fatty acids - plus the basic structural and energetic interme-
diates needed to sustain life, must be delivered to the neonate in a highly
absorbable form that is appropriate to the species and the stage of development
- all at minimal energy cost to the mother. Lactation research has illuminated
many of the biological processes needed to mobilize the essential biomolecules