Food Structure for Nutrition - Food Colloids: Self-Assembly and Material Science - page 5

essential nutrients. 10 Food matrices that compromised rapid absorption, as a
result of their structural complexity, were considered deleterious to bioavaila-
bility and hence to nutritional value. With these rather narrow but, in context,
reasonable assumptions about food structure and nutrition, food processing
steps that destroyed structure were advantageous and those that created
structure were considered deleterious. Now that scientific considerations have
begun to broaden beyond essential nutrients to nonessential food components
and the food structure itself, the absolute dynamics of the delivery of food and
food components is being studied. The key question then becomes: ''what is the
optimal situation - is it rapid complete absorption, or slow, perhaps even
incomplete, absorption?'' When such a question is asked, it becomes clear that
there are no biological models of optimal food structure. This being the case, it
is reasonable to ponder what is the preferable biological model one would wish
to interrogate to answer questions about rate and extent of absorption of
nonessential food components.
1.4 Models of Food Components, Food Structure, and
Health
Nutrition has begun to address the scientific questions associated with nones-
sential food components in the diet. To date, most of these components have
been derived from plants. The vast majority of small biological molecules as
candidate bioactive food components are indeed derived from secondary
metabolism in plants. The total number of secondary plant metabolites is
estimated 11 to exceed 2 10 5 . Nonetheless, in attempting to establish appro-
priate food components for nourishment beyond the essential nutrients, it is
reasonable to ask what was the driving force for the emergence of these
secondary metabolites within plants during evolution? For many of these
compounds and their respective pathways, the divergence of secondary metab-
olism was driven by the competitive advantage for those plants to avoid
predation. Because animals were a conspicuous source of predation of plants,
much of the secondary metabolism of plants evolved explicitly by Darwinian
selective pressure to avoid being eaten by animals. Thus, quite the opposite of
providing compounds to improve animal health, plant secondary metabolism
evolved to produce compounds that were explicitly toxic to animals. Examples
of the success of this evolutionary pressure abound, from soybean trypsin
inhibitors to alkaloids. 12,13 Thus, although the plant kingdom and the rapidly
arriving plant genomes are interesting targets for the development of knowl-
edge of toxicity and anti-nutritive components, it is difficult to defend plants
and plant metabolites per se as targets for healthful food structures.
To understand how to design food structures that optimize nutrient delivery,
it is necessary to examine a food system that ideally was under Darwinian
selective pressure during evolution to be explicitly nourishing in all its conno-
tations. Fortunately, there is such a model, with remarkable complexity and
genetic diversity - mammalian milk.