Agriculture Reference
In-Depth Information
widely consumed and are major ingredients in many pre-prepared foods, so
that they offer the opportunity to enrich the Se intake of a large proportion of
the population without the need to change eating habits (Griffiths
et al.
, 2002).
It is also known that consumption of excessive Se, perhaps as low as 600
g/day, is harmful, so supplementing Se intake via vegetables - which tend to
self-regulate their content of Se and other micronutrients - is probably safer
than recommending that people take Se directly as diet-supplementing pills.
In addition to onions, Se-enriched garlic has been studied as a potential
'functional food' for health enhancement (Block, 2005). The deliberate
enrichment and utilization of Se-enriched alliums is still in the early phase of
research and remains just a possibility for the future; this may be taken up
alone, or in parallel with Se enrichment of other crops (e.g. bread-making
wheat).
Conclusions
It seems that benefits to health deriving from alliums are manifold and multi-
faceted, although efficacy studies have not always shown benefits. Evidence for
positive effects on health is accumulating from studies ranging from
biochemical reaction chemistry to population epidemiology. All four major
categories of therapeutic substances from alliums - namely, flavour compounds,
antioxidants, fructans and selenium - act against several major classes of
disease. Studies show that a single biochemical, e.g. ajoene, can be active at
several points in a biochemical pathway of consequence to disease and can also
be active in several different such pathways of consequence to different diseases.
Research is continuing to refine our understanding of these processes and
to pinpoint more precisely which compounds and which enzymes and
biochemical pathways are involved. In addition, we could have benefits of not
just one of the therapeutic compounds in alliums but from the combination of
compounds from all four categories of therapeutic substance. It is possible that
there are synergistic effects between the many compounds found in alliums so
that, acting together, they give health benefits beyond those ascribable to single
compounds. It is important to remember that the mechanisms for health
benefits of different alliums may not be the same, since the types and amounts
of flavour compounds, fructans and flavonols differ between species and even
between cultivars.
It seems rarely asked why substances in alliums (and other vegetables) are
beneficial to health. We have seen that flavour compounds are likely to be
involved in chemical defence against pathogens and pests, and this must
involve interaction with, and disruption of, the invaders' biochemistries. It
maybe just fortuitous that alliums, in evolving their chemical defences, have
evolved substances that act as medicines in humans. The effects on humans of
ingesting the secondary metabolites and endogenous pesticides in crops are by
