...From the pages of Agricultural Research magazine
ForumIs Your Health What You Eat?
Ten years ago, phytonutrients were almost unheard of. Today, they are
one of the hottest research and consumer-interest topics imaginable.
The term "phytonutrient" refers to plant components that
promote human health. Unlike the traditional classes of nutrientsprotein,
fat, vitamins, mineralsphytonutrients are not considered essential
for day-to-day human life, but they may contribute to optimal human
Since the initial recognition of phytonutrients, we've found several
classes of compounds in foods that seem to promote health benefits.
Among these are carotenoids, which are found in a variety of plant foods
and appear to decrease the risk of age-related loss of vision; flavonoids,
found in berries, which mitigate nerve cell deterioration; and a wide
array of other compounds that appear to be antioxidants, preventing
cell function loss.
In what was a relatively new field of research just a decade or so
ago, we have already learned a great deal. On the other hand, what we've
mostly learned is that there is a lot more to learn.
We have begun to categorize food plants by the amount of phytonutrients
they contain. ARS has published three such databases for phytonutrients.
ARS' plant researchers have opened many new doors in phytonutrient
research. They have shown that levels of specific phytonutrients do
vary among plant varieties and that we can manipulate those levels through
conventional breeding and biotechnology.
We know it is possible to addthrough genetic engineeringa
phytonutrient across species where the phytonutrient did not previously
exist. We can also breed for over-expression of phytonutrients, as ARS
has recently done with a new tomato that has about 10 times the lycopene
levels of the average tomato. Lycopene is a pigment that gives watermelon
and tomatoes their red color. It is thought to act as a powerful antioxidant.
Our plant scientists are also devising ways to manipulate phytonutrient
levels through cultivation changes as well as developing new information
about the roles these phytonutrients play in plant physiology. But our
knowledge about which phytonutrients are in plants is far ahead of our
scientific understanding about their health benefits for humans.
There are many questions that still require solid scientific answers
before we can make specific recommendations to consumers. We may know
what a phytochemical does in plant physiology, but does it do the same
thing in human beings?
Among the research questions we need to ask are: How much of a phytonutrient
do you need to eat to get the potential health benefit? Is there a level
beyond which there is a possible problem? How do requirements differ
depending on gender, age, body type, and so forth?
We also need to investigate the interaction between phytonutrients
and other compounds within plants. Can people get the dietary benefits
from an isolated phytonutrient, or do these compounds confer their benefits
only when eaten as part of the whole plant? Eating that stem of broccoli
or that whole carrot may prove more beneficial than taking a supplement
made of an extracted phytonutrient. These are things we don't know right
Then there is the whole gamut of questions about how processing and
preparation affect phytonutrients. We know that cooking actually makes
lycopene more available in tomato productsin contrast to the traditional
understanding that cooking lessens levels of vitamins.
Answering such questions will be a fundamental part of building consumer
confidence, so that when foods specifically bred for phytonutrient content
reach the market, consumers will be willing to buy them. For example,
it will not be useful to develop a soybean extra high in phytoestrogens,
which may protect women from breast cancer, if women do not have enough
confidence in the concept to buy products made with the specialty bean.
The number of phytonutrients with scientifically proven health benefits
will only increase in the next few years. But research needs to provide
a lot of solid information before people start making major alterations
in their diets.
In the meantime, eating a balanced diet high in fruits, vegetables, and grains is still the best way to achieve optimum health.
Joseph T. Spence
"Forum" was published in the May 2003 issue of Agricultural Research magazine.