he authors emphasize that nutrient supplementation, particularly
for certain at-risk populations, has an important place
in health care. However, they point out that there is
an important difference between observing associations
between particular nutrients and health outcomes and detecting
causal connections.
"Perhaps no better example exists than the disheartening
results of the vitamin E intervention trials for the prevention
of cardiovascular disease," says Russell. Lichtenstein
explains that although observational studies suggest positive
effects, "we lack supporting evidence from intervention
trials, and that is critical for making recommendations
to the public."
Data are insufficient in other areas as well, according
to Lichtenstein. "Disease-nutrient relationships are by
their nature very complex. Within the context of high
dose nutrient supplementation, outcomes are frequently
unexpected. Not only have some studies failed to yield
positive results but, occasionally unanticipated negative
effects have been observed."
The authors point out that some of the unanticipated findings
from high dose single or nutrient cocktails may be because
the levels used are much higher than those necessary to
prevent deficiency disease. In one study, adding a nutrient
antioxidant cocktail to a well established cholesterol-lowering
drug treatment actually lessened the beneficial effect.
"We still have a lot to learn about the use of high doses
of nutrients. The important point is to prevent the cart
from getting in front of the horse; we need to validate
the science before there is wide scale adoption by the
general public as we saw with vitamin E. We can no longer
automatically assume there will be no adverse consequences,"
notes Lichtenstein.
In their overview of the existing literature, Lichtenstein
and Russell, both professors at Tufts University's Friedman
School of Nutrition Science and Policy and School of Medicine
note that their caution is "based on the lack of a complete
understanding of nutrient requirements and interactions,
and disappointing results of intervention studies with
single nutrients or nutrient cocktails."
"The identification, isolation, and purification of nutrients
in the early 20th century raised the possibility that
optimal health outcomes could be realized through nutrient
supplementation," write the authors, but this advance
has been "a double-edged sword."
While the current expert opinion is that there is not
enough evidence to justify emphasizing nutrient supplements
instead of food and diet for maintaining good health,
this topic remains under rigorous research, and new data
is published regularly. Based on the available information,
the authors say, "eat a diet rich in fruits, vegetables,
low-fat dairy products, whole grains and fish."
The Gerald J. and Dorothy R. Friedman School of Nutrition
Science and Policy at Tufts University is the only independent
school of nutrition in the United States. The School's
eight centers, which focus on questions relating to famine,
hunger, poverty, and communications, are renowned for
the application of scientific research to national and
international policy. For more than two decades, the Jean
Mayer USDA Human Nutrition Research Center on Aging at
Tufts University has studied the relationship between
good nutrition and good health in aging populations. Tufts
research scientists work with federal agencies to establish
the US Dietary Guidelines, the Dietary Reference Intakes,
and other significant public policies.
SOURCE:
INewswire.com
