| Proposed soy protein CHD health
claim criticized by FDA's toxicology center FDA's National
Center for Toxicological Research says it does not support
the agency's proposed health claim linking soy protein consumption
with a reduced risk of coronary heart disease because research
shows some soy isoflavones are toxic.
Some soy isoflavones, including genistein, demonstrate toxicity
in the human thyroid and in tissues sensitive to estrogen,
Daniel Sheehan, director of the center's Estrogen Base Program,
Division of Genetic and Reproductive Toxicology, told FDAs
Office of Special Nutritionals Feb. 18.
Considering the current evidence on the toxicity of some
soy isoflavones, it is inappropriate and unreasonable to
approve a soy protein/CHD health claim at this time, Sheehan
wrote.
FDAs Office of Special Nutritionals proposed the soy protein/CHD
health claim for food labels in the Nov. 10 Federal Register.
The claim would be permitted on labels of foods that
contain at least 6.25 grams of soy protein per serving (See
FLNN, Nov. 11, Page 8).
Sheehan cited research indicating that the soy isoflavone
genistein causes estrogenic responses in developing and
adult animals and in adult humans. Research indicates that
during pregnancy in humans, soy isoflavones could be a risk
factor for abnormal brain and reproductive tract development,
he added.
"Furthermore, pregnant Rhesus monkeys fed genistein
had serum estradiol (an estrogenic hormone) levels 50-100%
higher than the controls.
Given that the Rhesus monkey is the best experimental model
for humans, and that women's own estrogens are a very significant
risk factor for breast cancer, it is unreasonable to approve
the health claim until complete safety studies of soy protein
are conducted," Sheehan wrote.
Also of serious concern is the finding that fetuses of monkeys
fed genistein had a 70% higher serum estradiol level than
did the controls, Sheehan said, adding that about 50% of
the female offspring and a smaller fraction of male offspring
displayed one or more malformations in the reproductive
tract. |
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He said soy isoflavones may also
cause thyroid abnormalities, including goiter and autoimmune
thyroiditis. Sheehan said there is a significant body of animal
data that demonstrates goitrogenic and even carcinogenic effects
of soy products; and there are significant reports of goitrogenic
effects from soy consumption in human infants and adults.
Sheehan cited a study showing that children who received soy
formulas as infants were twice as likely to develop autoimmune
thyroiditis compared to children who received other forms
of milk.
Long-term consumption of soy products
may cause dementia: Sheehan
Sheehan said initial data from a study in Hawaii found
that Hawaiian men and Japanese men showed a significant dose-dependent
risk for development of dementia, caused by the deterioration
of blood vessels in the brain, and brain atrophy from consumption
of tofu, a soy product rich in isoflavones.
He said the Hawaii study provides evidence that soy (tofu)
phytoestrogens cause dementia, and it is important given the
great difficulty in discerning the relationship between exposures
and long latency adverse effects in the human population.
"While isoflavones may have beneficial effects at
some ages or circumstances, this cannot be assumed to be true
at all ages. Isoflavones are like other estrogens in that
they are two-edged swords, conferring both benefits and risk.
The health labeling of soy protein isolate for foods needs
to be considered just as would the addition of any estrogen
or goitrogen to foods, which are bad ideas," Sheehan
wrote.
Sheehan also pointed out that a claim made in the Nov. 10
Federal Register notice that soy protein relationship
between exposures and long latency adverse effects in the
human population.
That soy foods are generally recognized as safe (GRAS) is
in conflict with the Center of Food Safety and Applied Nutrition's
recent return of a petition requesting GRAS status for soy
protein. The petition was returned because of deficiencies
in reporting adverse effects, he said, adding that GRAS status
has not been granted. (*9FLN 2204, 7 pages, $6). |
