Large Doses of Bioflavonoids Linked to Leukemia in Children
April 18, 2000 -- Research in recent years has shown that heavy doses of
certain bioflavonoids -- chemicals found in some foods and supplements that are
often considered beneficial -- may be linked with leukemia in infants and
Now, University of Chicago genetics researchers have found the mechanism by
which bioflavonoids may damage genetic machinery and trigger leukemia, or blood
cancer, in children.
These researchers and other experts urge caution about reading too much into
the results, especially concerning bioflavonoids that naturally occur in foods.
But questions are being raised about supplements that deliver megadoses of the
substances, and experts say pregnant women should avoid these supplements.
"The public health message from this study is not yet clear," Janet
Rowley, MD, the University of Chicago molecular geneticist who directed the
study, tells WebMD. "The health benefits of a diet high in foods containing
bioflavonoids, such as soybeans, citrus fruits and, root vegetables, are
Bioflavonoids are chemical compounds derived from plants. They are not
vitamins and are not known to be essential for human nutrition.
Infant leukemias are rare, affecting 37 in 1 million American children. Some
researchers have contended infections cause the cancers. But studies have
suggested that mothers who consume large amounts of bioflavonoids may have
children who are at increased risk of infant and childhood leukemia. A study in
several major Asian cities, where soy consumption is at least twice that of the
United States, found their rate of infant leukemia is twice as high as in this
Rowley is a pioneer in linking cancers to genetic defects, such as when
chromosomes are swapped between genes, resulting in cancers. She is credited
with discovering the first of these DNA switches in the early 1970s.
In a test-tube study reported in the Proceedings of the National Academy
of Sciences, her team found that 10 of 20 bioflavonoids they tested caused
breaks in a small area of a gene known as MLL (short for myeloid-lymphoid
leukemia). Most adult leukemias involve a different part of the gene.
Rowley in 1992 discovered the MLL gene, which plays a role in eight of 10
infant leukemias. Some bioflavonoids were as potent in causing MLL damage as
etoposide, an anticancer agent that has caused some "secondary" bone
marrow cancers following therapy.
"This strongly supports the notion that bioflavonoids could be a
causative agent for infant and possibly childhood leukemias," Rowley says.
Mothers' intake of bioflavonoids during pregnancy may cause MLL damage in the
fetuses, leading to leukemia in infants and young children, she says.
Using blood and bone-marrow cells from healthy newborns and adults, as well
as leukemia cells, researchers uncovered the mechanism of DNA damage. Once the
MLL gene is broken, it can reconnect with more than 40 other genes. In extreme
cases, this can cause cell death. These so-called "translocations" of
genetic material also can cause uncontrolled cell growth, such as in