Corn fungus linked to fatal birth defects

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Corn fungus linked to fatal birth defects

Eating habits heighten risk for Hispanics, researchers say

By DAVID WAHLBERG

The Atlanta Journal-Constitution

Published on: 04/01/04

A toxin in a fungus that grows on corn could cause fatal birth

defects, researchers say, by interfering with folic acid, the vitamin

recommended to pregnant women to prevent such birth defects.

The toxin, fumonisin, already is known to cause brain and lung

diseases in horses and pigs. In a report published today in The

Journal of Nutrition, researchers — including some from Georgia — say

fumonisin could be a cause of neural tube defects in humans.

Those defects include anencephaly, a fatal condition involving an

undeveloped brain; and spina bifida, an improperly closed spine that

is often not serious but can cause major disability. Together, the

conditions occur in about six of every 10,000 births, though rates

are somewhat higher for Hispanics, who may eat more corn than other

ethnic groups.

Fumonisin in corn tortillas could explain a cluster of neural tube

defects in 33 Hispanic babies born in 1990-91 in Brownsville, Texas,

the researchers say. A lawsuit alleging that air pollution caused the

widely publicized problems — which occurred at a rate triple the

national average at the time — led in 1995 to a $17 million

settlement with dozens of companies that operated factories near the

Texas-Mexico border town.

Today's report summarizes the latest science on the topic,

emphasizing that the link between fumonisin and neural tube defects

remains a theory that should be studied further. Researchers released

the first results from a 1995-2000 survey of Hispanic women in 14

counties along the Texas-Mexico border.

A wave of defects

In April 1991, three babies were born within 36 hours of each other

at a Brownsville hospital with anencephaly: Each had only a fraction

of a brain. Epidemiologists from Texas and the Centers for Disease

Control and Prevention discovered the births were part of a wave of

similar defects in the area that had begun the previous year. But

they couldn't pinpoint a cause, said Dr. Kate Hendricks, one of the

lead Texas researchers and an author of today's report.

Later, after learning that high fumonisin levels in corn had been

connected to the animal diseases in Texas, Hendricks wondered if the

Hispanic women had been eating a lot of corn at the time they were

conceiving. Other studies have detected high levels of fumonisin in

corn and high levels of birth defects in parts of South Africa and

China where people's diets consist mostly of corn.

In the 1995-2000 survey, women who said they ate 301 to 400 tortillas

during their first trimester of pregnancy were 2 1/2 times more

likely to have babies with neural tube defects than those who ate

fewer than 100 tortillas.

That association comes on top of other evidence suggesting a link,

the researchers say: lab studies showing that fumonisin can inhibit

the metabolism of folic acid, which is known to prevent neural tube

defects; mouse studies in which fumonisin caused neural tube defects;

and the previous determination that fumonisin can cause a fatal brain

disease in horses and a deadly lung condition in pigs.

" When you put all these things together, this is something that can't

be ignored, " said Ron Riley, a toxicologist with the U.S. Department

of Agriculture in Athens, who co-authored the report with biochemists

Al Merrill of Georgia Tech and Vicky s of the Atlanta-based

American Cancer Society, among others.

The fungus containing fumonisin, called fusarium, is different

from " huitlacoche " (sometimes spelled " cuitlacoche " ), a smoky fungus

that grows on corn and is often eaten as a delicacy with quesadillas,

tamales and other Mexican dishes.

Knowledge about fumonisin has emerged in the past 16 years. Farmers

and agriculture researchers who had watched horses go mad and pigs

get pneumonia from what they dubbed " moldy corn disease " were pleased

in 1988 to learn that scientists in South Africa had isolated the

culprit: fumonisin, often found in corn " screenings " fed to animals.

Outbreaks of the horse and pig diseases in the Midwest and Texas in

1989 and '90 brought more attention to the toxin and the fungus

fusarium, which grows on corn when the plant is stressed, often

because of hot or dry weather, Riley said.

The five-year survey by Hendricks and others of 409 Mexican-American

women in southern Texas — 184 women whose babies had neural tube

defects and 225 women with healthy babies — found that those who ate

several tortillas a day early in their pregnancies were significantly

more likely to have the birth defects.

The association diminished for women who ate even more tortillas, but

Hendricks says that may support her theory: She suspects those

pregnancies may have been even more damaged by the defects, ending in

miscarriages, which aren't routinely recorded.

Though the neural tube defect rate has remained above average in the

Brownsville area, it dropped after the 1990-91 cluster. Hendricks

believes that also points to fumonisin, since levels of the toxin

vary from year to year and from place to place.

A spokeswoman for General Motors, one of the companies that settled

the air pollution lawsuit, said she couldn't comment on the new

research.

Folic acid blocked

The Cancer Society's s explained how fumonisin may cause birth

defects. The toxin blocks one of the transporters folic acid needs to

enter cells, she said, inhibiting the vitamin's role in ensuring that

the neural tube — which gives rise to the spinal cord and brain —

closes properly.

Fumonisin could create a double blow for women whose diets are

deficient in folic acid and rich in corn, said s, who did her

research while at Emory University. But the toxin also could cause

problems for women who get the recommended 400 micrograms of folic

acid a day. Many bread, pasta, corn and cereal products are fortified

with folic acid, or folate, under a 1998 government mandate.

" You may have adequate folate in your diet, but if the cells can't

take it up, then it won't do any good, " s said.

The U.S. Food and Drug Administration issued fumonisin guidelines to

the corn industry in 2001, suggesting maximum levels for human and

animal corn products, but the limits are not

requirements. " Currently, there is no direct evidence that fumonisins

cause adverse health effects in humans, " the FDA guidelines say.

Fumonisin is concentrated in the germ and hull of the corn kernel,

according to the FDA. Dry milling of corn can leave the toxin in corn

bread, grits and muffins, with low levels in cereals. Wet milling can

allow fumonisin to stay in the gluten and fiber fractions of corn,

usually fed to animals.

" The less-processed the product, the more fumonisin it's going to

have, " said Riley. Corn meal may contain substantial amounts of

fumonisin, he said, while refined products such as corn flakes, corn

starch and high fructose sugar have little or none.