Fumonisins and Neural Tube Defects (NTD)

The information regarding Fumonisin B1 as a potential teratogen in humans and animals has been  fully discussed by Gelineau-van Waes et al., 2006, 1999 and Marasas et al, 2003.  The major source of exposure to FB 1 is the dietary consumption of contaminated corn crops (i.e. Maize),  particularly along the Texas-Mexico Border, Guatemala, N. China, Transkei region of Africa and other parts of the world (e.g. Central and South America)  where maize is a dietary staple.  The evidence for NTD will be briefly reviewed bellow.  First, we need to understand the what neural tube defects (NTD) means.

NTD: The nervous system (brain and spinal cord) begins as a fold in the dorsum of  the developing animal.  This differentiates into the neuroectocerm becoming the neural fold that fuses forming the neural tube.

"The anatomy of the nervous system" by Stephen Walter Ranson, published W.B. Saunders, 1920

The anterior region becomes the brain and posterior portion forming the spinal cord.   If the anterior neuropore (groove) fails to close then a condition called anencephaly  (absent of the brain) occurs.  Failure of the posterior neural groove to fuse results in spina bifida. The extent of damage that results from spina bifida depends upon the level at which fusion failed, i.e. thoracic vs lumbar.

Anencephaly occurs in about 1 of 1000 births, while all NTD affect approximately   ≤ 3 in 1000 births in the U.S.A.  Let us now review the information available on FB 1 and NTD.

1.  Guatemala, Northern China, Transkei Region of Africa

2. Guatemala: The Guatemalans consume maize tortillas which contain from as low as 3.7 µg to 27 µg of Fumonisins per dry weight.  In Quetzaltenango, Guatemala where high consumption of tortillas occurs, the NTB was found at 106 NTD per 1000 births.

3. Transkei, S. Africa:  In rural regions where maize is is staple in the diet NTD ranges from 35 to 78 per 1000 births.  In contrast, the rates in urban areas of Africa are: Cape town (1.06/1000); Pretoria (0.99/1000); and Johannesburg (1.18/1000).

4. Northern China: In the northern provinces of China the NTD rates are from 57 to 73 per 1000).

5. Texas-Mexico Border:  The Spanish Americans that inhabit the communities along the Texas-Mexico border were noted in 1990-91 to have what appeared to be an elevated incidence of NTD. The NTD rates ranged from 15 to 27.1000 births.  The inhabitants consumed tortillas that were classified into high consumption during the first trimester of pregnancy.  The moderate consumption was classified as moderate (301-400) vs low (≤ 100).  The rate of NTD in the two groups was 2.7 vs 1.5 per 1000 live births. After adjusting for confounders the difference between the two groups was significant with an odds ratio of 2.5, 95 % Confidence Intervals, 1.1-5.3.  The authors concluded that the results suggest that fumonisin exposure increases the risk of NTD, proportionate to does, up to a threshold level, at which point fetal death may be more likely to occur.