Excessive Fat-Soluble Vitamins
Disruption of Normal Fetal Brain Development
Pregnant women should be aware that over-dosage of certain vitamins may present a potential risk to the fetus' developing organ systems, especially the brain.
There are numerous animal experiments that demonstrate potential damage to the embryo or fetus after the mother has been given excessive doses of certain nutrients. Overdosing a pregnant animal with vitamin A will have teratogenic effects . Similarly, an overdose of vitamin D can result in supravalvular aortic stenosis in guinea pigs and presumably also in humans. Toxicity from overdosing during pregnancy with these two fat-soluble vitamins has been recognized for many years (1).
Fat-soluble vitamins are stored in the liver where they are available for the release when maternal intake is insufficient. Therefore, maternal deficiency is rare, but because urinary excretion is low, over-dosage presents this potential risk of fetal toxicity (2,3).
Among the more important developments in the area of nutrition and reproduction is the recognition of a relationship between the timing of nutrition and its impact upon developing organ systems, especially the brain (2,4-6).
Normal human brain development consists of six basic stages: (1) primary and secondary neurulation, (2) proencephalic development, (3) neuronal proliferation, (4) neuronal migration,(5) organizational events, and (6) myelination. The time of occurrence for each stage is critical and for the purpose of this review, an excessive nutritional status during one or more of these stages may lead to a disruption of normal brain development (LIST 3) (2).
Normal Human Brain Development ; Time of Occurrence
Formation of the brain structure; 0-20 weeks of gestation
Primary and secondary neurulation; 3-4 weeks of gestation
Proencephalic development; 4-12 weeks of gestation
Neuronal migration; 5-20 weeks of gestation
Neuronal proliferation and brain growth; 0 weeks of gestation - 12 years of life
Organizational events; 12 weeks of gestation -12 years of life
Differentiation, maturation, synaptogenesis; 16 weeks of gestation - 12 years of life
Apoptosis; 24 weeks of gestation - 1 month of life
Myelination; 13 weeks – 30 years of life
LIST 3. Normal Human Brain Development and Time of Occurrence (2).
Two essential cofactors for brain development include vitamin A and folate (5,6).
References:
1. Guthrie HA. Introductory Nutrition, 4th ed. Toronto : CV Mosby Company, 1979.
2. Polin RA, Fox WW, Abman SH. Fetal and Neonatal Physiology, 3rd ed. Saunders. 2004;2:1771-1782
3. Combs GF. The Vitamins: Fundamental Aspects in Nutrition and Health. New York. Academic Press.
1992:388-500.
4. Vohration A, Siega-Riz Am, Scultz Da, Thorp JM. MultiVitamin Use and the Risk of Preterm Birth. Am J
Epid. 2004;160:886-892.
5. Halpern SL. Quick Reference to Clinical Nutrition. Toronto. J.B. Lippincott Company, 1989.
6. Mann J, Truswell SA. Essentials of Human Nutrition. OxfordUniversity press. 1998:194-476.
## Related articles ## : Nutrient Requirements:Detrimental Effects from Excessive Intake
## Related articles ##: Overdose of Vitamin A:Teratogenic Effects on the Fetus
