May 29, 2014
Science Daily/Penn State
Female mice deprived of dietary zinc for a relatively short time before conception experienced fertility and pregnancy problems more than mice that ingested zinc during the same times, according to researchers.
Zinc deficiency caused a high incidence of pregnancy loss, and embryos from the zinc-deficient diet group were an average of 38 percent smaller than those from the control group. Preconception zinc deficiency also caused approximately half of embryos to exhibit delayed or aberrant development.
Going without zinc prior to ovulation had marked effects on the mice's reproductive functions. Zinc deficiency caused a high incidence of pregnancy loss, and embryos from the zinc-deficient diet group were an average of 38 percent smaller than those from the control group. Preconception zinc deficiency also caused approximately half of embryos to exhibit delayed or aberrant development.
Defects in placenta development are a major cause of delayed embryo/fetal development because the developing embryos do not get enough nutrients to support normal growth. In the zinc-deficient group, the fetal side of the placenta was much less developed. Consistent with delayed development of the placenta, expression of key placental genes was sharply curtailed in mice with zinc-deficient diets.
Collectively, the findings provide evidence for the importance of preconception zinc in promoting optimal fertility and embryo, fetal and placenta development, explained Francisco Diaz, assistant professor of reproductive biology.
"The mineral zinc acts as a catalytic, structural and signaling factor in the regulation of a diverse array of cellular pathways involving hundreds of enzymes and proteins," he said. "Given these wide-ranging roles, it is not surprising that insufficient zinc during pregnancy causes developmental defects in many species. We have known that for a long time.
"However, the role of zinc during the preconception period in promoting later development during pregnancy is not clearly understood."
Diaz noted that this research and follow-up studies may result in a recommendation for women intending to get pregnant to make a special effort to eat foods containing zinc in the weeks prior to ovulation, or even to take zinc supplements. Foods containing higher levels of zinc include meats, seafood and milk. Fruits and vegetables contain lower amounts of the mineral.
"It looks like zinc is similar to folic acid, which is one of the few nutrients that are prescribed before a woman becomes pregnant, because it is needed preconception to ensure the quality of the egg," Diaz said. Zinc is very similar in that it is needed before conception -- so giving multivitamins or supplements to a woman after she has found out that she's pregnant doesn't really address the issue."
"It is certainly important during pregnancy, but if the egg development is already compromised, it may not help that aspect of development. I think our work suggests that you need zinc preconception, just like you need folic acid."
A woman's requirement for zinc is not large -- unlike for calcium or iron -- but there is a fairly rapid turnover of zinc in the body, so humans need a steady supply, Diaz pointed out.
"Actually, our mice become zinc deficient rather quickly," he said. "Animal studies have shown that some tissues can become zinc deficient within a few days."