Weightless or Pregnant: Maximizing Mineral Metabolism; Kimberly O'Brien Uses the College's New Human Metabolic Research Unit to Find out How Humans Metabolize Calcium and Other Minerals-Whether They Are Pregnant Teens or Weightless Astronauts

By Segelken, Jane Baker | Human Ecology, November 2006 | Go to article overview

Weightless or Pregnant: Maximizing Mineral Metabolism; Kimberly O'Brien Uses the College's New Human Metabolic Research Unit to Find out How Humans Metabolize Calcium and Other Minerals-Whether They Are Pregnant Teens or Weightless Astronauts


Segelken, Jane Baker, Human Ecology


Kimberly O'Brien, an associate professor in the Division of Nutritional Sciences, has been concerned about the nutritional needs of children since she began to understand that there was a huge gap in that knowledge, especially about how minerals are metabolized by the body under situations of physiological stress or increased needs. It was that realization that has led her to focus much of her research on the nutritional effect of pregnancy, particularly in teenagers who become pregnant before they reach age 19.

O'Brien, who joined Human Ecology's faculty in September 2005, uses the college's new 5,007-square-foot, state-of-the-art Frances A. Johnston & Charlotte M. Young Human Metabolic Research Unit for her research. She is also chair of the unit's advisory board. As such, she is responsible for its operation, research direction, and management.

Utilizing the unit's mass spectrometry lab, O'Brien investigates the absorption and metabolism of calcium, as well as iron and zinc. Mass spectrometry is a powerful analytical technique that is used to identify unknown compounds, to quantify known compounds, and to elucidate the structure and chemical properties of molecules. Detection of compounds can be accomplished with very minute quantities. This means that compounds can be identified at very low concentrations in chemically complex mixtures.

In her research, O'Brien found in one study that 30 percent of the adolescents, shortly after giving birth, had low bone mass when compared with expected total body or lumbar spine bone mass for a teen of the same age. In addition, in a separate study involving data obtained in 1,100 pregnant adolescents, O'Brien found that the femur of the developing fetus was significantly shorter in teens with low calcium (dairy) intake when they began prenatal care.

"Teenage mothers are still building much of their total bone mass during these years," O'Brien explains. The unborn baby's need to develop its skeleton may compete with the teenage mother's need for calcium to build her own bones, compromising her ability to achieve peak bone mass that will help protect her from osteoporosis later in life.

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Pregnancy is a calcium drain, and it is not known whether adolescent mothers can regain lost bone after their pregnancy ends and/or they stop breastfeeding, and will be able to go on to achieve their genetic potential in peak bone mass. Nor do experts agree on dietary recommendations for teens or what should be done to maximize the bone health of the teen mom and the baby.

In pregnant adolescents, O'Brien used oral and intravenous stable (nonradioactive) calcium isotopes as tracers to compare rates of calcium absorption during the teens' third trimester of pregnancy and the early postpartum period. The isotopes were then measured using mass spectrometric techniques. Total-body and lumbar spine bone-mineral densities were measured using dual-energy X-ray absorptiometry (DXA).

What O'Brien and colleagues found was that teens who consumed more calcium during pregnancy showed less bone loss when tested postpartum, compared to those with poor or average calcium intakes. They also found that a low calcium intake limits fetal bone growth in pregnant teens. Now she is taking her research and her advanced instrumentation to the next level to better understand the in-utero environment, as well as the long-term impact of early pregnancy and breastfeeding on a teen's ability to reach peak bone mass.

"We need the tools to trace what is happening between the teen and her fetus," O'Brien says. "The more we understand, the better we will know what to recommend to ensure that girls get adequate calcium to prevent or minimize losses and avert any detrimental, long-term effects on bone growth. …

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