Bone Turnover, Micronutrient Intake, and Blood Lead Levels in Women, NHANES
Bone Turnover, Micronutrient Intake, and Blood Lead Levels in Women, NHANES
Background: Blood lead levels (BLLs) have been shown to increase during periods of high bone turnover such as pregnancy and menopause.
Objectives: We examined the associations between bone turnover and micronutrient intake with BLLs in women 20–85 years of age (n = 2,671) participating in the National Health and Nutrition Examination Survey, 1999–2002.
Methods: Serum bone-specific alkaline phosphatase (BAP) and urinary cross-linked N-telopeptides (NTx) were measured as markers of bone formation and resorption, respectively. Lead was quantified in whole blood. The association between tertiles of BAP and NTx, and BLLs was examined using linear regression with natural log-transformed BLLs as the dependent variable and interpreted as the percent difference in geometric mean BLLs.
Results: In adjusted analyses, mean BLLs among postmenopausal women in the upper tertiles of NTx and BAP were 34% [95% confidence interval (CI), 23%–45%] and 30% (95% CI, 17%–43%) higher than BLLs among women in the lowest tertiles of NTx and BAP, respectively. These associations were weaker, but remained statistically significant, among premenopausal women (NTx: 10%; 95% CI, 0.60%–19%; BAP: 14%; 95% CI, 6%–22%). Within tertiles of NTx and BAP, calcium intake above the Dietary Reference Intake (DRI), compared with below the DRI, was associated with lower mean BLLs among postmenopausal women but not premenopausal women, although most of the associations were not statistically significant. We observed similar associations for vitamin D supplement use.
Conclusions: Bone resorption and bone formation were associated with a significant increase in BLLs among pre- and postmenopausal women.
Despite successful efforts to reduce sources of lead exposure over the past several decades, lead remains ubiquitous in the environment, providing a source of exposure to humans. In addition, lead bioaccumulates in bone, where it has a half-life of approximately 12–27 years, providing another source of exposure when it is mobilized (Bergdahl et al. 1998; Gerhardsson et al. 1993). Previous research has shown that blood lead levels (BLLs) increase during periods of high bone turnover such as pregnancy (Gulson et al. 1998, 1999; Hertz-Picciotto et al. 2000; Manton et al. 2003; Rothenberg et al. 1994), lactation (Gulson et al. 1998, 1999; Manton et al. 2003; Téllez-Rojo et al. 2002), menopause (Garrido-Latorre et al. 2003; Gulson et al. 2002; Korrick et al. 2002; Silbergeld et al. 1988; Symanski and Hertz-Picciotto 1995), and severe weight loss (Riedt et al. 2009), with levels modified by calcium intake (Ettinger et al. 2009; Hernandez-Avila et al. 2003; Hertz-Picciotto et al. 2000; Janakiraman et al. 2003). This increase in BLLs may put an individual at an increased risk for a variety of adverse health outcomes, because there is currently no known safe level of lead in blood.
To date, few studies have examined the association between markers of bone resorption and formation, and BLLs. Among pregnant women (n = 193) with high bone lead levels, Téllez-Rojo et al. (2004) found that plasma and whole BLLs increased significantly with increased bone resorption as measured by cross-linked N-telopeptides (NTx). Within a population of Japanese women (n = 1,225), investigators observed significantly higher BLLs in relation to bone formation levels above the median among perimenopausal women regardless of bone resorption levels, but not among pre- or postmenopausal women (Machida et al. 2009).
Because bone is continuously being remodeled, resulting in a constant, low-level exchange of lead between the blood and bone compartments (Rabinowitz et al. 1976), periods of low to moderate bone turnover may also be of importance among women with high bone lead levels (Silbergeld et al. 1993); however, little research has been done in this area. For this reason, as well as ongoing concerns associated with the adverse health effects of increased BLLs among adults (Berg 2009), we examined associations among bone formation and resorption, micronutrient intake, and BLLs in women 20–85 years of age participating in the National Health and Nutrition Examination Survey (NHANES) 1999–2002.
Abstract and Introduction
Abstract
Background: Blood lead levels (BLLs) have been shown to increase during periods of high bone turnover such as pregnancy and menopause.
Objectives: We examined the associations between bone turnover and micronutrient intake with BLLs in women 20–85 years of age (n = 2,671) participating in the National Health and Nutrition Examination Survey, 1999–2002.
Methods: Serum bone-specific alkaline phosphatase (BAP) and urinary cross-linked N-telopeptides (NTx) were measured as markers of bone formation and resorption, respectively. Lead was quantified in whole blood. The association between tertiles of BAP and NTx, and BLLs was examined using linear regression with natural log-transformed BLLs as the dependent variable and interpreted as the percent difference in geometric mean BLLs.
Results: In adjusted analyses, mean BLLs among postmenopausal women in the upper tertiles of NTx and BAP were 34% [95% confidence interval (CI), 23%–45%] and 30% (95% CI, 17%–43%) higher than BLLs among women in the lowest tertiles of NTx and BAP, respectively. These associations were weaker, but remained statistically significant, among premenopausal women (NTx: 10%; 95% CI, 0.60%–19%; BAP: 14%; 95% CI, 6%–22%). Within tertiles of NTx and BAP, calcium intake above the Dietary Reference Intake (DRI), compared with below the DRI, was associated with lower mean BLLs among postmenopausal women but not premenopausal women, although most of the associations were not statistically significant. We observed similar associations for vitamin D supplement use.
Conclusions: Bone resorption and bone formation were associated with a significant increase in BLLs among pre- and postmenopausal women.
Introduction
Despite successful efforts to reduce sources of lead exposure over the past several decades, lead remains ubiquitous in the environment, providing a source of exposure to humans. In addition, lead bioaccumulates in bone, where it has a half-life of approximately 12–27 years, providing another source of exposure when it is mobilized (Bergdahl et al. 1998; Gerhardsson et al. 1993). Previous research has shown that blood lead levels (BLLs) increase during periods of high bone turnover such as pregnancy (Gulson et al. 1998, 1999; Hertz-Picciotto et al. 2000; Manton et al. 2003; Rothenberg et al. 1994), lactation (Gulson et al. 1998, 1999; Manton et al. 2003; Téllez-Rojo et al. 2002), menopause (Garrido-Latorre et al. 2003; Gulson et al. 2002; Korrick et al. 2002; Silbergeld et al. 1988; Symanski and Hertz-Picciotto 1995), and severe weight loss (Riedt et al. 2009), with levels modified by calcium intake (Ettinger et al. 2009; Hernandez-Avila et al. 2003; Hertz-Picciotto et al. 2000; Janakiraman et al. 2003). This increase in BLLs may put an individual at an increased risk for a variety of adverse health outcomes, because there is currently no known safe level of lead in blood.
To date, few studies have examined the association between markers of bone resorption and formation, and BLLs. Among pregnant women (n = 193) with high bone lead levels, Téllez-Rojo et al. (2004) found that plasma and whole BLLs increased significantly with increased bone resorption as measured by cross-linked N-telopeptides (NTx). Within a population of Japanese women (n = 1,225), investigators observed significantly higher BLLs in relation to bone formation levels above the median among perimenopausal women regardless of bone resorption levels, but not among pre- or postmenopausal women (Machida et al. 2009).
Because bone is continuously being remodeled, resulting in a constant, low-level exchange of lead between the blood and bone compartments (Rabinowitz et al. 1976), periods of low to moderate bone turnover may also be of importance among women with high bone lead levels (Silbergeld et al. 1993); however, little research has been done in this area. For this reason, as well as ongoing concerns associated with the adverse health effects of increased BLLs among adults (Berg 2009), we examined associations among bone formation and resorption, micronutrient intake, and BLLs in women 20–85 years of age participating in the National Health and Nutrition Examination Survey (NHANES) 1999–2002.
Source...