Increased levels of mercury associated with high fish intakes among children from Vancouver, Canada.

OBJECTIVE: To assess exposure to mercury (Hg) among children in population subgroups whose traditional dietary practices include fish. STUDY DESIGN: We determined blood Hg, red blood cell phosphatidylethanolamine omega-3 eicosapentaenoic acid as a marker of fish intake, and assessed indexes of childhood behavior in preschool children 1.5 to 5 years of age (n = 228) living in an ethnically diverse neighborhood in Vancouver, British Columbia, Canada. RESULTS: The median blood Hg was 4.6 nmol/L, range 0-67.9 nmol/L. Twelve (6%) children, all of whom were Chinese, had a blood Hg > 28.9 nmol/L. Blood Hg, total fish intake, and eicosapentaenoic acid were higher among Chinese than Caucasian children; however, higher fish intake did not predict blood Hg. Blood Hg was inversely associated with attentional focusing in children over 3 years of age after adjusting for confounding family variables, iron deficiency anemia, and zinc deficiency. Major sources of fish among Chinese children were imported fish rather than local fish. CONCLUSION: Children from population subgroups within populations not considered at risk may be at increased risk of neurotoxicity caused by Hg exposure from fish.

Perinatal biochemistry and physiology of long-chain polyunsaturated fatty acids.

Docosahexaenoic acid (DHA) and arachidonic acid (ARA) are important structural components of the central nervous system. These fatty acids are transferred across the placenta, are present in human milk, and are accumulated in the brain and retina during fetal and infant development. The high concentrations of DHA in the retina and of DHA and ARA in brain gray matter suggests that these fatty acids have important roles in retinal and neural function. Animal studies have shown that depletion of DHA from the retina and brain results in reduced visual function and learning deficits. The latter effects may be explained by changes in the membrane bilayer that alter membrane-associated receptors and signal transduction systems, ion channel activity, or direct effects on gene expression. DHA can be formed in the liver from alpha linolenic acid, but it is unclear if the rate of DHA synthesis in humans is sufficient to support optimal brain and retinal development. Although there is no evidence that the ability to form ARA from linoleic acid is limiting, supplementation with DHA reduces tissue ARA, possibly creating a conditional need for ARA in infants with a dietary intake of DHA. The amount of DHA in human milk varies widely and is positively correlated with visual and language development in breast-fed infants. Advances in understanding essential fatty acid requirements will benefit from intervention studies that use functionally relevant tests to probe the deficiency or adequacy of physiologically important pools of DHA and ARA in developing infants.

Increased plasma homocysteine and S-adenosylhomocysteine and decreased methionine is associated with altered phosphatidylcholine and phosphatidylethanolamine in cystic fibrosis.

OBJECTIVE: We used a novel approach based on the intersection of phospholipid and methionine metabolism at the S-adenosylmethionine (SAM)-dependent methylation of phosphatidylethanolamine (PE) to study potential alterations in phospholipid metabolism in children with cystic fibrosis (CF). Methyl groups from methionine via SAM are used for sequential methylation of PE to form phosphatidylcholine (PC) with the generation of S-adenosylhomocysteine (SAH) and homocysteine. STUDY DESIGN: Plasma phospholipids and methionine metabolites and plasma and red blood cell phospholipid fatty acids were determined in 53 children with CF and 18 control children. RESULTS: Plasma methionine and the PC/PE ratio was lower and homocysteine, SAH, and PE were higher in children with CF than in control children (P<.001). Plasma methionine was inversely (P<.05) and SAH and homocysteine were positively (P<.001) correlated with the plasma PE. Docosahexaenoic acid (22:6n-3) was significantly lower in plasma phospholipids and triglycerides and in red blood cell PC and PE of children with CF than in control children (P<.05). CONCLUSIONS: These studies demonstrate that methionine metabolism is altered and associated with alteration of the plasma PC/PE ratio in CF. Altered phospholipid and methionine metabolism may contribute to the clinical complications associated with CF.

Docosahexaenoic acid and arachidonic acid enhance growth with no adverse effects in preterm infants fed formula.

OBJECTIVE: To determine if docosahexaenoic acid (DHA) and arachidonic acid (ARA) supplementation influences growth or visual acuity of formula-fed premature infants. STUDY DESIGN: Double-blind, multi-center study of 194 premature infants given preterm formula with no DHA or ARA (control), 0.15% energy DHA, or 0.14% DHA + 0.27% ARA from single-cell triglycerides for at least 28 days and then fed term formula (no DHA or ARA) to 57 weeks postmenstrual age (PMA), with 90 breast-fed term infants as reference. RESULTS: Infants fed DHA+ARA formula gained weight significantly faster (post-hoc analysis) during preterm formula feeding than control infants (34.7 vs. 30.7 g/d) and had weights and weight:length ratios not different from term breast-fed infants at 48 and 57 weeks PMA. Infants fed control or DHA formula had lower body weights than term infants. Red blood cell phosphatidylethanolamine ARA was significantly correlated to weight gain during preterm formula feeding and to weight and length at 40, 48, and 57 weeks PMA (r = 0.19 to 0.24, P =.004-.02). Providing DHA or DHA+ARA during the preterm period had no effect on subsequent visual acuity or incidence of adverse events. CONCLUSIONS: Feeding DHA+ARA from single-cell triglycerides enhances weight gain in formula-fed premature infants with no evidence of adverse effects.