ADHD symptoms caused by lead exposure, new study claims
S. L. Baker, features writer
Now two studies -- one published in the January issue of the Journal of Child Psychology and Psychiatry and the other published in the February issue of the journal Current Directions in Psychological Science -- provide the best evidence yet that lead could be one of the biggest culprits behind ADHD.
At very high levels, lead poisoning can cause seizures, coma, and even kill. But it is chronic, long term exposure that is the more common health threat, especially for children. Researchers have previously linked elevated blood levels of lead in kids to problems ranging from mental retardation to learning disabilities. In a statement the media, Oregon Health and Science University researcher Joel Nigg, who co-authored both of the new studies, pointed out that almost all Americans have a low-level exposure to lead, a well-known neurotoxin, making the metal an ideal candidate for causing ADHD.
Although government regulations drastically reduced environmental exposure to lead a generation ago by regulating automobile fuel and paint ingredients, lead is still found in everything from children's costume jewelry and toys to soil and some imported candies. In fact, Dr. Nigg stated that virtually all U.S. children have measurable levels of lead in their bodies.
Research shows link between lead exposure and ADHD diagnoses
The first of Dr. Nigg's recent studies looked at lead levels found in 236 children between the ages of six and 17 diagnosed with ADHD. When these measurements were compared to those of a control group of children without ADHD symptoms, the researchers found that the children diagnosed with hyperactivity/impulsivity symptoms (not inattention) had slightly higher levels of lead in their blood. In a second study, the research team concluded there was a much stronger link between blood lead levels and whether children were reported by parents and teachers to have ADHD symptoms.
According to the press statement, Dr. Nigg has an explanation for how lead could cause ADHD. Bottom line: he thinks lead attaches to sites in the brain's striatum and frontal cortex where the metal causes specific genes to turn on or remain inactive. This disrupts brain activity and alters psychological processes supported by these neurons, he theorizes, and contributes to hyperactivity and lack of vigilance.
What can parents do if they are concerned over their youngsters' exposure to lead? First, be aware that more than 80 percent of American homes built before 1978 have lead-based paint in them, according to the Centers for Disease Control and Prevention (CDC) -- so avoid old paint flakes and paint dust if you remodel. Older homes also frequently have lead in the water pipes or plumbing. That makes tap water a potentially dangerous source of lead.
Although it takes chelation with drugs to remove very high levels of lead from the body, the Minnesota Department of Health's Lead Poisoning Prevention web site offers these additional tips to keep lead levels in children as low as possible through good nutrition:
• Because it is easier to absorb lead on an empty stomach, kids should eat four to six small meals a day.
• Normal levels of iron can protect against lead's harmful effects. So make sure children eat iron-rich foods including raisins, prunes, and other dried fruits.
• Calcium also reduces lead exposure. Serve youngsters calcium-rich foods including yogurt, cheese, spinach, kale, collard greens, and other green leafy vegetables.
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Feb. 16, 2010