The influence of milk intake on the lead toxicity to the sensory nervous system in lead workers.
The dietary calcium supplement has been suggested to children and pregnant women for prevention of lead toxicity, because of lead-calcium interaction. Lead workers were supplied free milk in Taiwan; however, part of workers did not drink milk due to lactose intolerance. The goal of this study is to evaluate the effects of milk-intake on the peripheral nervous system in workers with long-term lead exposure. We measured 181 workers' current perception thresholds (CPT) as neurological outcomes. The outcome variables were then correlated to the subject's milk intake, blood lead levels, and index of long-term lead exposure that was calculated by the subject's serial blood lead data in a period of working duration. The potential confounders, including age, gender, body height, smoking and alcohol consumption, were also collected and analyzed in multiple regressions. 23 workers who reported never or rarely drinking milk, which meant that they have suffered from diarrhea or abdomen discomfort after drinking milk since childhood, had higher blood lead parameters but not statistically significant, and higher thresholds in sensory nerve tests, especially, statistically significance on 5 and 250 Hz of hand CPTs, which represent C fiber and A-delta fiber. In multiple regression models with control of potential confounders, significant protective effects of milk intake were found on reducing hand CPTs, but not on foot CPTs. Our study, using measurement of sensory nerve CPTs, revealed that drinking milk (two bottles a day, about 700 g per day) might have an effect to protect lead peripheral neurotoxicity. The detail biochemical mechanisms need further investigations. However, reduction of occupational lead exposure is the essential way to protect lead neuropathy. The authors did not emphasize that offers of milk to workers could be instead of occupational hygiene efforts. Furthermore, lead workers with lactose intolerance might be more susceptible, and need more industrial hygiene interventions.