Dietary/food-bound and waterborne manganese appear to be handled differently when ingested.
Waterborne manganese is more bioavailable.
Quite modest concentrations of manganese in drinking water have been linked to some undesirable health outcomes:
Full text - http://ehp.niehs.nih.gov/1002321/
Few data are available on the risks from exposure to manganese from drinking water. One study in adults (Kondakis et al. 1989) and three studies in children (Bouchard et al. 2007; He et al. 1994; Wasserman et al. 2006) suggest that high manganese levels in water can be neurotoxic. In the Chinese province of Shanxi, 92 children 11–13 years of age, exposed to 240–350 µg manganese/L in water, had elevated hair manganese concentration (MnH), impaired manual dexterity and speed, short-term memory, and visual identification when compared with children from a control area (He et al. 1994). In Bangladesh, higher manganese concentration in water (MnW) was significantly associated with lower intelligence quotient (IQ) in 142 children 10 years of age; the mean MnW was 800 µg/L (Wasserman et al. 2006). In Quebec (Canada), our pilot study on 46 children 6–15 years of age showed that those exposed to higher MnW had significantly higher MnH, and the latter was associated with teacher-reported hyperactive and oppositional behaviors (Bouchard et al. 2007). Finally, two case reports show child manganese intoxication from water containing > 1,000 µg manganese/L, one presenting with attention and memory impairments (Woolf et al. 2002) and the other with neurologic symptoms including a repetitive stuttered speech, poor balance, coordination, and fine motor skills (Sahni et al. 2007).
Manganese concentration in drinking water is not regulated in the United States or Canada. Health-based guidelines for the maximum level of manganese in drinking water are set at 300 µg/L by the U.S. Environmental Protection Agency (EPA) (2004) and at 400 µg/L by the World Health Organization (WHO) (2008).
New-ish (2010) study:
Intellectual impairment in school-age children exposed to manganese from drinking water.
Maryse F Bouchard, Sébastien Sauvé, Benoit Barbeau, Melissa Legrand, Marie-Ève Brodeur, Thérèse Bouffard, Elyse Limoges, David C Bellinger and Donna Mergler
Centre for Interdisciplinary Studies in Biology, Health, Society and Environment, Université du Québec à Montréal, Montreal, Québec, Canada. maryse.bouchard@umontreal.ca
BACKGROUND: Manganese is an essential nutrient, but in excess it can be a potent neurotoxicant. Despite the common occurrence of manganese in groundwater, the risks associated with this source of exposure are largely unknown.
OBJECTIVES: Our first aim was to assess the relations between exposure to manganese from drinking water and children's intelligence quotient (IQ). Second, we examined the relations between manganese exposures from water consumption and from the diet with children's hair manganese concentration.
METHODS: This cross-sectional study included 362 children 6-13 years of age living in communities supplied by groundwater. Manganese concentration was measured in home tap water (MnW) and children's hair (MnH). We estimated manganese intake from water ingestion and the diet using a food frequency questionnaire and assessed IQ with the Wechsler Abbreviated Scale of Intelligence.
RESULTS: The median MnW in children's home tap water was 34 µg/L (range, 1-2,700 µg/L). MnH increased with manganese intake from water consumption, but not with dietary manganese intake. Higher MnW and MnH were significantly associated with lower IQ scores. A 10-fold increase in MnW was associated with a decrease of 2.4 IQ points (95% confidence interval: -3.9 to -0.9; p < 0.01), adjusting for maternal intelligence, family income, and other potential confounders. There was a 6.2-point difference in IQ between children in the lowest and highest MnW quintiles. MnW was more strongly associated with Performance IQ than Verbal IQ.
CONCLUSIONS: The findings of this cross-sectional study suggest that exposure to manganese at levels common in groundwater is associated with intellectual impairment in children
Environ Health Perspect 119:1, 138-43
From the above study:
The present study shows that children exposed to higher concentration of manganese in tap water had lower IQ scores. This finding was robust to adjustment for socioeconomic status indicators and other metals present in water. The association between MnW and IQ scores was strong, with a 6.2 Full Scale IQ point difference between the children exposed to water with 1 and 216 µg manganese/L (median of lowest and highest quintiles). Manganese intake from water ingestion, but not from the diet, was significantly associated with elevated manganese concentration in children’s hair. These findings suggest that manganese exposure from drinking water is metabolized differently than that from the diet and can lead to overload and subsequent neurotoxic effects expressed by intellectual impairments in children...
In this study, dietary manganese intake was similar to the recommended dietary allowance of 1.5–1.9 mg/day for children 6–13 years of age (Food and Nutrition Board 2004). Manganese intake from ingestion of water was very small compared with the amount ingested from foods (by more than two orders of magnitude), yet only intake from water was significantly associated with MnH content. Previous studies have likewise reported a relation between the concentration of manganese in drinking water and hair (Agusa et al. 2006; Bouchard et al. 2007; He et al. 1994; Kondakis et al. 1989). This suggests that there might be differences in the regulation of manganese present in food and water. The chemical form of manganese, notably the valence state and solubility, might modify its toxicity, perhaps because of changes in toxicokinetic properties (Michalke et al. 2007). Moreover, manganese absorption is decreased in the digestive system with concurrent intake of dietary fiber, oxalic acids, tannins, and phytic acids (Gibson 1994)...
Assuming water consumption of 3 L/day, the children in the highest quintile were getting on average about 0.65 mg/day manganese from water - seemingly a very small amount.
QUESTIONS
Manganese is contained in most multivitamins (typically 2-5 mg per daily serve). Is this safe?
Is it possible that the forms of manganese contained in dietary supplements have greater bioavailability than food-bound manganese (similar to the way waterborne manganese is more bioavailable)?
Edited by blood, 10 November 2013 - 12:13 PM.
