Sources of manganese
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Sources of Manganese: Dietary and Environmental Insights
Dietary Sources of Manganese
Manganese in Human Diets
Manganese (Mn) is an essential trace element that plays a crucial role in various biological processes, including bone formation, amino acid metabolism, and antioxidant defense 27. The primary dietary sources of manganese include plant-based foods such as green tea, unrefined cereals, legumes, and vegetables . The adequate intake levels for manganese vary by region, with Japanese diets typically containing higher manganese levels compared to North American diets due to the higher consumption of manganese-rich foods .
Bioavailability of Manganese in Animal Diets
In animal nutrition, manganese is often supplemented in diets to ensure adequate intake. Studies on lambs have shown that both organic and inorganic sources of manganese, such as manganese sulfate (MnSO4) and manganese chelate of glycine hydrate (Mn-Gly), are effective in increasing manganese concentrations in tissues like the liver and plasma 13. However, the source of manganese does not significantly affect the overall tissue deposition or the activity of manganese-containing enzymes .
Environmental Sources of Manganese
Natural and Industrial Sources
Manganese is naturally found in the environment and is a critical component in various industrial processes. It is the fourth most important metal for industrial use, particularly in metal making . Manganese deposits are primarily derived from hydrothermal vents associated with volcanic rocks, with significant deposits found in sedimentary and karst-hosted environments .
Environmental Contamination
Environmental contamination of manganese can occur through industrial activities, such as mining and metal refining. For instance, in Yancheng, China, high levels of manganese in river sediments were linked to wastewater discharge from nearby stainless steel factories, leading to elevated manganese levels in drinking water sources . This contamination poses a risk to human health, particularly affecting the nervous system .
Health Implications of Manganese Exposure
Neurotoxicity and Safe Intake Levels
While manganese is essential for health, excessive intake can lead to neurotoxicity, manifesting in symptoms similar to Parkinson's disease 49. The European Food Safety Authority (EFSA) has established a safe level of manganese intake at 8 mg/day for adults, with lower levels recommended for other population groups to avoid adverse health effects .
Manganese and Cardiometabolic Health
Recent studies have begun to explore the relationship between manganese intake and cardiometabolic health. There is emerging evidence suggesting an inverse association between manganese intake and the risk of type 2 diabetes and metabolic syndrome . However, more research is needed to fully understand these associations and their implications for dietary recommendations.
Conclusion
Manganese is a vital nutrient with significant roles in both human and animal health. It is predominantly sourced from plant-based foods in human diets and supplemented in animal feeds. Environmental sources, particularly industrial activities, can lead to contamination and pose health risks. Balancing manganese intake is crucial to harness its benefits while avoiding potential neurotoxic effects. Further research is essential to refine dietary guidelines and understand the broader health implications of manganese exposure.
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