Nutritional Requirements for Manganese
Manganese (Mn) is a ubiquitous trace mineral that is essential for living organisms. This mineral is a cofactor of enzymes such as superoxide dismutase and arginase. It assumes a significant role in the metabolism of carbohydrates, amino acids and cholesterol, the formation of bone, digestion, and development. Food sources include whole grains, cereals, green leafy vegetables, nuts, and tea. Approaches to assess Mn requirements include metabolic balance, blood levels, and response of biomarkers. In the United States, the adequate intake (AI) of Mn is 1.8 and 2.3 mg day−1 for women and men, respectively. Negative balance has been reported in numerous studies, where Mn intake was greater than the AI; thus, the adequacy of current dietary recommendations is unclear. Factors that influence Mn requirements include life stage and gender, bioavailability (fiber, phytates, mineral interactions, polyphenolic compounds), and international considerations. Deficiency of Mn has been associated with adverse health conditions including dermatitis, osteoporosis, dyslipidemia, diabetes, metabolic syndrome, hypertension, epilepsy, cancer, asthma, problems with cognitive function, and poor birth outcomes. Toxicity of Mn may be a potential problem with contaminated drinking water, parenteral nutrition, individuals with hepatic dysfunction, and soy formula-fed infants. An understanding of Mn nutrient requirements is important for achievement of optimal health.