Your body uses the mineral manganese for nerve and brain function, keeping your blood sugar levels normal, calcium absorption, turning your food into energy, blood clotting and creating sex hormones, connective tissue and bone. The mineral zinc plays a role in immune function, growth and development, wound healing, the senses of smell and taste, cell division and the creation of DNA and protein. However, these minerals are needed only in small amounts. Too much of either zinc or manganese can be toxic.
The adequate intake level for manganese for adults is 2.3 mg per day for men, 1.8 mg per day for women, 2 mg per day for pregnant women and 2.6 mg per day for breastfeeding women. The recommended dietary allowance for zinc is 11 mg per day for men, 8 mg per day for women, 11 mg per day for pregnant women and 12 mg per day for breastfeeding women. Try to meet these recommendations through food rather than through supplements.
There are no reports of manganese toxicity just from food sources, according to the Linus Pauling Institute. Most cases of manganese toxicity are due to inhaled manganese, high levels of manganese in the solutions used for total parenteral nutrition, or feeding tubes, contaminated water or high intakes of supplements. Do not consume more than the tolerable upper intake level of manganese, or 11 mg per day, from supplements.
Do not consume more than the tolerable upper intake levels of zinc, which is 40 mg per day for adults, unless you are under the supervision of a doctor. Most people who suffer from zinc toxicity have consumed high levels of zinc through supplements or contaminated food, not from eating foods that naturally contain zinc, notes the Linus Pauling Institute. High levels of zinc consumption over an extended period of time can cause copper deficiency.
Meet the recommendations for vitamins and minerals by following a healthy diet to limit the risk of toxicity from any one nutrient. It is unlikely you will get toxic amounts of nutrients from food alone, and foods contain multiple nutrients as well as calories to provide you with energy. If you are worried about your intake of certain vitamins and minerals, stick to a multivitamin that doesn't provide more than 100 percent of the RDA for any nutrients rather than taking supplements of individual nutrients.