Apologies for the lack of a detailed response. I had to speak to the development team.
Plant origin foods such as tea, whole grain cereals, some dark green leafy vegetables, and nuts contain high amounts of manganese. How- ever, these products often concurrently contain high amounts of tannins, oxalates, phytates and fiber. These dietary constituents have been found to inhibit the absorption of other minerals; hence, might have a negative effect on manganese absorption.
Absorption of such minerals as iron, copper, phosphorus and calcium i s superior from animals products than from plant-originfoods. As reported by Kies et al. (in this book), manganese apparently is better absorbed by humans from meals containing meat and fish than from those contain- ingplant-proteinreplacementproducts.
Evaluations of standard diets from the United States, England, and Holland reveal average daily intakes of 2.3-8.8 mg Mn/day. Depending on individual diets, however, a normal intake may be well over 10 mg Mn/day, especially from a vegetarian diet. While the actual intake is higher, the bioavailability of manganese from a vegetarian diet is lower, thereby decreasing the actual absorbed dose. This is discussed in more detail in the Additional Studies / Comments Section.
Another issue of great importance to consider in the risk assessment for manganese concerns the bioavailability of different forms of manganese consumed under different exposure conditions. Various dietary factors as well as the form of manganese can have a significant bearing on the dose absorbed from the GI tract. Many constituents of a vegetarian diet (e.g., tannins, oxalates, phytates, fiber) have been found to inhibit manganese absorption presumably by forming insoluble complexes in the gut. In addition, high dietary levels of calcium or phosphorus have been reported to decrease manganese absorption. Individuals who are deficient in iron demonstrate an increase in manganese absorption. It is also recognized that manganese uptake and elimination are under homeostatic control, generally allowing for a wide range of dietary intakes considered to be safe.
Manganese found in vegetable products will have a lower bioavailability than that found in supplemental form. Due to the high quantity of vegetable based ingredients in Soylent, the absorption of manganese from these sources is expected to be low in comparison to the manganese sulfate in the vitamin/mineral premix. To ensure the adequate quantities of bioavailable forms of manganese, we listed only the supplemental form on the label, though small amounts of the manganese found in brown rice protein and oat flour can be absorbed.
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