Nee, is niet verplicht;-)
Hoeveel calcium zink nu in de weg gaat zitten, valt niet precies te zeggen.
Het beste vermijd je overdreven veel calcium-inname, gelijk met zink.
Ik ben geen chemicus, maar ik kan me voorstellen dat één en ander ook nog afhangt van de exacte calcium- en zinkverbinding.
Nutrient Interactions
Copper
Taking large quantities of zinc (50 mg/day or more) over a period of weeks can interfere with copper
bioavailability. High intake of zinc induces the intestinal synthesis of a copper-binding protein called metallothionein. Metallothionein traps copper within intestinal cells and prevents its systemic absorption (see
Copper). More typical intakes of zinc do not affect copper absorption and high copper intakes do not affect zinc absorption
(5).
Iron
Supplemental (38-65 mg/day of elemental iron) but not dietary levels of iron may decrease zinc absorption
(8). This interaction is of concern in the management of iron supplementation during pregnancy and lactation and has led some experts to recommend zinc supplementation for pregnant and lactating women taking more than 60 mg/day of elemental iron
(9, 10).
Calcium
High levels of dietary calcium impair zinc absorption in animals, but it is uncertain whether this occurs in humans. One study showed that increasing the calcium intake of postmenopausal women by 890 mg/day in the form of milk or calcium phosphate (total calcium intake, 1,360 mg/day) reduced zinc absorption and zinc balance in postmenopausal women (11), but increasing the calcium intake of adolescent girls by 1,000 mg/day in the form of calcium citrate malate (total calcium intake, 1,667 mg/day) did not affect zinc absorption or balance (12). Calcium in combination with phytic acid reduces zinc absorption. This effect is particularly relevant to individuals who very frequently consume tortillas made with lime (i.e., calcium oxide). For more information on phytic acid, see Food sources.
Folic acid
The
bioavailability of dietary folate is increased by the action of a zinc-dependent
enzyme, suggesting a possible interaction between zinc and folic acid. In the past, some studies found low zinc intake decreased folate absorption, while other studies found folic acid supplementation impaired zinc utilization in individuals with marginal zinc
status(4, 5). However, a more recent study reported that supplementation with a relatively high dose of folic acid (800 mcg/day) for 25 days did not alter zinc status in a group of students being fed low-zinc diets (3.5 mg/day); level of zinc intake did not impair folate utilization in this study
(13).
Vitamin A
Zinc and vitamin A interact in several ways. Zinc is a component of retinol-binding protein, a protein necessary for transporting vitamin A in the blood. Zinc is also required for the enzyme that converts retinol (vitamin A) to retinal. This latter form of vitamin A is necessary for the synthesis of rhodopsin, a protein in the eye that absorbs light and thus is involved in dark adaptation. Zinc deficiency is associated with decreased release of vitamin A from the liver, which may contribute to symptoms of night blindness that are seen with zinc deficiency
(14, 15).