The bioavailability of various nutrients and bioactive substances increases/decreases during various phases of the human life cycle, in particular pregnancy, and lactation. Explain and validate this statement with scientific evidence (provide scientific reference).
The bioavailability of various nutrients and bioactive substances may depend on the hormonal background. Since pregnancy and lactation are characterized by altered blood concentrations of progesterone, estradiol, oxytocin, and prolactin. These alterations are caused by increased metabolic demands. For example, The total additional need for calcium during pregnancy and lactation is 65 g and the additional zinc need is 370 mg. If there were no adjustments in calcium or zinc intake, this would result in a significant decrease in bone calcium and zinc affecting the structure of bones in a pregnant or lactating woman (King, 2001).
King JC. Effect of reproduction on the bioavailability of calcium, zinc and selenium. J Nutr. 2001 Apr;131(4 Suppl):1355S-8S. doi: 10.1093/jn/131.4.1355S..