PubMed Finan, B., Yang, B., Ottaway, N., Smiley, D.L., Ma, T., Clemmensen, C., Chabenne, J., Zhang, L., Habegger, K.M., Fischer, K., Campbell, J.E., Sandoval, D., Seeley, R.J., Bleicher, K., Uhles, S., Riboulet, W., Funk, J., Hertel, C., Belli, S., Sebokova, E., Conde-Knape, K., Konkar, A., Drucker, D.J., Gelfanov, V., Pfluger, P.T., Mller, T.D., Perez-Tilve, D., DiMarchi, R.D., & Tschp, M.H
At dark-night the pineal melatonin plasma levels show a 1020-fold increase in normally entrained individuals
This means they can't absorb B12 from food, though they can from a supplement
A woman can be on her premenopausal stage from early teenage years to her 50s