07/10/2026
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How fast nutrients leave your body, and how long they take to come back. Swipe for both.
Slide 1, leaving: how long until half of the body’s store is gone once none comes in. Thiamine (vitamin B1) is the quickest at 9 to 18 days, then vitamin C at 16 to 24 days and omega-3 EPA in red blood cells at about a month. Folate takes 3 to 5 months. Iron has no regulated exit, only small daily losses: dividing typical stores by measured losses, half of a woman’s stores would go in 4 to 7 months and half of a man’s in over a year. B12 lasts longest, 1 to 2 years.
Slide 2, refilling: how long to get halfway back from a low start with steady daily intake. Blood comes back first: omega-3 EPA in plasma in 3 to 5 days, vitamin D and folate in 2 to 3 weeks, vitamin C within days to 3 weeks depending on the amount. Cells and stores take longer: EPA in red blood cells about a month, folate in red blood cells 6 to 11 weeks, and iron stores 2 to 3 months even on iron tablets, after hemoglobin is half back in 2 to 3 weeks.
Read together: omega-3 EPA in red blood cells moves at the same pace both ways, half in about a month. Vitamin D appears only on slide 2: its washout data are weak, but its refill is well measured.
These are averages from small groups of mostly healthy adults. Most whole-body loss measurements come from tracer studies done between the 1960s and 2018, which current references (US Institute of Medicine, WHO, EFSA, Nordic Nutrition Recommendations 2023) still use. The refill trials mostly gave supplements or fortified foods to people who started low, and the iron trials were mostly in women. Half gone is not the same as deficient, and halfway back is not full. Both time axes are stretched so days and years fit on one screen.
Sources: IOM Dietary Reference Intakes (1998, 2000, 2001); WHO/FAO 2004; Katan et al. 1997, J Lipid Res; Gregory et al. 1998, J Nutr; Cai et al. 2018, Nutr Metab; Carr et al. 2013, Am J Clin Nutr; Crider et al. 2019, Nutrients; Li et al. 2020, JAMA Netw Open; Best et al. 2021, Am J Clin Nutr; Symington et al. 2026, Am J Clin Nutr
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