In the latest issue of Anticancer Research Garland et al. (Garland. 2011) published a study in which self-reported supplemental vitamin D intake in a cohort of 3,667 men and women from different ethnic backgrounds was assessed and corresponding serum vitamin D levels were measured.
|Figure 1: Reported daily intake of vitamin D vs. measured serum 25(OH)D levels in study cohort of 3,667 subjects (Garland. 2011)|
no intakes of 10,000 IU/d or lower producing 25(OH)D values above the lower-bound of the zone of potential toxicity (200 ng/ml).While you, as a regular visitor of the SuppVersity, already knew that doses up to 10,000 IU are generally save, this is probably the first time you read a reliable number on how much supplemental vitamin D it takes to bring 25(OH)D levels to >=40ng/ml (which is even below the concentration of 60-80ng/ml, where scientists believe the anti-cancer effects of vitamin D set in):
The supplemental dose ensuring that 97.5% of this population achieved a serum 25(OH)D of at least 40 ng/ml was 9,600 IU/d.In view of the authors conclusion that even "universal intake of up to 40,000 IU vitamin D per day is unlikely to result in vitamin D toxicity", and under the assumption that your vitamin D levels, as measured by blood tests, are low, you better invest in some high dose vitamin D supplements if you do not want to pop dozens of pills everyday.