Large doses (8-12 grams/day) of curcumin can cause adverse events like diarrhea, rash, and headache in up to 30% of participants, while lower doses are likely benign.

“large doses 8-12 grams per day necessary to provide quote-unquote adequate systemic exposure were administered for example phase one dose escalation study was carried out where three subjects in each of eight cohorts were treated with a single dose of commercial milled curcumin mixture over a range of escalating doses and they found adverse events diarrhea rash headache in 30 percent of the trial participants”