A recent pilot study found that curcumin, in certain patients with monoclonal gammopathy of undetermined significance (MGUS), decreases the paraprotein load and the urinary N-telopeptide of type 1 collagen bone turnover marker. While this result is encouraging, the easy availability of the food component turmeric, containing curcumin, may lead to intake by MGUS patients without medical supervision. Curcumin is generally considered safe. Nevertheless, it is known that curcumin inhibits interleukin-12 production in dendritic cells, thereby dampening the Th1 response. It is also well established that Th1 cells are protective against invading pathogens and tumors. The present study describes a case in which bronchitis developed upon turmeric intake for gastrointestinal complaints. While one case does not provide proof of curcumin toxicity, a thorough literature overview suggests that turmeric may have an immunosuppressive effect, notably in patients with a compromised immune system. A warning against the use of turmeric or curcumin without medical supervision in immunocompromised patients seems therefore very opportune. Patients with MGUS, in whom the levels of non-affected immunoglobulins are reduced, should be carefully monitored for toxicity when curcumin is administered.

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