Curcuma longa-tumeric-who hasn’t heard of this vibrant golden spice?! Like many botanical medicines with a history of significant traditional use, turmeric has been turned to for millennia for a myriad of different health complaints. But turmeric (or its popular bioactive constituent curcumin) has been able to affirm its treatment for many of these health indications through an impressive accumulation of clinical research that eclipses what is available for most other phytomedicines.
We all know it’s good for a whole lot of stuff. So much so that it is not worth referencing in this particular discussion the many things it has been demonstrated to treat effectively. However, with the list of validated conditions in which turmeric products have been shown to be beneficial constantly growing, as this supplement becomes even more commonly used, the incidence of its reported adverse events is likely to increase as well. One such example is a recent case study, authored by Smith and Ashar,1 that details a potential side effect of turmeric supplementation that has never been reported in human clinical literature before: iron deficiency anemia.
Turmeric has been shown to inhibit iron availability in simulated studies, in a dose-dependent manner, up to as much as 90%.2 In mice, curcumin has been shown to decrease tissue iron concentrations by over 50%, inducing iron deficiency anemia.3 Curcumin binds ferric iron and reduces the synthesis of ferritin and hepcidin in the liver.4 But despite the many long-term studies that have been conducted in humans, iron deficiency anemia has never been reported as an adverse event, though there has been some subjective consumer reports that have claimed resolution of anemia with stopping turmeric supplements.5
In Smith and Ashar’s case report, a 66 year old man who had been treated for a biochemical recurrence of prostate cancer had developed arthritis and myopathy secondary to the treatment he received. He decided to self-initiate turmeric supplementation to address these health concerns, taking 6 538 mg capsules of turmeric extract daily. The patient had a history of iron deficiency anemia for at least 4 months prior to initiating turmeric supplementation and was anemic when he began supplementation. He had been taking an oral iron supplement during these 4 months as well and his iron, ferritin and hemoglobin status continued to decline. Appropriate medical work-up was done to evaluate for blood loss; endoscopies and Hemoccult were normal. It is relevant to note that the patient had gone through a transient period of impaired lung function prior to and during this time of unknown etiology. After approximately 8 weeks of the turmeric supplementation, the patient read about a potential interaction with iron and discontinued the supplement. Within 2 weeks of stopping, his iron, ferritin and hemoglobin all began to steadily increase and returned to normal.
This case is relevant because it not only brings to light a potential adverse effect of a therapeutic intervention many practitioners commonly prescribe, but it is also particularly significant that this case involved a cancer patient, a certain patient demographic that has a higher likelihood of using turmeric products and is at higher risk of developing complications associated with iron deficiency anemia.
The main limitation of this case study is that, of course, the turmeric was never actually challenged to see if it induced anemia. The patient was never put back on the turmeric and observed to see if the anemia recurred; it was just observed that the previously existing anemia resolved after discontinuing the turmeric for 2 weeks and speculated that this was due to this supplement being removed. So, did this really happen due to the turmeric or was it all coincidence? The case raises a number of other questions too. The language referencing the supplement in the article is ambiguous, sometimes saying “turmeric” was used, at other times saying “turmeric extract” was used. Curcumin is never referenced, however. So what was this patient actually taking? Most turmeric supplements available now are curcumin extracts and most clinicians would recommend curcumin for therapeutic benefit. While literature does suggest that curcumin also possesses these iron-chelating properties in addition to the whole-spice turmeric,6 to what degree of difference in the potency of this effect is there between the whole-spice and the extracted constituent? Could the reason this effect has not been reported before is due to the relatively high use of curcumin supplements comparative to turmeric supplements? If this is more of a turmeric issue than a curcumin issue, then how much do we really care? The patient in this case is also atypical from the general population, in that he had cancer and there was also a previous history of iron deficiency anemia. How much did his health status pre-dispose him to developing anemia and was this what was actually responsible? The timeline this case was reported in, as well, doesn’t provide us with any information beyond the short period of time after the patient stopped the turmeric. We have no idea if the iron deficiency recurred again in 2 months or if the patient has continued to do fine, because there was no long-term reporting of the patient after the turmeric was discontinued.
While this particular case study is not compelling enough to demonstrate a direct causation of iron deficiency anemia with turmeric supplementation, the potential for this effect to happen is of clear significance to clinicians. Dealing with patient populations that are commonly already sub-optimal in iron may make physicians more closely evaluate the necessity of turmeric in their treatment recommendations and should prompt more informed monitoring of iron status in patients on this therapy.
But the fact that turmeric has the potential to decrease iron absorption and lower iron values is not all bad! In a clinical setting in which these effects are desired, turmeric may be a treatment to consider. For example, in iron storage disorders turmeric may provide direct benefit to controlling iron levels. Its anti-inflammatory and hepatoprotective actions would also make this an ideal treatment for these patients. Hemolytic disorders like sickle cell disease might benefit from this therapy for these reasons, as well.