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The number of clinical trials on turmeric—not in rats or petri dishes—but with actual people continues to climb—dozens a year, and most were randomized, double-blind, placebo-controlled trials––the gold standard for clinical trials. There have been so many trials published that there are now umbrella reviews on turmeric. You’ve heard of systematic reviews and meta-analyses, pooling multiple studies together. Well, an umbrella review can be like a systematic review and meta-analysis of systematic reviews and meta-analyses, meaning pooling multiple meta-analyses together, placing them at the very top of the hierarchy of evidence pyramid.
Dr. Greger has covered the benefits of the turmeric pigment curcumin for knee osteoarthritis––in some cases working as well as or even better than anti-inflammatory drugs and painkillers, without their side effects of injuring our gut, and in the 10 years since, a meta-analysis of 11 meta-analyses on the efficacy of curcumin for relieving osteoarthritis strongly supports that it can relieve pain, as well as improve joint mobility and shorten medication use. And more isn’t necessarily better; low-dose extracts appear to have similar pain relief effects to high-dose extracts. What about other arthritic conditions?
A pilot study in 2012 of 45 patients showed promise for rheumatoid arthritis, finding it is actually more effective at alleviating pain compared to the leading drug, and a recent meta-analysis including more than 500 patients found the same: curcumin was beneficial both for inflammation levels and clinical symptoms. Curcumin’s ability to lower some inflammatory biomarkers, like C-reactive protein, a marker of systemic inflammation, extends more broadly to patients with autoinflammatory conditions, and the stronger effects seemed to appear at relatively smaller doses.
You may recall that Dr. Greger talked about a 2012 study in prediabetic individuals where zero percent of those taking curcumin extract for nine months progressed to type 2 diabetes, while 16% of those on placebo did. There have been a lot of studies since. Fourteen systematic reviews and meta-analyses containing 61 individual randomized controlled trials were included in this umbrella review. Fasting blood sugars and HbA1c, a measure of longer-term blood sugar control, both improved no matter what formulation of turmeric or curcumin was consumed. But the quality of the studies was low, not including important information like their funding sources, and the types of turmeric/curcumin preparations were wide-ranging. What if we want to know the impact of turmeric alone, not a special curcumin formulation that supplement companies can charge us a bunch of money for? This dose-response meta-analysis breaks it out for us, with turmeric resulting in better results than curcumin-only treatments. Note that benefit was found for a variety of participants, not only those with diabetes,
What about cholesterol? Here’s another umbrella review. Although the authors concluded that curcumin could have ameliorating effects, there was only a half-point drop in LDL. Lower doses may work better, but a two-point drop is still nothing to write home about.
Turmeric curcumin “blocks obesity” in mice fed a high-fat diet, What about people? In an umbrella review of 50 randomized controlled trials, curcumin supplementation significantly decreased BMI, body weight, and waist circumference. It was significant statistically, but how much of a difference did it really make? A loss of about a half kilogram, or a little more than a pound of body weight. Waist circumference, a measure of abdominal obesity, decreased by about a centimeter, and triple the effect in trials with whole turmeric relative to curcumin extracts. So, for those with obesity or type 2 diabetes and wanting to lose weight, the primary prescription is lifestyle modification, and some turmeric on the side might be helpful, but may not make that much difference.
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