Clinical Trials Evaluating Turmeric Dietary Supplement Treatment of Obesity-Associated Disorders of Glucose Metabolism or Bone

Abstract

Abstract Curcumin-enriched turmeric dietary supplements (DS) are one of the top selling botanicals in the United States. Recent observational studies by our research group have documented turmeric DS use by almost a quarter of breast cancer survivors concurrent with anti-estrogen therapy and a third of those with rheumatoid arthritis. However, some recent reviews have suggested that there is no evidence of any biological effect of curcumin in humans, albeit without rigorous review of published reports. A scoping review of the literature was therefore undertaken to identify clinical trials testing oral curcumin-containing turmeric dietary supplements in humans. Using a defined search strategy, eight databases were reviewed (thru 05/29/2019), identifying 4767 potential English language reports for inclusion, from which all but n = 315 were excluded after review by three independent observers. The majority of studies reported significant effects of turmeric DS on clinical endpoints. Obesity-associated disorders of glucose and lipid metabolism (n =69, including type 2 diabetes mellitus [T2DM], metabolic syndrome and/or hyperlipidemia) or musculoskeletal disorders (n = 46), of which half related to osteoarthritis, were among the most commonly studied diseases in turmeric DS clinical trials, with reported benefits related to inhibition of inflammation, amelioration of hyperlipidemia, increases in adiponectin, and improved glucose control. As is common for botanical clinical trials, the quality of the studies were variable due to lack of clarity about product content as well as study design (e.g. only 60% of T2DM trials and 74% of osteoarthritis trials were randomized, placebo-controlled and double-blinded). However, particularly with respect to treatment of osteoarthritis and metabolic consequences of insulin resistance, the preponderance of the data were suggestive of beneficial physiologic effects. Given the current widespread use of turmeric DS by Americans and existing evidence of possible clinical benefits, further evaluation of turmeric DS efficacy and safety may be warranted.