Spice and Sugar: Curcumin and Type 2 DM

Abstract & Commentary

By Russell H. Greenfield, MD. Medical Director, Integrative Oncology Services, Carolinas Medical Center, Charlotte, NC; Clinical Assistant Professor, University of North Carolina School of Medicine, Chapel Hill, NC; Visiting Assistant Professor, University of Arizona College of Medicine, Tucson, AZ. Dr. Greenfield reports no financial relationships relevant to this field of study. This article originally appeared in the September issue of Integrative Medicine Alert.

Synopsis: Results of this year-long intervention trial suggest that an ethanolic extract of curcumin could, together with appropriate dietary and lifestyle changes, play a role in slowing the progression from prediabetes to type 2 diabetes.

Source:Chuengsamarn S, et al. Curcumin extract for prevention of type 2 diabetes. Diabetes Care 2012; Jul 6. [Epub ahead of print].

Strategies aimed at preventing type 2 diabetes mellitus (DM) typically focus primarily on diet and lifestyle changes, together with select drug therapy where appropriate. The rationale is reasonable, but results have been largely disappointing. An increasing number of people are diagnosed with type 2 DM each year and not just in industrialized nations. There is urgent need for safe, economical interventions that can effectively help prevent, or at least delay, further spread of this scourge. In an attempt to answer the need, the authors of this 12-month, randomized, double-blind, placebo-controlled, cohort trial explored the effects of an ethanolic extract of curcumin on Thai people older than 35 years with known prediabetes.

The study was performed at a major university medical center in Thailand where subjects (n = 240) with prediabetes based on American Diabetes Association (ADA) guidelines were screened for participation (n = 237 were enrolled). Exclusion criteria included the use of oral hypoglycemic agents as well as use of herbal remedies. Subjects were advised that the study aimed to compare two different interventions, and all began their participation by attending a 20- to 30-minute, one-on-one educational session with an instructor detailing the benefits of a healthy diet and lifestyle program they should try to follow. There was no further intervention for 3 months. Participants were randomly assigned to take either a) three placebo capsules twice a day, or b) three capsules of an extract of curcumin twice daily for a period of 9 months both beginning 3 months after the educational session. Compliance was determined via pill count at follow-up visits at 3, 6, and 9 months. Curcuminoid content of the curcumin extract capsules was 250 mg per capsule. Each batch of capsules containing curcumin extract was subjected to High Performance Thin Layer Chromatography (HPTLC) to ensure consistency over the 9-month course of treatment. Capsules containing the extract or placebo were identical in appearance and were manufactured by the Government Pharmaceutical Organization of Thailand.

Primary outcome of interest was the number of subjects who, by the end of the trial, developed type 2 DM according to ADA guidelines. Secondary outcomes of interest included changes in beta-cell function, insulin resistance, adinopectin levels, and waist circumference, among others. Monitoring took place at baseline and at the 3-, 6-, and 9-month post-intervention follow-up appointments.

Two hundred one subjects completed the study (n = 234 subjects were included in the intention-to-treat analysis). Mean values for blood chemistries such as 2-hour OGTT, fasting glucose, and HbA1c were significantly lower in those subjects who received the curcumin extract as compared to the placebo group at all follow-up visits (P < 0.01). Measures of insulin resistance declined significantly after 6 and 9 months in the active group compared with placebo, and those in the active group had higher adinopectin levels at 9 months. By trial's end, 19 (16.4%) in the placebo group had developed type 2 DM compared with none in the curcumin-treated group. No serious side effects were reported. The authors conclude that an ethanolic extract of curcumin may help prevent progression of prediabetes to type 2 DM.

Commentary

Prevention trumps treatment in any discussion of health and disease, but preventing type 2 DM has proved a frustratingly difficult task. How crazy would it be if a simple herbal remedy might be part of the answer? Crazy, indeed, but don't jump on the bandwagon too quickly — there are devils in the details of this paper. For example, all subjects underwent a brief discussion on the importance of dietary and lifestyle measures for optimal health, emphasizing the impact of such measures on blood sugar and inflammation. Three months later the first capsules, placebo or curcumin, were taken. It is unlikely that such a brief intervention had a significant impact on the majority of participants, but there is no way of knowing whether people altered their daily habits to help prevent the development of DM, short- or long-term, because it was not monitored. Although the dropout rate (15%) was impressive for a year-long trial, the sample size was relatively small. In addition, the rate of conversion in the placebo group from prediabetes to frank type 2 DM was quite high (16.7%), higher than what is typically seen in industrialized countries. The authors believe that aspects of Thai culture may be to blame, but the argument falls short because the considerations described (older, overweight population with significant family histories for hypertension and DM) are not unique to Thailand. Finally, pill count is a notoriously inexact way to determine compliance.

On the upside, the researchers posed a unique question that was investigated over a significant time frame and explored through a variety of laboratory tests. Curcumin, derived from the rhizome (underground stem) of the turmeric plant (Curcuma longa), is commonly used as a spice in Asian cuisine and has been the focus of intense study in recent years due to its antioxidant and anti-inflammatory capacity. Studies suggest that curcumin may help in the treatment and prevention of a variety of illnesses, including Alzheimer's and certain types of cancer. Results from the current study point to a possible role for curcumin in improving beta-cell function and insulin sensitivity, like through anti-inflammatory actions.

This is a very interesting study that raises intriguing questions — could curcumin, a potent natural anti-inflammatory agent with additional physiologic actions, help stem the tide of type 2 DM? Would eating curry dishes on a regular basis have the same effect? If curcumin has a protective effect, is it independent of diet and lifestyle habits? It's too early to begin recommending curcumin to our patients at risk for type 2 DM, as the current study raises questions more than it provides answers, but it seems likely a novel line of inquiry and investigation has been opened as a result of the findings, making awareness of the trial important.