Cinnamon Intake Lowers Fasting Blood Glucose: Meta-Analysis
Paul A. Davis1and Wallace Yokoyama2
1Department of Nutrition, University of California—Davis, Davis, California, USA.
2Western Regional Research Center, U.S. Department of Agriculture, Albany, California, USA.
been used for centuries in Chinese medicine and has been shown to affect blood glucose and insulin signaling. Cinnamon’s
effects on blood glucose have been the subject of many clinical and animal studies; however, the issue of cinnamon intake’s
effect on fasting blood glucose (FBG) in people with type 2 diabetes and/or prediabetes still remains unclear. A meta-analysis
of clinical studies of the effect of cinnamon intake on people with type 2 diabetes and/or prediabetes that included three new
clinical trials along with five trials used in previous meta-analyses was done to assess cinnamon’s effectiveness in lowering
FBG. The eight clinical studies were identified using a literature search (Pub Med and Biosis through May 2010) of
randomized, placebo-controlled trials reporting data on cinnamon and/or cinnamon extract and FBG. Comprehensive Meta-
Analysis (Biostat Inc., Englewood, NJ, USA) was performed on the identified data for both cinnamon and cinnamon extract
intake using a random-effects model that determined the standardized mean difference ([i.e., Change 1control– Change
2cinnamon] divided by the pooled SD of the post scores). Cinnamon intake, either as whole cinnamon or as cinnamon extract,
results in a statistically significant lowering in FBG (–0.49–0.2mmol/L; n=8, P=.025) and intake of cinnamon extract only
also lowered FBG (–0.48mmol/L–0.17; n=5, P=.008). Thus cinnamon extract and/or cinnamon improves FBG in people
with type 2 diabetes or prediabetes.
Cinnamon, the dry bark and twig of Cinnamomum spp., is a rich botanical source of polyphenolics that has
KEY WORDS: ? cinnamon ? cinnamon extract ? fasting blood glucose ? prediabetes ? type 2 diabetes
improve taste and aroma of food, but it is also an important
ingredient of traditional Chinese medicine.1Of 98 common
cinnamon contains the highest level (8.1% wet weight basis)
of procyanidins, compounds that are also abundant in blue-
berries and chocolate and medically of great interest given
their potent antioxidant activity and demonstrated biological
activity.2,3Cinnamon has been extensively studied in rela-
tion to its effects on insulin and insulin signaling. Poor in-
sulin sensitivity is a precursor to type 2 diabetes, which
affects over 300 million people worldwide, and is often
characterized by high fasting blood glucose (FBG), defined
as blood glucose levels of 5.5–6.9mmol/L.4The epidemic
of type 2 diabetes worldwide has resulted in a pressing
need to explore low-cost therapeutic approaches that reduce
Animal and in vitro studies have consistently shown that
cinnamon powder or extracts improve insulin sensitivity and
ne of the oldest and most popular spices, cinnamon,
the dry bark and twig of Cinnamomum spp., is added to
insulin signaling by increasing tyrosine phosphorylation
activity and by decreasing phosphatase-mediated insulin
receptor inactivation.6Cinnamon extract has been reported
to reduce blood glucose, plasma insulin, triglycerides, and
total cholesterol in fructose-fed rats7and more recently to do
so while altering plasma adipose-derived factors and ex-
pression of multiple genes related to carbohydrate metabo-
lism and lipogenesis in adipose tissues.8In the db/db mouse,
a methanol extract of cinnamon improved FBG, decreased
hepatic free fatty acids, and increased serum insulin and
adiponectin.9A recent short-term study in healthy human
subjects showed lower postprandial blood glucose concen-
trations and improved insulin sensitivity when 5g of cin-
namon was eaten 12 hours before or ingested at the same
time as an oral glucose tolerance test was performed.10In a
small pilot trial, cinnamon extract also lowered homeostasis
model of assessment–insulin resistance in women with
polycystic ovary syndrome.11The long-term effects of
cinnamon consumption in human subjects have not been
studied; however, its use as a spice for thousands of years
suggests that any adverse effects of long-term use are likely
minimal, although high doses of whole cinnamon may be of
concern. For example, concerns about coumarin intake with
high doses of Cinnamomum cassia have been raised and
evaluated.12The total dietary intake for a 70-kg individ-
ual for aqueous cinnamon extracts is less than 7% of the
Manuscript received 9 August 2010. Revision accepted 10 October 2010.
Address correspondence to: Paul A. Davis, Ph.D., Department of Nutrition, Meyer Hall,
University of California, Davis, Davis, CA 95616, E-mail: firstname.lastname@example.org
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DAVIS AND YOKOYAMA