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There has been some preliminary research on the effect of cinnamon on blood sugar in humans, but the studies have been small and the findings need to be confirmed with larger trials.
One of the first human studies was published in 2003 in the journal Diabetes Care. Sixty people with type 2 diabetes took 1, 3, or 6 grams of cinnamon in pill form daily -- an amount roughly equivalent to one quarter of a teaspoon to one teaspoon of cinnamon.
After 40 days, all 3 amounts of cinnamon reduced fasting blood glucose by 18 to 29%, triglycerides by 23 to 30%, LDL cholesterol (bad cholesterol) by 7 to 27%, and total cholesterol by 12 to 26%.
There are concerns with this study, however, because a couple of findings were atypical. For example, there was no difference in benefit between the 3 doses of cinnamon. Also, people who take a placebo normally show improvement, but that wasn't the case with this study.
Another study looked at the effect of cinnamon on 79 people with type 2 diabetes who weren't on insulin therapy but were taking oral anti-diabetic medications or modifying their diet. They took approximately 3 grams of cinnamon or a placebo 3 times a day for 4 months.
There was a significant reduction in blood glucose in the people taking cinnamon compared to people taking the placebo. Surprisingly, there was no difference in glycosylated hemoglobin (HbA1C) levels, a test that measures how well blood sugar has been controlled during the previous 3 to 4 months.
In a 6 week study involving 25 postmenopausal women with type 2 diabetes, women were given 1.5 grams of cinnamon daily or a placebo. There was no effect on blood sugar, insulin sensitivity, or cholesterol levels.
A very small Swedish study published in the American Journal of Clinical Nutrition looked at the effect of cinnamon on 14 people. People were given either rice pudding alone or rice pudding with cinnamon. The researchers found that the added cinnamon lowered the post-meal rise in blood glucose compared to people who didn't consume cinnamon.
Using cinnamon in cooking or having a cup of cinnamon tea is a great way to add more of this delicious spice into your diet. There are some precautions to be aware of when using cinnamon, though.
Taking cinnamon in large amounts or taking it in supplement form may change the dosage of medication you require.
Also, people who have been prescribed medication to manage their blood sugar should not reduce or discontinue their dose and take cinnamon instead, especially without speaking with a doctor. Improperly treated diabetes can lead to serious complications, such as heart disease, stroke, kidney disease, and nerve damage.
Cassia cinnamon, the kind of cinnamon normally found in grocery stores and in supplement form, naturally contains a compound called coumarin. Coumarin is also found in other plants such as celery, chamomile, sweet clover, and parsley.
At high levels, coumarin can damage the liver. Coumarin can also have a "blood-thinning" effect, so cassia cinnamon supplements shouldn't be taken with prescription anti-clotting medication, such as Coumadin (warfarin), or by people with bleeding disorders.
Cinnamon can also be found in a concentrated oil form that comes from cinnamon bark. Some of these products are not intended for consumption, but instead are used for aromatherapy essential oils. Also, the oil is highly potent and an overdose can depress the central nervous system. People should not take the oil to treat a condition unless under the close supervision of a qualified health professional.
Pregnant women should avoid excessive amounts of cinnamon and should not take it as a supplement.
Hlebowicz J, Darwiche G, Björgell O, Almér LO. Effect of cinnamon on postprandial blood glucose, gastric emptying, and satiety in healthy subjects. American Journal of Clinical Nutrition. 85.6 (2007): 1552-1556.
Khan A, Safdar M, Ali Khan MM, Khattak KN, Anderson RA. Cinnamon improves glucose and lipids of people with type 2 diabetes. Diabetes Care. 26.12 (2003): 3215-3218.
Mang B, Wolters M, Schmitt B, Kelb K, Lichtinghagen R, Stichtenoth DO, Hahn A. Effects of a cinnamon extract on plasma glucose, HbA, and serum lipids in diabetes mellitus type 2. European Journal of Clinical Investigation. 36.5 (2006): 340-344.
Vanschoonbeek K, Thomassen BJ, Senden JM, Wodzig WK, van Loon LJ. Cinnamon supplementation does not improve glycemic control in postmenopausal type 2 diabetes patients. Journal of Nutrition. 136.4 (2006): 977-980.