"We are looking for safe, durable and cost-effective approaches to reduce the progression from prediabetes to type 2 diabetes," said study author Dr. Giulio Romeo, a staff physician at Boston's Joslin Diabetes Center and the division of endocrinology at Beth Israel Deaconess Medical Center. The study published Tuesday in the Journal of the Endocrine Society.
"Our 12-week study showed beneficial effects of adding cinnamon to the diet on keeping blood sugar levels stable in participants with prediabetes," Romeo said. "These findings provide the rationale for longer and larger studies to address if cinnamon can reduce the risk of developing type 2 diabetes over time."
Harvested from the inner bark of a tropical evergreen plant, cinnamon has been used in Ayurvedic medicine to treat respiratory and digestive problems for centuries. Ancient Egyptians used cinnamon as a perfume during the embalming process, while Romans used it in funeral pyres to mask the stench of burning flesh.
There are two basic types of cinnamon: Ceylon, which is grown in Sri Lanka, and cassia, which is widely produced in China and Indonesia. Cassia has the stronger flavor and odor of the two and, due to its much lower cost, is what most of us buy in the store to sprinkle on our food.
Past research has linked cassia cinnamon to better blood sugar levels. A small study of 18 people with type 2 diabetes found cassia was more effective than diet alone in lowering blood glucose levels; It was even comparable to oral diabetes medications.
Another study of 60 people with type 2 diabetes found that small doses of cassia cinnamon reduced blood sugar levels while improving LDL, or "bad" cholesterol, triglycerides and total cholesterol.
Other studies, however, have failed to duplicate those findings. A 2012 review of 10 randomized controlled trials, for example, didn't find sufficient evidence to support using cinnamon to control blood sugars.
Romeo believes part of the issue is that people diagnosed with type 2 diabetes are likely on various medications that might interfere with study results.
So he and a group of researchers in South Korea decided to focus specifically on people with prediabetes who were not yet on medications. South Korea was included, Romeo said, because the rates of diabetes in East and South Asia have been rising at a particularly fast rate over the last three decades.
The small, double-blind, placebo-controlled, randomized clinical trial gave study participants in Boston and South Korea a 500-milligram capsule of cassia cinnamon or a placebo three times a day over 12 weeks. The study used a very sensitive, fasting plasma glucose test to measure the response.
"The difference between the groups of patients was significant," Romeo said. "Blood glucose levels of people on cinnamon would not go as high as the participants on placebo after meals and also would return to baseline much faster."
As the US Centers for Disease Control and Prevention says, "Don't let the 'pre' fool you -- prediabetes is a serious health condition where blood sugar levels are higher than normal, but not high enough yet to be diagnosed as diabetes. Prediabetes puts you at increased risk of developing type 2 diabetes, heart disease, and stroke."
More than 88 million Americans -- one in three adults -- have prediabetes, according to the CDC. Around the world, studies estimate some 352 million were prediabetic in 2017. By 2045 that number is estimated to grow to 587 million people.
Prediabetes occurs when cells in your body don't respond normally to insulin, a hormone made by your pancreas. Insulin serves as a key, unlocking the doors of cells to allow glucose in the bloodstream to enter and be used for energy, and then stores any leftover glucose in the liver.
When cells fail to open, beta cells in the pancreas produce more and more insulin in a bid to force the cells to respond. After some time, those beta cells wear out, and glucose levels in the bloodsteam build up, creating prediabetes, and if left unchecked, type 2 diabetes.
You have prediabetes if your glucose level after an overnight fast is 100 to 125 milligrams per deciliter (mg/dL) of blood, according to the American Diabetes Association. A reading of 126 mg/dL and higher means you have type 2 diabetes. Prediabetes can exist for years with no clear symptoms. In fact, the CDC says more than 84% of people who have the condition have no clue they are in danger.
But they are. Diabetes can impact every major organ in the body and lead to kidney failure, blindness, heart disease, stroke and damage to both the large and small blood vessels of the body. This can lead to impotence in men and sexual dysfunction in women as well as nerve damage in the legs, feet and toes, which can lead to amputation.
Lifestyle measures are key to preventing prediabetes from escalating into type 2 diabetes. Even a small amount of weight loss, such as 5% to 7% of your body weight, can make a difference, experts say. For a 200-pound person, that's 10 to 14 pounds.
Consider the Mediterranean diet, which has been shown to prevent the development of chronic diseases such as diabetes, cancer and atherosclerosis, as well as helping with weight loss.
Regular physical activity is another necessity -- 30 minutes a day, five days a week of brisk walking or a similar activity can also make a difference.
While science continues to test the true effectiveness of cinnamon, experts say sprinkling cinnamon on food won't harm you and may a good substitute for sugar, salt and other flavoring agents not good for diabetes.
Be careful, however, not to use too much on food or in capsules. Cassia cinnamon, the most common form, can contain relatively high concentrations of coumarin, a plant compound that can damage the liver.
A study of 91 cinnamon samples from various stores in Germany found 63 times more coumarin in cassia cinnamon powder than in Ceylon powder, the more expensive version grown in Sri Lanka. Cassia sticks, which look like a thick layer of rolled bark, also contained 18 times more coumarin than Ceylon sticks, which have thin layers.
The Food and Drug Administration's recommended limit is 6 grams a day of cinnamon, which is about a tablespoon, said registered dietitian Lisa Drayer, who writes about nutrition for CNN, in a prior interview.
"I think the bottom line is that cinnamon is a perfect pantry staple, a pleasant spice that can add flavor to foods for minimal calories, with antioxidant properties that may give an edge to those looking to better control their blood sugar," Drayer said.
"But we need to see more research before we can make any solid health claims linking cinnamon to reduce risk of disease or improved health."
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