(CNN) Cinnamon is one of the world's most popular spices, sprinkled on lattes, boiled with ciders and enjoyed in numerous dishes. Without it, Thanksgiving and Christmas meals might well become tasteless and definitely less fragrant.

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.

The Bible mentions cinnamon several times, most commonly as a way to perfume bedding, clothes and anointing oil. The essential oil form is made from the bark, leaves or twigs of the plant.

But it's cinnamon's use as a medicinal agent that has scientists buzzing, trying to determine just how well its antioxidant capabilities might work to better our health.

"Medicine started as herbs and plants," said Lauri Wright, a spokeswoman for the Academy of Nutrition and Dietetics. "So it almost comes full circle, as we're now going back and proving what some of these plant substances may do for health."

Not all cinnamon is created equal

There are two basic types of cinnamon. Ceylon, or Cinnamomum verum, is grown in Sri Lanka. C. cassia, C. loureiroi and C. burmannii, communally known as cassia, are 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 we buy in the store to sprinkle on our food.

But it's the more expensive Ceylon version, with a milder, sweeter flavor, that might be the best for your health.

Cassia 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 Ceylon powder. Cassia sticks, which look like a thick layer of rolled bark, also contained 18 times more coumarin than Ceylon sticks, which have thin layers.

"A challenge with some of these herbal solutions, because they are not a regulated drug, is that you don't know exactly what you are getting," said registered dietitian Melinda Maryniuk, who serves on the professional practice committee for the American Diabetes Association. "A lot of things affect the makeup of the product: where it's grown, the soil, growing conditions, even how the spice was stored and dried."

That problem also plagues research on cinnamon. Scientists have used different doses, species and compounds of the spice for their research.

"The doses have varied greatly among the studies, from less than 1 gram to levels that would be toxic in humans," Wright said. "The duration of taking the capsules has also varied greatly. That's the problem with translation of all of this work. Even when we find positive results, how do we come up with the correct compounding and dosage for maximum safety?"

Keep that in mind as you read on about where science stands on cinnamon.

Diabetes and cholesterol

"I think the strongest evidence lies so far with diabetes and the promise of cinnamon and blood sugar control," Wright said, pointing to studies in test tubes and mice and even small studies in people showing that cinnamon helps with insulin sensitivity and glucose transport while decreasing inflammation.

"A lot of the studies have been in postmenopausal women and men of that age," said biochemist Amy Stockert, who studies cinnamon at Raabe College of Pharmacy at Ohio Northern University. "Some have found positive effects; other studies have not."

Stockert co-authored a small study of 18 people with type 2 diabetes that showed the cassia species of cinnamon was more effective than diet alone in lowering blood glucose levels. In fact, her study found that it was comparable to oral diabetes medications.

Another study of 60 people with type 2 diabetes found that small doses of cinnamon reduced blood sugar levels and improved LDL, or "bad" cholesterol, triglycerides and total cholesterol.

"I like the fact that the amount that showed benefits for blood sugar and cholesterol in that study was 1 to 6 grams, which is the range of half-teaspoon to three teaspoons, or one tablespoon, so it's easy to sprinkle on cereal or in yogurt or use in recipes," said registered dietitian Lisa Drayer, who writes about nutrition for CNN. The Food and Drug Administration's recommended limit is 6 grams a day.

But while the future looks promising, the American Diabetes Association urges caution.

"The ADA believes there's not enough evidence," Maryniuk said. "A 2013 meta-analysis, which is one of the most rigorous of reviews, found that cinnamon had no impact on hemoglobin A1c levels, which is what we look at to measure how well blood sugar is being controlled over time. If that had gone down, I'd be more impressed."

Still, if you want to see whether cinnamon works for you, Maryniuk suggests that people with type 2 diabetes do a self-test.

"Do some paired blood glucose testing," she said. "Use a half a teaspoon in the morning, on fruit or oatmeal or in coffee, and see what happens to your blood sugar levels before and after you eat. Check again two to three hours later and see if there's a difference.

"But keep taking your medicine," she warned. "You don't want to try something to the exclusion of the medicine you're taking."

"We still need a bit more work before we roll this out," Wright agreed. "And you must be careful to work with your doctor when using cinnamon with diabetes medications, as it might drop your blood sugars too low."

Dementia, HIV, cancer and more

The antioxidant properties of cinnamon are also being studied for their impact on the formation of the plaques and tangles of Alzheimer's disease and other dementias. Cinnamaldehyde, a compound responsible for the spice's sweet smell, and epicatechin, a powerful antioxidant that's also in blueberries, red wine and chocolate, seem to offer some protection against the oxidative stress that damages tau, a key player in the development of dementia.

Another study found a component of Ceylon cinnamon to have the same effect. However, research has occurred only in mice, rats and laboratory Petri dishes.

"It appears to work as an anti-inflammatory or antioxidant, protecting the body on a cellular level from bad things that happen," Wright said, "by getting rid of waste products and keeping the cells healthy."

Cinnamon and other traditional Indian medicinal plants are also being tested in the fight against HIV. One study found that green tea, elderberry and some extracts of cinnamon rich in flavonoids blocked the virus from entering and infecting certain cells.

"That's how AZT works, which is one of the early HIV drugs," said Wright, who specializes in nutrition for infectious disease at the University of South Florida. "And while that's interesting, what I would hate is that patients will use cinnamon and other supplements instead of their HIV medications.

"Having worked with many HIV clients over the years, I know there's definitely a big interest in supplements," she said. "But I would always caution them to always use the meds that we know work, that have been tested and dosed, and then look carefully to make sure there are no conflicts with any additional supplements."

The research on cinnamon doesn't stop there. Ceylon cinnamon has also been associated with cancer-fighting properties in rodents, anti-parasitic effects, improved diabetic neuropathy, lower blood pressure and wound healing, including liver damage. Studies have shown that solutions of cinnamon oil can kill a number of common bacteria, such as streptococcus and E. coli. The National Center for Complementary and Integrative Health is investigating cinnamon's impact on multiple sclerosis.

Using a computer model, biochemist Stockert found that cinnamon was as effective as resveratrol, an antioxidant in red wine known for anti-aging and disease-fighting properties, in activating SIRT-1 -- also known as the longevity gene because of its role in repairing DNA.

"In some cases, it did better than resveratrol," Stockert said. "We're talking anti-cancer, anti-aging, a very, very big deal if that is what is going on."

Cinnamon as health aid

Based on all this preliminary research, the potential of cinnamon seems enormous. But experts caution that it's still too early in the scientific process to suggest cinnamon as a daily supplement.

"I don't recommend capsules. There's not enough science to tell us to take capsules," Wright said.

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"You are affecting your body's signaling," Stockert said, "and that's significant. We're at an early stage in research where we don't know how cinnamon will affect most people. Is it healthy to cook with spices and use them liberally? I'm sure that's fine. But I would be cautious about taking any supplements on their own."

"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 agreed. "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."