Cinnamon

Studies have shown that just 1/2 teaspoon of cinnamon per day can lower LDL cholesterol.
Several studies suggest that cinnamon may have a regulatory effect on blood sugar, making it especially beneficial for people with Type 2 diabetes. The active principle appears to be a water-soluble compound called MHCP, which is a polyphenol (related chemically to tannins). This has little to do with the taste and smell of cinnamon, and the fact that it's the water-soluble fraction that has the main effect means that cinnamon oil will not help blood sugar control.
In some studies, cinnamon has shown an amazing ability to stop medication-resistant yeast infections.
In a study published by researchers at the U.S. Department of Agriculture, cinnamon reduced the proliferation of leukemia and lymphoma cancer cells.
Cinnamon has an anti-clotting effect on the blood.
In a study at Copenhagen University, patients given half a teaspoon of cinnamon powder combined with one tablespoon of honey every morning before breakfast had significant relief in arthritis pain after one week and could walk without pain within one month.
When added to food, cinnamon inhibits bacterial growth and food spoilage, making it a natural food preservative. This is probably due to the oil; most essential oils are anti-bacterial (which is probably why the cinnamon plant produces it).
One study found that smelling cinnamon boosts cognitive function and memory.
Researchers at Kansas State University found that cinnamon fights the E. coli bacteria in unpasteurised juices.
Cinnamon is a great source of manganese, fibre, iron, and calcium. However, in the amounts likely to be used, it probably won't make much of a contribution to nutrition.
Caution: Cinnamon lowers blood sugar and slows down clotting of the blood. Therefore, if you are on medication for either of these purposes, cinnamon should only be taken after medical advice, as it will probably reduce the dosage needed of either type of drug.