Cinnamomum zeylanicum Photo: Sudhir Ahluwalia
Cassia and cinnamon both contain coumarin. Coumarin is toxic to humans when ingested regularly. Prolonged use can cause liver inflammation and jaundice. The maximum recommended daily intake of coumarin is 0.1 mg per kilogram of body weight. 1 teaspoon of cassia powder contains between 6–12 mg coumarin. European Food Safety Authority limits the quantity of cassia that can be safely ingested.
Traditionally, these plants are used to treat a range of common gastrointestinal ailments like flatulence, dyspepsia, stomachache, nausea,
diarrhea, cramps, and loss of appetite. The species is believed to purify the blood and assuage disorders caused by high blood pressure.
The bark is useful in treating cold, cough, bronchitis, chest pain, and respiratory ailments. Bark oil contains cinnamaldehyde, phenol, coumarin,
benzaldehyde, chavicol, aromatic aldehyde, isoeugenol, and other aromatic aldehydes. The plant is also used to treat patients with menstrual problems, menorrhea, and menopausal symptoms, and to assist in an abortion.
Some research indicates that the spice has antidiabetic properties and could help lower lipid levels (Liu et al., 2014), but these claims have not
been validated in clinical trials. Besides, contradictory findings have also been discovered (Yu et al., 2010). The plant’s antibacterial property has
been validated in animal trials, but most traditional uses of the plant have not been validated by scientific experiments.
More on sources of cinnamon and cassia, botany, medicinal and other uses, history, etc here. There is a section devoted to these species.