Other names: Lime (blossom - no relation to the fruit), Linden
Actions: Diaphoretic, antihypotensive, vasodilator, astringent, antispasmodic, carminative
Qualities: warming, drying
Affinities: Circulatory system (cardio tonic)
Constituents: High proportion of potassium, flavonoids
Safety: Can cause contact sensitivity
Tilia trees usually grow to be large, with small, creamy-yellow and scented flowers and a large strap-like bract. Although well over a hundred species have been described, recent molecular studies and research show many names merely represent variations between populations. Tilia has also been subject to "taxonomic shuffling", previously given its own family, but now part of the Mallow group. Hybridisation within the genus is common, with Tilia x europea being a cross between the "large-leaved" and "small-leaved" species. Leaf buds are red, with one small one large scale, resembling a boxing glove. Leaves are borne on long pedicles, dark green, cordate and flimsy, 6–10cm in length. They are more or less hairless, except for creamy-buff or white hairs on the underside of the leaf between the joints of the veins.
The main traditional uses of Tilia centre around its febrifuge/diaphoretic and antihypotensive action. It is traditionally used as an infusion, especially to encourage cooling persipration. It can also be given in the bath and is generally safe for children, despite the suggestion that it has been associated with contact irritation. Hoffman designates Tilia as a "cardiotonic", i.e. having broad and non-specific benefits for health function without containing cardiac glycosides, much like Crataegus. In this way, it is a gentle, long-term remedy for chronic heart conditions.
Modern research sheds some light on how Tilia can be useful. Firstly, it has a very high proportion of potassium when compared to sodium, suggesting it is useful as a diuretic and won't deplete the body's resources of potassium, like old style diuretics did. Diuretic action is a manner in which it may affect blood pressure positively. Tilia also produces large amounts of flavonoids, the polyphenol group assoctaed with good cardio- and cerebral- vascular health. Various studies have shown a range of positive effects on blood pressure and, by extrapolation, should benefit CV health outcomes. These constituents are believed to increase the acitivity of endogenous NO, which plays an important role in the body''s natural vasodialtion mechanism. They have also been associated with counteracting unhealthy endothelium tissue, a precursor to atherosclerosis. One review from Rees et al., The Effects of Flavonoids on Cardiovascular Health: A Review of Human Intervention Trials and Implications for Cerebrovascular Function (2018), found mixed evidence of the effect of flavonoids, and indicate, as ever, that more research is needed.
Problems with research on flavonoids, as with other groups of complex phytochemicals, is that so many things play a part in their use and consumption, and there are many variables that influence their effect on us, including but not limited to: age, sex, bioavailability (which varies greatly) and gut biota. Generally speaking, flavonoids aren't very well absorbed, which suggests we probably need a great deal of them in out diet in order to benefit. Also, research on one isolated flavonoid may not reflect how they work synergistically in our bodies - a perennial problem of applying biomedical research to herbal medicine.