Anticancer properties of silver birch

Silver birch (Betula pendula

) is one of two birches native to the British Isles, the other being the downy birch (Betula pubescens), with which it often crosses.

It is a “pioneer” species, quickly colonising ground cleared by agriculture, forestry or fire. The almost weightless, winged seeds are blown great distances, and will germinate in poor soils.

The leaves rot readily, enriching the soil for follow-on species such as oak and beech, which deprive the birch of light, eventually killing it.

The silver birch was revered by pagans as a holy tree. It has long found use in traditional medicine for a wide range of ailments, including inflammatory conditions, urinary tract disorders, psoriasis and eczema.

Oil extracted from the bark contains methyl salicylate, and decoctions were traditionally used for their anti-inflammatory effects in arthritis and gout, and oil of wintergreen is produced from birch tar. In Russia, the buds were preserved in vodka and used as a treatment for inflammatory conditions. Because of the presence of salicylates, products containing birch extracts are contraindicated in those patients sensitive to aspirin.

The leaves contain flavonoids, which have a diuretic action, but studies have shown that diuresis may not be due to flavonoids alone, and it has been suggested that the high potassium content of the leaves may also be contributory.

A controlled human study, in which birch tea was given to patients with urinary tract infections, showed that after three weeks, urinary microbial counts in the birch tea group had reduced by 39 per cent, compared with only 18 per cent in the placebo group.

Recent research has centred on a compound found in the bark of the tree, betulinol. Tests have shown that betulinic acid, synthesised from betulinol, inhibits division of human prostate cancer cells implanted into mice, and may even facilitate the death of those cells. Encouragingly, betulinic acid does not seem to have any effect upon healthy cells.