Like art deco hotels, vibrant pink neon, spicy creole chicken wings and Disney World, saw palmetto entered the British consciousness in the mid 90s when the sunshine state of Florida became inexplicably fashionable. For centuries, Native Americans on the tropical Atlantic seaboard had eaten the seeds and fruit of Serenoa repens - a hardy, fan-shaped palm - in the belief that it was an aphrodisiac. Steam from the cooked fruit was inhaled to ease bronchitis and colds, and a traditional drink, shiope sofkee, was made from the juice. Only in the late 19th century did saw palmetto come to the attention of the US medical establishment - and from there, its lusty reputation gradually spread to Europe. Now it is widely available as an extract and is America's sixth-best-selling herb. Annual sales are estimated at US$45m (£31m), and although no such breakdown exists for the UK, it comprises a significant slice of the £360m supplement market.
One reason the herb has sprung to prominence is that the native Americans were right. The fatty acids in saw palmetto (caproic, lauric and palmitic) are now known to tone and strengthen the male reproductive system by counteracting the effects of oestrogen and progesterone and controlling testosterone levels. Less scientifically plausible are beliefs held earlier this century that the herb increases sperm production in men and breast size in women. What has been demonstrated is that saw palmetto is rich in sterols - fats found in all plants, including fruits and vegetables - which have been shown in rats to have anti-inflammatory properties similar to cortisone. This explains the herb's traditional use for treating inflammation of the airways, excessive discharge of mucus from the sinuses, and genito-urinary problems. The plant also contains steroidal saponins - chemicals that may play a part in boosting the immune system, fighting infection and lowering cholesterol levels.
Despite its aphrodisiac qualities, recreational use of saw palmetto only partly explains its position near the top of the herb league table. In 1998, a paper published in Jama (the Journal of the American Medical Association) reported that it helped to alleviate the symptoms of enlarged prostate - a condition affecting 50% of men over the age of 60 and 90% of men over 85. Not to be confused with prostate cancer, enlarged prostate - or BPH (benign prostatic hyperplasia) - results in frequent urination, a need to empty the bladder at night and poor urine stream, due to the swelling of a doughnut-shaped gland round the urethra. The condition is thought to be caused by testosterone accumulating in the prostate, where it is converted by an enzyme into the chemical DHT (dihydrotestosterone). DHT causes tissue cells to multiply too quickly, leading to enlargement of the prostate.
Saw palmetto appears to block the effect of the enzyme that converts testosterone into DHT, as well as stopping it binding to receptor sites on cells - thus accelerating its chemical breakdown and its excretion from the system. In the Jama paper, analysis of 18 randomised trials showed that the herb improved urine flow and other urological symptoms significantly more than a placebo.
In subsequent studies, saw palmetto was demonstrated to be as effective as finasteride (marketed as Proscar), an orthodox drug used to treat the symptoms of an enlarged prostate. While Proscar can take up to a year to have a beneficial effect, many patients taking it report an improvement within 30 days.
Naturally, there is a downside. As well as causing minor side effects such as nausea and diarrhoea when taken in large quantities, saw palmetto introduces another danger. Because the symptoms of BPH have been so widely publicised, increasing numbers of men are self-medicating with over-the-counter products instead of going to a GP. Since some symptoms of enlarged prostate are similar to those of prostate cancer, doctors believe early detection may be missed.
Available in capsules and tablets, saw palmetto extract is made from the dark purple, olive-like berries that ripen on the tree from October to December. Though it grows mainly in Florida, Texas and South Carolina, it is also found in the West Indies. The saw prefix comes from the saw-toothed edges of the plant's leaves. Any similarity to spicy creole chicken wings is purely coincidental.
· Next time: devil's claw
