During a flight of seven to 12 hours duration, most people will notice their ankles and legs start to swell due to lack of movement, insufficient circulation of blood through the veins and accumulation of fluid in the tissues. The conditions within the aircraft cabin - that is, water loss in compressed environment and decreased low fluid intake - can also contribute.
In some passengers, the cumulative effects of these factors can cause a blood clot to develop - a condition known as DVT or 'economy class syndrome', since it is more likely to occur in cramped conditions.
Research has suggested that DVT can occur in as many as 10 percent of air travelers, but in most the clot disintegrates of its own accord causing no ill effects. However in some cases it becomes dislodged and travels through the blood stream, and if it reaches the lungs it can cause potentially fatal pulmonary embolism.
According to the National Institutes of Health, DVT affects 2 million Americans a year, 600,000 of whom develop pulmonary embolism and 60,000 of these die.
The double-blind, placebo controlled study is published in the July issue of Clinical and Applied Thrombosis/Hemostasis. It builds on earlier research published in the same journal in October 2004, which concluded that the supplement is effective in protecting against thrombotic events (DVT and superficial vein thrombosis) in moderate to high-risk subjects during long haul flights.
The new study involved 169 participants, who were divided into two groups: one received a placebo and the other was supplemented with Pycnogenol pine bark extract, supplied in the US by Natural Health Science.
Prior to the flight, the ankle size of participants in both groups was similar. But when the researchers measured their ankles again at the end of the flight, those who took the placebo had experienced more than twice the swelling of the Pycnogenol group.
"Pycnogenol showed effectiveness in improving circulation and helping to prevent leg and ankle swelling," said author Dr Peter Rohdewald of the University of Muenster's Institute of Pharmaceutical Chemistry.
He attributed the results to the pine bark extract's strengthening action on the veinous walls, which helps them resist the increased pressure better so that less liquid seeps into the tissue.
Pycnogenol is derived from the bark of the Maritime pine from Gascony in southwest France, which is rich in procyanidins, bioflavonoids and organic acids. Other research has indicated that Pycnogenol is an effective anti-inflammatory and can be used to lower blood pressure, to control diabetes and in eye health.