Eating fish may help to reverse some of the damage caused by smoking, according to new research by scientists in Ireland.
The researchers found that taurine, an amino acid present in fish, restored normal vessel function in smokers, thus preventing arteries from hardening - a cause of heart disease and stroke. Vitamin C also improved blood vessel health, but to a lesser extent.
"When blood vessels are exposed to cigarette smoke it causes the vessels to behave like a rigid pipe rather than a flexible tube, thus the vessels can't dilate in response to increased blood flow," said Dr David J. Bouchier-Hayes, senior author of the taurine study and professor of surgery at the Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin. This condition is called endothelial dysfunction.
Endothelial dysfunction is one of the earliest signs of the atherosclerosis, which is a major cause of heart attacks and stroke. "We're not trying to find a therapeutic treatment for smoking, because we believe that the best therapy for smokers is to stop smoking," said Bouchier-Hayes. "Nonetheless, smokers provide a good clinical model for treatment of endothelial dysfunction."
Bouchier-Hayes and colleagues recruited 15 healthy smokers aged 20 to 37 and 15 healthy non-smoking volunteers. The smokers were given either 2 grams per day of vitamin C for five days or 1.5 grams per day of taurine. Smokers then waited for a two-week "wash-out" period and switched therapies for five more days.
Researchers assessed blood vessel functioning by flow mediated dilation (FMD), which takes ultrasound images of blood vessel diameter in the arm after a tourniquet was placed on the forearm. Greater diameter after FMD assessment indicates good endothelial function. They assessed FMD at baseline and after taurine and vitamin C supplementation.
The researchers report that taurine restored normal vessel function according to FMD measurements. At baseline, non-smokers' blood vessel diameter was 3.39mm and smokers' diameter was 3.33mm. Before treatment, FMD increased dilation in non-smokers to 3.7mm, while smokers' vessels were virtually unchanged at 3.36mm after FMD. When they took vitamin C, smokers' vessel diameter increased to 3.45mm after FMD. When the were given taurine, the smokers' vessel response was the same as the non-smokers' at 3.7mm after FMD.
Taurine is found in many foods but is most abundant in fish, said Bouchier-Hayes. He added that taurine is present even in mild, white fish not just fatty fish. The taurine supplement used in the study is equivalent to that found in one serving of fish.
The study is published in today's rapid access issue of Circulation: Journal of the American Heart Association.