Low tar "lite" cigarettes impair blood flow through the heart as severely as regular cigarettes, reveals a small study published ahead of print in the journal Heart.
The findings are based on 62 people in their mid 20s, with no evidence of coronary artery disease.
Twenty had smoked low tar, low nicotine cigarettes (8 mg tar, 0.6 mg nicotine, and 9 mg carbon monoxide) for at least three years.
Twenty others had smoked regular cigarettes for the same period (12 mg tar, 0.9 mg nicotine, and 12 mg carbon monoxide), and the remainder were non-smokers.
Cigarette smoking is responsible for a fifth of all deaths from cardiovascular disease and triples the risk of heart failure in later life.
All participants were assessed for cardiovascular fitness, and in the case of the smokers, these tests were carried out two days before and 30 minutes after smoking two of their usual cigarettes within the space of 15 minutes.
The researchers focused on coronary flow velocity reserve (CFVR), which is a measure of how readily coronary arteries can dilate in response to increased blood flow.
The two groups of smokers were similar in terms of their general health and the number of cigarettes they regularly smoked.
The test results showed that blood pressure and heart rate both climbed after smoking, irrespective of cigarette type.
Similarly, CFVR, which was already lower in both groups of smokers than it was in the non-smokers, fell further still after smoking. This was irrespective of cigarette type.
CFVR fell sharply from 2.68 to 2.05 in the low tar smokers, and from 2.65 to 2.18 in the regular tar smokers. The CFVR was 3.11 in the non-smokers.
The authors say their results show that both light cigarettes and regular cigarettes impair blood flow through the coronary arteries to a similar degree. They add that many smokers switch to low tar, low nicotine cigarettes in the mistaken belief that they will reduce some of the hazardous effects of smoking.