Richard Donnelly, professor of vascular medicine at the University of Nottingham, replies: High blood pressure is indeed harmful - the risk of stroke, heart attack, kidney failure and heart failure is much higher among those people who have even modest increases in blood pressure. Generally, people within the population who have lower levels of blood pressure fare better in terms of being at lower risk of cardiovascular disease.
So, no, low blood pressure is never harmful among otherwise well and asymptomatic people. Of course, if you get run over by a bus and start to haemorrhage a lot of blood, then complications will result from a fall in blood pressure due to blood loss. But in otherwise well, ambulatory people within the normal range of blood pressure, it is better to be at the bottom of the range.