Action on Smoking and Health (ASH-UK) has a web page on its old web site which attempts to recruit employees who have suffered health damage from secondhand smoke at work to sue their employers. The page, prepared in collaboration with the Thompsons Solicitors law firm, advises the public that if an employee believes he has suffered health damage as a result of secondhand smoke exposure at work, he should consider filing a lawsuit against the employer to receive compensation for personal injuries.
One of the key pieces of information provided by ASH-UK to the public is the following: "Exposure [to secondhand smoke] for just 30 minutes has been shown to reduce coronary blood flow, increasing the risk of angina, heart attacks and strokes."
oronary flow velocity reserve is a measure of the ability of the coronary arteries to dilate in order to increase blood flow under experimental conditions. What a decline in coronary flow velocity reserve indicates is something called endothelial dysfunction - an impairment of the ability of the coronary arteries to dilate in response to a variety of stimuli. This ability to dilate is mediated by the endothelial cells -- the cells which line the blood vessel.
The endothelial cells respond to certain stimuli by producing nitric oxide and other chemicals which diffuse into the smooth muscle in the artery wall, sending a chemical message that causes the muscle to relax and therefore causing the artery to dilate. There are a number of exposures that impair the ability of the endothelium to accomplish this function; among them are active smoking, secondhand smoke, high cholesterol, consumption of trans-fats, and consumption of a high-fat meal.
When endothelial dysfunction is triggered repeatedly over a long period of time, it has been shown to result, ultimately, in atherosclerosis (narrowing of the coronary arteries). When this occurs, coronary blood flow is reduced.
It is important to note that a reduction in coronary blood flow is not observed acutely when the endothelial dysfunction is being measured from a single experimental exposure (such as in the Otsuka et al. study). The reduction in coronary blood flow does not occur until the process has been sustained long enough that atherosclerosis has progressed and the coronary artery has actually narrowed. It is the narrowing of the artery that causes reduced coronary blood flow.
A single high-fat meal has been documented to cause endothelial dysfunction. If you were to go to Burger King for a Whopper, fries and a milk shake and then go to a laboratory to have your coronary flow reserve velocity tested, you would find that it is reduced. In fact, it will probably be reduced to the same level as in an active smoker.
Would it therefore be accurate for an anti-obesity group to claim that eating a hamburger reduces coronary artery blood flow in healthy young adults?
I would argue that it would not. In fact, I think such a statement would be very misleading and deceptive to the public.
Instead, what the science shows is that eating a hamburger or any high-fat food causes endothelial dysfunction. Therefore, if you chronically eat lots of fatty foods over a long period of time (many years), the evidence indicates that this could cause atherosclerosis and heart disease. If you do develop heart disease, then your coronary blood flow will be decreased and you will be in danger of possibly suffering a heart attack. But there is no danger of death or a heart attack after simply eating one Whopper.
By conflating coronary blood flow with coronary flow velocity reserve, anti-smoking groups have, I think, been able to deceive people into thinking that the effects of acute secondhand smoke exposure are much more severe than they actually are.