Hi Adrienne,
> 
> I think there is a substance in celery besides magnesium that is primarily
> responsible for its effect on BP. This little article explain more:
> 
> _The Benefit Of Celery on Blood Pressure_
> (http://www.highbloodpressureinfo.org/benefit-of-celery.html)
> 
[Ron] Thanks for the link. The focus of that article is on potassium and
phthalide. While potassium is critical to cardiovascular health and even
survival, we are less inclined to become deficient in potassium than
magnesium. When I tried a PubMed search for peer reviewed articles regarding
phthalide and blood pressure, I could only find one in Chinese and another
in Italian. The article you cited credits a Chinese medical student (Quang
T. Le) and a clinical pharmacologist (W. Elliot) at U of Chicago yet I can't
find a PubMed publication on phthalide in association with either of their
names. The only study reports I could find on phthalide and vascular
dilation were animal studies.  

Perhaps phthalide will soon be shown to be a potent agent for reducing blood
pressure in humans, but magnesium is well documented as being similarly
beneficial. The phthalide may well add to that positive impact. I don't
know. Celery's typically high content of potassium and magnesium suggest
that it is a very heart-healthy food and phthalide may make it even better. 
Best Wishes, 
Ron