Well, this happens a lot in science, and is good reason not to jump at the first papers.
A new paper came out where they gave potassium citrate to women and found no improvement in bone density.
Here is the link:
http://www.ajcn.org/cgi/content/abstract/88/2/465
Their conclusion:
Conclusions: Two-year potassium citrate supplementation does not reduce bone turnover or increase BMD in healthy postmenopausal women, which suggests that alkali provision does not explain any long-term benefit of fruit and vegetable intake on bone.
Go figure.