In people 40 or younger, the body produces sodium bicarbonate as a buffer to correct a blood pH that is too acidic. However, after the age of 40, this buffering capacity declines rather dramatically.
http://www.alkalife.eu/bicarbonate.html
In order to compensate for this decline in pH buffering capacity, the body will mobilize the alkaline minerals calcium and magnesium from the bones in order to raise the pH of the blood if it’s too acidic and thereby ensure that it stays within a very narrow range -- between 7.35 and 7.45.
It is this process of bone demineralization caused by a blood pH that is too acidic that contributes to osteoporosis and osteopenia in older men and women. The cause of a blood pH that is too acidic is diet. The standard American diet contains a very high a level of meat, fish, cheese, eggs, grains, nuts and legumes, which while nutritious, are nonetheless highly acidic. In order to avoid bone demineralization, these acid forming foods need to be buffered by potassium rich foods like fruits and vegetables, which comprise a relatively small portion of the American diet.
One way to determine if one’s diet is too acidic is by testing the pH of one’s urine or saliva. You can buy diagnostic test strips for that purpose.
http://www.amazon.com/PHion-Balance-Diagnostic-Test-Strips/dp/B000VRU4US
If your pH tests below 7 to 7.25, it’s an indication that you’re consuming too many acid-forming foods and not enough alkaline-forming foods and potentially causing a gradual depletion of bone mineral. I’ve done this test myself, and discovered that it’s next to impossible to maintain a sufficiently alkaline pH without eliminating or severely curtailing the acid forming foods and dramatically increasing one's intake of fruits and vegetables. But I found another way to boost my body’s pH to the desired level, and that is by taking a supplement of potassium bicarbonate. If I take the potassium bicarbonate along with my meals, I don’t have to worry about including a lot of fruits and vegetables and eliminating or reducing some of my favorite foods, like whole grains, beans, meat and fish.
Below are three articles from peer-reviewed medical journals documenting the benefits of potassium bicarbonate as protection against osteopenia and osteoporosis.
http://www.ncbi.nlm.nih.gov/pubmed/8190153
http://jcem.endojournals.org/content/94/1/96.abstract
http://jcem.endojournals.org/content/90/2/831.full
If you decide to take potassium bicarbonate, you can purchase it from the following company:
http://www.life-enhancement.com/featuredProducts.aspx?IDList=628,629 -- 1-800-543-3873.
The product is called "Potassium Basics." As far as I know, Life Enhancement is the only company that sells potassium bicarbonate in capsule form, which makes it easy to take. It is also relatively inexpensive. You can buy it in powder form, but its very unpalatable to take it that way. You’re better off with the capsules. I take 6 capsules a day in three divided doses -- 2 with each meal -- for a total of 3,159 mg. I've discovered that I need this much every day in order to keep my pH in the desired range.
According to the studies that I've included here, people who have taken the potassium bicarbonate have achieved dramatic improvement in bone mineral density within just a couple of years.



A linked study from the first one
http://jcem.endojournals.org/content/94/1/96.abstract
shows that the pottasium had no effect and sodium bicarbonate was just as effective. So save your money and eat baking soda perhaps?