Those with high protein intakes would have tended to be high in both meat and dairy, and those with high calcium intakes would have been high specifically in dairy. Potassium absorption was separately analyzed in those above and below the median intakes for the 2 nutrients. Potassium absorption remained above 90% on both sides of the protein and calcium medians (Table 1), and the small differences between them were not statistically significant. From the failure to find a difference at low and high meat and dairy intakes, it can be concluded that potassium is uniformly well absorbed regardless of dietary source. A notable feature of the calcium economy is that adjustments of calcium absorption and excretion can diminish the impact of a high calcium intake or compensate for a low calcium intake. Quantifying various nutrient and whole-food effects on the calcium economy provides valuable data for public health professionals, clinicians, and nutritionists to counsel patients on achieving calcium balance; however, simply put, all true nutrient effects on the calcium economy can be managed either by reducing excess intake of the nutrient concerned or by increasing calcium intake. The most effective approach to improving calcium nutriture and preserving the calcium economy is to increase consumption of those foods naturally nutrient-rich in calcium, vitamin D, protein, phosphorus, and potassium. At present, the food source that best achieves such a naturally nutrient-rich designation is dairy.

According to Tvlasvsky, Spence & Harkness (2008), the role of dietary potassium in moderating bone mass rests in the intricate interaction between...

The bone's interstitial fluid has greater amounts of potassium and sodium and lower concentrations of calcium and phosphorus than bone crystals or plasma. The potassium content of the bone's interstitial fluid is directly related to the amount of potassium consumed and is the skeletal infrastructure's first means of buffering metabolic acid loads. Therefore, if potassium intake is higher no matter what the food source, there will be changes that impact the calcium balance and metabolic indices of bone metabolism, such as resorption Potassium and bicarbonate that is found in fruits and vegetables may be doubly important in establishing greater buffering capacity, although other components such as essential oils may also help.
In addition, protein intake is thought to be a net acid-producing substance and therefore a negative risk factor for bone dissolution. Yet, many studies have found the beneficial impact on skeletal metabolism when higher protein levels are consumed along with the necessary amount of minerals, such as calcium and potassium, despite the protein source.

References

Frassetto, R., Morris, R.C., Sellmeyer, D.E., & Sebastian, a. (2008) Journal of Nutrition 138(1): 419S-425

Rafferty, K. & Heaney, R.P. (2008) Economy: Emphasizing the potassium controversy.

Journal of Nutrition 138(1): 166S-172

Tylavsky, F.A., Spence, L.A., & Harkness (2008). Importance of calcium and acid-base homeostasis in bone health and osteoporosis. Journal of Nutrition 138(1): 164S-166