Bad To The Bones

By the age of 40, the body starts to lose bone mass. By losing just 10% of your bone mass, your odds of a hip or spine fracture doubles. And it's not just weak bones, but weak muscles, that lead to debilitation fractures. As balance decreases, our risk of falls increases, creating more opportunity for fractures.
The acid-base balance of the diet has the greatest impact on bone and muscle tissue. The acid-load of many diets is not handled well by older adults due to declining kidney function. As we become gradually, mildly, but progressively acidotic, muscle and bone wasting progresses as well. Foods producing the high acid load are proteins and grains; not the acidic foods such as tomatoes or citrus fruits. When grains and proteins are metabolized, they release sulfuric and other acids into the bloodstream. In contrast, fruits and vegetables get broken down into bicarbonate when metabolized, so they add alkali to the system. And that's what helps neutralize acid. When the diet is poor in fruits and veggies relative to grains and proteins, that's a "net acid-producing" diet.
To complicate things further, not all proteins are alike. The acid producing quality depends on the amount of sulfur-containing amino acids within the protein. Plant protein generally comes in foods like beans, which have an accompanying alkaline source which is less acid-producing than the same amount of beef protein.
How to Drop Acid
Cutting protein to lower acid-load would be counter productive. Instead, it is recommended to cut back on the grain foods, which in many cases are calorie laden besides acid producing. This includes donuts, cookies, crackers, pasta, etc. Be more selective - make the grains count by choosing nutrient dense items. Include 9 to 11 servings of fruits and vegetables daily to the diet. Also, make sure to get enough vitamin D, as there are vit. D receptors in muscle tissue as well.
The low acid diet is extremely beneficial for people prone to gout and osteo arthritis.
Here is a sample of foods with high negative PRALs (potential renal acid load). The high-negative PRALs neutralize the high-positive PRALs.

• Raisins (1/4 cup) -8.4
• Apricots (4) -6.7
• Kiwi (2) -6.1
• Watermelon (2 C) -5.3
• Orange (1) -4.2
• Pineapple & Strawberries -3.1
• Spinach (1/2 C uncooked) -12.6
• Zucchini " -4.1
• Carrot " -3.8
• Tomato (1) -2.6
• Lettuce (3 C) -2.1
• Milk chocolate (1.5 oz) 1.0
• Oatmeal (1 C cooked) 8.7
  
• White bread (1 slice) 1.6
• Whole wheat " 0.8
• Whole milk (8 oz) 1.7
• Fruit yogurt 2.0
• Cottage cheese (1/2 C) 9.6
• Haddock (5 oz raw) 9.7
• Beef & Pork " 11.2
• Turkey 14.1
• Red wine (5 oz) -3.5
• Draft beer (16 oz) -1.0
• Coca-Cola (12 oz) 1.5

~ List provided by the Journal of the American Dietetic Assoc., 1995
~ Tufts University, 2010