There is a claim that alkaline-producing diets counteract acidity, help the body regulate its pH, and thus prevent osteoporosis. According to the claim, high dietary protein intakes are detrimental to bone health since protein is an “acid generating” diet component, and bone calcium is removed from the bone to neutralize the acid. In contrast, a diet rich in fruit and vegetables is thought to have the opposite effect, that of an alkaline-producing diet, which would be protective of bone health.
Based on a thorough review of the literature published in 2011, the relationship between dietary acid with risk of osteoporosis is not confirmed. It is possible that fruit and vegetables are beneficial to bone health through mechanisms other than via the acid-alkaline hypothesis since there is some preliminary human and animal evidence that some fruits and some vegetables have supportive effects on bone.
See the Literature Review