Is it true that animal protein is acidic and leaches calcium from the bones?

No, this is a misconception and the European Food Safety Authority have substantiated the fact that protein is needed for bone health ( EU Register of Nutrition and Health Claims made on Foods ). The ‘acid-base’ hypothesis has been debated in the scientific literature for some time and the most comprehensive evidence shows that overall, the effect of dietary protein on bone appears to be slightly favourable, not harmful.

During digestion, protein gets broken down into various metabolic acids but the body efficiently manages these by using them for various functions, excreting them via the kidneys or buffering them with other dietary components. Where the confusion lies is that a high protein diet can potentially increase urinary calcium excretion, but this is only when calcium intakes are inadequate ( Dawson & Harris SS, 2002; Mangano et al. 2014 ). Dairy foods are nutritionally well placed to balance this as they provide high quality protein but are also among the best sources of dietary calcium.

The human body is highly efficient at maintaining blood pH under tight control and can manage higher protein levels when they are consumed as part of a balanced diet, regardless of the source of protein. However, for those with impaired kidney function, high protein diets are not well tolerated.

Furthermore, when looking at the effect on bone health, several studies have established that although a high-protein diet may increase urinary calcium excretion this does not result in a negative skeletal calcium balance, bone loss or the risk of an osteoporotic fracture ( Bonjour, 2011, 2013 ; Kerstetter et al. 2011 ; Fenton et al. 2009 , 2011 ). In fact, much of the research suggests that protein works synergistically with calcium to improve calcium retention and bone metabolism ( Kerstetter et al. 2011 ; Thorpe & Evans, 2011 ; Bonjour, 2005 ) .