It is known that protein intake contributes to the maintenance and growth of body mass, including muscle mass. But is it also beneficial to our bones? Twelve experts in bone health published a consensus report summarising the most recent insights on protein intake and bone health. One of their main conclusions is that protein contributes to the maintenance of bone mass, provided that calcium intake is adequate.
An adequate protein intake contributes to various bodily functions, including the maintenance and growth of body mass, like muscle mass and the maintenance of bones. In healthy adults, current protein recommendations of 0.8 gram/kg body weight/day are advised. Higher intakes are proposed for the elderly, especially the frail elderly, of 1.0-1.2 gram/kg body weight/day or even 1.2-1.5 gram/kg body weight/day. (1) Several studies in the past have investigated if a higher protein intake could also have an adverse effect on bones.
Twelve bone health experts have reviewed these studies again. What is their conclusion? Protein contributes to the maintenance of body mass, including bone mass, and has no adverse effects on bones, provided that the calcium intake is adequate.
Background: Acid base balance
Several years ago, there was a lot of discussion about the acid base balance theory; it was thought that proteins, in particular, but also dietary phosphate intake, made blood more acid. According to the underlying theory of acid base balance, proteins in the diet as well as phosphates increase the acidity of the blood. As a result of a slightly lower acidity (in more acidic blood) calcium is drawn from the bones as the body attempts to neutralise the blood. Although a higher protein intake does lead to a higher acid level in the urine and more calcium excretion via the urine, this has no effect on the overall calcium balance in the body, i.e. the difference between the dietary intake of calcium and excretion of this via urine and faeces. Scientific research shows that with a higher protein intake, the body more calcium from food absorbs. Similarly, an increased phosphates content does not have any effect on the calcium balance. (2-8)
Twelve bone health experts reviewed scientific literature on protein intake and bone health. Their findings are summarised in a recent published consensus report: ‘Benefits and safety of dietary protein for bone health—an expert consensus paper endorsed by the European Society for Clinical and Economical Aspects of Osteoporosis, Osteoarthritis, and Musculoskeletal Diseases and by the International Osteoporosis Foundation’. (1)
The bone health experts reviewed various types of studies, ranging from cohort studies, intervention studies, systematic reviews and meta-analysis aimed at protein intake and bone health. Based on these studies they draw the following conclusions (1):
- Bone mineral density (BMD), which is an important determinant of bone strength, appears to be positively associated with dietary protein intake.
- Although acid loading or a high protein diet is associated with increased urinary calcium excretion, higher protein intake, whatever the origin (animal or vegetable), does not appear to contribute to weaker bones.
- Protein intake above the current recommendation does not have an adverse effect on bone health, provided that calcium intake is adequate.
Professor René Rizzoli reflects on the report:
“Adequate intake of dietary protein, together with calcium, contributes to the maintenance of normal bones at all ages. This review of the literature confirms that a balanced diet with sufficient protein intake, regardless whether of animal or vegetable source, contributes to bone health when accompanied by adequate calcium intake. This is particularly important for seniors with weaker bones, and individuals with unintended weight loss due to acute or chronic illness, or recovering from an injury.” (1)
- Rizzoli, R. et al (2018). Benefits and safety of dietary protein for bone health—an expert consensus paper endorsed by the European Society for Clinical and Economical Aspects of Osteoporosis, Osteoarthritis & Musculoskeletal Diseases and by the International Osteoporosis Foundation. Osteoporosis International, 2018. doi: 10.1007/s00198-018-4534-5.
- Buclin et al (2001). Diets acids and alkalis influence calcium retention in bone. Osteoporosis int 2001, 12: 493-499.
- Calvez, J. et al (2012). Protein intake, calcium balance and health consequences. European Journal of Clinical Nutrition (2012) 66, 281–295.
- Fenton T.R., et al (2009). Meta-analysis of the effect of the acidash hypothesis of osteoporosis on calcium balance. J Bone Miner Res 2009, 24: 1835-1840.
- Fenton T.R., et al (2009). Phosphate decreases urine calcium and increases calcium balance: a meta-analysis of the osteoporosis acidash hypothesis. Nutr J 2009, 8: 41.
- Fenton, T.R. et al (2011). Casual assessment of dietary acid load and bone disease: a systematic review & meta-analysis applying Hill’s epidemiologic criteria for causality. Nutrition Journal 2011, 10:41
- Heaney R.P. and Rafferty K (2001). Carbonated beverages and urinary calcium excretion. Am J Clin Nutr 2001, 74: 343-347.
- Spence L.A. et al (2005). The effect of soy protein and isoflavones on calcium metabolism in postmenopausal women: a randomized crossover study. Am J Clin Nutr 2005, 81:916-922.