Does too little protein increase your risk of bone fractures as you age?

Too little protein harms your bones in two ways at once: it affects bone mass itself and it weakens your muscles. Weaker muscles mean more falls, and with fragile bones a fall is more likely to result in a fracture. In addition, adequate protein stimulates the production of a growth factor needed for bone formation. A low level of that growth factor is an independent risk factor for hip fracture¹.

The strongest evidence comes from a randomised trial involving 7,195 nursing home residents with an average age of 86 in Australia. Residents who received extra dairy every day increased their protein intake from 0.9 to 1.1 grams per kilogram of body weight. The result: 46% fewer hip fractures, 33% fewer fractures overall and 11% fewer falls. Mortality remained unchanged². Those are large reductions in a vulnerable group.

Protein does not work on your bones alone. Protein, calcium and vitamin D complement one another. Older adults who received extra protein after a hip fracture maintained their hip bone density better and had shorter hospital stays. That effect only occurred when calcium and vitamin D intake were also adequate. If one of the three was missing, the benefit was smaller¹. Sufficient protein also improves the absorption of calcium in your intestines³.

People who follow a vegan diet have an elevated risk of bone fractures based on several large prospective studies. Vegetarians fall somewhere in between. Lower protein intake is one of the suspected causes, alongside lower calcium, lower vitamin D and a lower body weight. This is observational research, so direct causality has not been established. Deliberately choosing protein-rich plant foods such as legumes, nuts and soy products, supplemented with vitamin D and calcium, appears to partially offset the risk⁴.

Adequate protein now features explicitly in guidelines. The North American Menopause Society recommends that all postmenopausal women consume sufficient protein, calcium and vitamin D before medication is even considered⁵. European guidelines go further: anyone using prednisone for three months or longer must maintain adequate protein intake as a mandatory part of treatment⁶. For older adults the general recommendation is 1.0 to 1.2 grams of protein per kilogram of body weight per day, and more after a fracture or during rehabilitation.