Dietary protein intake from different animal and plant sources plays a minor role in the bone health of adults with or without intermittent fasting for decades.

We examined whether bone health is related to protein intake from different sources by utilising a distinct, rare dietary pattern: avoidance of animal foods for approximately half of the year according to Christian Orthodox Church fasting. Four-hundred adults, of whom 200 had been following religious fasting for a median of 15 years and 200 were non-fasters, underwent anthropometry, measurements of bone mineral density (BMD) and bone mineral content (BMC), and completed a food frequency questionnaire. Groups did not differ significantly in anthropometric measures, BMD, or BMC. Fasters had higher consumption of seafood and lower consumption of red meat, poultry-eggs, dairy products, and grains-cereals than non-fasters. Protein intake from these food groups exhibited similar differences; overall, fasters had lower protein intake than non-fasters. BMD and BMC were positively, though weakly, correlated with red meat and poultry-egg consumption. Thus, protein intake seems to play a minor (if any) role in bone health.