A Finnish study has found that increasing the share of dietary protein from plant versus animal sources leads to increased bone turnover and possible fracture risk.
The 136 adult participants followed one of three diets for a period of three weeks. One of them was modelled on the typical Finnish diet where 70% of protein came from animal sources and the rest from cereals. The second had half the protein come from animal sources and the other half from plants, and the third had 70% of protein from plants and the rest from animal sources
Dairy milk, which is fortified with vitamin D in Finland, was substituted with unfortified plant-based milk, which may have been a confounding variable. There was a marked increase in bone formation and resorption markers, which in the long term could indicate bone loss. These findings are in line with the Oxford-EPIC study, which followed participants for 18 years and found a higher rate of fractures in vegetarians compared to those on an omnivorous diet.
“The results could be different if fluid dairy products had been replaced with plant-based drinks fortified with vitamin D and calcium,” said Docent Suvi Itkonen, Department of Food and Nutrition, Faculty of Agriculture and Forestry, University of Helsinki. “Then again, the average vitamin D intake was also below the recommended level in the group where subjects consumed the animal protein-rich diet, but not to the same extent as in the other groups.”
Journal information: Itkonen, S. T., et al. (2021) Partial Replacement of Animal Proteins with Plant Proteins for 12 Weeks Accelerates Bone Turnover Among Healthy Adults: A Randomized Clinical Trial. The Journal of Nutrition.doi.org/10.1093/jn/nxaa264.