While an increase in protein intake had no effect on body height in the boys and young men, a clear relationship was found in the girls. According to the scientists' calculations, an average increase of about seven grams of protein daily above the intake recommendations leads on average to an increase in height of one centimeter. "If no increase in height is desired, girls may even achieve a reduction in their later adult height by a few centimeters during growth by adjusting their protein intake to the recommendations, i.e. by not unnecessarily raising their protein intake," says Remer.
In boys, there are interactions with sex hormones
Even at intakes clearly above requirements, protein still has significant growth-promoting effects in girls, according to the data. "This effect on height does not seem to play a relevant role in boys with protein intakes above requirements," says Yifan Hua. "Apparently, for them, significantly stronger effects of sex hormones - including testosterone - on the growth hormone axis leave less room for an additional anabolic nutritional effect from protein." In principle, protein intake should not be markedly higher than recommendations, such as 48 grams per day for 15- to 17-year-old female adolescents, the researchers said.
However, in reality, daily protein intake for many children is considerably higher, in some cases by 1.7 to 2 times. "Possible long-term consequences of correspondingly high protein intakes have not yet been satisfactorily examined," says Prof. Remer. "Only for bone stability have we been able to observe positive relations with increased protein intake in past studies, provided that the fruit and vegetable intake was not too low and thus the diet-dependent acid load was not too high."
The DONALD study
The DONALD study is a long-term investigation of the effects of nutrition on physiological and health-related outcomes during and after the completion of growth, funded by the state of North Rhine-Westphalia. Currently, more than 1000 healthy children, adolescents and young adults are participating.
Detailed data on nutrition, growth, development, metabolism and health status have been collected from the subjects at regular intervals since 1985, from infancy to adulthood. Since January 2012, the long-term study conducted in Dortmund is a branch of the Institute of Nutrition and Food Sciences (IEL) at the University of Bonn.