27 May 2015

man doing strength training with personal trainerNew research at the University of South Australia published in the journal Clinical Nutrition suggests that soy proteins reduce the benefits of strength training compared to a protein matched dairy-enriched diet.

The results were uncovered in a new study, funded by the dairy industry, looking at how diet can support the development of strength gains for older people during strength or resistance training.

Director of UniSA’s Alliance for Research in Exercise, Nutrition and Activity (ARENA), Professor Jon Buckley led the study and says the research has implications for the management of diet and health and fitness regimes.

“It is now well accepted that strength training with weights or resistance training is especially good for people as they age because it helps them to maintain muscle strength that is so vital to remaining mobile, active and independent,” Prof Buckley says.

“In our research we were looking at different types and amounts of protein intake during strength training to see what relationships there might be to strength gains.”

The study took a group of middle-aged adults and had them undertake a program of resistance training in accordance with recommended guidelines.

At the same time, they consumed diets with different levels of protein from different sources. All of the people in the study received a diet with a proportion of protein typical of the Australian diet with most protein coming from meat sources.

A portion of the study group remained on this typical diet while others were asked to consume extra protein in the form of either dairy foods or soy foods.

“While the whole group increased their strength, those participants who were eating the soy foods as a supplementary source of protein did not increase strength as much as those consuming the amount of protein typical of the Australian diet or those taking their extra protein in dairy foods,” Prof Buckley says.

“This means people eating the soy supplements were reaping less benefit for all the hard work done in the training.

“All of the participants were undertaking the same exercise regime so we need to look at why soy foods might have limited the increase in strength that could be achieved.

“It may be due to soy foods containing isoflavones which have estrogenic properties which oppose or dampen the muscle building actions of the testosterone that is released immediately after weight or resistance training.

“The take home message here is that people wanting to get the most out of strength training should concentrate on high quality protein sources such as dairy and meat to supplement their diets and avoid soy foods.”

Contact for interview: Jon Buckley office (08) 8302 1853 mobile 0417 880 030 email jon.buckley@unisa.edu.au

Media contact: Kelly Stone office (08) 8302 0963 mobile 0417 861 832 email Kelly.stone@unisa.edu.au

Michèle Nardelli office (08) 8302 0966 mobile 0418 823 673 email michele.nardelli@unisa.edu.au

This study was supported by a competitive peer-reviewed grant from the Dairy Health and Nutrition Consortium.

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