Powdered protein supplements are one of the most commonly consumed nutritional supplements, whether by professional athletes or amateurs, even by those who use them for aesthetic purposes instead of sporting ones. This study, led by a researcher from the Area of Human Motility and Sporting Performance at the University of Seville, has analysed the quality of these products in function of their source, treatment and storage.

"During the preparation of powdered protein supplements, the thermal treatment involved can reduce the nutritional value of the product, an aspect that, until now, has received little research attention. Lysine, an amino acid involved in this reaction, is transformed into other compounds that are not biologically usable. In addition, according to the thermal treatment received, changes can be produced in the protein structure, which means that these supplements are less digestible for the body. Therefore, it was importance to investigate this matter deeply," explains the University of Seville teacher Antonio J. Sánchez.

The results indicate that half the supplements analysed contain more than 6% of blocked Lysine, but only 9% had a content of more than 20% of blocked lysine. In addition, the supplements with the highest concentrations of blocked lysine were hydrolysed and peptide serums (12%), while the lowest concentrations were registered by serum and casein isolates. The study also served to prove that the content of carbon hydrates as shown on the label could be an "indirect but useful" indication of the thermal damage done to milk serum supplements.

However, the experts indicate that, a priori, the consumption of protein supplements does not offer any health problems, provided that a product has complied with quality controls, is bought in a specialised and approved establishment and is made using the correct criteria. "There are increasingly more cases in which the consumption of supplements means, unknown to the consumer, the consumption of substances that can have adverse effects on their health. Therefore, nutritional evaluation must be the first step when advising sportspeople on diet strategies or the use of supplements," the researcher adds.

Nutritional evaluation must always be tailored to the individual and done by a professional who takes into account the person's detailed medical and nutritional history, evaluation of their diet, anthropometry, and analysis of their body and biochemical composition, before prescribing any supplement.

Real benefit for health and for sporting performance

According to the experts, the consumption of good quality protein supplements, as can be the case with an isolate of milk serum, can produce benefits for both health and sporting performance. There is scientific evidence that backs the idea that they can help to minimise the loss of muscle mass in old people or help those who practise sports in which strength is important to achieve an optimised level of muscle performance, for example.

This study was part of a multidisciplinary project, in which more than 5,000 individuals of different profiles participated: international sportspeople, whole national teams, amateur sportspeople, gym users, etc. "Knowing what use is made of these supplements can help us to understand the legal and educational needs in that regard, and improve the information we give to society."

This project had the collaboration of various Spanish, European and Latin-American universities.