Quality Control of Protein Supplements: A Review

Abstract

The growing consumer awareness regarding health and fitness has been leading to a huge rise in the consumption of nutritional supplements and, consequently, to an increase in concerns about their quality. In this sense, one of the most consumed products is protein supplements and, despite being safer than other types of supplements, there are several studies showing incompatibilities between what is present on the labels and their actual content. Therefore, this review is focused on gathering information about the problems arising from poor manufacturing practices and inadequate quality control of sport protein supplements. These issues are mainly related to three aspects: reduction of the supplements’ nutritional value, the presence of pharmacological substances, and contamination with microorganisms or toxic metals. Regarding the first aspect, reports about the “classic” addition of nitrogen-rich compounds to mask the protein content measured by the Kjeldahl method were discussed, as well as recent topics such as the addition of cheaper proteins to produce an “undetectable” adulteration in whey protein supplements. With respect to the presence of pharmacological compounds, it is a finding that is not very common in protein supplements; however, even trace amounts of foreign substances in this type of product may cause adverse effects to consumers, and, in the case of an elite athlete, may result in doping. Finally, we discuss about the contamination with microorganisms and toxic metals, this latter being a subject that should be further explored due to few studies in the literature.

Focus on the Protein Fraction of Sports Nutrition Supplements

“…The amount of TAA, expressed as g/100 g product, did not always correspond to the protein content reported in Table 1 . An incomplete recovery was expected considering the partial degradation of some amino acids (e.g., Trp, Tyr) during acid hydrolysis and the partial loss of Lys due to the irreversible glycosylation during product manufacturing and storage [ 4 ]. Gasparini et al [ 11 ] also reported a recovery of TAA after acid hydrolysis of WPC that was 25% lower than the protein content determined by the Kjeldahl method.…”

“…Notably, the literature in this research area is increasing as well, and the derived scientific knowledge is constantly evolving [ 2 , 3 ]. Sports supplements are basically nutrient-dense foods, with milk protein representing the main component [ 4 ]. Minor ingredients are vitamins, minerals, essential fatty acids, selected amino acids, fiber, among others.…”

“…However, the more recently available high-protein powders from whey, namely whey-protein concentrates (WPC) and isolates (WPI), are today extensively used in sports supplements, as well as in other nutritional and health preparations and in protein-fortified bars or fermented beverages [ 5 , 6 ]. These products, therefore, lack the casein fraction, which is considered a slow-digesting protein [ 4 , 7 , 8 ].…”

Caffeine content of energy drinks marketed in Brazil

“…Finally, we encourage future studies to investigate the presence of undeclared stimulants in energy drinks. Even though many related studies regarding the presence of prohibited substances in nutritional supplements exist, [22][23][24][25] there is still this gap in the literature for energy drinks.…”

Fast and simple analysis of the content of Zn, Mg, Ca, Na, and K in selected beverages widely consumed by athletes by flowing liquid cathode atmospheric pressure glow discharge optical emission spectrometry

“…14,15 Unfortunately, there are very few papers regarding the mineral content in these supplements and when they appear, they focus on heavy metals. [14][15][16] Generally, to assess the elemental content of selected metals in the above-mentioned supplements, graphite furnace atomic absorption spectrometry (GF-AAS), inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS) are applied. 14 Nevertheless, the analysis performed using the above-mentioned instruments may be challenging due to certain issues related to their practical application.…”