Physiological mechanisms determining eccrine sweat composition

Abstract

The purpose of this paper is to review the physiological mechanisms determining eccrine sweat composition to assess the utility of sweat as a proxy for blood or as a potential biomarker of human health or nutritional/physiological status. Methods This narrative review includes the major sweat electrolytes (sodium, chloride, and potassium), other micronutrients (e.g., calcium, magnesium, iron, copper, zinc, vitamins), metabolites (e.g., glucose, lactate, ammonia, urea, bicarbonate, amino acids, ethanol), and other compounds (e.g., cytokines and cortisol). Results Ion membrane transport mechanisms for sodium and chloride are well established, but the mechanisms of secretion and/or reabsorption for most other sweat solutes are still equivocal. Correlations between sweat and blood have not been established for most constituents, with perhaps the exception of ethanol. With respect to sweat diagnostics, it is well accepted that elevated sweat sodium and chloride is a useful screening tool for cystic fibrosis. However, sweat electrolyte concentrations are not predictive of hydration status or sweating rate. Sweat metabolite concentrations are not a reliable biomarker for exercise intensity or other physiological stressors. To date, glucose, cytokine, and cortisol research is too limited to suggest that sweat is a useful surrogate for blood. Conclusion Final sweat composition is not only influenced by extracellular solute concentrations, but also mechanisms of secretion and/or reabsorption, sweat flow rate, byproducts of sweat gland metabolism, skin surface contamination, and sebum secretions, among other factors related to methodology. Future research that accounts for these confounding factors is needed to address the existing gaps in the literature.

The (in)dependency of blood and sweat sodium, chloride, potassium, ammonia, lactate and glucose concentrations during submaximal exercise

“…Since extracellular fluid is the precursor for primary sweat in the coil of eccrine sweat glands (Kuno 1956), direct relations between blood and sweat composition are sometimes assumed. However, before eccrine sweat is released onto the skin surface, modifications to the primary solution are made during its passage along the sweat glands duct (Baker and Wolfe 2020). Due to such modifications, blood and sweat composition do not necessarily relate.…”

Different Waters for Different Performances: Can We Imagine Sport-Related Natural Mineral Spring Waters?

“…Therefore, assuming that athletes need medium/high-mineralized spring waters according to intensity, environmental conditions and sweat, it is conceivable to hypothesize that the hydro-chemical composition of NMSW may be the key to optimize the hydration status of the athletes and maximize their performance. In this perspective, some authors have recently investigated the sweat response (electrolyte loss) of team sports athletes [85][86][87][88] at different exercise intensities. These preliminary results can be matched with the specific mineral content of spring waters (Table 2) to compare the reported sweat losses in both low-intensity exercise (LIE) and moderate-intensity exercise (MIE).…”

A wearable fluidic collection patch and ion chromatography method for sweat electrolyte monitoring during exercise

“…1,11 However, papers that present Na + and Clmeasurements together with changes in hydration status, show mixed results. 12 One of the main reasons for this is the lack of standardized collection and analysis methods. For K + , part of the secretion mechanism is known.…”