Researchers from Texas Tech and Samford University recently explored emerging evidence surrounding the efficacy and practicality of nutritional and hydration strategies to counter exertional heat stress and accelerate adaptations to mitigate chronic heat.
They highlighted that risks are accentuated in elite athletes competing across climates and in military and firefighter populations subjected to thermal extremes in the field that spike susceptibility to exertional heat illness/stroke (EHI/EHS).
“Despite difficulties quantifying the prevalence of EHI/EHS due to inconsistencies in terminology and criteria for diagnosis, endurance sports and military populations experience the highest rates of heat-related illnesses globally, with ~674.0 cases of EHI per 10,000 athlete-exposures,” they wrote in the journal Nutrients. “Therefore, exercise performance in the heat can be suboptimal, with tailored heat mitigation and nutritional strategies required to attenuate heat-mediated decrements in performance and health.”
Heat, humidity and human health
Heat stress can lead to dehydration, exhaustion and cardiovascular strain, and high humidity not only increases the severity of a heatwave but worsens air quality by trapping pollutants, exacerbating respiratory issues like asthma. In a warming world, certain populations—like the elderly, young children, the socio-economically disadvantaged and people with chronic conditions—are also particularly vulnerable, and mortality from heat exposure is on the rise.
Research published last year in the Journal of the American Medical Association (JAMA) reported an increase in heat-related deaths in the United States starting around 2016, with the largest number since 1999 occurring in 2023.
“This trend has emerged as warming has accelerated in recent years, with 2023 and 2024 shaping up to be the hottest years on record,” said Jeffrey Howard, PhD, associate professor in the Department of Public Health at the University of Texas at San Antonio and co-author on the JAMA paper.
“The results reinforce the need for multifaceted strategies to mitigate extreme heat exposure, such as public cooling centers, hydration centers, public awareness campaigns, heightened awareness of healthcare providers and so forth. Another aspect is that the risk is evenly distributed, and some of the more susceptible areas of the country are the ones that have not historically had to deal with extreme heat.”
Various nutritional strategies, degrees of efficacy
To examine nutrition and ergogenic aids as strategy to target acute responses and chronic adaptations to exertional heat exposure, the review analyzed studies extracted from the PubMed, SPORTDiscus, Scopus and Google Scholar databases.
In the studies selected, the ambient temperature of exercise performance conditions had to exceed 82 °F, simulating predicted environmental temperatures of major sporting events.
During the last Summer Olympics, for example, temperatures neared 100 °F as a heat dome settled over Paris, with the NASA Earth Observatory reporting that temperatures have risen by 5.5 °F since the city hosted the event a century ago. At the preceding summer games in Tokyo, extreme humid heat led to 146 reported cases of heat-related illness among Olympic and Paralympic athletes.
The review presented evidence surrounding hydration and fluid replacement, carbohydrates, protein, caffeine, nitrate, tyrosine and creatine for potentially enhancing various aspects of physiological, cognitive and recovery outcomes during acute and chronic exertional heat—some more promising than others.
Potential effect of ergogenic aids on acute responses and chronic adaptation to exertional-heat exposure
Protein: increases exercise recovery rate and performance, decreases core temperature and maintains body mass
Nitrate: increases core temperature and vasolidation
Sodium: increases plasma volume, sweat rate and exercise performance, decreases core temperature
Caffeine: increases core temperature and brain dopamine
Creatine: increases body mass and time to exhaustion
Tyrosine: increases brain dopamine and exercise performance
Carbohydrates: increases intestinal integrity, glycogen storage and exercise capacity
“As exercise in the heat alters the efficacy of numerous dietary supplements, the results of certain ergogenic aids in thermoneutral conditions do not always transfer to conditions of high ambient temperatures,” the researchers noted.
Given the sometimes-ambiguous nature of the findings across studies, they called for further research into dose-response relationships, sex- and exercise modality-specific responses and performance measures tied to proposed mechanisms of action.
Source: Nutrients
doi: 10.3390/nu16223792
“The Efficacy of Nutritional Strategies and Ergogenic Aids on Acute Responses and Chronic Adaptations to Exertional-Heat Exposure: A Narrative Review”
Authors: Ryan A. Dunn et al.
