Dietary Supplements Could Protect the Body During Hot Weather Workouts: New Research from the American Physiology Summit

The pursuit of peak physical performance in high-temperature environments has long presented a challenge for athletes, outdoor workers, and fitness enthusiasts. As global temperatures continue to fluctuate and extreme heat events become more frequent, the physiological toll of "exercise heat stress" has moved to the forefront of sports science. At the American Physiology Summit, held from April 23 to April 26, 2026, in Minneapolis, Minnesota, a team of researchers presented evidence suggesting that three specific dietary supplements—berberine, curcumin, and New Zealand blackcurrant—may significantly improve the body’s ability to tolerate and perform under intense heat.

The study, titled "Integrated Effects of Berberine, Curcumin and New Zealand Blackcurrant on Physiological, Perceptual and Gastrointestinal Responses During Exercise Heat Stress," provides a data-driven look at how these naturally derived compounds interact with the human body’s cooling mechanisms and inflammatory responses. While researchers emphasized that these supplements are not a replacement for traditional hydration and heat-acclimatization protocols, the findings suggest they could serve as a vital secondary defense against heat-related performance degradation and physiological strain.

The Science of Exercise Heat Stress and the Minneapolis Summit

The American Physiology Summit is a premier annual gathering for the American Physiological Society, attracting thousands of scientists to discuss breakthroughs in human health and performance. This year’s focus on heat stress reflects a growing urgency within the medical community to address the risks associated with physical exertion in warming climates. Matthew Kuennen, PhD, an associate professor in the Department of Health and Human Performance at High Point University and a lead researcher on the study, noted that the search for "heat-protective" agents has shifted toward dietary supplements due to their accessibility and low barrier to entry.

"Dietary supplements are particularly attractive because they are easy to use, can be given over a short amount of time, and tend to be tolerated well by users," Kuennen stated during the presentation. The research aimed to move beyond anecdotal evidence, utilizing rigorous clinical trials to determine if these compounds could exert a measurable influence on core body temperature, heart rate, and gastrointestinal integrity during a simulated heat crisis.

Study Design and Research Methodology

To test the efficacy of the supplements, Kuennen and his team conducted a series of double-blind, placebo-controlled trials. This gold-standard research design ensured that neither the participants nor the researchers knew who was receiving the active supplement versus a placebo, thereby eliminating bias.

The study participants were subjected to a rigorous exercise challenge designed to mimic the conditions of a mid-summer outdoor run or a high-intensity training session in a non-climate-controlled environment. Each participant performed a 60-minute treadmill run at an intensity of 60 to 70 percent of their VO2 max—a level typically associated with a steady, challenging aerobic pace. The environment was strictly controlled to maintain temperatures between 93 and 98.6 degrees Fahrenheit (34 to 37 degrees Celsius).

The researchers implemented a specific timeline for supplementation to ensure the compounds reached effective levels in the bloodstream:

• Berberine: Administered for seven consecutive days prior to the exercise trial.
• Curcumin: Administered for three consecutive days prior to the trial.
• Blackcurrant Extract: Administered for seven consecutive days prior to the trial.

During and after the exercise bouts, researchers collected a wide array of data, including core body temperature, cardiometabolic metrics, and subjective heat perception. Furthermore, the team analyzed blood and urine samples to monitor changes in inflammatory markers and the function of the gastrointestinal (GI) barrier—a system that often fails under extreme heat stress, leading to what is commonly known as "leaky gut."

Statistical Findings: Heart Rate, Temperature, and Perception

The results of the data analysis revealed that all three supplements provided distinct physiological advantages. Perhaps most significantly, all three compounds were associated with a reduced increase in core body temperature compared to the placebo group. In the high-stakes world of endurance sports, even a fraction of a degree in core temperature can be the difference between finishing a race and suffering from heat exhaustion.

The cardiovascular data was equally compelling. Participants who utilized berberine and curcumin exhibited heart rates that were consistently lower by three to eight beats per minute (bpm) throughout the 60-minute run. This reduction in heart rate suggests a decrease in "cardiac drift," a phenomenon where the heart must work progressively harder to maintain the same output as the body struggles to cool itself.

Furthermore, the supplements influenced how the participants perceived the difficulty of the workout. Berberine, in particular, was linked to a reduction in the "Rating of Perceived Exertion" (RPE). This indicates that while the external workload remained the same, the athletes felt as though they were working less hard, which can have significant psychological benefits during competition.

Mechanisms of Action: How These Compounds Function

To understand why these three specific supplements were chosen, it is necessary to look at their biochemical profiles.

1. Berberine and Metabolic Efficiency
Berberine is a bioactive compound extracted from several different plants, including the Berberis shrub. In a sports nutrition context, its primary value lies in its ability to activate an enzyme called AMPK (adenosine monophosphate-activated protein kinase), often referred to as a "metabolic master switch." Albert Matheny, a sports nutritionist and co-founder of SoHo Strength Lab, explains that a more efficient metabolism generates less waste heat. "If you are more metabolically efficient, you are going to lower your heat stress," Matheny noted. By optimizing how the body processes fuel, berberine may help keep the internal "engine" from overheating.

2. Curcumin and Gastrointestinal Integrity
Curcumin, the active polyphenol in turmeric, is widely recognized for its anti-inflammatory properties. During intense exercise in the heat, blood flow is diverted away from the internal organs and toward the skin to facilitate cooling through sweat. This can lead to intestinal ischemia, causing the gut barrier to weaken and allow toxins into the bloodstream. Scott Keatley, a registered dietitian, noted that curcumin helps maintain gut barrier integrity under this specific type of stress, thereby reducing systemic inflammation and the overall physiological strain of the workout.

3. Blackcurrant and Vasodilation
New Zealand blackcurrant is particularly rich in anthocyanins, a type of antioxidant that promotes the production of nitric oxide. This leads to vasodilation—the widening of blood vessels. When blood vessels expand, the body can move hot blood from the core to the surface of the skin more effectively. Keatley explained that this improved blood flow allows the body to dissipate heat more efficiently through the skin, helping to stabilize core temperatures during prolonged exertion.

Clinical Recommendations and Dosage

Based on the findings presented at the summit, Matthew Kuennen outlined specific protocols for those looking to utilize these supplements as an adjunct to their heat-training routines. He emphasized that these are not meant for daily, year-round use, but rather for targeted windows of heat exposure.

The recommended dosages identified in the research include:

• Berberine: 500 mg taken three times daily (1,500 mg total) for the seven days leading up to an event.
• Curcumin: 500 mg taken twice daily (1,000 mg total) for the three days prior to an event.
• Blackcurrant Extract: 300 mg to 600 mg of standardized extract taken for seven days prior to an event.

Kuennen advised that both curcumin and berberine should be taken with food to maximize absorption. He further clarified that these protocols are best suited for the week prior to a major competition or for individuals facing sudden heat exposure, such as traveling from a cool climate to a tropical one for a race.

Expert Analysis: A Supplement, Not a Substitute

Despite the promising data, the scientific community remains cautious about over-relying on pills to combat environmental extremes. The consensus among the researchers and independent experts is that hydration remains the primary pillar of heat safety.

"You can take all of this stuff, but if you’re not hydrated, it’s not going to work," said Matheny. Hydration is essential for maintaining plasma volume; without enough fluid in the blood, the heart rate will spike and the body will lose its ability to produce sweat, regardless of what supplements are in the system.

Scott Keatley also pointed out the limitations of the study, noting that while the results were statistically significant, the "effect size" is relatively small. "These were small, controlled lab studies looking at indirect signals like heart rate and inflammation, not real-world outcomes like heatstroke prevention or Olympic-level performance gains," he cautioned.

Broader Implications and Future Research

The research presented in Minneapolis has implications that extend far beyond the world of elite athletics. As climate change increases the number of "dangerously hot" days per year, occupational health experts are looking for ways to protect outdoor laborers, firefighters, and military personnel. If a simple week-long regimen of natural supplements can reduce heart rate and internal strain, it could represent a cost-effective tool for improving safety in high-risk industries.

Future research is expected to focus on whether combining these three supplements (a "stack") produces a synergistic effect that is greater than taking any one of them individually. Additionally, longitudinal studies are needed to determine if there are any long-term side effects of repeated short-term use during summer training seasons.

For now, the findings offer a new "marginal gain" for those who must perform when the mercury rises. While the fundamentals of shade, water, and electrolytes remain unchanged, berberine, curcumin, and blackcurrant may provide the physiological edge needed to turn a grueling workout into a productive one. As Kuennen concluded, these supplements should be viewed as "adjuncts, rather than replacements, for established heat illness countermeasures."