Hot weather and gut health: why hydration and prebiotics make a smart partnership

Hotter weather can affect more than our ability to keep cool. The gut may also feel the effects as higher temperatures increase fluid loss through sweating and place greater demands on the body to regulate core temperature. For the gastrointestinal (GI) tract, dehydration, physical exertion and heat stress may affect digestive comfort and can compromise intestinal barrier function.

This raises the question for product developers of whether combining hydration with targeted gut health ingredients could provide complementary support for gut health during hotter weather and periods of increased physiological stress.

How hot weather affects the gut

The GI tract is sensitive to changes in homeostasis, the body’s internal environment, including osmoregulation. During hot weather, increased sweating can lead to greater fluid and mineral loss. If fluid intake does not keep pace, dehydration may contribute to changes in gastrointestinal function and bowel habits^[1].

Managing heat is also more challenging for the gut during exercise. As physical activity increases, blood flow is directed towards working muscles. In hot conditions, blood flow to the skin also increases to help the body dissipate heat. Together with rising core temperature and fluid and mineral loss, this can reduce blood flow to the gastrointestinal tract and place additional stress on the intestinal lining. Another consequence of fluid loss is a higher chance of constipation. Research indicates that exertional heat stress can exacerbate gastrointestinal perturbations associated with exercise, including changes in gut barrier integrity and gastrointestinal symptoms^[2].

Controlled studies have reported greater gastrointestinal perturbations when endurance exercise is performed at 30°C and 35°C compared with 22°C^[2]. Heat therefore adds to the physiological demands of exercise, particularly when fluid and mineral loss and rising core temperature are also factors.

Hydration

Adequate hydration helps replace fluids and minerals lost through sweating and supports normal physiological function. As prebiotics like galactooligosaccharides (GOS) can help lower gut pH to create a more favourable environment for nutrient absorption, this makes building around hydration a naturally important consideration for product developers looking at gut health as part of sports nutrition and active lifestyle products.

Pairing hydration with prebiotic support

Dietary fibre and prebiotics are often discussed together, but they are not interchangeable. Dietary fibres are typically insoluble and contribute to water retention in the gut by and form stool bulk and can thus support regularity. Prebiotics, meanwhile, are typically soluble and are substrates that are selectively utilised by beneficial microorganisms in the gut which in turn, have many associated benefits ranging from gut comfort to immunity and brain function[SR5.1][MF5.2]. Galactooligosaccharides (GOS), for example, can selectively nourish beneficial bacteria, particularly bifidobacteria[3].

The combination with hydration is relevant during warmer weather: one helps replace fluids and minerals, while the other provides targeted support for the gut microbiome. For formulators, this combination could translate into convenient product concepts for summer, sports nutrition, travel and active lifestyles.

Heat, sleep and the gut

Hotter nights can also disrupt sleep, and emerging research indicates a relationship between sleep, circadian rhythm and the gut microbiome ^[4]. This becomes particularly relevant during travel. Holidays can bring later nights, unfamiliar foods, introduction to new bacteria unfamiliar to the body and different eating patterns, alongside exposure to warmer temperatures. Together, these changes may affect digestive comfort, gut health as well as immune function.

What does the research show?

The evidence for Bimuno GOS extends beyond heat-specific research, with clinical studies reporting reductions in gastrointestinal symptoms including bloating, flatulence and abdominal pain[5].

Furthermore, in a 2026 randomised, double-blind, placebo-controlled study, 26 male team-sport athletes consumed either Bimuno GOS or a placebo for 7 weeks. On days 0 and 42, participants completed a football-specific intermittent exercise protocol at 33°C and 50% relative humidity[6].

After 6 weeks, the Bimuno GOS group showed a significant reduction in -plasma intestinal fatty acid-binding protein (I-FABP)[DP7.1][MF7.2], a biomarker associated with intestinal epithelial damage, compared with placebo. The study also found reduced gastrointestinal discomfort and a more favourable salivary IgA secretion following exercise[6].

The findings support a potential role for targeted prebiotic supplementation in reducing GI disruption associated with demanding exercises in hot conditions.

Additionally, two double blind, placebo controlled human studies have investigated Bimuno GOS in[MF8.1][SR8.2] travellers, providing clinical evidence for a microbiome-targeted approach.

In the 2010 study by Drakoularakou et al, involving 159 travellers, daily Bimuno GOS supplementation beginning one week before departure significantly reduced the incidence of diarrhoea by approximately 15% and shortened its duration by around two days, while also reducing the duration of associated abdominal pain[7].

A larger 2017 study by Hasle et al, involving 334 participants at the Oslo Travel Clinic also found a significant reduction in diarrhoea incidence among those who adhered closely to the supplementation protocol, with the effect becoming statistically significant from day 8 onwards[8].

Together these findings demonstrate the potential for targeted prebiotic supplementation to support digestive resilience before and during travel. For formulators, this broadens the opportunity beyond heat and hydration alone to products designed to support gut health when routines and environmental conditions change.

An opportunity for summer wellness products

For formulators, the combination of heat, hydration, exercise and changing routines creates an opportunity to look beyond hydration alone.

Potential applications include:

• Prebiotic hydration powders: combining fluid replacement with targeted microbiome support in a convenient format.
• Ready-to-drink beverages: bringing hydration and digestive health together in an accessible format.
• Gut and immune health supplements: incorporating prebiotic support into daily health products.
• Active lifestyle products: incorporating prebiotic support into products designed around exercise and performance.

Bimuno GOS is suitable for a range of food and supplement formats, including powder blends, sports RTDs, tablets and functional foods.

Supporting the gut when conditions change

Hot weather does not necessarily mean poor gut health. However, dehydration, exercise, travel and disrupted routines can introduce additional demands on the body.

For formulators, combining hydration with targeted prebiotic support offers a way to address two complementary aspects of health: replacing fluids lost through heat and sweating while supporting beneficial bacteria in the gut.

As interest grows in convenient, multi-benefit products, this combination could offer an interesting direction for summer, sports and active lifestyle formulations.

For more information about Bimuno® GOS and its formulation opportunities, visit Clasado Biosciences.

References

1. Arnaud MJ. Mild dehydration: a risk factor of constipation? European Journal of Clinical Nutrition. 2003;57(Suppl 2)–S95. doi:10.1038/sj.ejcn.1601907.
2. Costa et al., 2020. Exertional-heat stress-associated gastrointestinal perturbations during Olympic sports: Management strategies for athletes preparing and competing in the 2020 Tokyo Olympic Games. Temperature. 2019;7(1):58–88. doi:10.1080/23328940.2019.1597676.
3. Vulevic et al., 2008. Modulation of the fecal microflora profile and immune function by a novel trans-galactooligosaccharide mixture (B-GOS) in healthy elderly volunteers. American Journal of Clinical Nutrition. 2008;88(5):1438–1446. doi:10.3945/ajcn.2008.26242.
4. Olson M, et al., 2026. What is the nature of sleep and circadian rhythm health on gastrointestinal microbiota? A systematic review of studies in humans. Sleep Medicine Reviews. 2026;86:102256. doi:10.1016/j.smrv.2026.102256.
5. Vulevic et al., 2018. Effect of a prebiotic galactooligosaccharide mixture (B-GOS®) on gastrointestinal symptoms in adults selected from a general population who suffer with bloating, abdominal pain, or flatulence. Neurogastroenterology & Motility. 2018;30(11). doi:10.1111/nmo.13440.6. Parker et al., 2023. Prebiotic Bimuno® GOS reduces illness symptoms and supports gut barrier function and immunity after intermittent exercise in the heat. Experimental Physiology. Published online March 24, 2026. doi:10.1113/EP092682.
6. Drakolarakou et al., 2009. A double blind placebo-controlled, randomized human study assessing the capacity of a novel galacto-oligosaccharide mixture in reducing travellers’ diarrhoea. Pubmed. 2009. Doi:10.1038/ejcn.2009.120
7. Hasle G et al., 2017. Can a galacto oligosaccharide reduce the risk of traveller’s diarrhoea? A placebo-controlled, randomized, double blind study. Oxfor Academic. Doi: 10.1093/jtm/tax057