Why Rooibos is the unofficial fuel of SA’s ocean-endurance athletes

When marathon swimmers clip their feed-bottles to a skipper’s rail off Dassen Island or False Bay, they’re often reaching not for energy gels or neon sports drinks but for a humble, red brew: Rooibos. Long treated in many South African households as a comforting evening cup, rooibos (Aspalathus linearis) has quietly become a staple on open-water support boats — favoured for its gentleness on the stomach, antioxidant profile and ability to be adapted into a warm, lightly sweetened feeding that helps swimmers hydrate and steady their core temperature during icy crossings.

That cultural reality — practised for decades by local skippers and swimmers — is now meeting scientific scrutiny. South African researchers and recent systematic reviews suggest rooibos has properties that are relevant to endurance exercise: antioxidants that reduce oxidative stress, anti-inflammatory compounds that may speed recovery, and a palatable, caffeine-free hydration matrix that athletes tolerate well under prolonged exertion. Cape Long Distance Swimming Association

From tradition to the boat: why swimmers choose rooibos

Veteran open-water crews have long favored rooibos for practical reasons. Brewed strong and served warm in small bottles, sometimes with a spoonful of honey, a pinch of salt or added maltodextrin, rooibos offers a mild, easily digestible sweetness that helps counteract salt taste after hours in seawater and provides quick carbohydrates without the gastrointestinal upset that some commercial sports drinks can cause. In cold-water swims — where water temps in places like False Bay often fall into the low-teens Celsius — a warm feed also helps buoy body temperature between feedings. Local swim organisers and the Cape Long Distance Swimming Association (CLDSA) document these feeding rhythms across the season.

What the science says — antioxidant, anti-inflammatory, recovery support

Rooibos contains polyphenols and unique flavonoids (aspalathin and nothofagin among them) that act as antioxidants. A growing body of research from South African universities — notably work led by researchers at the Cape Peninsula University of Technology (CPUT) — has explored rooibos’ impact on exercise-induced oxidative stress, inflammation and recovery markers. Controlled dietary-intervention trials and pilot studies have reported promising signals: reductions in oxidative stress markers, improved recovery profiles, and in some submaximal exercise trials small but meaningful improvements in endurance metrics.

A recent systematic literature review (Speer et al., 2024) summarised the human evidence on rooibos and found mixed but encouraging outcomes: several clinical studies reported beneficial effects on cardiometabolic markers and oxidative stress, while others showed no statistically significant change — an overall picture of potential that requires larger, well-powered trials.

More targeted exercise research has progressed rapidly. CPUT teams (including Prof. Simeon Davies and collaborators) have produced pilot and controlled trials exploring rooibos supplementation in exercise settings and even a pilot expedition study on high-altitude oxidative stress. Ongoing work published or deposited in 2024–2025 investigates rooibos’ modulatory role on exercise-induced oxidative stress and uses metabolomics to map metabolic responses and genotype–phenotype interactions — modern techniques that deepen biological plausibility for the anecdotal benefits swimmers report.

Practical benefits for open-water athletes

From a coach’s and skipper’s perspective, rooibos ticks several boxes:

• Gastrointestinal tolerance: mild on the stomach compared with some concentrated commercial sports drinks.

• Caffeine-free: avoids potential thermal or sleep effects that can be undesirable in long expeditions or multiple-day events.

• Flexible energy delivery: easily combined with honey, maltodextrin or a light electrolyte mix for quick carbs and sodium.

• Antioxidant load: provides polyphenols that may blunt oxidative stress during prolonged exertion and aid muscle recovery.

CPUT researchers note that in some controlled trials athletes consuming rooibos before/during exertion showed improved markers of fatigue and recovery — modest performance edge in a sport where 3–5% can separate podium places. But they caution that findings are preliminary and that rooibos is best seen as a complement to, not a replacement for, established sports-nutrition strategies.

From local ritual to international curiosity

While the practice is rooted in South African open-water culture, visiting marathon swimmers who come to train and race here often adopt local feeding protocols. Reports from local swim communities and event pages show rooibos on support boats as an accepted norm in Cape waters; international athletes have sampled — and, in some cases, incorporated — rooibos into their feeding regimens during South African swims. The combination of cultural availability, palatability and emerging evidence makes the brew an appealing, low-risk option in long swims.

Cautions and the research path ahead

Important caveats: not all studies find a benefit, effect sizes are often small, and methodological differences (fermented vs. unfermented rooibos, serving concentration, co-ingested carbohydrates) matter. The 2024 systematic review concluded the evidence is mixed and called for standardized, larger trials — exactly what CPUT researchers and international collaborators are now pursuing. Future studies that combine metabolomics, standardized feeding protocols and performance endpoints will clarify how robust rooibos’ ergogenic effects are across athlete populations.

The bottom line

For South Africa’s ocean endurance community, rooibos is more than folklore: it’s a low-risk, locally abundant beverage with a plausible biological mechanism and growing empirical support. It hydrates, soothes the gut, and supplies antioxidants — and when fortified with simple carbs or electrolytes it becomes a practical mid-swim fuel. For athletes and coaches chasing marginal gains in brutal marine conditions, that combination matters.

As research teams translate the anecdote into controlled evidence, one thing is clear on Cape waters this season: the red tea in the feed-bottle is as much a part of the kit as goggles and vaseline — and, for many, it’s a proudly South African performance secret worth sharing.