Hypobaric hypoxia imposes various challenges at high altitude that initiate differentphysiological responses as part of the acclimatization process. Current interventions foraccelerating and/or improving acclimatization to high altitude are limited. Preliminarystudies of the multi-strain probiotic SLAB51 (O2booster; Hecto, Seoul, South Korea)have shown its potential to improve oxygenation, a crucial component ofacclimatization, in clinical conditions of hypoxemia. We hypothesized that treatment withSLAB51 at high altitude will lead to improved acclimatization as measured by oxygensaturation (SpO2) and scores from the Acute Mountain Sickness (AMS) survey (2018Lake Louise Questionnaire). A group of 17 (9 males, 8 females) healthy Latino/a adultsfrom the San Diego area, ranging from ages 19-63, were taken from sea-level to WhiteMountain Barcroft Station (3800 m) for up to four days. Participants underwent adouble-blind, placebo-controlled study where nine participants consumed the SLAB51probiotic and eight consumed a placebo up to three times a day. SpO2 was measuredusing a forehead pulse oximeter, and an AMS survey score was attained daily. Ouranalyses revealed that SpO2 was significantly higher in participants who received theSLAB51 probiotic at high altitude versus those who received the placebo (Two-wayANOVA, p-value < 1.12e-05). Furthermore, AMS scores were significantly lower inparticipants treated with SLAB51 than those who received the placebo (Two-wayANOVA, p-value < 0.007). Our results indicate that SLAB51 ingestion at high altitudeimproved SpO2 compared to a placebo and may improve acclimatization to high altitude. Funding: LEA Altitude Performance Fund. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.