Author(s): BONDI, D., DE THOMASIS, F., LATTANZI, B., VERRATTI, V., PICCINELLI, R., CANTARELLI, S., PILATO, S., SANTANGELO, C., Institution: UNIVERSITY OF CHIETI - PESCARA, Country: ITALY, Abstract-ID: 381

INTRODUCTION:
High-altitude environments cause changes to body composition, water-electrolyte levels and several physiological systems [1]. Therefore, nutritional and homeostatic assessment is vital for high-altitude expeditions to prevent risks, preserve performance, and speed recovery. This Himalayan trek study aimed to address these issues.
METHODS:
A total of 21 participants (12 m and 9 f, aged 43 ± 15 years and with a BMI of 24.2 ± 3.70 kg/m²) took part in the expedition. The uphill trek to the Pyramid Laboratory, during which participants took a 250 mg pill of acetazolamide once daily, took place over six days, interspersed with a day of rest. The descent trek after a five-day stay in the Pyramid took place in four days. Urine and blood samples were collected prior to the trek, in Kathmandu (LA, 1400 m a.s.l.), during the high-altitude phase at Pyramid (HA, 5000 m a.s.l.), and upon return in Kathmandu (LApost). Blood samples were also collected in Italy before and after the expedition. The food diaries were recorded on three separate days during the trek and further analysed through the FOODCONS software. Comparisons were made with the use of either the random effects analysis of variance (RM-ANOVA) or the mixed-effects
RESULTS:
In almost all participants, the mean daily energy intake was found to be considerably lower than the estimated total daily energy expenditure. The intake of water and protein was lower than recommended during the expedition. A lower body mass index was observed once back in Kathmandu (p=0.036, F(0.79, 14.2)=5.79). With regard to the urinary analyses, osmolality was higher at LApost, and pH at HA (p=0.063, F(2, 36)=2.99; p=0.012, F(2, 40)=4.93). With regard to the blood analysis, the levels of iron, ferritin and thyrotropin were lower at HA (p<0.001, F(2.47, 37.1)=10.9; p=0.011, F(1.83, 27.5)=5.55; p=0.003, F(2.05, 30.7)=7.09). Conversely, transferrin and free triiodothyronine levels were higher at HA (p=0.007, F(3.20, 56.8)=4.37; p=0.021, F(2.85, 42.7)=3.68). Creatinine levels did demonstrate a non-significant increase at HA (p=0.065, F(2.34, 37.4)=2.82). The alterations in blood urea nitrogen levels exhibited heterogeneity among the study participants.
CONCLUSION:
An overall negative energy balance during the course of the expedition emerged. The HA-induced renal compensation for balancing pH (a process further supported by acetazolamide) and mobilisation of iron reserves were in evidence. The increase in urinary osmolality upon returning to Kathmandu indicated a potential dehydration. The thyroid axis was activated at HA, followed by subsequent inhibition of the pituitary gland. During HA expeditions, in addition to medical examinations and pre-expedition advice [2], specific dietary strategies are strongly encouraged to support adequate physiological responses.
REFERENCES:
[1] Santangelo et al. (2024), Appl. Physiol. Nutr. Metab.
[2] Burtscher et al. (2025), Minerva Med.