Lower Reported Energy Intake Relative to Estimated Requirements Is Associated with Impaired Lung Function, Reduced Respiratory Muscle Strength and Reduced Levels of Pulmonary and Systemic IL-10 and Klotho in Older Adults

Background: Caloric deficiency may adversely affect respiratory and immune function in older adults, but its association with pulmonary function, respiratory muscle strength, and pulmonary immunoregulatory mediators remains poorly understood. Methods: In this cross-sectional observational study, community-dwelling older adults were classified according to habitual energy intake relative to estimated energy requirements as normocaloric or hypocaloric. Pulmonary function, handgrip strength, maximal inspiratory and expiratory pressures (MIP and MEP), 1-min sit-to-stand (STS) performance, and systemic and pulmonary concentrations of IL-6, TNF-α, IL-10, and Klotho were assessed. Associations between energy adequacy and study outcomes were additionally investigated. Results: Participants with hypocaloric intake exhibited lower FVC (92.23 ± 14.66 vs. 101.32 ± 19.41% predicted; p = 0.012) and FEV1 (87.31 ± 18.09 vs. 102.93 ± 21.82% predicted; p = 0.002), while FEV1/FVC and expiratory flows were preserved. Handgrip strength (p < 0.001), MIP (p = 0.013), MEP (p = 0.038), and 1-min STS performance (p < 0.001) were also lower. Plasma IL-10 (p = 0.002) and Klotho (p = 0.012), and exhaled breath condensate IL-10 (p = 0.010) and Klotho (p = 0.003), were lower in the hypocaloric group, whereas IL-6 and TNF-α did not differ. Energy adequacy was positively associated with FVC, FEV1, functional capacity, and systemic and pulmonary IL-10 and Klotho. Conclusions: Hypocaloric dietary intake was associated with reduced pulmonary function, respiratory and peripheral muscle strength, functional capacity, and lower systemic and pulmonary IL-10 and Klotho in older adults, without concomitant elevations in IL-6 or TNF-α.