Chronic obstructive pulmonary disease (COPD) induces a severe loss of muscle strength and mass, in addition to reflecting significant pulmonary changes and causing cardiovascular, immunohematological, and renal alterations. In this regard, strategies capable of restoring or at least slowing the loss of muscle strength and mass are highly desirable. In this context, in addition to pulmonary rehabilitation with aerobic and strength exercises, supplementation with whey protein has been considered the gold standard for promoting muscle strength and mass gain in athletes. However, the potential effects of whey protein supplementation in patients with COPD remain unclear, which constitutes one of the objectives of the present study. A high percentage of elderly individuals present with lactose intolerance, milk protein allergies, or discomfort caused by components such as albumin, lactoferrin, casein, and alpha- and beta-globulin, making whey protein supplementation prohibitive for many elderly individuals, including those with COPD. Conversely, supplementation with collagen, particularly hydrolyzed collagen, offers a "pre-digested" protein option free from typical milk proteins. Additionally, the food industry has developed low molecular weight hydrolyzed collagen peptides, which may render such products hypoallergenic. To investigate these effects, 320 individuals aged 45 to 80 years with mild, moderate, severe, or very severe COPD (as defined by GOLD COPD 2025 criteria) will be recruited. Participants will be randomly assigned to four groups: Control Group (GC; subjected only to pre- and post-assessments; mild COPD n = 20; moderate COPD n = 20; severe COPD n = 20; very severe COPD n = 20), Whey Supplemented Group (GW; supplemented with whey protein; mild COPD n = 20; moderate COPD n = 20; severe COPD n = 20; very severe COPD n = 20), Hydrolyzed Collagen Supplemented Group (GH; supplemented with hydrolyzed collagen; mild COPD n = 20; moderate COPD n = 20; severe COPD n = 20; very severe COPD n = 20), and Rehabilitation Group (GR; subjected to rehabilitation; mild COPD n = 20; moderate COPD n = 20; severe COPD n = 20; very severe COPD n = 20). As outlined in the objectives and methodology of the project, the primary goals are to evaluate: (1) the effects of whey protein and (2) the effects of low molecular weight hydrolyzed collagen on pulmonary, cardiovascular, immunohematological, muscular, and renal parameters. The supplementation period will span three months, with evaluations conducted at baseline and after the supplementation period. Statistical analyses will be performed using the paired Student's t-test for intragroup comparisons and the unpaired Student's t-test for intergroup comparisons. A p-value of less than 0.05 will be considered statistically significant.

As an inclusion criterion, patients with COPD must be included and must have been undergoing clinical-medication treatment for at least 90 days. As exclusion criteria, they should not have any type of autoimmune disease, must not be active smokers for at least 1 year, and in the case of ex-smokers, they must have quit smoking for at least 3 years, and must not have been engaging in any regular physical activity (˃1x/week) for at least 1 year.