Collagen may not be universally recommended because unrealistic expectations can lead to disappointment. It does not replace lifestyle fundamentals; if high sugar intake, smoking, heavy UV exposure, and low protein persist, results may be limited. Some individuals experience digestive discomfort due to product quality, additives, or sensitivities. In specific medical conditions—such as kidney disease—overall protein load should be considered as part of a broader plan. Marketing terms like “plant collagen” can also be misleading; plants do not contain true collagen, but may provide nutrients that support collagen synthesis. In short, collagen can be meaningful when matched to the right person, goal, and formulation. The main reasons it is “not recommended” usually involve wrong expectations, poor product selection, or weak lifestyle foundations.