Physiology of aging with respect to gastrointestinal, circulatory and immune system changes and their significance for energy and protein metabolism

Abstract

Age-related changes in body composition can be considered the consequence of changes in energy and protein metabolism, while also having a leverage effect on protein and energy requirements. Changes in organ and systems weights obviously affect energy balance regulation. Considered at the system level, age-related changes are numerous, but it is still debated whether they are related to aging per se or to conditions (such as poor nutrition, disease, drug treatments etc.) that prevail in elderly persons. It is likely that most changes occuring in the gastrointestinal, circulatory and immune system do not affect energy and protein requirements at rest. However, aging is associated with difficulties in adapting to new environmental conditions that lead to stress. Repeated episodes of stress might lead to accumulation of deficits that can affect energy and protein balances.