In older age, as saliva production decreases, which of the following can be affected?

A. Vision changes in older adults, such as presbyopia, cataracts, or macular degeneration, are caused by age-related alterations in the eyes themselves, not by saliva production. Vision decline is independent of oral secretions.

B. Smell depends on olfactory receptors in the nasal cavity. Although aging can reduce the sensitivity of smell receptors (hyposmia), this is unrelated to saliva levels, so decreased saliva does not impair olfactory function.

C. Hearing loss, often due to presbycusis or damage to inner ear structures, is not influenced by saliva production. The auditory system, not the oral cavity, governs hearing function.

D. Taste is directly affected by saliva production. Saliva is essential for dissolving food particles so that taste buds on the tongue can detect flavors. In older adults, reduced saliva production, called xerostomia or dry mouth, can diminish perception of sweet, salty, sour, and bitter flavors, make chewing and swallowing more difficult, increase the risk of dental caries and oral infections, and reduce appetite, potentially leading to nutritional deficiencies. Because taste and flavor perception depend on adequate saliva, a decrease can significantly affect food enjoyment and nutritional intake. Managing dry mouth with hydration, sugar-free gum, saliva substitutes, and proper oral hygiene helps maintain taste perception and overall nutrition.

A. Anabolism is the metabolic process of building larger molecules from smaller ones, such as synthesizing proteins from amino acids. While it is essential for growth and repair, it does not specifically refer to the total energy required to maintain vital functions at rest.

B. Basal metabolism refers to the minimum amount of energy expended by the body at rest to sustain essential physiological functions, including breathing, circulation, body temperature regulation, and cellular processes. Basal metabolic rate (BMR) is typically measured under strict conditions: the individual is at rest, in a post-absorptive state (not actively digesting food), and in a thermoneutral environment. BMR accounts for the largest portion of daily energy expenditure in most adults.

C. Energy balance refers to the relationship between calories consumed and calories expended. While energy balance influences body weight, it is a broader concept and not limited to the metabolic processes at rest.

D. Catabolism is the process of breaking down larger molecules into smaller ones to release energy, such as breaking down glycogen into glucose. Although catabolic processes contribute to energy production, the term does not describe the overall metabolic requirement for maintaining vital functions at rest.