The Threonine Requirement in Healthy Adults Over 60 Years

Threonine is an essential amino acid and must be obtained from the diet. The body's capacity to maintain adequate mucin synthesis is directly related to the bioavailability of certain amino acids, including threonine, serine and proline (1). Moreover, the rate of mucin synthesis has been demonstrated to be directly related to the availability of dietary threonine in healthy rats (2) and piglets (3,4). Intestinal inflammation is known to increase gastrointestinal threonine uptake and mucin synthesis in enterally fed minipigs (5). Additionally, in animals, mucin function/barrier has been shown to decline with age, leaving them more susceptible to bacterial penetration. Thus, with advancing age (6), a higher dietary supply of threonine may be needed for maintaining intestinal mucosal health. Despite this, the current threonine requirement is based on studies conducted exclusively in young adults. Thus, there is a need to determine the threonine requirement directly in older adults.