VICIOUS CIRCLE

Reduced absorption, increased excretion and increased consumption of Vitamin A in infection

Charles B Stephensen: VITAMIN A, INFECTION, AND IMMUNE FUNCTION Annu. Rev. Nutr. 2001. 21:167–92

Figure Infectious diseases impair vitamin A status. This figure illustrates three mechanisms by which infections are known to impair vitamin A status: decreased intake due to anorexia; decreased absorption; and increased urinary excretion. Infection may also affect vitamin A status by impairing utilization of retinol stores in the liver (by diminishing transport from stores to peripheral tissues) or by increasing requirements (e.g. by increasing oxidative degradation of retinol at sites of inflammation), although proof for these two mechanisms is lacking.

Acute phase reaction (APR): following inflammation.

• Positive APR proteins (abundantly produced): CRP (C-reactive protein) and similar.
• Negative APR proteins (scarcely produced): transferrin, albumin, and RBP.