posted                      

quote:

---

Deficiencies of vitamin A depress both humoral immunity and cell-mediated immunity.

The principal effects of vitamin A inadequacy on immune function may be a consequence of impaired growth and differentiation of myeloid tissues.

Vitamin A has been labeled the anti-infection vitamin from early in this century, and the reason for this may be due to the depression in plasma retinol caused by infection.

The depression in serum retinol levels may expose an individual to inadequate plasma vitamin A concentrations in areas where the dietary intake was already marginal.

In particular, vitamin A is specifically important for the integrity of the epithelium and the maintenance of mucosal secretions, which, if impaired, may increase exposure to microorganisms and the risk of infection.

Epithelial tissues of the eyes, the lungs, and the gut are impaired by VAD. These are all tissues where epithelial cell turnover is high.

In humans, numerous studies using the impression cytology test have shown that low circulating vitamin A levels are associated with an increased risk of epithelial damage in the eye.

Impaired gut integrity is common in malnutrition.

Damage to the integrity of epithelia and mucosal barriers facilitates translocation of microorganisms and contributes to the increased severity of infections.

Thus, low plasma vitamin A levels may compromise immune function by impairing epithelial integrity and by depressing lymphocyte numbers, and, although the capacity of immune cells may still be normal, the overall immune response is depressed.

---

quote:

---

Thus, under normal physiological conditions, the function of vitamin A is minimally affected by wide variations of intake.

Marked reductions in absorption efficiency, whether due to disease, parasitic infestation, or lack of fat in the diet, and impaired liver and kidney functions adversely affect vitamin A status.

---

Posts: 4881 | From Middlesex County, NJ | Registered: Jul 2006  |  IP: Logged |