The immune system: a target for functional foods?

Abstract

The immune system acts to protect the host from infectious agents that exist in the environment (bacteria, viruses, fungi, parasites) and from other noxious insults. The immune system is constantly active, acting to discriminate ‘non-self’ from ‘self’. The immune system has two functional divisions: the innate and the acquired. Both components involve various blood-borne factors (complement, antibodies, cytokines) and cells. A number of methodologies exist to assess aspects of immune function; many of these rely upon studying cells in cultureex vivo. There are large inter-individual variations in many immune functions even among the healthy. Genetics, age, gender, smoking habits, habitual levels of exercise, alcohol consumption, diet, stage in the female menstrual cycle, stress, history of infections and vaccinations, and early life experiences are likely to be important contributors to the observed variation. While it is clear that individuals with immune responses significantly below ‘normal’ are more susceptible to infectious agents and exhibit increased infectious morbidity and mortality, it is not clear how the variation in immune function among healthy individuals relates to variation in susceptibility to infection. Nutrient status is an important factor contributing to immune competence: undernutrition impairs the immune system, suppressing immune functions that are fundamental to host protection. Undernutrition leading to impairment of immune function can be due to insufficient intake of energy and macronutrients and/or due to deficiencies in specific micronutrients. Often these occur in combination. Nutrients that have been demonstrated (in either animal or human studies) to be required for the immune system to function efficiently include essential amino acids, the essential fatty acid linoleic acid, vitamin A, folic acid, vitamin B6, vitamin B12, vitamin C, vitamin E, Zn, Cu, Fe and Se. Practically all forms of immunity may be affected by deficiencies in one or more of these nutrients. Animal and human studies have demonstrated that adding the deficient nutrient back to the diet can restore immune function and resistance to infection. Among the nutrients studied most in this regard are vitamin E and Zn. Increasing intakes of some nutrients above habitual and recommended levels can enhance some aspects of immune function. However, excess amounts of some nutrients also impair immune function. There is increasing evidence that probiotic bacteria improve host immune function. The effect of enhancing immune function on host resistance to infection in healthy individuals is not clear.

Gold kiwifruit (Actinidia chinensis‘Hort16A’) for immune support

“…It is well known that deficiencies in certain nutrients such as vitamins A, C, E, B 6 and B 12 , folic acid, Zn, Cu, Fe and Se can lead to significant impairment of immune function and an increased susceptibility to infection and chronic diseases (27) . In most cases, supplementation has been shown to restore immune function in deficient individuals.…”

It's good to talk: children's views on food and nutrition

“…Evidence suggests that the typical adolescent diet has low levels of essential nutrients (notably calcium and iron) and is high in saturated fat, sugar and salt (Gregory & Lowe, 2000). In the short-term, poor dietary practices may negatively impact on concentration, cognitive and immune function (Nelson, 2000;Calder & Kew, 2002). In the long-term, some of the physiological processes that influence the development of chronic diet-related diseases (eg obesity, diabetes, cardiovascular disease, osteoporosis) in adulthood have their antecedents in childhood diet (Lauer et al, 1988;Lauer & Clarke, 1989;Webber et al, 1991;Nieto et al, 1992;Must & Strauss, 1999).…”

Probióticos e prebióticos: o estado da arte

“…Essa relação simbiótica impede uma produção excessiva de nutrientes, a qual favoreceria o estabelecimento de competidores microbianos com potencial patogênico ao hospedeiro. Além disso, os probióticos podem impedir a multiplicação de seus competidores, através de compostos antimicrobianos, principalmente as bacteriocinas (Kopp-Hoolihan, 2001;Calder, Kew, 2002;Guarner, Malagelada, 2003).…”