How compelling are the data regarding nutritional influences on our immunity?

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The interaction of nutrition and immunology has become increasingly well understood and has emerged as an important and growing field. Recent findings have provided a basis for understanding the nature of the signaling that links nutrition and immunity. These findings include the following: 1. Studies demonstrating that nutrients can modulate innate immunity in ways that affect its activity as a barrier to infection, its surveillance of mucosal surfaces, the functions of complement, natural killer, and polymorphonuclear cell functions. 2. Studies seeking to understand iron metabolism have shown a rich biology, wherein control of iron levels and the signaling molecules involved modulate a host of key systems, including the ratio of T to B cells, their subsets, e.g., CD4+ to CD8+ ratio, lymphoproliferation, cytokine balance, and antibody production and function. 3. Developmental studies have shown that lymphoid tissues and cells are particularly vulnerable to environmental (e.g., nutritional) insult during fetal and neonatal growth and differentiation (vulnerable period), which have short-term as well as long-term consequences. 4. Nutritional deficits can impact the immune response in both developed and developing countries. 5. The nutrition-immunity-infection model has been classically considered a more-or-less "one way" model, but there is also evidence of reverse flow. For example, infection can induce similar immunological changes to that observed under different nutritional states and can induce metabolic effects on nutritional status, e.g., the effect of measles on vitamin A, Epstein-Barr virus infection, and HIV on essential fatty-acid status. Nutrients can also affect pathogen genotype and virulence and possibly vertical transmission. The nutrition-immunity-infection model is therefore more complex than originally thought. Foods and their associated components, as with any other substances, are not harmless. This is particularly evident when ingested in supraphysiological amounts. For example, some foods high in one "good nutrient" also contain toxic contaminants (i.e., mercury). Other foods carry potential mutagens (either intrinsically, such as the hydrazine derivatives found in mushrooms, or as contaminants, such as corn or peanuts with their fungal-derived metabolites (i.e., fumosin and aflatoxins), while still others may just contain higher than acceptable levels of salt (i.e., some carrot juices). One area of burgeoning interest that can be characterized as more macronutrient oriented is that of the growing appreciation of 1) the biological activity of adipose tissues, and 2) the degree and the level of signaling between adipose tissues and the immune system. The identification of leptin, as well as ghrelin, as immune-system signals link nutrition to immune status in ways that will require extensive investigation to fully map and comprehend. Our current understanding notwithstanding, it would be a leap of logic to conclude that we understand what role nutritional therapy has in the treatment of cancer. Certainly, adequate nutrition and appropriate supplementation are important for host resistance, while there are clear data demonstrating that nutrition plays a role in the prevention of cancer. However, using nutritional-based therapy to treat tumors is another matter, and all data have to be interpreted in light of the purpose of the therapy and whether it is specific for treating a tumor or for generic host health. One area that reflects the level of complexity now being appreciated is that associated with anemia. Recently it has been shown that in patients with cancer treatments aimed at reducing cancer-related anemia, i.e., use of erythropoietins to upregulate iron metabolism, while quality of life is enhanced, such treatments appear to also decrease survival. This effect appears to be attributable to the role of erythropoietin in iron and oxidant metabolism, specifically HO-1, an increase that has been shown to be anti-apoptotic, which results in reduced cancer-cell killing during therapy. Finally, for an otherwise healthy immune system, it is unlikely that nutritional therapy can produce enhancement. However, during periods of stress and for the very young and the elderly (defined herein as over 55!!!), there is a basis for a rigorous research program designed to improve and enhance immune function. These areas will require much more work so as to allow for an appreciation of the positive and negative effects and allow a realistic cost benefit analysis when research programs are designed.

Original languageEnglish (US)
JournalJournal of Nutrition
Issue number12
StatePublished - Dec 2005


  • Innate immunity
  • Nutrition-immunity-infection model

ASJC Scopus subject areas

  • Medicine (miscellaneous)
  • Food Science


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