Macronutrient balance mediates trade-offs amongst competing life-history and immune traits

Cotter, Sheena C., Simpson, Stephen J., Raubenheimer, David and Wilson, Kenneth (2011) Macronutrient balance mediates trade-offs amongst competing life-history and immune traits. Functional Ecology, 25 (1). pp. 186-198. ISSN 0269-8463

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1. Diet and health are intimately linked and recent studies have found that caloric restriction can affect immune function. However, when given a choice between diets that differ in their macronutrient composition, pathogen–infected individuals can select a diet that improves their survival, suggesting that the nutritional composition of the diet, as well as its calorie content, can play a role in defence against disease. Moreover, as individuals change their diet when infected, it suggests that a diet that is optimal for growth is not optimal for immunity, leading to trade-offs.
2. Currently, our knowledge of the effects of diet on immunity is limited because previous experiments have manipulated either single nutrients or the calorie content of the diet without considering their interactive effects. By simultaneously manipulating both the diet composition (quality) and its caloric density (quantity), in both naive and immune-challenged insects, we asked how do diet quality and quantity influence an individual’s ability to mount an immune response? And to what extent are allocation trade-offs driven by quantity- versus quality-based constraints?
3. We restricted individuals to 20 diets varying in their protein and carbohydrate content and used 3D response surfaces to visualise dietary effects on larval growth and immune traits. Our results show that both constitutive and induced immune responses are not limited by the total quantity of nutrients consumed, but rather different traits respond differently to variation in the ratios of macronutrients (diet quality), and peak in different regions of macronutrient space. The preferred dietary composition therefore represents a compromise between the nutritional requirements of growth and immune responses. We also show that a non-pathogenic immune challenge does not affect diet choice, rather immune-challenged insects modify their allocation of nutrients to improve their immune response.
4. Our results indicate that immune traits are affected by the macronutrient content of the diet and that no diet can simultaneously optimise all components of the immune system. To date the emphasis has been on the effects of micronutrients in improving immunity, our findings indicate that this must be widened to include the neglected impact of macronutrients on defence against disease.

Additional Information:Article first published online: 19 AUG 2010
Keywords:Spodoptera, parasite, trade-offs, nutritional ecology, life-history, bacteria, caloric restriction, self medication
Subjects:C Biological Sciences > C550 Immunology
C Biological Sciences > C360 Pest Science
C Biological Sciences > C111 Parasitology
C Biological Sciences > C182 Evolution
C Biological Sciences > C340 Entomology
C Biological Sciences > C150 Environmental Biology
C Biological Sciences > C180 Ecology
C Biological Sciences > C120 Behavioural Biology
C Biological Sciences > C300 Zoology
C Biological Sciences > C110 Applied Biology
C Biological Sciences > C100 Biology
Divisions:College of Science > School of Life Sciences
ID Code:16021
Deposited On:16 Nov 2014 17:07

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