Immunonutrition: the key strategy to enhance health in aquaculture

The unstoppable growth of global aquaculture to meet the demand for seafood brings with it a constant challenge: maintaining the health and productivity of stocks in increasingly intensive systems. High-density conditions, water quality, and frequent handling expose fish to stress that can weaken their immune system, making them more vulnerable to diseases. In this context, immunonutrition emerges as a strategic and non-pharmaceutical tool to strengthen fish defenses and build a more resilient and sustainable sector.

A recent and exhaustive scientific review, published in Aquaculture International by a scientist from Universiti Malaysia Kelantan, synthesizes the current knowledge on how functional nutrients can modulate the immune system of aquatic species. This approach not only seeks to improve resistance to pathogens but also to reduce the dependency on antibiotics and optimize the overall health of the animals. Below, we break down the most relevant findings of this study.

The role of vitamins in the first line of defense

Vitamins are essential micronutrients that act as key modulators of the immune response in fish. The study highlights the fundamental role of four of them:

• Vitamin A: It acts as a guardian of mucosal barriers and skin integrity, the first physical defense against pathogens. Its active form, retinoic acid, is crucial for the differentiation of immune cells like lymphocytes and for improving the response against bacteria. However, a balance is vital, as an excess (hypervitaminosis A) can be counterproductive and affect growth.
• Vitamin C: Known for its potent antioxidant capacity, vitamin C is essential for neutralizing the free radicals generated during immune responses, protecting cells from oxidative damage. Furthermore, it enhances the activity of phagocytic cells (such as macrophages and neutrophils) and promotes the proliferation of lymphocytes, improving both innate and adaptive immunity.
• Vitamin D: Beyond its role in calcium metabolism, vitamin D modulates the immune response, helping to regulate inflammation and prevent chronic immune responses that can affect the fish’s health. The study indicates that its supplementation can mitigate the effects of certain bacterial infections. Even so, it is acknowledged that its specific mechanism in fish remains an area with significant research gaps.
• Vitamin E: This fat-soluble antioxidant is essential for protecting cell membranes from oxidative damage, especially in high-density environments. By integrating into the membranes, it neutralizes free radicals and improves the function and proliferation of lymphocytes and macrophages, which translates into greater disease resistance.

Minerals: The micronutrients that make a difference

Certain trace minerals, although required in small amounts, have a huge impact on immune function.

• Zinc: It is an essential element for the development and proliferation of T-lymphocytes, key cells of adaptive immunity. Its availability directly affects the function of the thymus, a vital organ for the maturation of these immune cells.
• Selenium: Its main function is as a component of the antioxidant enzyme glutathione peroxidase (GPx), which protects cells from oxidative stress by neutralizing harmful peroxides. Adequate selenium supplementation strengthens this defense system, improving the fish’s resilience to environmental stressors like lack of oxygen or pollutants.
• Iron: This mineral presents an interesting duality. It is vital for oxygen transport and as a cofactor for enzymes that produce reactive oxygen species (ROS) to destroy pathogens. However, an excess of iron can be detrimental, as it increases oxidative stress and can be utilized by the pathogens themselves for their proliferation, which underscores the need for carefully regulated supplementation.

Functional amino acids: The builders of resilience

Beyond their role in protein synthesis, certain amino acids have specific and direct immunomodulatory functions.

• Arginine: It acts as the sole precursor for the synthesis of nitric oxide (NO), a molecule used by macrophages to destroy pathogens. Adequate supplementation with arginine can, therefore, improve the immune system’s ability to manage infections.
• Glutamine: It is a primary energy source for rapidly proliferating cells such as lymphocytes and macrophages. Furthermore, it is crucial for gut health, as it promotes the integrity of the intestinal barrier, making it difficult for pathogens to enter from the digestive tract.
• Methionine: This sulfur-containing amino acid is a precursor to cysteine, which in turn is necessary to synthesize glutathione (GSH), one of the most important intracellular antioxidants. In this way, methionine indirectly supports the fish’s ability to combat oxidative stress.

Towards functional and sustainable feeds

The study not only focuses on individual nutrients but also opens the door to new sources of feed ingredients that are both functional and sustainable. It highlights the potential of functional additives such as probiotics, prebiotics, and phytochemicals to positively modulate the microbiota and intestinal immunity.

One of the most promising areas is the use of insect-derived ingredients, such as black soldier fly (Hermetia illucens) meal. These ingredients are not only a sustainable alternative to fishmeal but are also rich in bioactive compounds like antimicrobial peptides and chitin, which have been shown to improve mucosal immunity and gut health in several aquatic species.

Challenges and the future of immunonutrition research

Despite the progress, the document identifies significant challenges. One of the main ones is the need to define the specific nutritional requirements for each species, as the immune response to the same nutrient can vary enormously between a carnivorous salmonid and an omnivorous tilapia.

The future of immunonutrition involves integrating technologies like nutrigenomics, which allows for understanding how nutrients interact with genes to regulate immunity. This will facilitate the design of precision diets, adapted not only to the species but also to its developmental stage and the specific environmental stressors it faces, such as temperature changes or low oxygen.

Conclusion

The nutritional modulation of the immune system is no longer a simple theory but a practical and fundamental strategy for the future of healthy and sustainable aquaculture. As this exhaustive review demonstrates, the strategic use of functional vitamins, minerals, and amino acids in feeds allows for the strengthening of the fish’s natural defenses, improving their stress tolerance, and reducing the need for chemical interventions. The way forward involves more research to develop precision diets and the adoption of sustainable ingredient sources, transforming feed from a simple input into a powerful health management tool.

Contact
Zulhisyam Abdul Kari
Department of Agricultural Sciences, Faculty of Agro-Based Industry, Universiti Malaysia Kelantan
Jeli Campus, 17600, Jeli, Malaysia
Email: zulhisyam.a@umk.edu.my

Reference (open access)
Abdul Kari, Z. Nutritional immunomodulation in aquaculture: functional nutrients, stress resilience, and sustainable health strategies. Aquacult Int 33, 441 (2025). https://doi.org/10.1007/s10499-025-02122-5

Milthon Lujan

Editor at the digital magazine AquaHoy. He holds a degree in Aquaculture Biology from the National University of Santa (UNS) and a Master’s degree in Science and Innovation Management from the Polytechnic University of Valencia, with postgraduate diplomas in Business Innovation and Innovation Management. He possesses extensive experience in the aquaculture and fisheries sector, having led the Fisheries Innovation Unit of the National Program for Innovation in Fisheries and Aquaculture (PNIPA). He has served as a senior consultant in technology watch, an innovation project formulator and advisor, and a lecturer at UNS. He is a member of the Peruvian College of Biologists and was recognized by the World Aquaculture Society (WAS) in 2016 for his contribution to aquaculture.