Staying immune fit: how to train the body’s defence system

The immune system is the body’s surveillance system that responds to infections. It’s our defence against the various challenges that we encounter every day, most of which are fought off without notice, reports Ruud Albers, CSO, NutriLeads

Optimal functioning of the immune system is crucial to remain fit and enjoy life to its fullest. To respond to infections, the immune system deploys two interconnected defence methods: the innate and the adaptive immune system. The innate immune system is the body’s first line of defence; it can quickly respond to infections without needing to first learn how to recognise an invading pathogen.

It also triggers the adaptive immune system, which takes time to identify a particular infection and generate immunological memory. Effective innate immune responses limit the extent of an infection early on and ensure that many infections are curbed before their presence can even be realised.

Just like other parts of the body, the immune system needs to be nourished and trained to effectively respond to challenges. A fit immune system ensures the best outcomes: quick, appropriate and effective responses against infections. Immune fitness provides the resilience required for the body to remain in a healthy balanced state — or quickly bounce back to it — in the face of daily infectious challenges from potentially harmful agents.

The majority (70–80%) of immune cells within the human body are found in the stomach where they work together with the gut microbiota to regulate immune balance. The immune system co-evolves with the gut microbiota and both work together to defend against pathogens and to develop tolerance for beneficial microbes.

The immune system senses what passes through the gut and its responsiveness is tuned by the signals it detects from food, especially from specific fibres and the gut microbiota.

Cells from the immune system circulate from the gut to other parts of the body to relay the messages they picked up in the gut. A healthy diet comprising sufficient fibres that contain appropriate signals, combined with the crosstalk between the gut microbiota and the immune system, supports protective responses against pathogens, promotes tolerance to harmless microbes and avoids harmful chronic inflammatory responses.

The maintenance of this delicate balance between consumed food, the gut microbiota that grows on it and the immune system is crucial to human health, especially when faced with harmful agents that threaten to adversely affect our well-being.

The immune system requires energy and micronutrients to perform its basic functions. However, to be at its best, it also needs to be trained through exposure to specific patterns (signals) from the diet and the gut microbiota. Fibres are particularly important when it comes to training the immune system and reinforcing a healthy level of crosstalk between the gut microbiota and the immune system.

However, similar to the fact that not all vitamins are the same, not all fibres have the same characteristics … and some are more effective than others. A fit immune system requires that nutritional deficiencies (vitamin B6, C, D and zinc, for example) are adequately supplemented and that it receives appropriate “training” stimuli in the gut from the diet and the microbiota.

Recently, it was discovered that a specific fibre derived from carrot pomace (rhamnogalacturonan-I or cRG-I) has unique properties when it comes to supporting immune fitness. When unlocked from the plant cell wall, complex chemical patterns in cRG-I are recognised by the innate immune system in the gut, contributing to its training.

cRG-I is not digested, but preferentially fermented by beneficial micro-organisms that produce metabolites — such as short chain fatty acids — which also affect the immune system.1 With this dual mode of action, cRG-I contributes to immune fitness by training immune cells in the gut, which, after migration through the body, improves immune system responsiveness.

NutriLeads’ clinical studies have shown that cRG-I produced by upcycling carrot pomace, a side stream of carrot juice production, is safe for human consumption, signals to the innate immune system and stimulates beneficial micro-organisms and their production of immune supportive metabolites.2–5

In a unique clinical trial, it was subsequently shown that the daily intake of 0.3 g of cRG-I accelerates protective immune responses against a common pathogen, significantly reducing its impact.6

Immune fitness requires more than the right micronutrients; the immune system needs training. Carrot RG-I has been clinically demonstrated to prepare the immune system to be fit all year round and is now commercially available for the first time. It offers the opportunity to develop new dietary supplements, functional foods and beverages with a differentiating immune health claim and communication versus micronutrient supplementation alone.


  1. D. Wu, et al., “Rethinking the Impact of RG-I Mainly from Fruits and Vegetables on Dietary Health,” Critical Reviews in Food Science and Nutrition 60(17), 2938–2960 (2020).
  2. D. Jonker,et al., “Safety Assessment of Rhamnogalacturonan-Enriched Carrot Pectin Fraction: 90-Day Oral Toxicity Study in Rats and In Vitro Genotoxicity Studies,” Food and Chemical Toxicology 139, 111243 (2020).
  3. S. McKay, et al., “Development of an Affordable, Sustainable and Efficacious Plant-Based Immunomodulatory Food Ingredient Based on Bell Pepper or Carrot RG-I Pectic Polysaccharides,” Nutrients 13(3), 963 (2021).
  4. P. Van den Abbeele, et al., “A Novel Non-Digestible, Carrot-Derived Polysaccharide (cRG-I) Selectively Modulates the Human Gut Microbiota While Promoting Gut Barrier Integrity: An Integrated In Vitro Approach,” Nutrients 12(7), 1917 (2020).
  5. P. Van den Abbeele, et al., “Consistent Prebiotic Effects of Carrot RG-I on the Gut Microbiota of Four Human Adult Donors in the SHIME® Model Despite Baseline Individual Variability,” Microorganisms 9(10), 2142 (2021).
  6. R. Lutter, et al., “Dietary Intake of Carrot-Derived Rhamnogalacturonan-I Accelerates and Augments the Innate Immune and Anti-Viral Interferon Response to Rhinovirus Infection and Reduces Duration and Severity of Symptoms in Humans,” submitted for publication.

Article in Nutraceutical Business Review, date: 4 November 2021.