Crohn’s immunopathology
Crohn’s is characterised by dysregulated innate and adaptive immune activation in the gut wall:
- Th1/Th17 skewing:Unlike ulcerative colitis (predominantly Th2), Crohn’s involves elevated IL-12, IL-18, IFN-γ (Th1) and IL-17, IL-23 (Th17). TNF-α is a central effector cytokine — hence anti-TNF biologics (infliximab, adalimumab) are primary therapies.
- Macrophage NOX2 activation:Lamina propria macrophages in Crohn’s lesions show elevated NOX2 expression and superoxide generation. This contributes to the local oxidative environment, tissue damage, and sustained NF-κB activation in intestinal epithelium.
- Transmural inflammation:Crohn’s involves the full bowel wall thickness — leading to strictures (narrowing), fistulae (abnormal connections between gut loops or to skin), and abscesses. This distinguishes it from ulcerative colitis, which is mucosal only.
- Intestinal permeability:Crohn’s disrupts tight junction proteins, increasing permeability — allowing luminal bacteria and antigens to enter the lamina propria and perpetuate the inflammatory cycle.
Iron deficiency in Crohn’s
Iron deficiency is the most common nutritional deficit in Crohn’s:
- Causes: GI blood loss from mucosal ulceration, impaired absorption in inflamed small bowel mucosa (primary iron absorption site), and hepcidin upregulation from chronic inflammation (reducing ferroportin activity — “anaemia of chronic disease”)
- Prevalence: 30–70% of Crohn’s patients have iron deficiency or anaemia of chronic disease
- Ferrous sulfate is frequently poorly tolerated in IBD due to GI side effects and may worsen mucosal oxidative stress (free luminal iron generates ROS in the inflamed gut). Ferrous bisglycinate or IV iron is preferred.
- Spirulina’s food-matrix iron is generally better tolerated than ferrous sulfate in GI-sensitive patients. However, absorption through inflamed small bowel mucosa may be impaired — IV iron is the gold standard for correction in active IBD.
B12 absorption: the terminal ileum concern
B12 requires binding to intrinsic factor (secreted by gastric parietal cells) and absorption in the terminal ileum (TI). Crohn’s frequently affects the terminal ileum:
- Active inflammation or surgical resection of the TI impairs B12 absorption — sometimes completely
- B12 deficiency in Crohn’s (especially ileocolonic disease) causes macrocytic anaemia and neurological damage
- Critical note: spirulina’s pseudocobalamin is not bioavailable as B12. It also blocks true B12 absorption by occupying intrinsic factor and ileal receptors. In Crohn’s with TI involvement, where B12 deficiency is already a risk, spirulina’s pseudocobalamin is a specific concern. True B12 must come from hydroxocobalamin injections or methylcobalamin supplements in TI-affected patients.
NK cell stimulation and biologic therapy
Spirulina’s polysaccharides activate NK cells and increase IFN-γ — which could theoretically interfere with the immunosuppressive environment required for biologic therapy:
- Anti-TNF biologics (infliximab, adalimumab, golimumab): TNF is a downstream cytokine from NF-κB. Phycocyanin’s NF-κB inhibition is actually complementary in direction — but NK cell stimulation adds unpredictable immune activation in a setting where immune regulation is complex and carefully balanced.
- Anti-integrin (vedolizumab): gut-selective mechanism; NK stimulation from spirulina is a lower concern here than with systemic immunosuppressants.
- Anti-IL-12/23 (ustekinumab): directly targets the IL-12/23 pathway; spirulina’s Th1-promoting IFN-γ induction is in the same pathway direction as what ustekinumab is blocking. Potential antagonism — discuss with gastroenterologist.
- Mesalazine (aminosalicylates): low concern. NF-κB inhibition from spirulina is complementary.
- Azathioprine/6-MP (thiopurines): NK stimulation from spirulina during thiopurine immunosuppression requires discussion.
GLA and eicosanoid balance
GLA from spirulina converts to DGLA, reducing leukotriene B4 (LTB4) synthesis via competitive inhibition of 5-LOX. LTB4 is a potent chemoattractant for neutrophils in the Crohn’s intestinal lesion — reducing LTB4 is the same mechanism as 5-ASA drugs (mesalazine inhibits 5-LOX). GLA from spirulina is a very modest dose, but directionally appropriate.
Practical guidance
- Always discuss with gastroenterologist before starting spirulina in Crohn’s — particularly regarding interaction with current biologic or immunosuppressive therapy
- In remission, not on biologics: 3–5 g/day is appropriate; spirulina’s NF-κB inhibition and iron provision are relevant
- During active flare: reduce to 1–2 g or pause — active Crohn’s involves a complex immune state; additional immune stimulation is unpredictable
- Check B12 status if you have terminal ileum disease — true B12 supplementation (not spirulina) is required if deficient
- Test ferritin and transferrin saturation — IV iron is preferred over oral supplementation in active IBD