From NAFLD to MAFLD: why the renaming matters
For decades, fatty liver disease not caused by excess alcohol consumption was called non-alcoholic fatty liver disease (NAFLD) — a purely negative definition that said what the disease was not. In 2020, an international expert panel led by Eslam, Sanyal, George, and colleagues proposed a new name and new diagnostic criteria: metabolic dysfunction-associated fatty liver disease (MAFLD). The renaming reflected a fundamentally different conceptual framing. MAFLD is a positive diagnosis based on the presence of metabolic dysfunction, not merely the absence of alcohol use.
The diagnostic criteria for MAFLD require hepatic steatosis (detectable fat accumulation in the liver, established by imaging, blood biomarkers, or biopsy) combined with at least one of three metabolic criteria: overweight or obesity (BMI ≥ 25 kg/m² in non-Asian populations, or ≥ 23 in Asian populations); type 2 diabetes mellitus; or evidence of metabolic dysregulation, defined as two or more of: waist circumference above population-specific cut-offs, hypertension (≥ 130/85 mmHg or on antihypertensives), plasma triglycerides ≥ 1.7 mmol/L, HDL cholesterol below sex-specific thresholds, prediabetes (fasting glucose 5.6–6.9 mmol/L or HbA1c 39–47 mmol/mol), insulin resistance by HOMA-IR ≥ 2.5, or elevated hs-CRP.
This framework deliberately places metabolic dysfunction at the centre rather than treating the liver disease as an isolated finding. Prevalence estimates for MAFLD range from 25–30% of the global adult population, with higher prevalence in individuals with obesity (approximately 75%) and type 2 diabetes (approximately 60%).
The spectrum from simple steatosis to NASH
MAFLD encompasses a spectrum of histological severity. At the benign end is simple hepatic steatosis — fat droplets visible in hepatocytes, but minimal inflammation and no significant fibrosis. This stage has a low risk of progression and may reverse with weight loss and metabolic improvement. Roughly 20–30% of individuals with simple steatosis will progress over time to non-alcoholic steatohepatitis (NASH, or what is now sometimes called MASH — metabolic-associated steatohepatitis).
NASH involves not just steatosis but active hepatocyte injury, lobular inflammation, and a pattern called ballooning degeneration — hepatocytes that swell as their protein handling mechanisms fail. NASH can progress to hepatic fibrosis (scarring), cirrhosis, and hepatocellular carcinoma (HCC). The fibrosis stage, not the inflammatory activity per se, is the strongest predictor of liver-related mortality.
Understanding this spectrum matters for evaluating spirulina’s potential role. Animal models of NASH typically use high-fat, high-fructose, or methionine/choline-deficient diets to induce a phenotype resembling human NASH. Most spirulina hepatoprotective studies use these models — and the findings are more relevant to prevention and early steatosis than to reversal of established fibrosis.
AMPK activation and the suppression of de novo lipogenesis
AMP-activated protein kinase (AMPK) is sometimes described as the cell’s energy sensor. It is activated by rising AMP-to-ATP ratios — situations where energy is scarce — and its activation throws molecular switches that shift metabolism from anabolic (building) to catabolic (breaking down) modes. In the liver, activated AMPK suppresses de novo lipogenesis (DNL) — the synthesis of new fatty acids from glucose and acetyl-CoA — through several mechanisms.
AMPK phosphorylates and inactivates acetyl-CoA carboxylase (ACC), the enzyme that converts acetyl-CoA to malonyl-CoA, the first committed step in fatty acid synthesis. Malonyl-CoA is also an allosteric inhibitor of carnitine palmitoyltransferase 1 (CPT1) — the enzyme that shuttles long-chain fatty acids into mitochondria for beta-oxidation. When AMPK suppresses DNL and relieves CPT1 inhibition simultaneously, the liver switches from making fat to burning it.
Additionally, AMPK phosphorylates and inactivates SREBP-1c (sterol regulatory element-binding protein 1c) — the master transcription factor driving expression of the full suite of lipogenic genes including fatty acid synthase (FASN), stearoyl-CoA desaturase-1 (SCD1), and ACC itself. AMPK-mediated suppression of SREBP-1c therefore provides sustained, transcriptional-level reduction of hepatic lipogenesis.
Several in vitro and animal studies have shown spirulina extract and phycocyanin increase AMPK phosphorylation (activation) in hepatocytes. A 2014 study by Wu and colleagues in the journal Food and Chemical Toxicologyfound that phycocyanin treatment in HepG2 hepatocellular carcinoma cells increased AMPK phosphorylation and reduced SREBP-1c expression and downstream lipogenic gene expression. In a high-fat diet mouse model, spirulina supplementation reduced hepatic triglyceride content and improved markers of AMPK activity. The upstream mechanism likely involves phycocyanin’s antioxidant activity reducing the oxidative inhibition of AMPK.
Nrf2 and the HO-1 pathway in hepatic oxidative stress
Oxidative stress plays a central role in the progression from simple steatosis to NASH. Lipid-laden hepatocytes have elevated mitochondrial ROS production from incomplete fatty acid oxidation. Free fatty acids activate inflammatory Kupffer cells (liver-resident macrophages) and recruit monocyte-derived macrophages that amplify the inflammatory signal. The resulting cytokine storm — dominated by TNF-α, IL-6, and TGF-β — drives hepatocyte apoptosis, stellate cell activation (the primary fibrosis-producing cell), and disease progression.
Nrf2 (nuclear factor erythroid 2-related factor 2) is the master regulator of the cellular antioxidant response. Under basal conditions, Nrf2 is sequestered in the cytoplasm by Keap1 (Kelch-like ECH-associating protein 1), which targets it for ubiquitin-mediated degradation. When ROS or electrophilic compounds modify specific cysteine residues on Keap1, Nrf2 escapes and translocates to the nucleus, where it activates the antioxidant response element (ARE) — a promoter sequence controlling expression of dozens of protective genes.
Key Nrf2 target genes include heme oxygenase-1 (HO-1), which catabolises pro-oxidant free haem; NAD(P)H quinone dehydrogenase 1 (NQO1); glutathione S-transferases (GSTs); and ferritin. HO-1 is particularly important in liver disease because it generates biliverdin (which is converted to the antioxidant bilirubin) and carbon monoxide (which has anti-inflammatory and anti-apoptotic signalling properties in low concentrations).
Phycocyanin and phycocyanobilin are Nrf2 activators — this has been consistently demonstrated in cell and animal studies. A 2018 paper by Zheng and colleagues in Biochemical and Biophysical Research Communications showed phycocyanin activated Nrf2/HO-1 signalling in LPS-treated macrophages, reducing inflammatory marker production. In hepatic models, Nrf2 activation by phycocyanin has been associated with reduced malondialdehyde (a lipid peroxidation marker), increased superoxide dismutase and catalase activity, and improved liver histology scores in high-fat diet mice.
Animal model evidence: what the NASH studies show
The most detailed hepatoprotective evidence for spirulina comes from rodent models. Several study designs have been used.
A frequently cited study is that of Ou and colleagues (2012) in Lipids in Health and Disease, examining a high-fat diet obesity model in mice. Spirulina supplementation at 1% of diet reduced hepatic triglyceride content by approximately 27%, reduced plasma alanine aminotransferase (ALT) — a marker of hepatocyte damage — by approximately 30%, and improved hepatic histology. Mechanistic analyses found reduced SREBP-1c expression and increased PPAR-alpha expression (a nuclear receptor driving fatty acid oxidation genes including CPT1a, acyl-CoA oxidase).
A methionine-choline-deficient (MCD) diet model, which produces rapid NASH-like liver injury with inflammation and early fibrosis, was used in a 2017 study by Ferreira and colleagues. Phycocyanin supplementation reduced hepatic TNF-α and IL-1β mRNA, reduced stellate cell activation markers (alpha-smooth muscle actin), and reduced collagen deposition (Sirius red staining). This suggested an effect not just on steatosis but on the inflammatory and early fibrotic components.
A note on model interpretation: MCD diet-induced NASH differs from human metabolic MAFLD in important ways — MCD mice lose weight rather than gaining it, and the model is not driven by the same insulin resistance mechanisms as human MAFLD. Results from MCD models should be considered mechanistic evidence rather than direct translational prediction.
Clinical evidence in humans
Human clinical trial data for spirulina in liver disease is limited. A small randomised trial by Ferreira and colleagues (2014, Journal of Medicinal Food) in patients with non-alcoholic fatty liver disease found that 2 g/day of spirulina for three months reduced hepatic steatosis on ultrasound in a majority of subjects, and reduced ALT and AST (aspartate aminotransferase) levels. The sample size was 22 patients across groups — insufficient for definitive conclusions but mechanistically consistent.
A 2017 randomised trial in type 2 diabetic patients with NAFLD (Haidari and colleagues, International Journal of Preventive Medicine) found 8 g/day of spirulina for 12 weeks reduced ALT, AST, total cholesterol, LDL cholesterol, and triglycerides, with non-significant changes in liver steatosis grade by ultrasound. The absence of significant steatosis change may reflect the short duration or the severity of established disease in a diabetic population.
The GLP-1 context: what pharmacological intervention offers
Any honest discussion of MAFLD must acknowledge the rapid development of pharmacological treatments that now show substantial efficacy. Semaglutide (a GLP-1 receptor agonist) and the newer dual GIP/GLP-1 agonist tirzepatide have demonstrated significant reductions in hepatic steatosis in large clinical trials — with NASH resolution rates above 50% in some trials. Resmetirom (Rezdiffra), a thyroid hormone receptor beta agonist, became the first FDA-approved treatment specifically for NASH with fibrosis in 2024.
Spirulina operates in a different category. The AMPK, Nrf2, and anti-inflammatory mechanisms are real and mechanistically meaningful, but the evidence base does not support spirulina as a treatment for established MAFLD, and certainly not for NASH with advanced fibrosis. The more reasonable positioning is as an adjunct in early steatosis — alongside dietary modification and exercise — or as a metabolically supportive supplement for individuals with obesity or metabolic syndrome who are at risk. At realistic supplementation doses (3–8 g/day), the hepatoprotective effects are modest relative to the magnitude of intervention needed to reverse established disease.
Practical context
For individuals in the early steatosis stage — liver fat above 5% without significant inflammation or fibrosis — lifestyle intervention remains the primary and most effective treatment. A 7–10% reduction in body weight reliably reduces hepatic fat and improves liver enzyme levels. Spirulina, with its effects on lipid metabolism, inflammation, and oxidative stress, is mechanistically aligned with this goal and may provide modest additive benefit.
Anyone with abnormal liver enzymes, suspected fatty liver, or risk factors for MAFLD should have formal clinical assessment rather than relying on any dietary supplement. The trajectory from steatosis to cirrhosis is slow but consequential, and monitoring by a clinician who can stage the disease appropriately — via elastography (FibroScan) or, where indicated, biopsy — is irreplaceable.