Benefits
Oxidative stress markers in a 12-week placebo-controlled trial
In 40 adults with metabolic syndrome, a liquid spirulina extract giving about 20 mg of phycocyanin a day for 12 weeks did not change the registered primary outcome, the ratio of oxidized to total LDL, compared with placebo. Urinary isoprostanes, a secondary marker of lipid oxidation, were lower than placebo at week 12 but not at week 6. One small trial, funded by the extract maker.
Triglycerides and other blood fats in the same small trial
In that 40-person trial, triglycerides were lower than placebo at week 12 (1.23 vs 1.97 g/L), but they were already lower in the extract group at the start (1.35 vs 1.83 g/L) and no change from baseline was tested. HDL was also higher from the start. LDL, total cholesterol, fasting glucose and liver enzymes did not differ from placebo. One small, maker-funded trial.
Joint comfort in adults with long-standing joint discomfort
In a 2-week trial of 24 adults with chronic joint pain, a phycocyanin-rich extract (2.3 g/day) lowered rated pain more than placebo. Two other 12-person studies of 1 g/day (open-label) and 250 or 500 mg/day (single-blind) reported less pain within 1 to 2 weeks. All three were sponsored by the extract maker and were very short.
Clotting and platelet markers at a high daily dose
In a 2-week placebo-controlled trial in 24 adults, 2.3 g/day of an extract supplying about 1 g of phycocyanin did not change clotting times, fibrinogen or platelet activation markers compared with placebo, and the liver enzyme AST fell versus placebo. One person reported mild bruising and three reported mild gum bleeding while brushing on the extract.
Self-rated sport performance in trained water polo players
In 20 male water polo players, 8 weeks of a liquid extract supplying about 30 mg of phycocyanin a day, with added copper, raised self-rated and coach-rated performance versus a placebo group, but the muscle damage marker CPK did not differ. The paper calls itself an observational case series and reports inconsistent blinding.
Exercise-related muscle stress in animal research
In rats on an 8-week swimming program, phycocyanin at 100 or 200 mg per kg of body weight lowered markers of oxidative damage, muscle fatigue and muscle wasting and raised antioxidant (Nrf2) signaling. This is animal work at doses far above those in human products; no human trial has measured the same outcomes.
Mechanism of action
Digested into small colored peptide fragments
Phycocyanin is a protein, so stomach enzymes break it down. In lab digestion with pepsin it was cut into peptides of 2 to 13 amino acids that still carried the blue chromophore and showed antioxidant and metal-binding activity in test tubes and cells. Whether these fragments are absorbed and active in people is not known.
Phycocyanobilin and the NADPH oxidase hypothesis
The pigment part of the protein is phycocyanobilin. A review proposed, based on rodent studies, that it may inhibit NADPH oxidase, an enzyme that makes reactive oxygen species, possibly after being converted to a compound resembling bilirubin. This remains a hypothesis that has not been tested in clinical trials.
Antioxidant and COX-2 activity in cell tests
In lab tests of a phycocyanin-rich water extract, both the phycocyanin fraction and the rest of the extract reduced reactive oxygen species made by human immune cells, and COX-2 inhibition was linked to the phycocyanin fraction. The whole extract was the most active, so its effects cannot be credited to phycocyanin alone.
Clinical trials
Randomized, double-blind, placebo-controlled, parallel trial of a phycocyanin-concentrated liquid spirulina extract (Spirulysat, 20 mL a day before breakfast) against a blue-colored placebo, funded by the extract maker AlgoSource, which also supplied the product; one author lists an AlgoSource affiliation. (Koite et al. 2022, Mar Drugs)
40 adults aged 18 to 65 with metabolic syndrome and a BMI of 25 to 35 (20 per group).
The registered primary outcome (NCT02817620), the oxidized LDL to total LDL ratio, did not differ from placebo at any visit (week 12 P = 0.36). Urinary isoprostanes, a secondary outcome (2.31 vs 3.51 micrograms per 24 hours, P = 0.014), and triglycerides (1.23 vs 1.97 g/L, P = 0.003) were lower at week 12 only; triglycerides were already lower in the extract group at inclusion (1.35 vs 1.83 g/L, P = 0.11) and no change from baseline was tested. HDL was higher at every visit, including inclusion. LDL, total cholesterol, glucose and liver enzymes did not differ. Registered outcomes including total antioxidant status, antioxidant enzymes and hsCRP were not reported. No side effects were reported.
Randomized, double-blind, placebo-controlled safety trial of an aqueous Arthrospira platensis extract (Cyactiv, about 40% phycocyanin) focused on clotting and platelet activation, sponsored by its maker Cerule LLC; one author is a Cerule employee. (Jensen et al. 2016, J Med Food)
24 adults aged 25 to 65 with chronic joint pain (19 women, 5 men; 12 per group).
About 1 g/day of phycocyanin for 2 weeks did not change activated partial thromboplastin time, thrombin clotting time, fibrinogen or platelet P-selectin compared with placebo (thrombin time rose slightly in both groups). AST fell versus placebo (P < 0.02) and the ALT drop was not significant. Rated chronic pain fell more than with placebo (P < 0.05). On the extract, one person reported mild bruising and three reported mild gum bleeding.
Two pilot studies of the same aqueous extract (over 30% phycocyanin): a 4-week open-label study at 1 g/day and a single-blind, placebo-controlled crossover of 250 mg, 500 mg and 0 mg/day for 1 week each. Sponsored by Cerule LLC, which employed two authors; not indexed in PubMed. (Jensen et al. 2016, Nutrition and Dietary Supplements)
Two groups of 12 adults aged 45 to 75 with chronic joint-related pain for more than 6 months.
In the open-label study, pain ratings fell from week 2 (P < 0.01) and average BMI fell from 31.4 to 29.4 (P < 0.01), an implausibly large change for 4 weeks. In the crossover, pain during activity at a secondary site fell at both doses versus placebo, but the paper reports different P values for the 500 mg dose in the abstract (P < 0.065) and the results (P < 0.01). No placebo group in the first study.
Observational clinical case series with a placebo comparison group of a spirulina liquid extract standardized to 1 mg/mL phycocyanin with added copper (BluVIS, 15 mL twice a day); the paper describes double-blinding in its methods but a lack of blinding and randomization in its discussion. No funding reported. (La Mantia et al. 2024, Nutrients)
20 male water polo players (10 per group).
Self-rated performance scores and coach ratings rose in the extract group versus placebo (P < 0.001). The muscle damage marker CPK rose in both groups with no difference between them (P = 0.115). Some baseline values differ between the text and tables, and the copper makes the effect of phycocyanin itself impossible to separate.