Edible Algae Reduce Blood Pressure in Humans: A Systematic Review and Meta-Analysis of Randomised Controlled Trials

BACKGROUND: Edible algae contain bioactive compounds such as peptides, fucoidan, polyphenols, potassium, omega-3 fatty acids, and antioxidants that may benefit cardiovascular health, particularly in lowering blood pressure (BP) regulation. Certain species, including Nori and Kelp, are also rich in inorganic nitrate, known for its BP-lowering effects. However, the relationship between algae consumption and hypertension remains controversial. This study evaluated the effects of edible algae on BP in humans, considering factors such as algae type, format, dosage, intervention duration, health status, and baseline BP.

METHODS: A systematic search of Medline-Pubmed, Scopus and Cochrane databases was conducted through December 2024. Randomised controlled trials (RCTs) in adults (≥ 18 years), healthy or with a cardiometabolic condition, with interventions ≥ 4-weeks and BP outcomes were included. Risk of bias was assessed using the Cochrane RoB 2 tool. Random-effects meta-analyses were conducted; heterogeneity and publication bias were assessed using statistical tests and plots. Sensitivity, subgroup, and meta-regression analyses were conducted to explore sources of heterogeneity.

RESULTS: Twenty-nine RCTs encompassing 1583 participants were included. Edible algae intake significantly reduced systolic BP (SBP: -2.05 mmHg; 95% CI: -3.80, -0.31; p = 0.022) and diastolic BP (DBP: -1.87 mmHg; 95% CI: -3.10, -0.64; p = 0.001). Heterogeneity was high for SBP (Q-value: 230; I 2  = 75%; p < 0.001) and moderate for DBP (Q-value: 102; I 2  = 68%; p < 0.001). Spirulina was the most effective algae, reducing SBP by -5.28 mmHg (p = 0.032) and DBP by -3.56 mmHg (p = 0.044). Dosage of algae > 3 g/day significantly lowered SBP (-3.71 mmHg; p = 0.004) and DBP (-3.05 mmHg; p = 0.022). Whole algae intake showed greater effects than extracts. Benefits were more pronounced in individuals with cardiometabolic risk. Meta-regression found no independent association between algae dosage and SBP change, but baseline SBP significantly predicted both SBP and DBP reductions.

CONCLUSION: Consuming over 3 g/day of whole edible algae, especially Spirulina, for at least 12 weeks significantly lowers BP, particularly in those with elevated levels. This suggests that edible microalgae may serve as a natural approach to managing hypertension, complementing pharmacological treatments.