Algae supplements for heart risk markers and gut health

Algae Effects in Markers of Cardiovascular Risk and Gut Microbiome: a Placebo-controlled Randomized Double-blind Trial

This trial will test whether daily supplements of spirulina or Gelidium corneum change gut microbes and improve heart‑disease risk markers in adults over 50 with cardiovascular disease, diabetes, or related conditions.

Quick facts

• Phase: Not applicable
• Study type: Interventional
• Enrollment: 150 (estimated)
• Ages: 50 Years and up
• Sex: All
• Sponsor: Universidade do Porto (Academic / other)
• Locations: 1 site (Porto)
• Trial ID: NCT07173062 on ClinicalTrials.gov

What this trial studies

Adults with prior cardiovascular or metabolic disease will receive daily Spirulina (Arthrospira platensis), Gelidium corneum, or a placebo and will be followed to compare changes. Investigators will measure gut microbiome composition and metabolites such as trimethylamine‑N‑oxide (TMAO) and short‑chain fatty acids (SCFA), along with blood lipids and blood pressure. Participants must be 50 or older, have relevant diagnoses (stroke, CAD, MI, PAD, CKD, albuminuria, or diabetes), and have had no antibiotics in the prior 30 days. The interventions are intended to probe whether algae supplements shift microbiome‑derived metabolites toward a profile associated with lower cardiovascular risk.

Who should consider this trial

Good fit: Adults aged 50 or older with BMI ≥20 and a history of stroke, coronary artery disease, myocardial infarction, peripheral artery disease, chronic kidney disease (eGFR <75 ml/min for ≥3 months), albuminuria >300 mg/g, or diabetes, who have not taken antibiotics in the previous 30 days and who meet the trial's pregnancy/contraception rules for women.

Not a fit: People younger than 50, those who recently took antibiotics, pregnant women or those unable to use required contraception, and individuals without the listed cardiovascular or metabolic conditions are unlikely to be eligible or to gain benefit from this intervention.

Why it matters

Potential benefit: If successful, algae supplementation could lower harmful TMAO, raise beneficial SCFAs, improve lipids and blood pressure, and thereby reduce cardiovascular risk markers.

How similar studies have performed: Prior small clinical and observational studies have suggested spirulina can improve blood lipids and lower blood pressure, but microbiome‑focused benefits and effects on TMAO/SCFA remain preliminary and not yet confirmed in large trials.

Eligibility criteria

Inclusion Criteria:

* ≥50 years
* BMI ≥20 kg/m2
* History of stroke, coronary artery disease, myocardial infarction, peripheral artery disease, chronic kidney disease (eGFR \<75 ml/min at least for 3 months), albuminuria \>300 mg/g, or diabetes mellitus
* No antibiotics in the previous 30 days
* If a woman, she must be a woman of non-childbearing potential. That is, she must be:

  * Surgically sterilized (e.g. underwent hysterectomy, bilateral salpingectomy or bilateral oophorectomy);
  * Clinically diagnosed infertile;
  * In a post-menopausal state, defined as no menses for 12 months without an alternative medical cause.
* A woman patient of childbearing potential must have a negative serum pregnancy test at Visit 0 (Day 0) and must agree to use consistently and correctly (from 28 days prior to first study treatment administration until at least 7 days after last study treatment administration) one of the following highly effective methods of contraception:

  * Abstinence of heterosexual intercourse (when this is in line with preferred and usual lifestyle of the subject);
  * Progestogen-only hormonal contraception associated with inhibition of ovulation (oral, injectable, implantable);
  * Combined (oestrogen and progestogen containing) hormonal contraception associated with inhibition of ovulation (oral, intravaginal, transdermal);
  * Intrauterine device;
  * Intrauterine hormone-releasing system;
  * Bilateral tubal occlusion;
  * Vasectomized partner, who has received medical assessment of the surgical success, or clinically diagnosed infertile partner.

Exclusion Criteria:

* Unwilling to sign the informed consent form (if the patient wants to participate but cannot sign for any reason, then a third-person testimony may sign/complete the informed consent form on the patient's behalf).
* Involvement in the planning and/or conduct of the study (applies to both Investigator staff and/or staff at the study site).
* Participation in another clinical study with an investigational product during the last month.
* In participants recruited at Unidade Local de Saúde de São João, the exclusion criteria applied is estimated Glomerular Filtration Rate (eGFR) \<30 ml/min/1.73m2 estimated with the CKD-EPI (2021) formula or dialysis. For participants recruited at community, this exclusion criteria is adapted for diagnosis of end-stage renal disease or dialysis (no need to quantify the eGFR).

Where this trial is running

Porto

• Unidade Local de Saúde de São João — Porto, Portugal (Recruiting)

Study contacts

• Principal investigator: João Pedro Ferreira, MD, PhD — Universidade do Porto
• Study coordinator: Francisca Saraiva, PhD

Conditions Stroke; Coronary Arterial Disease; Myocardial Infarction; Diabetes Mellitus; Peripheral Artery Disease; Chronic Kidney Disease; Albuminuria; Spirulina Arthrospira platensis