Phaeophyceae, commonly known as brown algae or brown seaweeds (such as Laminaria, Fucus, and Ascophyllum), have been investigated in scientific studies for their potential benefits in treating or supporting metabolic syndrome. Metabolic syndrome encompasses a cluster of conditions, including insulin resistance, obesity, dyslipidemia, and hypertension. The bioactive compounds present in brown algae, particularly fucoxanthin (a carotenoid), alginates, and phlorotannins, are believed to contribute to their metabolic effects.

Preclinical and some clinical studies have shown that these compounds may help lower blood glucose, improve lipid profiles, reduce body weight, and exert anti-inflammatory effects. For example, fucoxanthin has been reported to increase energy expenditure and decrease abdominal fat in animal models and in small-scale human studies. Alginates can reduce dietary fat absorption, thereby aiding weight management. Additionally, phlorotannins may improve insulin sensitivity and reduce oxidative stress.

However, the evidence base is still emerging. While there is promising data from animal studies and some early human trials, large-scale, long-term clinical trials are lacking. Thus, although there is scientific rationale and preliminary support for the use of Phaeophyceae in metabolic syndrome, the evidence is moderate (rated 3/5), and further research is needed to establish efficacy and safety in humans.