Secret heroes of the sea: brown macroalgae and their bioactive powers—a narrative review

Macroalgae have been used for nutritional and medicinal purposes in many cultures throughout history and they are an important part of traditional diets, especially in Asian countries. This narrative review provides an integrative overview of the effects of bioactive compounds present in brown macroalgae (Phaeophyceae) on nutrition and health. Brown macroalgae are rich in various bioactive compounds such as fucoxanthin, phlorotannin, fucoidan, alginate, and laminarin. These bioactive compounds have antioxidant, anti-inflammatory, antidiabetic, anticancer, and antihypertensive effects and may also exhibit immunoregulating or neuroprotective properties. Macroalgae contain high amounts of protein and polyunsaturated fatty acids, dietary fiber, vitamins, and minerals. Their nutrient contents vary depending on factors such as species, environmental conditions, and harvest time. Pigment and polyphenol derivatives, especially fucoxanthin and phlorotannins, have protective effects against chronic diseases associated with oxidative stress by reducing the effects of free radicals. However, there are very few studies on the bioavailability and mechanisms of the nutrients, phenolics, and flavonoids in macroalgae. Since the metabolic transformations of these metabolites in humans are overlooked, their effects on health are also unclear. More <i>in vivo</i> and clinical studies are needed on the potential use of brown macroalgae in the field of health. Overall, the findings summarized in this narrative review suggest that brown macroalgae represent promising, sustainable, and natural sources of bioactive compounds for future nutritional and health-related applications.