Arsenic and Nutrient Composition Across Different Edible Seaweeds From Hawaii

OBJECTIVES: Seaweed is used for various cultural, culinary, and medicinal purposes in Hawaii and has been consumed for generations around the world (i.e., the Pacific, Asia, and parts of Europe). In the US, seaweed is gaining popularity because of its reputation for being highly nutritional. However, some types of seaweed are known to accumulate heavy metals, including inorganic arsenic (iAs) species. While some seaweed species have been studied, there is still limited species-specific compositional data. The purpose of this study was to quantify arsenic and nutrient (i.e., macronutrient and mineral) levels in edible seaweeds. METHODS: Brown algae (Sargassum aquifolium and Sargassum spp.), red algae (Gracilaria parvispora, Halymenia formosa, and Halymenia hawaiiana, and green algae (Ulva ohnoi) were analyzed using HPLC-ICP-MS for arsenic speciation. Proximate (protein, dietary fiber, ash, moisture, carbohydrate, crude fat, and crude protein) and mineral (P, K, Ca, Mg, Na, Fe, Mn, Zn, Cu, B) analyses were conducted. Values were expressed per freeze-dried weight (FDW) or fresh weight serving (FW) of seaweed. RESULTS: Brown algae had the highest concentration of total and iAs compared to all others. Statistical differences amongst macronutrients and minerals existed across seaweed species, with G. parvispora having higher Mn (∼510 µg/g FDW) and K (∼4.6 g/100g FDW) levels compared to all other samples (P < 0.05). Based on recommended nutritional daily values, G. parvispora (∼80 g FW) was high in Mn, H. formosa (∼100 g FW) was high in Fe, U. ohnoi (∼100 g FW) was high in Mg, and H. hawaiiana (∼100 g FW) was high in Mg, Fe, and Zn. CONCLUSIONS: Overall, these findings indicate significant differences in composition across seaweed species. As some seaweeds were excellent sources of essential nutrients while others were high in iAs, it is critical to continually expand compositional data to assess both nutritional adequacy and safety of diets. FUNDING SOURCES: USDA-ARS, FDA.