Nutritional value of the marine algae wakame (Undaria pinnatifida) and nori (Porphyra purpurea) as food supplements

Abstract

The nutritional properties of seaweeds are incompletely known, and studies on nutrient bioavailability are scarce, although such information is required to evaluate seaweed as a foodstuff. In the present study, samples of wakame (Undaria pinnatifida) and nori (Porphyra purpurea) were analysed to determine their chemical composition. To evaluate the algae as dietary supplements, the effects on rats of the inclusion of these seaweeds in a standard rodent diet were investigated. The control rats were fed a diet containing 100 % standard rodent diet. The wakame diet was obtained by mixing 10 % dried wakame with 90 % standard rodent diet, and the nori diet was obtained by mixing 10 % dried nori with 80 % standard rodent diet and 10 % starch. Food intake and the body weight were measured. Nitrogen ingested and excreted were determined to calculate true digestibility, biological value, net protein utilization and nitrogen balance. Biochemical determinations were made on serum blood samples. The protein content was high (16.8 % for wakame and 33.2 % for nori), the fat content was low (1 % for wakame and 2.8 % for nori) and the carbohydrates comprised 37 % for both seaweeds. The fibre and ash contents in wakame were 16.9 and 28.3 %, respectively, and in nori, they were 7.5 and 21.3 %, respectively. Both seaweeds contain high concentrations of calcium, sodium, potassium, iron and magnesium, and the most abundant vitamin was vitamin A. Few changes were observed in the nutritional parameters, but LDL cholesterol levels were significantly lower in rats fed with seaweed-supplemented diets than in the control rats. Wakame and nori are excellent sources of nutrients and are well accepted by experimental animals.