The conflicting findings of Jensen et al and Odunsi

The conflicting findings of Jensen et al. [31,33] and Odunsi et al. [34] may be the result of different modes of alginate delivery. The greater volume of drinks compared to the volume of capsules may stimulate gastric stretch receptors, increase satiety and therefore reduce energy consumption. El Khoury et al. [38] investigated the effect of adding strong-gelling sodium alginate to chocolate milk on glycemia, insulinemia, appetite and food intake. In this randomized crossover study (see Table 1), 24 healthy men were provided with isovolumetric (325mL) beverages of chocolate milk, 1.25% alginate chocolate milk, 2.5% alginate chocolate milk or 2.5% alginate solution. The drinks were standardized for lactose, sucrose and calcium content, and administered 120min before an ad libitum pizza meal during which food intake was measured. Appetite as well as plasma glucose and insulin were measured at baseline and at intervals pre- and post-meal. Addition of 2.5% alginate to chocolate milk led to a decrease in peak glucose concentrations, at 30min, by an average of 6% and 13% compared with 1.25% alginate chocolate milk and chocolate milk alone, respectively. Insulin peaks at 30min were lower by 46% after 2.5% alginate chocolate milk compared to chocolate milk. Pre-meal appetite was reduced dose-dependently by alginate chocolate milk. Chocolate milk with 2.5% alginate reduced mean appetite by an average of 134% in comparison with chocolate milk alone. However, there were no differences regarding total caloric intake at the pizza meal [38]. Some of the studies presented above suggest that energy consumption can be reduced by the dietary intake of seaweed isolates such as alginate. Hall and her colleagues [39] investigated the effect of adding whole seaweed to bread on energy intake. They studied the acceptability of Ascophyllum nodosum enriched bread as part of a meal, and measured its effect on energy consumption and nutrient MLN9708 in overweight healthy men. The acceptability study including 79 untrained sensory panelists indicated that it is acceptable to add seaweed (Ascophyllum nodosum) to bread at concentrations of up to 4% per 400g wholemeal loaf. In a single blind cross over trial (see Table 1), the authors compared both energy intake and nutrient uptake following a breakfast meal using the enriched bread (4% A. nodosum) or control bread (no A. nodosum). Consumption of the enriched bread at breakfast significantly reduced (16.4%) energy intake, but not nutrient uptake at a test meal consumed 4h later [39]. Plasma blood glucose and cholesterol levels did not differ between groups. The alginate in the seaweed enriched bread may have caused gastric stretching due to bulking.
Anti-obesity activity of seaweed components in animals and humans Mitochondrial uncoupling protein-1 is usually expressed only in brown adipose tissue and a key molecule for metabolic thermogenesis to avoid an excess of fat accumulation [40]. Adaptive thermogenesis by uncoupling protein-1 may be a physiological defense mechanism against obesity [41] and the dysfunctioning of uncoupling protein-1 has been shown to be involved in the development of obesity [42]. Little brown adipose tissue is found in adult humans. The expression of mitochondrial uncoupling protein-1 in tissues other than brown adipose tissue is therefore expected to reduce abdominal fat. Maeda et al. [40] investigated the effect of feeding mice Undaria pinnatifida lipids (mainly glycolipids and seaweed carotenoid, fucoxanthin). While there was little expression of uncoupling protein-1 in white adipose tissue of mice fed control diet, clear signals of uncoupling protein-1 and its mRNA were observed in white adipose tissue of mice fed Undaria lipids. In mice receiving fucoxanthin, white adipose tissue was markedly reduced and uncoupling protein-1 clearly expressed. No difference in white adipose tissue weight was observed in mice fed glycolipids.