Elsevier

Food Hydrocolloids

Volume 25, Issue 2, March 2011, Pages 263-266
Food Hydrocolloids

The key role alginates play in health

https://doi.org/10.1016/j.foodhyd.2009.09.009Get rights and content

Abstract

The role of alginates, widely utilised gelling agents in pharmaceutical and food applications, in human health has broadened recently with the recognition that they have a number of potentially beneficial physiological effects in the gastrointestinal tract. These include an effect on intestinal absorption and colonic health. Importantly, alginates have also been shown to moderate human appetite and energy intake. It has been proposed that, following ingestion, ionic gelation of alginate in stomach acid can modulate feeding behaviour through slowed gastric clearance, stimulation of gastric stretch receptors and attenuated nutrient uptake. It should be recognised however that these alginate formulations utilise gastric acid as the ‘trigger mechanism’ for gelation which can be unreliable because a number of factors may reduce gastric acidity. To address this concern, we have developed an alginate:calcium carbonate powder mix that when reconstituted with water and ingested, does not rely on stomach acid to ‘trigger’ ionic gelation. The formulation development process and a series of randomised, controlled trials to assess whether the novel alginate beverage could modulate feeding behaviour are discussed. The findings suggest a role for appropriately designed alginate formulations in the management of overweight and obesity.

Section snippets

Alginates

Alginates are polysaccharides that provide the main structural component of brown algae (seaweeds). Alginates are linear copolymers of (1 → 4) linked β-d-mannuronic acid (M) and α-l-guluronic acid (G). The distribution of M and G in alginate chains gives rise to three different block types, namely blocks of poly-M, blocks of poly-G and alternating MG blocks. The chemical composition of alginate is variable according to the seaweed species, within different parts of the same plant (stem or

Healthcare uses of alginates

Alginate anti-reflux preparations are used for the treatment for gastro-oesophageal reflux disease (GORD). These provide a physical barrier upon contact with the stomach contents in the form of a neutral floating gel or ‘raft’. Products such as Gaviscon® contain a high G sodium alginate, calcium carbonate and sodium (or potassium) bicarbonate which are formulated to undergo ionic gelation in the stomach. Alginate rafts are formed by the action of gastric acid on a soluble sodium alginate to

Alginate & satiety

Alginates have been shown to modulate appetite and energy intake in models of acute feeding. These studies used alginate formulations that undergo ionic gelation upon reaction with gastric acid (acid-soluble calcium source) to form an alginate gel that can slow gastric emptying, stimulate gastric stretch receptors and reduce intestinal nutrient uptake and influence the glycaemic response.

Wolf et al. (2002) measured the postprandial glycaemic index in response to a glucose-based beverage with

Alginate formulation development

The sodium alginate satiety beverage was designed to undergo enhanced ionic gelation within the stomach but independent of gastric acidity. This ability to gel regardless of endogenous acid secretion and pH was achieved by addition of the acidulant glucono-delta-lactone (GDL). Reconstitution of the beverage in water hydrolyses the GDL to glucuronic acid with controlled reduction in the pH of the beverage. This controls the solubilisation of calcium carbonate which in turn controls the rate of

Clinical study 1

A randomised, controlled two-way crossover study was carried out to evaluate the influence of a one-off dose of the sodium alginate satiety beverage (or control) upon test meal consumption and perceptions of fullness and hunger. Using state-of-the-art methodology consumption of a test meal could be monitored and visual analogue scale (VAS) questionnaires were displayed before, during and 2 h after commencement of the meal to monitor hunger and fullness. The protocol was such that subjects ate a

Clinical study 2

A randomised, controlled two-way crossover study was carried out to evaluate the influence of a daily dose of the sodium alginate satiety beverage (or control) upon energy and macronutrient consumption over seven days (Paxman et al., 2008, Paxman et al., 2008). Free-living adults ingested a single dose of pre-load either 30 min before breakfast or evening meal for seven days. In the treatment arm subjects ingested sodium alginate satiety beverage (Table 1) and in the control arm subjects

Clinical study 3

A randomised, controlled, two-way crossover study into the acute effect of the sodium alginate satiety beverage upon lipidaemic, glycaemic and cholestrolaemic response was carried out (Paxman et al., 2008, Paxman et al., 2008). The protocol was such that each subject was given a set meal the evening before the study to be consumed before 10.00 pm after which they fasted until attending the unit for the study day. Anthropometric measures (height, weight, % body fat) were taken and a controlled

Conclusions

In clinical studies 1.5 g pre-load of alginate in the form of a specifically developed satiety beverage was shown in acute studies to reduce the onset of hunger following a test meal, reduce the desire to eat between meals and reduce blood cholesterol and glucose levels in subjects with BMI > 25 compared to control. In a chronic setting over 7 days a 1.5 g pre-load of alginate in the form of a specifically developed satiety beverage was shown to affect a clinically significant reduction in

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