Functional foods are those which exert significant health-promoting effects beyond the provision of adequate nutrition (Hill & Peters, 2002). Such products are a promising approach for lessening the adverse impact of poor diet on health status, including the current public health threat posed by obesity (Boobier et al., 2005). Because a major cause of obesity is energy imbalance (whereby intake surpasses expenditure), successful approaches to weight management are obliged to amend at least one of these mechanisms (Sweeting, 2007). This paper therefore presents a rationale for using chia (Salvia hispanica L.) as a FF to prevent obesity in young adults due to its impact on satiation (the satisfaction of hunger that marks the cessation of eating) and satiety (inhibition of appetite as a result of eating).
Chia is a novel wholegrain rich in alpha-linolenic acid (ALA), fibre, protein, minerals and antioxidants. As a dietary intervention to reduce obesity risk, chia has several favourable properties to recommend its use. Foremost is its capacity to decrease excessive caloric intake through subjective appetite suppression (Lee, 2009). Specifically, evidence suggests that its proportion of vegetable proteins, fibre and polyunsaturated fat may operate in an additive fashion to amplify satiety and satiation. For example, chia is enriched with calcium, which exerts regulatory effects on fat metabolism by influencing lipogenesis, lipolysis and fat oxidation; all factors which mediate appetite parameters (Zemel et al., 2000). Chia is naturally high in protein (the most satiating macronutrient; Westerterp-Plantenga et al., 2006) and has an adjusted Protein Efficiency Ratio of 91% (Lee, 2009). It is also rich in dietary fibre (a nutrient whose intake is implicated in diminished hunger and reduced risk of obesity; Slavin & Green, 2007). Indeed, fibre has relevant properties for impacting specifically on appetite, including viscosity (satiety) and bulk (satiation). Specifically, chia contains high levels of viscous soluble fibres (beneficial for protracting intestinal digestion and absorption) resulting in lengthier periods for nutrients to interact with pre-absorptive satiation/satiety mechanisms and extending the duration of post-absorptive satiation/satiety signals (Slavin & Green, 2007). Finally, chia consumption is associated with reduced post-prandial glycemia (Vuksan et al., 2010), a metabolic mechanism postulated to enhance satiety through promoting stable blood sugar levels (Raben et al., 1994). Indeed, preliminary studies have indicated beneficial physiological effects for Chia in lowering adiposity. For example, Vertommen and colleagues (2004) found that after one month of daily chia consumption, participants exhibited a significant decrease in waist circumference independent of body weight, suggesting a specific reduction in fat mass. Similarly, animal models have shown that dietary chia seed significantly reduces viscereal adiposity (epididymal and retroperitoneal fat) compared to controls (Chicco et al., 2009).
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Such qualities give chia a superior constitution compared to commonly-consumed oily seeds and wholegrains (see Table 1). It is therefore proposed to add ground chia to a specially formulated range of carbohydrate products, including bread, pasta, tortillas and rice. This choice is guided by two considerations. Firstly, although chia contains little carbohydrate (and therefore does not have a precise glycemic index; GI) it has the capacity to reduce glycemic response when added to high-carbohydrate foods (Lee, 2009). Studies evaluating the effect of GI on satiety (which control for palatability, energy density and caloric intake) have suggested that low-GI meals are associated with lower subsequent energy intake and greater subjective satiety (e.g., Holt et al., 1996; Roberts, 2000; Tremblay et al., 2002). Such effects may be partially explained by the manner in which high-GI foods promote rapid spikes in plasma glucose, inducing insulin release, hypoglycemia and heightened hunger signals (Ludwig, 2000). Furthermore, low-GI carbohydrates are digested more slowly, resulting in greater levels of undigested starch within the ileum (McMillan-Price & Brand-Miller, 2006), which in turn promotes secretion of satiety-signalling hormones like GLP-1 (Qualmann et al., 1995). Secondly, these foods are popular choices amongst the target population of consumers (Harker et al., 2010; Kendzierski & Costello, 2004), yet may be a characteristic of human obesity syndromes when consumed in excess (Samaha et al., 2003). These products are therefore a good example of popular food choices that can be healthily redesigned and favourably consumed.
3. Product Validation
In addition to claims about chiaââ‚¬â„¢s general nutritional value (e.g., its high levels of micronutrients and anti-oxidants), packaging will advise consumers that the products will reduce hunger and promote feelings of fullness. Proof of concept will be determined by confirming product functionality through biomedical assessment (Blundell, 2010). Blinded, placebo-controlled, randomized trial will be used whereby subjective satiety/satiation will be assessed using visual analogue scales. Appetite ratings will be converted to numerical values, and incremental scores examined using two-way ANOVA to determine whether significant time x meal interactions exist for the experimental group compared to controls.
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Acceptability will be ascertained through testing relevant sensory properties (organoleptic assessment). Consumer preferences for standard and modified products will be determined using randomized, blinded control trials.
One factor which may comprise product efficacy is the use of ground chia as opposed to whole grains. The discrepancy in particle size means less force will be required during mastication, possibly affecting satiety despite equicaloric properties (Haber et al., 1977). Furthermore, grain size may have implications for product capacity to lower postprandial glycemia, as the latter is positively correlated with increasing grain volume (due to the reduced accessibility of bigger particles to digestive enzymes and the consequent prolonged glucose response; Jenkins et al., 1988). However, given that carbohydrate is a primary nutritional candidate for raising plasma glucose (and that chia contains only negligible levels) is can still be argued that adding the grain to carbohydtate meals supplies an inconsequential quantity of carbohydrate while providing components (protein, fat and fibre) known to decrease postprandial glycemia.
5. Concluding Comments
Although subjective satiety may not definitively reduce food intake, convincing evidence suggests that hunger ratings do correlate with actual caloric consumption (Akhavan & Anderson, 2007). The health crisis posed by obesity renders controlled food intake a valuable preventative strategy, in which using FF to curtail short-term appetite may cumulatively reduce long-term consumption, ultimately precluding excessive weight gain and its associated health problems.
Table 1. Nutritional composition of chia and common grains (100g)
Soluble dietary fibre
Insoluble dietary fibre
Vitamin C (ascorbic