Polyphenols are known to exhibit a number of health promoting effects such as reducing the postprandial glycaemic response. It has been proposed that polyphenols in combination, as found together naturally in foods exert synergistic health effects compared to isolated polyphenols. In the body, polyphenols undergo structural changes throughout digestion which can alter their bioavailability and thus their health impact.

Previous results from our lab found that after being baked into white bread in isolation, the polyphenol rich green tea extract (GTE) at 0·4%, grape seed extract (GSE) at 0·2%, resveratrol (RES) at 0·22% and baobab fruit extract (BAO) at 1·88% reduced rapidly digestible starch (RDS)(1,2). RDS takes place 20 minutes into the duodenal stage of digestion when sugar release is most pronounced and therefore contributes greatest to the glycaemic index (GI) of the food. Using the same optimal isolated extract doses for reducing sugar release from bread in previous studies (with a 75% variation to increase the variety of extract combinations used), the objective was to determine if polyphenol rich extracts showed a synergistic effect in reducing sugar release from high GI white bread.

Bioaccessibility of polyphenols was analysed using an in vitro digestion model adapted from Ryan et al.(3) to determine the stability of polyphenols throughout the digestive process. RDS sugar release was measured using the method by Mishra & Monro(4) followed by a colourimetric method by Englyst & Hudson(5).

Bioaccessibility increased for all extracts (p < 0·05; non-significant for RES) illustrating that polyphenols become potentially more available in the body throughout digestion. Although polyphenol rich extracts in isolation were shown to reduce sugar release from high GI bread, in combination there was no reduction. Therefore, many factors must be considered when using polyphenols as functional food additives.

1. Coe S & Ryan L (2013) Proc Nutr Soc, 72, E201.
2. Coe S et al. (2013) Nutr Res, 33, 888–896.
3. Ryan L et al. (2008) Pla Food Hum Nutr, 63, 127–133.
4. Mishra S & Monro JA (2009) J Cereal Sci, 50, 61–66.
5. Englyst HN & Hudson GJ (1987) Food Chem, 24, 63–76.

The baobab fruit is high in both dietary fibre and polyphenols. Results from previous studies show that foods rich in low glycaemic dietary fibre(1) and those that are abundant in polyphenols(2), can improve cognitive function. The aim of the study was to measure the effect of baobab fruit extract on different measures of cognition in healthy adults. This study was a one-day single blind randomised crossover design (3 day washout) conducted on 20 participants (7 men, 13 women; aged 21–40 year; BMI 18–30 kg/m2). Participants were randomised to consume either a test smoothie consisting of 15g of baobab extract (1914μg/ml polyphenols) or a control smoothie without the addition of baobab (776μg/ml polyphenols), on different days in the morning after an overnight fast at Oxford Brooke University. Cognitive tests were administered 90 mins post consumption after a brief familiarisation of the tests. Cognitive measures were based on previous literature into polyphenols, and included executive function utilising the Stockings of Cambridge test(3) and spatial working memory (PsychoPy v1·82) designed by the researchers(4).

Results are means and standard deviations (SD) of all measures after the consumption of control and baobab smoothies in Percentages (%), Seconds (s) or Milliseconds (ms). Stockings of Cambridge (SOC); Response (Resp).* = p < 0·05 performed significantly better. PsychoPy and SOC test data were analysed using a Wilcoxon – Signed Rank test. Consumption of the baobab enriched smoothie significantly reduced movement duration (p < 0·05) but also increased unsuccessful move type in the Stockings of Cambridge test (p < 0·05). There were no significant differences between testing order. Compared with the taste and nutrient matched control, there were several trends in favour of the baobab smoothie (albeit not significant). Baobab consumption administered at 15 g in a smoothie significantly improved reaction time in executive planning tests, but also increased the amount of unsuccessful move types. This research has positive implications for the use of baobab consumption first thing in the morning for improving cognitive function in the hours post prandial.

References
1. Ingwerson et al. (2007) Appet 49, 240–244.
2. Lamport et al. (2012) Nutr Aging 1, 5–25.
3. File et al. (2005) Menopa 12, 193–201.
4. Field et al. (2011) Phys Behav 103, 255–60.

The baobab fruit (Adansonia digitata L.) is found throughout regions of Africa and is becoming increasingly recognized for its high nutrient and polyphenol content. Polyphenols have been beneficial for their effects on reducing the glycemic response (GR) and for improving various other metabolic parameters. Based on previous research, it was hypothesized that the baobab fruit extract would reduce starch digestion in vitro and would show potential for reducing the GR and for increasing satiety and diet-induced thermogenesis in humans. Six extracts of baobab from 6 different locations in Africa were measured for their antioxidant and polyphenol content using the ferric ion–reducing antioxidant power and the Folin-Ciocalteu methods, respectively. Baobab extract was baked into white bread at different doses to determine the optimal dose for reducing starch breakdown and sugar release from white bread after an in vitro digestion procedure. In vivo, baobab extract was consumed in solution at both a low-dose (18.5 g) and a high-dose (37 g) aqueous drink in 250 mL of water along with white bread, and resulting GR, satiety, and postprandial energy expenditure were measured. All extracts in this study were shown to be good sources of polyphenols. Baobab fruit extract added to white bread at 1.88 % significantly (P < .05) reduced rapidly digestible starch from white bread samples. In vivo, the baobab fruit extract at both low and high doses significantly (P< .05) reduced GR, although there was no significant effect on satiety or on energy expenditure.