Heidi Taylor, Kirsten Webster, Andrew R. Gray, Siew Ling Tey, Alex Chisholm, Karl Bailey, Shivani Kumari, Rachel C. Brown

Recommendations to soak nuts prior to consumption to reduce phytate concentrations and improve gastrointestinal tolerance have received much attention in the popular press. This is despite no supporting scientific evidence for the practice. There is also a lack of information about how soaking nuts might affect consumer acceptability. This study primarily assessed the effects of soaking almonds on consumer acceptance and secondly assessed effects on gastrointestinal tolerance. In this 8-week randomised crossover trial, 76 participants were allocated in balanced order to receive 30 g/day of four different preparations of almonds for 12 days: whole unsoaked, whole soaked, sliced unsoaked, and sliced soaked. Ratings of overall liking, desire to consume, and likelihood of future consumption, and severity of gastrointestinal symptoms were measured daily on visual analogue scales. The phytate concentrations were measured in all four nut types using high-performance liquid chromatography. Mean acceptance ratings of all nut types were above the neutral point indicating they were acceptable. However, sliced soaked almonds were rated significantly lower overall for all three acceptance scales compared to the other treatments (all P ≤ 0.003). The sliced unsoaked almonds were rated lower than both whole nut treatments (all P ≤ 0.006), while there were no significant differences between the two whole nut treatments (all P ≥ 0.511). Gastrointestinal symptoms were minimal, but flatulence was rated significantly higher for all time points combined for soaked whole nuts compared to unsoaked whole nuts (P = 0.005). Compared to the whole unsoaked nuts (mean [SD] 531 [9] mg/100 g), phytate concentration was higher for the whole soaked almonds (563 [38] mg/100 g, P = 0.016), with no evidence of a difference for the sliced soaked almonds (548 [27] mg/100 g, P = 0.197) and no difference between the soaked forms (P = 0.262). This research supports previous results suggesting nuts, including different forms, are an acceptable food. They are also well tolerated gastrointestinally, but soaking does not improve gastrointestinal tolerance or acceptance as claimed in the lay literature.