“…TPA was developed further by Icek Ajzen and Martin Fishbein with an explanation that behaviour can be predicted by intended behaviour, resulting from three factors of attitude towards behaviour, subjective norm, and perceived behavioural control (Fishbein and Ajzen, 2011). This theory has been previously applied to explain behaviours related to dietary supplements (Conner, Kirk, Cade, and Barrett, 2001;Alami, Sany, Lael-Monfared, Ferns, Tatari, Hosseini, and Jafari, 2019;Jalambadani, and Hosseini, 2022). However, O'Connor and White (2010) found that perceived behavioural control failed to predict the willingness to purchase functional foods and vitamin supplements.…”