Vitamin A is rapidly degraded in retinyl palmitate-fortified soybean oil stored under household conditions

Oil fortification with retinyl palmitate is intended to lower the prevalence of vitamin A deficiency in populations at risk. Although the stability of vitamin A in vegetable oil has been shown to depend on environmental factors, very little information is known about the stability of vitamin A in preoxidized vegetable oils. The present study investigated the stability of retinyl palmitate in mildly oxidized (peroxide value < 2 mequiv O₂/kg) and highly oxidized (peroxide value > 10 mequiv O₂/kg) soybean oil stored under domestic and retail conditions. Soybean oil was filled in transparent bottles, which were exposed to cold fluorescent light at 22 or 32 °C for 56 days. Periodic oil sampling increased the headspace, thereby mimicking consumer handling. Loss of retinyl palmitate in soybean oil by a maximum of 84.8 ± 5.76% was accompanied by a decrease of vitamin E by 53.3 ± 0.87% and by an increase of the peroxide value from 1.20 ± 0.004 to 24.3 ± 0.02 mequiv O₂/kg. Fortification of highly oxidized oil with 31.6 IU/g retinyl palmitate led to a doubling of the average decrease of retinol per day compared to fortification of mildly oxidized oil. In conclusion, oil fortification programs need to consider the oxidative status of the oil used for retinyl palmitate fortification.