Allergenicity of refined vegetable oils

Several commercially important refined vegetable oils are derived from plants which are recognized as potent food allergens (e.g. peanut, soy). Full refining of oils results in the almost complete removal from oils of protein, which is responsible for allergic reactions. However, it is uncertain whether the minute amounts remaining could provoke allergic reactions in highly susceptible individuals. This has led to a vigorous debate about the safety of refined oils and specifically whether to label each oil individually because of the potential risk of allergenicity. Peanut oil has been the most thoroughly studied. It has been shown, in well-designed studies, that refined peanut oil can be safely consumed by the vast majority of peanut-allergic individuals, whereas unrefined oil can provoke reactions in some of the same individuals. However, some other studies report cases of allergic individuals reacting to oils, which are presumed to be refined. While it is likely that the discrepancy between these observations is due to differences in the processing of the oils, and possibly the protein content, this has not been formally demonstrated. Few data exist on the potential allergenicity of other edible vegetable oils; what data there are suggest that the major oils (soy, maize, sunflower, palm) do not provoke allergic reactions in susceptible individuals. Determining the content and immunoreactivity of the residual protein of refined oils is crucial to assessing the allergenic risk they present. Current methodology is inadequate and has not been validated for use with oils and aqueous extracts from oils. Little is known about the importance of different processing steps on allergenicity, although this information is crucial to risk assessment, particularly when considering process modifications. Available data suggest that the protein content of crude oils is of the order of 100–300 μg and that refining results in levels up to about 100-fold lower. The review concludes that peanut oil, and by extrapolation other edible vegetable oils, presents no risk of provoking allergic reactions in the overwhelming majority of susceptible people. However, there is a need to standardize and validate methodology for measuring the protein content and immunoreactivity of such so that they can be used to maintain process specifications. Thresholds of reactivity to allergens in man also need to be established in order to assess fully the risk from very small amounts.