Abstract
In this manuscript, a series of research reports focused on dietary lipid oxidation products (LOPs), their toxicities and adverse health effects are critically reviewed in order to present a challenge to the mindset supporting, or strongly supporting, the notion that polyunsaturated fatty acid-laden frying oils are “safe” to use for high-temperature frying practises. The generation, physiological fates, and toxicities of less commonly known or documented LOPs, such as epoxy-fatty acids, are also considered. Primarily, an introduction to the sequential autocatalytic peroxidative degradation of unsaturated fatty acids (UFAs) occurring during frying episodes is described, as are the potential adverse health effects posed by the dietary consumption of aldehydic and other LOP toxins formed. In continuance, statistics on the dietary consumption of fried foods by humans are reviewed, with a special consideration of French fries. Subsequently, estimates of human dietary aldehyde intake are critically explored, which unfortunately are limited to acrolein and other lower homologues such as acetaldehyde and formaldehyde. However, a full update on estimates of quantities derived from fried food sources is provided here. Further items reviewed include the biochemical reactivities, metabolism and volatilities of aldehydic LOPs (the latter of which is of critical importance regarding the adverse health effects mediated by the inhalation of cooking/frying oil fumes); their toxicological actions, including sections focussed on governmental health authority tolerable daily intakes, delivery methods and routes employed for assessing such effects in animal model systems, along with problems encountered with the Cramer classification of such toxins. The mutagenicities, genotoxicities, and carcinogenic potential of aldehydes are then reviewed in some detail, and following this the physiological concentrations of aldehydes and their likely dietary sources are considered. Finally, conclusions from this study are drawn, with special reference to requirements for (1) the establishment of tolerable daily intake (TDI) values for a much wider range of aldehydic LOPs, and (2) the performance of future nutritional and epidemiological trials to explore associations between their dietary intake and the incidence and severity of non-communicable chronic diseases (NCDs).
Highlights
The Western diet contains large quantities of lipids which have been exposed to high temperature frying, cooking or processing episodes, and according to today’s standards, consumers have expressed a high level of public health concern relating to the inherence, distribution and dietary consumption of adversely generated toxins and contaminants in foods [1]
We have shown that such alternative fried foods and fried food products such as fried chicken and pork sausages [47] contain patterns of aldehydic and further hazardous lipid oxidation products (LOPs), the latter including epoxy-fatty acid toxins such as 9,10-epoxy-12-octadecenoate and its more potent corresponding diol [23, 47, 54], which have leukocyte degeneration and necrotizing properties [23], and are involved in the pathogenesis of multiple organ failure and breast cancer [54]; they can interfere with the reproductive functions of rats [23]
A consideration of this 30 g average daily consumption quantity for global fast-food chain French fry servings yields a total human α,β-unsaturated aldehyde consumption rate as high as 17 μmoles/day from the investigation reported in Le Gresley et al [63], a value which is ca. 1.8- and a striking nearly 30fold higher than the above WHO and AGDH daily consumption limits, respectively. This total value includes lower levels of the even more reactive and toxic substituted α,βunsaturated aldehydes 4,5-epoxy-trans-2-alkenals, 4-hydroxyand 4-hydroperoxy-trans-2-alkenals; these aldehydes were detectable in French fry samples analysed and not in those of the investigation described in Moumtaz et al [47] in view of the higher sensitivity and selectivity of the 600 MHz NMR spectrometer facility employed for these analyses in the former investigation
Summary
A series of research reports focused on dietary lipid oxidation products (LOPs), their toxicities and adverse health effects are critically reviewed in order to present a challenge to the mindset supporting, or strongly supporting, the notion that polyunsaturated fatty acid-laden frying oils are “safe” to use for high-temperature frying practises. An introduction to the sequential autocatalytic peroxidative degradation of unsaturated fatty acids (UFAs) occurring during frying episodes is described, as are the potential adverse health effects posed by the dietary consumption of aldehydic and other LOP toxins formed. Further items reviewed include the biochemical reactivities, metabolism and volatilities of aldehydic LOPs (the latter of which is of critical importance regarding the adverse health effects mediated by the inhalation of cooking/frying oil fumes); their toxicological actions, including sections focussed on governmental health authority tolerable daily intakes, delivery methods and routes employed for assessing such effects in animal model systems, along with problems encountered with the Cramer classification of such toxins.
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