Soybean oil intake may influence tissue fatty acid levels
MedWire News: Researchers suggest that an increase in the consumption of soybean oil over time is partly responsible for significant changes in human tissue concentrations of essential fatty acids.
"The apparent increased consumption of linoleic acid (LA), which was primarily from soybean oil, has likely decreased tissue concentrations of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) during the 20th century," explain the researchers in the American Journal of Clinical Nutrition.
Using food availability data from the Economic Research Service of the US Department of Agriculture, Joseph Hibbeln (National Institutes of Health, Rockville, Maryland, USA) and team quantified changes in the consumption of essential fatty acids in the US from 1909 to 1999.
The nutrient compositions of foods consumed in 1909 were modeled using current foods (1909-C model) and foods produced by early 20th century traditional practices (1909-T model).
The authors report an increase in general oil consumption over time, with the most significant change being for soybean oil, which accounted for just 0.006% of energy in 1909 compared with 7.38% in 1999 - an increase of more than a 1000-fold.
The researchers say that this increase in soybean oil consumption resulted in significant changes in the availability of LA and α-LA (ALA); the percentage of total energy available from LA increased from 2.79% in 1909 to 7.21% in 1999, while ALA availability increased from 0.39% to 0.72%, respectively.
Furthermore, the 1909-T model, but not the 1909-C model, indicated that dietary availability of n-6 arachidonic acid, EPA, n-3 docosapentaenoic acid, and DHA decreased by 20%, 60%, 69%, and 30%, respectively, over this time period.
Hibbeln et al predicted that the net effect of these dietary changes, primarily the changes in LA availability, would result in declining tissue membrane concentrations of fatty acids throughout the 20th century.
Indeed, between 1909 and 1999, the predicted percentage of n-3 human fatty acids decreased from 36.81% (1909-T model) or 31.28% (1909-C model), to 22.95%, and the estimated omega-3 index decreased from 8.28 (1909-T model) or 6.51 (1909-C model), to 3.84.
The team concludes that the relevance to human health of these LA-induced reductions in n-3 human fatty acids is yet to be established.
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By Nikki Withers