Changes in consumption of omega-3 and omega-6 fatty acids in the United States during the 20th century.
Level 4 - case-series / case-control
Historical ecological food-disappearance modeling study (graded by design analogy, not clinical CEBM)
PubMed 21367944 · doi:10.3945/ajcn.110.006643
What was done
The authors estimated US per capita consumption of essential fatty acids from 1909 to 1999 using annual economic food disappearance data across 373 food commodities. Nutrient composition for 1909 was modeled two ways: using modern food compositions (1909-C) and foods produced using traditional early-20th-century agricultural practices (1909-T). From these data, changes in dietary fatty acid availability and predicted tissue fatty acid levels were calculated.
What was found
Estimated per capita soybean oil intake increased >1000-fold between 1909 and 1999. Linoleic acid (LA) availability rose from 2.79% to 7.21% of energy under 1909-C modeling (P < 0.000001) and was 2.23% of energy under 1909-T modeling. Alpha-linolenic acid (ALA) rose from 0.39% (1909-C) or 0.35% (1909-T) to 0.72% of energy in 1999. The LA:ALA ratio rose from 6.4 in 1909 to 10.0 in 1999. Under 1909-T modeling, dietary availability of arachidonic acid, EPA, and DHA declined substantially. Modeled tissue omega-3 highly unsaturated fatty acid status fell from 36.81% (1909-T) or 31.28% (1909-C) to 22.95% in 1999, and the predicted omega-3 index fell from 8.28 (1909-T) or 6.51 (1909-C) to 3.84 in 1999.
Why it matters
This paper quantifies the 20th-century shift in US dietary fats, showing that massive increases in soybean oil and linoleic acid intake likely suppressed biological tissue incorporation of EPA and DHA.
Limits
The analysis relies entirely on aggregate national food disappearance data rather than actual individual dietary intake measurements. Tissue fatty acid levels and omega-3 indices were mathematical predictions from models rather than directly sampled biological tissues across the century.
Cited by
- supports US consumption of soybean oil has increased a thousandfold since 1900.
- supports About 40% of linoleic acid in the American diet comes from soybean oil alone.
- supports Soybean oil accounts for approximately 10% of total caloric intake in the United States.