As Americans started eating more processed vegetable oils, rates of insulin resistance and diabetes went up at almost the same time—this timing suggests the two might be connected.
Scientific Claim
The rise in RBD seed oil consumption in the U.S. since 1909 closely parallels the rise in insulin resistance and type 2 diabetes prevalence, suggesting a potential temporal association that warrants further investigation.
Original Statement
“It is notable that over the last century we can appreciate a striking similarity between the rise of RBD oil consumption and the rise of metabolic disease, as illustrated in Figure 1.”
Evidence Quality Assessment
Claim Status
appropriately stated
Study Design Support
Design supports claim
Appropriate Language Strength
association
Can only show association/correlation
Assessment Explanation
The claim is based on ecological trend data and correctly uses correlational language. No causation is claimed, and the limitation of ecological fallacy is acknowledged implicitly.
Gold Standard Evidence Needed
According to GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this specific claim, ordered from strongest to weakest evidence.
Prospective Cohort StudyLevel 2bWhether individual-level RBD oil intake predicts future insulin resistance or diabetes onset.
Whether individual-level RBD oil intake predicts future insulin resistance or diabetes onset.
What This Would Prove
Whether individual-level RBD oil intake predicts future insulin resistance or diabetes onset.
Ideal Study Design
A 15-year prospective cohort of 15,000 U.S. adults with repeated dietary assessments (FFQ, biomarkers) and annual HOMA-IR and HbA1c measurements, analyzing whether RBD oil intake quintiles predict incident prediabetes/T2DM.
Limitation: Residual confounding from overall diet quality and physical activity.
Cross-Sectional StudyLevel 3In EvidenceWhether current RBD oil intake correlates with insulin resistance markers in a representative population.
Whether current RBD oil intake correlates with insulin resistance markers in a representative population.
What This Would Prove
Whether current RBD oil intake correlates with insulin resistance markers in a representative population.
Ideal Study Design
A nationally representative cross-sectional analysis of NHANES data (2010–2020) with 10,000+ adults, correlating dietary RBD oil intake (via 24-hr recall) with HOMA-IR and fasting insulin, adjusting for age, BMI, and activity.
Limitation: Cannot determine if oil intake preceded insulin resistance.
Case-Control StudyLevel 3Whether individuals with insulin resistance have higher historical RBD oil intake than matched controls.
Whether individuals with insulin resistance have higher historical RBD oil intake than matched controls.
What This Would Prove
Whether individuals with insulin resistance have higher historical RBD oil intake than matched controls.
Ideal Study Design
A case-control study of 500 adults with T2DM and 500 matched controls, using dietary recall and adipose tissue fatty acid profiles to reconstruct 20-year RBD oil intake history.
Limitation: Recall bias and difficulty reconstructing long-term diet.
Evidence from Studies
Supporting (1)
This study says that the processed seed oils we eat a lot more of now (like soy and canola oil) might be causing our bodies to become resistant to insulin, which leads to type 2 diabetes—and the timing matches up: as we ate more of these oils, diabetes rates went up too.