A Critical Review of the Seed Oil Safety Study (PMID 40048719)
- Shane Caraway
- Jul 6
- 3 min read
The recent publication in Advances in Nutrition claiming seed oils are safe and beneficial to health (PMID: 40048719) has been widely circulated. While it presents a polished case grounded in epidemiological consensus, it overlooks multiple critical dimensions—biochemical, methodological, and contextual—that demand deeper scrutiny. Let us explore those flaws in detail.
1. Category Contamination: Olive Oil Is Not a Seed Oil
The study’s methodology lumps all plant-based unsaturated oils together, including olive oil. This is scientifically irresponsible for several reasons:
Olive oil is derived from fruit, not seed, and has a dramatically different fatty acid profile. Unlike actual seed oils, olive oil is rich in oleic acid and polyphenols while also low in omega-6. Comparatively, actual seed oils (Canola, Soybean, etc) are high in omega-6 fats with no polyphenol content.
Including olive oil in seed oil analysis dilutes risk signals that might be attributable specifically to high-linoleic, refined seed oils.
2. Failure to Address Oxidative Byproducts
The paper is silent on one of the most important variables in seed oil health risk: oxidation.
Seed oils are highly prone to oxidative degradation when processed or heated.
Oxidized lipids produce reactive aldehydes like 4-hydroxynonenal (4-HNE), which have been implicated in cellular dysfunction, atherosclerosis, and neurodegeneration.
These real-world culinary effects are not accounted for.
3. Overreliance on Epidemiological Data
The majority of the study’s “support” comes from large cohort studies using FFQs (Food Frequency Questionnaires)—a method fraught with bias and error.
FFQs cannot distinguish between oils used for deep frying, sautéing, or salad dressing.
Confounders (e.g., higher PUFA use among health-conscious individuals) further blur any causal conclusions.
4. Mechanistic Oversight
Numerous rodent and in vitro studies suggest excess omega-6 PUFA (particularly linoleic acid) may:
Disrupt endocannabinoid signaling
Increase hypothalamic inflammation
Promote adipogenesis and metabolic dysfunction
These mechanistic findings are either dismissed or ignored entirely in the review.
5. Absence of Stratification by Processing, Use, or Source
A meaningful study would stratify oils by:
Source: seed, nut, fruit
Processing method: cold-pressed vs. refined
Culinary use: raw, sautéed, deep-fried
Instead, the study glosses over these distinctions, drawing generalized conclusions from an unstratified pool of data.
6. Downplaying of Omega-6/Omega-3 Imbalance
The study fails to acknowledge the drastic shift in omega-6:omega-3 ratio in modern Western diets—from an estimated 1:1–4:1 historically to 15:1–25:1 today, largely due to seed oil proliferation.
This imbalance has been implicated in chronic low-grade inflammation, and even the WHO has recognized the need to rebalance these ratios.
7. Narrative Conformity and Institutional Bias
Though not funded by the seed oil industry, the study is authored by researchers deeply embedded in legacy nutritional institutions like Harvard. These organizations were pivotal in displacing saturated fat with polyunsaturated fat in dietary guidelines—creating a potential conflict of ideological interest.
Conclusion
The conclusions presented in this study are not rooted in a balanced or mechanistically rigorous framework. By relying on epidemiological data, ignoring oxidative degradation, and failing to stratify oils based on meaningful distinctions, the authors draw generalized and potentially misleading inferences.
Seed oils may not be universally harmful, but neither is there sufficient evidence to declare them categorically safe—especially under real-world conditions of processing and overconsumption.
At Evidentia Health, we favor nuance over dogma, and mechanism over consensus.
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