Seed oils harm your health in 7 ways, and decrease Vitamin D in 4 ways

Seed oils decrease health

Polyunsaturated fats (PUFAs) are chemically unstable — they oxidize easily during:
- Industrial extraction (high heat, pressure)
- Refining/deodorizing (temps up to 230°C)
- Storage (light and air degrade them)
- Cooking (especially reheating)
Oxidized linoleic acid produces toxic aldehydes like 4-HNE (4-hydroxynonenal) and acrolein
- These are directly cytotoxic, damage DNA, mitochondria, and LDL particles
- Restaurant fryers reusing oil are particularly dangerous

Refining and high-heat processing creates small amounts of trans fats even in nominally "non-hydrogenated" oils
Not labeled because amounts fall below regulatory thresholds

Displacement of omega-3s
Chronic pro-inflammatory signaling
Linoleic acid accumulates in cell membranes and adipose tissue — half-life in fat tissue is ~2 years

Oxidized PUFAs impair mitochondrial membrane function
Cardiolipin (a mitochondrial membrane lipid) is particularly vulnerable to linoleic acid substitution
Linked by some researchers (Tucker Goodrich, Brad Marshall) to metabolic syndrome

Early trials showed seed oils lowered LDL cholesterol, so they were deemed heart-healthy
But the Minnesota Coronary Experiment (conducted 1968–73, data suppressed until 2016) showed that replacing saturated fat with linoleic acid increased all-cause mortality even while lowering cholesterol
Oxidized LDL — not total LDL — is now considered the actual atherogenic particle

Linoleic acid metabolites influence eicosanoid signaling (prostaglandins, thromboxanes)
May affect insulin sensitivity and adipogenesis
Some evidence of effects on thyroid function

The dramatic rise in seed oil consumption (~1900 to present) closely tracks the rise of:

This is correlational, but the mechanistic pathways (oxidation, aldehyde toxicity, membrane disruption) give it biological plausibility.

Mitochondrial damage from oxidized PUFAs may impair 25-hydroxylation of vitamin D in the liver
Chronic low-grade inflammation from seed oils may upregulate CYP24A1, accelerating vitamin D catabolism
Omega-6 blocks Omega-3. Omega-3 increases Vitamin D levels
There's emerging research suggesting that chronic inflammation from omega-6 dominance may impair vitamin D receptor sensitivity and signaling

Oil	Omega-6 (approx.)
Safflower Oil	~75% (worst)
Grapeseed Oil	~70% (worst)
Sunflower Oil	~65%
Corn Oil	~54%
Cottonseed Oil	~52%
Soybean Oil	~51%
Rice Bran Oil	~35%
Canola Oil	~19% (the least Omega-6, also has Omega-3)

Canola and Rice Bran are the outliers — relatively lower in omega-6, with canola being notably higher in omega-3 (ALA) and monounsaturated fats
Safflower and Grapeseed are among the worst offenders
The concern many researchers raise is the omega-6 to omega-3 ratio — modern Western diets run roughly 15:1 to 20:1, whereas evolutionary estimates suggest 4:1 or lower is optimal
High omega-6 intake is associated with pro-inflammatory signaling, as linoleic acid competes with omega-3s for the same metabolic enzymes (delta-5 and delta-6 desaturase)