Tallow or oil?
Seed-oil deep dive for regular folks: facts and fiction.
You’ve heard "industrial seed oils cause inflammation."
Let’s walk through the evidence in plain English.
What’s solid, what's iffier, how to use that knowledge in your own kitchen, and the underlying why RFK Jr. harps on seed oils.
Myth
The idea: "Vegetable oils like soybean, canola, sunflower make your body 'inflamed' and hurt your heart."
The reality: When scientists measure inflammation in people, the oil swap usually lowers it or leaves it unchanged.
This isn't just one or two studies or even dozens.
A 2023 "umbrella" review mashed together over 200 studies on vegetable oils.
Result: most health outcomes-heart disease, stroke, diabetes risk, inflammation markers were neutral or better when people used these oils instead of hard animal fats. [1]
What is inflammation?
Doctors track it with blood chemicals such as C-reactive protein (CRP) and interleukin-6 (IL6) [2].
High numbers mean your immune system is burning up (not good).
(Beyond diet, factors like stress, sleep, and exercise heavily influence these markers. Diet swaps are just one piece of the puzzle.)
But lower is better.
Real food swap #1
Finnish study: 37 adults with metabolic issues, each person spent 6 weeks eating butter, then 6 weeks using canola oil.
What did they find?
Butter phase: inflammation went UP.
Oil phase: "bad" LDL cholesterol fell 11%. A sticky form called oxidized-LDL fell 16%. [3]
Real food swap #2
Sixty people tried four diets in rotation.
One used a palm-oil blend (high in saturated fat); one used a high-oleic soybean oil (mostly unsaturated).
The palm blend raised LDL and nudged CRP up.
The soybean oil lowered LDL and left CRP flat. [4]
Trials
A 2025 review pulled together 11 good-quality experiments where vegetable oils replaced butter, lard or palm.
CRP dropped about 10 %
IL-6 dropped about 8 %
Oxidative stress markers also fell.
None of the trials showed vegetable oils raising those numbers. [5]
Everyday life data
U.S. nutrition survey (NHANES): people with the highest blood levels of trans-fat (from old-school partially-hydrogenated oils) had CRP and clotting factors that were higher.
People who used liquid, non-hydrogenated vegetable oils had the lowest levels. [6]
Quick detour: what's a trans-fat?
Before 2015 many margarines and fryer shortenings were made by hardening vegetable oil with hydrogen gas. That process created trans-fat, which definitely raises heart risk. It’s mostly gone from the food supply now [7].
Liquid oils ≠ trans-fat.
In fact, there is a theory that circulates on social media that the science on seed oils is manipulated to sell more junk foods.
But trans fats were profitable products for food companies.
So why did the data show they were bad, while showing the opposite for veg oils?
Genetics back this up
Big databases following 68,000 heart events show: people who genetically produce more linoleic acid (the main fat in seed oils) in their blood have 7% fewer heart attacks-and less inflammation-than those who have less. [9]
Now, online claims link linoleic acid to cancer, but large cohorts like the NIH-AARP study show no increased risk—and possibly lower—for prostate and other cancers with higher intake, aligning with the genetic data here [10].
"But two famous trials found higher deaths with seed oil"
True, Sydney (1970s) and Minnesota (1970s) stuck people on pure safflower or corn oil, extremely high in omega-6 and very low in vitamin E, while the control groups kept eating trans-fat margarines. [11,12]
But both trials had major confounding: inadequate vitamin E and excess trans-fat in control arm. That's the same trans fat that we know is harmful: they gave the control group the harmful fat!
Newer, better trials do not repeat that result [13].
Influencers often cite these re-analyses to claim seed oils increase mortality, but they ignore that the oils lacked antioxidants and controls had trans-fats—flaws not present in post-1980s studies, which show no such harm [14].
"Seed oils oxidize in the bottle and create toxins."
Frying 10 g of sunflower oil makes ~1 mg of an aldehyde called 4-HNE.
But your own metabolism creates ~50 mg of similar aldehydes every day whether you touch seed oils or not.
But here's the thing:
Beef tallow fried over and over produces comparable amounts. [15]
Concerns about aldehydes link to conditions like Alzheimer's in animal models, but human epidemiology shows no clear tie to vegetable oil consumption; in fact, Mediterranean diets high in olive oil correlate with lower dementia risk [16].
"Seed oils were invented as engine lube"
Yes, rapeseed oil stuck well to ship gears in WWII because it's slippery.
Steam locomotives, on the other hand, packed their pistons with tallow and lard for the same reason. [17,18]
Processing myth #1: "They soak the oil in toxic hexane."
Yes, hexane is used to pull oil out of soy or rapeseed flakes.
Then it's boiled off under vacuum.
A tablespoon of oil: 0.000004 mg per kilogram of body weight: about 90,000 times lower than doses that harm rats. [19,20]
For those concerned, cold-pressed or expeller-pressed oils skip solvents entirely, though they're pricier and less shelf-stable.
Processing myth #2: "Animal fats are natural; seed oils are over-heated."
To make supermarket lard or tallow shelf-stable, factories also:
Wash it with lye.
Bleach it with chlorine dioxide.
Heat it to ~190°C under vacuum.
Vegetable oils get hotter (around 240°C) but for a shorter time and under deeper vacuum.
Both processes aim to remove smells and make the fat last. [21,22,23]
Can we trust nutrition science?
Different methods (trials, population studies, genetics) agree [24].
The same datasets show a clear signal of harm from trans-fat but benefit/neutrality for liquid oils [25].
Databases like NHANES and UK Biobank are public; anyone can rerun the stats [26].
A 2022 analysis found only ~20% of veg oil studies are industry-funded, versus 50%+ for sugar or meat; independent ones still show benefits [27].
Open questions
Nobody has tested a modern diet that's ultra-high in omega-6 and very low in vitamin E. It's worth exploring.
Early mouse work hints oxidized linoleic metabolites could affect nerve pain; human data pending [28].
Another open area: some observational data links high omega-6 to depression risk, but RCTs with balanced diets show no effect or improvements; more research needed on ultra-processed contexts [29].
Plain-English takeaway
Swapping some butter, ghee or bacon fat for liquid (non-hydrogenated) canola, soybean, sunflower or olive oil lowers "bad" cholesterol and doesn't raise inflammation [30].
Keep total added fats moderate (roughly 2-3 tablespoons a day).
Add omega-3 sources-fatty fish, chia, flax, to balance things out.
Critics point to ancestral diets low in seed oils, but those diets were also low in total fats and high in whole foods—modern swaps still beat high-saturated fat intakes in trials mimicking Paleolithic patterns [31].
Spend more energy worrying about ultra-processed snacks (sugar, salt, refined starch) than about the oil you saute veggies in.
Bottom line
Everyday seed oils are safe-and often helpful-when they replace hard animal fats or old trans-fat shortenings. The scary stories leave out crucial details. The broader body of evidence doesn't.
RFK Jr.’s angle
Ah, the final section you have all been waiting for. Or dreading, depending on who you are.
If seed oils vs. tallow don’t really matter, why is RFK Jr. harping on seed oils?
First of all, I don’t really know if he believes the things he says.
What I do know is that the anti-seed oil discourse started mainstreaming in the 2000s and has become more popular.
As a heuristic, it makes sense. Seed oils are a stand-in for modernity and centralized industrial food production.
If you’re anti-authoritarian or skeptical of centralized power (and believe me, I understand that), you might be naturally inclined toward skepticism toward seed oils.
And so I think that’s part of where it comes from.
It’s therefore a Granola Inc. shibboleth—a cultural thing reflecting understandable attitudes and heuristics.
But if it doesn’t make a difference to health, as most things RFK Jr. focuses on don’t, then what is it?
We can repeat an oft-cited right-wing tenet: What things are is what they do.
And what the anti-seed oil discourse does is promise radical change while delivering no change.
Swapping tallow for seed oils doesn’t make any difference, but it creates the illusion of movement.
It promises to challenge established power and re-entrench tradition, but challenges nothing fundamental about the food system or health.
We all get to participate in the change without really changing.
I’m sorry for being so cynical, but after RFK Jr.’s promises to “make America healthy again,” I really am disappointed.
See you on the battlefield.
What do you think? Share your thoughts in the comments, and subscribe for more evidence-based breakdowns.
References
[1] Voon PT et al. Health Effects of Various Edible Vegetable Oil: An Umbrella Review. Adv Nutr 2024. PubMed: https://pubmed.ncbi.nlm.nih.gov/39053603/ (DOI: 10.1016/j.advnut.2024.100277).
[2] Ridker PM. (2016). From C-reactive protein to interleukin-6: Which inflammatory marker is ready for prime time? Circulation. DOI: 10.1161/CIRCULATIONAHA.115.020772.
[3] Palomäki A et al. Cold-pressed rapeseed oil vs butter in men with metabolic syndrome. Lipids Health Dis 2010. DOI: 10.1186/1476-511X-9-137 (PubMed: https://pubmed.ncbi.nlm.nih.gov/21122147/).
[4] Wilson TA et al. High-oleic soybean oil versus palm-oil blend: a randomized crossover trial. J Lipid Res 2021. DOI: 10.1002/lipd.12298 (PubMed: https://pubmed.ncbi.nlm.nih.gov/33596340/).
[5] Zhang M et al. Plant oils and inflammation: systematic review of 11 RCTs. Front Nutr 2025 (in press).
[6] Mazidi M et al. Serum trans-fatty acids and CRP/Fibrinogen—NHANES 1999-2000. J Am Coll Nutr 2017. DOI: 10.1080/07315724.2017.1336816
[7] Food and Drug Administration. (2018). Final determination regarding partially hydrogenated oils (removing trans fat). Federal Register.
[8] Nestle M. (2018). Unsavory Truth: How Food Companies Skew the Science of What We Eat. Basic Books. ISBN 978-1541697119.
[9] Zhao JV, Schooling CM. Mendelian randomisation of linoleic acid and ischemic heart disease. BMC Med 2019. DOI: 10.1186/s12916-019-1293-x (PubMed: https://pubmed.ncbi.nlm.nih.gov/30866921/).
[10] Pelser C, Mondul AM, Hollenbeck AR, Park Y. Dietary fat, fatty acids, and risk of prostate cancer in the NIH-AARP diet and health study. Cancer Epidemiol Biomarkers Prev. 2013;22(4):697-707. DOI: 10.1158/1055-9965.EPI-12-1196-T.
[11] Ramsden CE et al. Sydney Diet Heart Study re-analysis. BMJ 2013. DOI: 10.1136/bmj.e8707.
[12] Ramsden CE et al. Minnesota Coronary Experiment recovered data. BMJ 2016. DOI: 10.1136/bmj.i1246.
[13] Mozaffarian D, et al. (2010). Effects on coronary heart disease of increasing polyunsaturated fat in place of saturated fat: a systematic review and meta-analysis of randomized controlled trials. PLoS Med. DOI: 10.1371/journal.pmed.1000252.
[14] Hooper L, et al. (2020). Reduction in saturated fat intake for cardiovascular disease. Cochrane Database Syst Rev. DOI: 10.1002/14651858.CD011737.pub3.
[15] Ganesan K et al. Aldehyde formation in frying fats vs endogenous production. Food Chem 2024.
[16] Shannon OM, et al. Mediterranean diet adherence is associated with lower dementia risk, independent of genetic predisposition: findings from the UK Biobank prospective cohort study. BMC Med. 2023;21(1):81. DOI: 10.1186/s12916-023-02772-3.
[17] Saturday Evening Post. Rapeseed oil as WWII naval lubricant. https://www.saturdayeveningpost.com/2020/11/navy-a-word-the-creation-of-rapsol-o-oil/ (No DOI).
[18] DiscoverLiveSteam article on beef-tallow cylinder lubrication. https://www.discoverlivesteam.com/magazineold/76.htm/.
[19] Directive 2009/32/EC—Residual hexane max 1 mg/kg. Summary. https://www.euf.org/en/misinformation/article/is-hexane-in-food-a-cause-for-concern.
[20] Cravotto C et al. Towards substitution of hexane as extraction solvent. Foods 2022. DOI: 10.3390/foods11213412 (PubMed: https://pubmed.ncbi.nlm.gov/36360023/).
[21] OxyChem. Upgrading Tallow & Grease with Chlorine Dioxide (tech bulletin). tinyurl.com/tallow-bleach.
[22] Chemists Corner forum thread on tallow bleaching & deodorising. https://chemistscorner.com/cosmeticsciencetalk/discussion/bleaching-and-deodorizing-tallow/.
[23] Liston T. (2015). Rendering: The Invisible Industry.
[24] Burgess S, et al. (2020). Mendelian randomization: Methods for causal inference using genetic variants. Chapman and Hall/CRC. DOI: 10.1201/9780429324161.
[25] De Souza RJ, et al. (2015). Intake of saturated and trans unsaturated fatty acids and risk of all cause mortality, cardiovascular disease, and type 2 diabetes: systematic review and meta-analysis of observational studies. BMJ. DOI: 10.1136/bmj.h3978.
[26] Ioannidis JPA. (2018). The challenge of reforming nutritional epidemiologic research. JAMA. DOI: 10.1001/jama.2018.11025.
[27] SNI Global. Seed Oil Studies – A Closer Look at Funding. 2025. https://sniglobal.org/seed-oil-studies-a-closer-look-at-funding/.
[28] Osth E et al. Oxidized linoleic acid metabolites maintain mechanical and thermal hypersensitivity during sub-chronic inflammatory pain. Biochem Pharmacol. 2022. DOI: 10.1016/j.bcp.2022.114905.
[29] Hibbeln JR. Potential for military diets to reduce depression, suicide, and impulsive aggression: a review of the evidence. Mil Med. 2014. DOI: 10.7205/MILMED-D-14-00400.
[30] Jauhiainen T, et al. (2005). Effects of canola oil on serum lipids in hyperlipidemic subjects. J Intern Med. DOI: 10.1111/j.1365-2796.2005.01546.x.
[31] Otten J et al. Effects of a Paleolithic diet with and without supervised exercise on fat mass, insulin sensitivity, and glycemic control: a randomized controlled study in individuals with type 2 diabetes. Diabetes Metab Res Rev. 2017. DOI: 10.1002/dmrr.2838.
To be honest I don't know what to think anymore.
When ever I read any nutrition studies all I see is confounders. That's not a jab at the people that conduct it, they do their best with the data they have....but there are so many confounders it's hard not to take what you want from "health" studies.
While I have a great deal of regard for the scientific method, the scientific industry has become exactly that. Enslaved by endless grant grubbing, lurching into whatever the latest fad is to attract those grants, riddled with mediocrity and beholden to easily gameable metrics.
I am old enough to have seen 4 cycles of "eggs are good", "eggs are bad". It's difficult to put much value in a field when results like that are pretty frequent.
That sets aside the cultush aspects of "the science", God knows how many times some idiot quoted "science" at me during COVID, clearly not understanding what they were talking about. They were acting on faith and tribalism, nothing logical. Scientists are fallable humans and do the same things.
But throwing everything out the window is also not rational.
Broadly, human health studies do seem to say the same thing: Exercise is clearly good (although not ultra marathoning!). Sleep is clearly important. Generally, fasting seems to be useful. Fruits and vegetables are at their worst neutral but almost certainly positive. Meat and dairy is fine.
Everything else is probably fine in moderation.
I am suspicious of preservatives (they are antibacterial and your gut biome is clearly important) and too much emulsification in your gut may also be a problem for your gut biome although I'm not aware of studies showing that.
But focusing on any specific aspects of diet to save your health, seems counter intuitive. And I often wonder if the stress of worrying about all this stuff negates what moderate good a restrictive diet might do.
In the end adages become adages because they speak to a truth.
I think "Everything in moderation, including moderation" will probably give you as good a result as anything.
I thought the problem was partially hydrogenated oils, not all vegetable oils. The one study you referenced was cold-pressed turnip rapeseed oil vs butter. This doesn't mean much to me. I still think labels that list "canola oil" may or may not be hydrogenated and or heated with the use of solvents. This is what I would try to avoid. Check your labels, canola oil is in everything.