Seed Oils vs Saturated Fats: Clearing the Confusion

Alastair Hunt
May 3
9 min read

Updated: 2 days ago

Part 5 of the Seed Oils Series

The saturated fat debate has been reignited repeatedly over the last decade. Popular articles, like TIME Magazine’s 2014 cover story "Eat Butter" suggested that saturated fats had been wrongly demonised. However, closer scrutiny of the evidence - especially large-scale studies and systematic reviews - reveals that the relationship between fats and health is more nuanced.

Saturated fats, found in animal products such as butter, lard, cheese, and fatty meats, do raise LDL cholesterol (low-density lipoprotein cholesterol) levels, a well-established risk factor for atherosclerosis and cardiovascular disease. Early dietary guidelines recommended lowering total fat intake, but modern guidance focuses on replacing saturated fats with unsaturated fats rather than eliminating fats altogether.

Large cohort studies and meta-analyses consistently show that replacing saturated fats with polyunsaturated fats (PUFAs) - such as those found in seed oils, nuts, and fish - leads to significant reductions in cardiovascular events. For example, the 2025 JAMA Internal Medicine study (Zhang et al.) found that higher intakes of canola, soybean, and olive oil were associated with a 17% reduction in total mortality compared to butter consumption.

Clinical interventions and systematic reviews such as Schwab et al. (2021) and Hooper et al. (2020, Cochrane Review) conclude that lowering saturated fat intake and replacing it with unsaturated fats results in modest but important reductions in cardiovascular disease risk. See links to supporting studies at Bottom of Page.

Newer lipid science has further clarified that it is not only the quantity of LDL cholesterol that matters, but also the number and size of LDL particles. Diets high in saturated fats tend to increase the number of small, dense LDL particles, which are more atherogenic (more likely to contribute to plaque build-up). In contrast, diets richer in unsaturated fats, especially polyunsaturated fats, improve overall lipid profiles by lowering ApoB (the number of atherogenic particles), triglycerides and LDL particle numbers.

Importantly, not all saturated fats are equal. Saturated fat from minimally processed foods, like dairy, may have different health effects compared to saturated fats from processed meats. Yet, when public health advice is issued at the population level, reducing saturated fat intake while increasing intake of polyunsaturated fats remains a robust, evidence-based strategy.

Nutrition science evolves. Individual responses to dietary fats can vary based on genetics, metabolic health, and overall diet quality. Always consult your doctor, dietitian or medical professional before making significant changes to your diet, particularly if you have pre-existing conditions, are managing a chronic illness or are pregnant.

The strongest body of evidence supports replacing excess saturated fat with polyunsaturated fats - including those from seed oils - as part of a varied, whole-food diet. For more studies on this subject area, scroll to bottom of page.

Next... Part 6: Seed Oils: Omega-6, Omega-3 and Health: Striking the Right Balance

Final Thoughts

While seed oils can be a divisive issue online, we are relatively agnostic when it come to diet and eating patterns. If you enjoy cooking with olive oil, a dab of butter, avocado oil or (as a treat) duck fat, we do too. In the same regard, we are not concerned about a splash of canola in our stir fry and we try to avoid ultra-processed foods as part of our daily eating.

Changing health for the better is about progress, not perfection, and even small changes can make a meaningful difference over time. For most people, improving health is about finding motivation and prioritising self-care - with an ultimate goal of taking action. If you want to take effective and targeted steps that fit into your unique lifestyle and circumstances, The Whole Health Practice is here to help.

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Stay Healthy,

Alastair

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Related Studies

Zhang Z, Ding L, Liang Y, Yang H, Zhu Y. The association of dietary fatty acids intake with overall and cause-specific mortality: a prospective cohort study from 1999-2018 cycles of the NHANES. Front Nutr. 2025 Feb 19;12:1468513. doi: 10.3389/fnut.2025.1468513. PMID: 40046766; PMCID: PMC11879808.

"After adjusting for potential confounders, the highest butter intake was associated with a 15% higher risk of total mortality compared to the lowest intake. In contrast, the highest intake of total plant-based oils compared to the lowest intake was associated with a 16% lower total mortality. There was a statistically significant association between higher intakes of canola, soybean, and olive oils and lower total mortality, with hazard ratios per 5-g/d increment of 0.85, 0.94, respectively. Every 10-g/d increment in plant-based oils intake was associated with an 11% lower risk of cancer mortality and a 6% lower risk of CVD mortality, whereas a higher intake of butter was associated with higher cancer mortality. Substituting 10-g/d intake of total butter with an equivalent amount of total plant-based oils was associated with an estimated 17% reduction in total mortality (and a 17% reduction in cancer mortality.

Conclusions and Relevance: In this cohort study, higher intake of butter was associated with increased mortality, while higher plant-based oils intake was associated with lower mortality. Substituting butter with plant-based oils may confer substantial benefits for preventing premature deaths." Zhang Y, Chadaideh KS, Li Y, Li Y, Gu X, Liu Y, Guasch-Ferré M, Rimm EB, Hu FB, Willett WC, Stampfer MJ, Wang DD. Butter and Plant-Based Oils Intake and Mortality. JAMA Intern Med. 2025 Mar 6:e250205. doi: 10.1001/jamainternmed.2025.0205. Epub ahead of print. PMID: 40048719; PMCID: PMC11886867.

Maleki Sedgi F, Mohammad Hosseiniazar M, Alizadeh M. The effects of replacing ghee with rapeseed oil on liver steatosis and enzymes, lipid profile, insulin resistance and anthropometric measurements in patients with non-alcoholic fatty liver disease: a randomised controlled clinical trial. Br J Nutr. 2024 Jun 28;131(12):1985-1996. doi: 10.1017/S0007114524000564. Epub 2024 Mar 19. PMID: 38501177.

Zhao B, Gan L, Graubard BI, Männistö S, Fang F, Weinstein SJ, Liao LM, Sinha R, Chen X, Albanes D, Huang J. Plant and Animal Fat Intake and Overall and Cardiovascular Disease Mortality. JAMA Intern Med. 2024 Oct 1;184(10):1234-1245. doi: 10.1001/jamainternmed.2024.3799. PMID: 39133482; PMCID: PMC11320333.

"This study shows that, in addition to energy restriction and weight loss, choices of dietary FA intake may be of importance for persons with NAFLD. When analysing the whole study population, in which dietary fat content differed considerably between study groups, we found that reducing the intake of total fat and especially SFA could have beneficial effects on liver stiffness and plasma cholesterol. Furthermore, an increased intake of both n-3 and n-6 PUFA affects the plasma composition of FA, which also may be beneficial for the reduction of liver fat, plasma cholesterol levels and TAG." Tillander V, Holmer M, Hagström H, Petersson S, Brismar TB, Stål P, Lindqvist C. Associations between dietary fatty acid and plasma fatty acid composition in non-alcoholic fatty liver disease: secondary analysis from a randomised trial with a hypoenergetic low-carbohydrate high-fat and intermittent fasting diet. Br J Nutr. 2024 Sep 18;132(4):1-13. doi: 10.1017/S0007114524001673. Epub ahead of print. PMID: 39290088; PMCID: PMC11499086.

Wang Y, Fang Y, Witting PK, Charchar FJ, Sobey CG, Drummond GR, Golledge J. Dietary fatty acids and mortality risk from heart disease in US adults: an analysis based on NHANES. Sci Rep. 2023 Jan 28;13(1):1614. doi: 10.1038/s41598-023-28738-2. PMID: 36709394; PMCID: PMC9884296.

Pigsborg K, Gürdeniz G, Rangel-Huerta OD, Holven KB, Dragsted LO, Ulven SM. Effects of changing from a diet with saturated fat to a diet with n-6 polyunsaturated fat on the serum metabolome in relation to cardiovascular disease risk factors. Eur J Nutr. 2022 Jun;61(4):2079-2089. doi: 10.1007/s00394-021-02796-6. Epub 2022 Jan 9. PMID: 34999928; PMCID: PMC9106625.

Conclusion: Although only limited data were available, replacement of saturated fats with other macronutrients, such as polyunsaturated fats, was associated with reduced cardiovascular disease occurrence. Supporting evidence from research in the general population increases confidence in these findings. Until more data are available to better comment on dietary fat intakes in cardiovascular disease risk of those with type 2 diabetes, it appears appropriate that saturated fats be replaced in the diet with other macronutrients, such as polyunsaturated fats." Schwab U, Reynolds AN, Sallinen T, Rivellese AA, Risérus U. Dietary fat intakes and cardiovascular disease risk in adults with type 2 diabetes: a systematic review and meta-analysis. Eur J Nutr. 2021 Sep;60(6):3355-3363. doi: 10.1007/s00394-021-02507-1. Epub 2021 Feb 21. PMID: 33611616.

"In this large prospective cohort, intakes of butter and margarine were associated with higher all-cause, cardiometabolic, and other major cause-specific mortality, whereas intakes of canola oil and olive oil were related to lower mortality. Substituting corn oil, canola oil, or olive oil for butter and margarine was associated with lower all-cause, cardiometabolic, cancer, respiratory disease, and Alzheimer's disease mortality." Zhang, Y., Zhuang, P., Wu, F. et al. Cooking oil/fat consumption and deaths from cardiometabolic diseases and other causes: prospective analysis of 521,120 individuals. BMC Med 19, 92 (2021). https://doi.org/10.1186/s12916-021-01961-2

"High saturated and trans fat intake (which elevates LDL like saturated fat) in the Nurses and Health Professional Follow-Up Studies combined is associated with an 8–13% higher mortality and replacement of saturated fat with any carbohydrate, PUFA and MUFA is associated with lower mortality with PUFA being more effective than MUFA (19% reduction versus 11%).

With CVD mortality only PUFA and fish oil replacement of saturated fat lowers risk with a 28% reduction in CVD mortality per 5% of energy. Replacing saturated fat with PUFA or MUFA is equally effective at reducing CHD events and replacement with whole grains will lower events while replacement with sugar and starch increases events.

Replacement of saturated fat with carbohydrate has no effect on CHD events or death. Only PUFA replacement of saturated fat lowers CHD events and CVD and total mortality. Replacing saturated fat with linoleic acid appears to be beneficial based on the Hooper Cochrane meta-analysis of interventions although other analyses with fewer studies have shown no effect." Clifton PM, Keogh JB. A systematic review of the effect of dietary saturated and polyunsaturated fat on heart disease. Nutr Metab Cardiovasc Dis. 2017 Dec;27(12):1060-1080. doi: 10.1016/j.numecd.2017.10.010. Epub 2017 Oct 18. PMID: 29174025.

Zhang Y, Zhuang P, Wu F, He W, Mao L, Jia W, Zhang Y, Chen X, Jiao J. Cooking oil/fat consumption and deaths from cardiometabolic diseases and other causes: prospective analysis of 521,120 individuals. BMC Med. 2021 Apr 15;19(1):92. doi: 10.1186/s12916-021-01961-2. PMID: 33853582; PMCID: PMC8048052.

Kruse M, Kemper M, Gancheva S, Osterhoff M, Dannenberger D, Markgraf D, Machann J, Hierholzer J, Roden M, Pfeiffer AFH. Dietary Rapeseed Oil Supplementation Reduces Hepatic Steatosis in Obese Men-A Randomized Controlled Trial. Mol Nutr Food Res. 2020 Nov;64(21):e2000419. doi: 10.1002/mnfr.202000419. Epub 2020 Oct 7. PMID: 32920973.

"Authors' conclusions: The findings of this updated review are suggestive of a small but potentially important reduction in cardiovascular risk on reduction of saturated fat intake. Replacing the energy from saturated fat with polyunsaturated fat appears to be a useful strategy, and replacement with carbohydrate appears less useful, but effects of replacement with monounsaturated fat were unclear due to inclusion of only one small trial. This effect did not appear to alter by study duration, sex or baseline level of cardiovascular risk. Lifestyle advice to all those at risk of cardiovascular disease and to lower risk population groups should continue to include permanent reduction of dietary saturated fat and partial replacement by unsaturated fats. The ideal type of unsaturated fat is unclear." Hooper L, Martin N, Abdelhamid A, Davey Smith G. Reduction in saturated fat intake for cardiovascular disease. Cochrane Database Syst Rev. 2015 Jun 10;(6):CD011737. doi: 10.1002/14651858.CD011737. Update in: Cochrane Database Syst Rev. 2020 May 19;5:CD011737. doi: 10.1002/14651858.CD011737.pub2. PMID: 26068959.

Rosqvist F, Kullberg J, Ståhlman M, Cedernaes J, Heurling K, Johansson HE, Iggman D, Wilking H, Larsson A, Eriksson O, Johansson L, Straniero S, Rudling M, Antoni G, Lubberink M, Orho-Melander M, Borén J, Ahlström H, Risérus U. Overeating Saturated Fat Promotes Fatty Liver and Ceramides Compared With Polyunsaturated Fat: A Randomized Trial. J Clin Endocrinol Metab. 2019 Dec 1;104(12):6207-6219. doi: 10.1210/jc.2019-00160. PMID: 31369090; PMCID: PMC6839433.

Zhuang P, Zhang Y, He W, Chen X, Chen J, He L, Mao L, Wu F, Jiao J. Dietary Fats in Relation to Total and Cause-Specific Mortality in a Prospective Cohort of 521 120 Individuals With 16 Years of Follow-Up. Circ Res. 2019 Mar;124(5):757-768. doi: 10.1161/CIRCRESAHA.118.314038. PMID: 30636521.

Bjermo H, Iggman D, Kullberg J, Dahlman I, Johansson L, Persson L, Berglund J, Pulkki K, Basu S, Uusitupa M, Rudling M, Arner P, Cederholm T, Ahlström H, Risérus U. Effects of n-6 PUFAs compared with SFAs on liver fat, lipoproteins, and inflammation in abdominal obesity: a randomized controlled trial. Am J Clin Nutr. 2012 May;95(5):1003-12. doi: 10.3945/ajcn.111.030114. Epub 2012 Apr 4. PMID: 22492369.

Masson CJ, Mensink RP. Exchanging saturated fatty acids for (n-6) polyunsaturated fatty acids in a mixed meal may decrease postprandial lipemia and markers of inflammation and endothelial activity in overweight men. J Nutr. 2011 May;141(5):816-21. doi: 10.3945/jn.110.136432. Epub 2011 Mar 23. PMID: 21430255.

Mozaffarian D, Micha R, Wallace S. 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. 2010 Mar 23;7(3):e1000252. doi: 10.1371/journal.pmed.1000252. PMID: 20351774; PMCID: PMC2843598.