Nutrition Fact Check: Seed Oils

Vegetable oils represent a diverse category of oils obtained from various plant sources, including seeds (such as flaxseed and canola), nuts (including peanuts), fruit pulp (such as olives and palm) and cereal bran (such as rice bran). For decades there has been a significant interest in evaluating the relationship between dietary fat intake and risk of chronic disease. More recently the focus has shifted to type of fat rather than total fat intake. Guidelines or recommendations on this topic focus on limiting intake of saturated fat and replacing saturated fat intake with unsaturated fatty acids.

In recent years, the nutritional value of seed oils — often referred to as vegetable oils — has come under increased scrutiny. There is considerable uncertainty surrounding their impact on health, particularly regarding their fatty acid composition, such as the essential omega-6 polyunsaturated fat linoleic acid (LA). Additionally, the industrial processing methods used to produce these oils have raised further health-related concerns. This brief report summarizes current evidence on the effects of seed oils on health outcomes.

Nutrient Profile of Seed Oils and Related Concerns

Seed oils are a rich source of omega-6 fatty acids, especially linoleic acid, and contain a minimal amount of saturated fat. Like any source of fat, seed oils contain different types of fatty acids and their composition vary widely. For example, olive oil is about 55-83% monounsaturated fatty acids (MUFA), 3.5-21% polyunsaturated fatty acids (PUFA) and 7.5-20% saturated fatty acids (SFA). Canola oil is about 63% MUFA, 30% PUFA and 7% SFA.

Polyunsaturated fats encompass both omega-3 and omega-6 fatty acids. There is a belief that this high omega-6 content may contribute to chronic inflammation. This concern stems from the fact that linoleic acid, the predominant omega-6 in seed oils, can be metabolized into arachidonic acid, a precursor to pro-inflammatory compounds in the body. However, research indicates that a small percentage of linoleic acid is converted to arachidonic acid. Furthermore, there is evidence to show that higher intake of omega-6 is associated with better cardiovascular health.

Emerging evidence also suggests that bioactive compounds in seed oils such as tocopherols, biophenols, phytosterols, stigmastadienes, terpenes and squalene may have potentially beneficial health implications.

Another concern is regarding the ratio of omega-6 to omega-3 fatty acids. For a long time, this ratio used to be 1:1. The recent western diet has increased this ratio to 10:1 or greater. However, there is no clear evidence to indicate what the best ratio is. There is significant evidence to indicate that omega-3s have stronger anti-inflammatory effects but there is no clear evidence to indicate that omega-6 has pro-inflammatory effects. Achieving adequate dietary intake of omega-3 fatty acids often involves consuming foods that concurrently contain omega-6 fatty acids.

Another concern stems from the harmful changes that potentially occur during the processing and cooking of these oils. Many seed oils undergo high-temperature industrial processing that can introduce harmful oxidation products or trans fats. However, toxic products like hexane are almost entirely removed from the final product during the refining process.

Seed oils can also be processed by mechanically extracting oil from seeds through cold processing or expeller pressing, without the use of chemical solvents. However, these oils tend to have lower smoke points for cooking, shorter shelf lives and are more expensive.

Existing national and global dietary guidelines recommend limiting total fat intake and saturated fat intake. Some also recommend replacing saturated fat intake with polyunsaturated fat intake, which consist of high omega-6 fatty acids.

Evidence on the Effect of Seed Oils on Health Outcomes

In recent years there has been an increase in research that documents positive associations of seed oil intake and health outcomes. Most of the evidence on this topic is based on studies examining seed oil consumption, overall PUFA intake or linoleic acid intake.

A large 2025 cohort indicated that the highest intake of total plant-based oils compared to the lowest intake was associated with 16% lower total mortality, whereas the highest butter intake compared to lowest intake was associated with 15% higher risk of total mortality. This study further indicates that there is a significant association between higher intakes of canola, soybean and olive oils and lower total mortality. Higher plant-based oil intake was associated with an 11% lower risk of cancer mortality and 6% lower risk of cardiovascular mortality. The cohort also demonstrated that substituting total butter intake with an equivalent amount of total plant-based oils was associated with 17% reduction in total mortality and 17% reduction in cancer mortality.

Two umbrella reviews focused on current evidence of vegetable oils suggest that intake of vegetable oils rich in MUFAs and PUFAs have desirable health effects. One review synthesized findings from 48 systematic reviews and found oils such as canola oil, rice bran oil and virgin olive oil are beneficial in reducing total cholesterol and low-density lipoproteins (LDL). Beneficial effects on glycemic control and weight reduction were also observed. Certainty of evidence ranged from moderate to very low across different outcomes. The second review focused on nutrient and bioactive components of edible oils and fats beyond just their fatty acid content. They reported that the beneficial effects of these may be attributed to compounds such as biophenols and flavonoids. Emerging evidence also suggests potential health benefits from tocopherols and squalene, which are present in certain edible vegetable oils like palm, soybean, canola and sunflower oil.

Multiple systematic reviews suggest that higher intake of PUFAs generally, and linoleic acid specifically, have multiple positive health effects. This, along with the replacement of SFA with either LA or other PUFAs, has the potential to improve CVD related outcomes and reduce risk of developing Type 2 diabetes. A 2025 systematic review based on 11 RCTs indicated that seed oils, such as canola, flaxseed and sesame, can positively improve lipid profile and glycemic control while potentially modulating oxidative stress markers. Additionally, a few systematic reviews of RCTs and individual RCT trials focused on specific vegetable oils consistently shows that higher intake of these vegetable oils is associated with improvements in lipid profiles. Similarly, a network meta-analysis of RCTs indicates replacement of SFA with oils rich in PUFA and MUFA improve lipid profiles.

There is some evidence to address concerns that higher PUFA intake can promote inflammation and oxidative stress. Two systematic reviews of RCTs demonstrated that higher intake of LA did not increase or had no effect on inflammatory markers. Oxidation of PUFAs has been demonstrated in both in vitro and ex vivo studies, however, RCTs show no effect of omega-6 or PUFA on oxidative stress markers.

Conclusion

Current scientific literature supports incorporating seed oils into a well-rounded diet, particularly as an alternative to saturated fat. Although some debates persist around their potential inflammatory or oxidative effects, the majority of peer-reviewed studies do not support these concerns when seed oils are consumed in typical dietary amounts. Health authorities continue to recommend seed oils over animal fats due to their potential to lower cardiovascular risk. Like all dietary fats, seed oils are best used in moderation and as part of a diet that emphasizes whole foods — such as fruits, vegetables, whole grains and lean proteins — while limiting highly processed products.

Note from the Academy of Nutrition and Dietetics:
This summary reflects findings from evidence-based research and is a high-level overview of seed oils; this summary is not a comprehensive deep-dive on the topic. The information shared in this summary is up to date as of June 2025.

Download Summary of Science (PDF)

References

• Neuenschwander M, Barbaresko J, Pischke CR, et al. Intake of dietary fats and fatty acids and the incidence of type 2 diabetes: A systematic review and dose-response meta-analysis of prospective observational studies. PLoS medicine. 2020;17(12):e1003347.
• Ruan L, Cheng SP, Zhu QX. Dietary Fat Intake and the Risk of Skin Cancer: A Systematic Review and Meta-Analysis of Observational Studies. Nutrition and cancer. 2020;72(3):398-408.
• Gopinath A, Cheema AH, Chaludiya K, et al. The Impact of Dietary Fat on Breast Cancer Incidence and Survival: A Systematic Review. Cureus. 2022;14(10):e30003.
• Di Sebastiano KM, Mourtzakis M. The role of dietary fat throughout the prostate cancer trajectory. Nutrients. 2014;6(12):6095-6109.
• Teasdale SB, Marshall S, Abbott K, Cassettari T, Duve E, Fayet-Moore F. How should we judge edible oils and fats? An umbrella review of the health effects of nutrient and bioactive components found in edible oils and fats. Critical reviews in food science and nutrition. 2022;62(19):5167-5182.
• Petersen KS, Maki KC, Calder PC, et al. Perspective on the health effects of unsaturated fatty acids and commonly consumed plant oils high in unsaturated fat. The British journal of nutrition. 2024;132(8):1039-1050.
• Petersen KS, Messina M, Flickinger B. Health Implications of Linoleic Acid and Seed Oil Intake. Nutrition Today. 9900:10.1097/NT.0000000000000746.
• 2020. DGAC. Scientific Report of the 2020 Dietary Guidelines Advisory Committee: Advisory Report to the Secretary of Agriculture and the Secretary of Health and Human Services. U.S. . In: Department of Agriculture ARS, Washington, DC. , ed2020.
• Johnson SA, Kirkpatrick CF, Miller NH, Carson JAS, Handu D, Moloney L. Saturated Fat Intake and the Prevention and Management of Cardiovascular Disease in Adults: An Academy of Nutrition and Dietetics Evidence-Based Nutrition Practice Guideline. Journal of the Academy of Nutrition and Dietetics. 2023;123(12):1808-1830.
• Zhang Y, Chadaideh KS, Li Y, et al. Butter and Plant-Based Oils Intake and Mortality. JAMA internal medicine. 2025;185(5):549-560.
• Voon PT, Ng CM, Ng YT, et al. Health Effects of Various Edible Vegetable Oil: An Umbrella Review. Advances in nutrition (Bethesda, Md). 2024;15(9):100276.
• Farvid MS, Ding M, Pan A, et al. Dietary linoleic acid and risk of coronary heart disease: a systematic review and meta-analysis of prospective cohort studies. Circulation. 2014;130(18):1568-1578.
• Li J, Guasch-Ferré M, Li Y, Hu FB. Dietary intake and biomarkers of linoleic acid and mortality: systematic review and meta-analysis of prospective cohort studies. The American journal of clinical nutrition. 2020;112(1):150-167.
• Schwingshackl L, Bogensberger B, Benčič A, Knüppel S, Boeing H, Hoffmann G. Effects of oils and solid fats on blood lipids: a systematic review and network meta-analysis. Journal of lipid research. 2018;59(9):1771-1782.
• Marklund M, Wu JHY, Imamura F, et al. Biomarkers of Dietary Omega-6 Fatty Acids and Incident Cardiovascular Disease and Mortality. Circulation. 2019;139(21):2422-2436.
• Hooper L, Martin N, Jimoh OF, Kirk C, Foster E, Abdelhamid AS. Reduction in saturated fat intake for cardiovascular disease. The Cochrane database of systematic reviews. 2020;8(8):Cd011737.
• 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 medicine. 2010;7(3):e1000252.
• Mensink RP, World Health O. Effects of saturated fatty acids on serum lipids and lipoproteins: a systematic review and regression analysis. Geneva: World Health Organization; 2016.
• Fornari Laurindo L, Fornari Laurindo L, Dogani Rodrigues V, et al. Evaluating the effects of seed oils on lipid profile, inflammatory and oxidative markers, and glycemic control of diabetic and dyslipidemic patients: a systematic review of clinical studies. Frontiers in Nutrition. 2025;Volume 12 - 2025.
• Ghobadi S, Hassanzadeh-Rostami Z, Mohammadian F, Zare M, Faghih S. Effects of Canola Oil Consumption on Lipid Profile: A Systematic Review and Meta-Analysis of Randomized Controlled Clinical Trials. Journal of the American College of Nutrition. 2019;38(2):185-196.
• Amiri M, Raeisi-Dehkordi H, Sarrafzadegan N, Forbes SC, Salehi-Abargouei A. The effects of Canola oil on cardiovascular risk factors: A systematic review and meta-analysis with dose-response analysis of controlled clinical trials. Nutrition, metabolism, and cardiovascular diseases : NMCD. 2020;30(12):2133-2145.
• Jolfaie NR, Rouhani MH, Surkan PJ, Siassi F, Azadbakht L. Rice Bran Oil Decreases Total and LDL Cholesterol in Humans: A Systematic Review and Meta-Analysis of Randomized Controlled Clinical Trials. Hormone and metabolic research = Hormon- und Stoffwechselforschung = Hormones et metabolisme. 2016;48(7):417-426.
• Baer DJ, Henderson T, Gebauer SK. Consumption of High-Oleic Soybean Oil Improves Lipid and Lipoprotein Profile in Humans Compared to a Palm Oil Blend: A Randomized Controlled Trial. Lipids. 2021;56(3):313-325.
• Kris-Etherton PM, Derr J, Mitchell DC, et al. The role of fatty acid saturation on plasma lipids, lipoproteins, and apolipoproteins: I. Effects of whole food diets high in cocoa butter, olive oil, soybean oil, dairy butter, and milk chocolate on the plasma lipids of young men. Metabolism: clinical and experimental. 1993;42(1):121-129.
• Utarwuthipong T, Komindr S, Pakpeankitvatana V, Songchitsomboon S, Thongmuang N. Small dense low-density lipoprotein concentration and oxidative susceptibility changes after consumption of soybean oil, rice bran oil, palm oil and mixed rice bran/palm oil in hypercholesterolaemic women. The Journal of international medical research. 2009;37(1):96-104.
• Vega-López S, Ausman LM, Jalbert SM, Erkkilä AT, Lichtenstein AH. Palm and partially hydrogenated soybean oils adversely alter lipoprotein profiles compared with soybean and canola oils in moderately hyperlipidemic subjects. The American journal of clinical nutrition. 2006;84(1):54-62.
• Maki KC, Hasse W, Dicklin MR, et al. Corn Oil Lowers Plasma Cholesterol Compared with Coconut Oil in Adults with Above-Desirable Levels of Cholesterol in a Randomized Crossover Trial. The Journal of nutrition. 2018;148(10):1556-1563.
• Polley KR, Oswell NJ, Pegg RB, Paton CM, Cooper JA. A 5-day high-fat diet rich in cottonseed oil improves cholesterol profiles and triglycerides compared to olive oil in healthy men. Nutrition research (New York, NY). 2018;60:43-53.
• Prater MC, Scheurell AR, Paton CM, Cooper JA. Blood Lipid Responses to Diets Enriched with Cottonseed Oil Compared With Olive Oil in Adults with High Cholesterol in a Randomized Trial. The Journal of nutrition. 2022;152(9):2060-2071.
• Su H, Liu R, Chang M, Huang J, Wang X. Dietary linoleic acid intake and blood inflammatory markers: a systematic review and meta-analysis of randomized controlled trials. Food & function. 2017;8(9):3091-3103.
• Johnson GH, Fritsche K. Effect of dietary linoleic acid on markers of inflammation in healthy persons: a systematic review of randomized controlled trials. Journal of the Academy of Nutrition and Dietetics. 2012;112(7):1029-1041, 1041.e1021-1015.
• Sanders TAB. Omega-6 Fatty Acids and Cardiovascular Disease. Circulation. 2019;139(21):2437-2439.
• Da Silva MS, Bilodeau JF, Julien P, Rudkowska I. Dietary fats and F(2)-isoprostanes: A review of the clinical evidence. Critical reviews in food science and nutrition. 2017;57(18):3929-3941.