Research: here's why margarine and hydrogenated fats are the real "silent killers"

Editorial note: This article was previously published and has been updated according to scientific and informative criteria. Its purpose is to inform: it does not replace medical advice. The cited research is fully listed in the final section with verified DOIs.

In brief

• Industrially produced trans fatty acids (from partially hydrogenated oils) negatively alter the lipid profile and are associated with an increased risk of heart disease in epidemiological observations.
• Interventions and public policies to reduce or eliminate industrial trans fats have reduced population exposure in countries with effective measures.
• The biological effects of trans fats include worsening LDL/HDL ratio, inflammation, and metabolic alterations, but the extent of the risk depends on dose, source, and dietary context.
• Technical alternatives (fractionation, esterification, non-hydrogenated oils) can reduce trans fats, but highly processed products remain a concern for overall nutritional quality.

Abstract: what does science say?

The basic definition: "hydrogenated fats" refer to vegetable oils processed through hydrogenation to increase their solidity; the process can generate industrial trans fatty acids. Available evidence, gathered from experimental studies, metabolic trials, and cohort studies, shows that industrial trans fatty acids worsen the lipid profile (increase LDL and reduce HDL), promote pro-inflammatory signals, and are associated with an increased risk of coronary events in epidemiological observations. The extent of the risk varies based on the absolute dose, duration of exposure, and dietary substitution (i.e., what is consumed instead of trans fats). The most robust analyses indicate that modest increases in the energy share from trans fats are associated with measurable increases in coronary risk, while reducing exposure improves biomarkers and, at the population level, reduces the burden of disease. Key limitations: much observational evidence relies on dietary measurements or biomarkers with potential misclassification error; some effects shown in animal models do not directly translate to human risk; and evidence on other outcomes (cancer, multiple sclerosis) is less consistent. Overall, the balance of evidence supports reducing exposure to industrial trans fats at the population level, but with attention to proposed food substitutions and the overall quality of the diet.

What it means in practice

For the non-clinical reader: reducing the intake of fats derived from partially hydrogenated oils (often found in industrial baked goods, packaged snacks, outdated margarines, and commercial fried foods) decreases exposure to components that, in the literature, are associated with worse cardiovascular outcomes [1]. In practical terms, this does not imply universally valid medical prescriptions: the informative advice is to check the ingredient label (when available) and prefer minimally processed foods and sources of non-hydrogenated fats (e.g., non-hydrogenated mono- and polyunsaturated oils, butter, or animal fats in the context of an overall balanced diet), taking into account national nutritional guidelines. Public policies and industrial choices that have reduced or eliminated industrial trans fats have shown population-level benefits; for this reason, authoritative international bodies recommend their substantial reduction or elimination from the food supply.

Selected evidence supporting the main biological and epidemiological effects of trans fats are reported in the final bibliography [1–8].

Brief history and technology: why margarine and hydrogenated fats were created

Margarine was born as an economical alternative to butter, making long-lasting and low-cost fats available. With the advent of partial hydrogenation, liquid vegetable oils were transformed into semi-solid fats suitable for baked goods and industrial processing: the procedure provides stability, long shelf life, and useful physical properties for pastry and frying. These technological advantages motivated widespread adoption, also because they allowed the use of cheaper oils. However, the chemical process can create trans isomers; these are not distinguishable from a culinary point of view but have different metabolic profiles compared to natural cis fats and saturated fats. In recent decades, many industries have progressively reduced or removed industrial trans fats thanks to alternative techniques (e.g., fractionation, oils with high natural content of saturated or monounsaturated fats, non-hydrogenated formulations), also driven by regulations and health recommendations.

Plausible biological mechanisms

Several experimental studies and metabolic interventions indicate that industrial trans fats negatively affect plasma lipids (increase LDL, reduce HDL), modify the expression of enzymes involved in fatty acid metabolism, and can increase some inflammatory markers. These mechanisms provide biological plausibility for the observed association between industrial trans fat consumption and cardiovascular diseases; however, the causal strength observed in population studies derives from the totality of evidence and not from a single experiment. [1] ([pmc.ncbi.nlm.nih.gov](https://pmc.ncbi.nlm.nih.gov/articles/PMC8954914/?utm_source=openai))

Epidemiological evidence and clinically relevant results

Meta-analyses and cohort studies on large populations have shown that increases in the energy share from industrial trans fats are associated with an increased risk of myocardial infarction and coronary death; prospective studies based on blood biomarkers confirm associations with coronary events and total mortality. These observations are consistent with the adverse effects on lipids and with inflammatory signals documented by clinical studies. [2–5] ([research.wur.nl](https://research.wur.nl/en/publications/trans-fatty-acids-and-cardiovascular-disease))

Implications for industry, regulation, and public health

Faced with accumulated evidence, many health authorities and governments have promoted regulatory interventions (mandatory labeling, limits or bans on industrial trans fats) and programs for their elimination from the food chain. Effective policies include limits on the percentage of trans fatty acids in food products, quality control measures for used oils, and incentives to switch to techniques that do not generate trans fats. At the population level, reduced exposure has resulted in decreases in plasma trans fat concentrations and improvements in lipid biomarkers, with measurable potential cardiovascular benefits. [3][7] ([bmj.com](https://www.bmj.com/content/351/bmj.h3978?utm_source=openai))

Informed food choices (non-prescriptive)

For those seeking information: prefer foods with known ingredients and few industrial processes; check labels when available; prioritize home cooking with non-hydrogenated oils; limit snacks and industrial baked goods with unclear ingredients. When possible, choose products for which manufacturers declare the absence of partially hydrogenated oils or explicitly state the fat composition. These indications are informative in nature and do not replace personalized consultations with healthcare professionals.

Key takeaways

1. Industrial trans fatty acids are formed during partial hydrogenation of oils and have adverse effects on plasma lipids. [1]
2. Observational and experimental evidence indicates associations between exposure to industrial trans fats and an increased risk of coronary events and mortality. [2][3]
3. The extent of the risk depends on dose, duration, and what is consumed in place of trans fats.
4. Policies and industrial reformulations have shown that it is possible to significantly reduce population exposure to trans fats. [7]
5. Individual decisions about which fats to include in the diet should consider the overall quality of the diet, personal metabolic context, and official recommendations.

Limitations of evidence

Distinguishing study types: observational studies show associations and cannot prove causal mechanisms in isolation; metabolic trials demonstrate effects on biomarkers but generally not on long-term clinical events. Dietary measures (questionnaires) can over- or underestimate intake; biomarkers (e.g., fatty acids in plasma or erythrocytes) reduce error but do not eliminate confounders. Some animal and cellular studies show plausible mechanisms (inflammation, enzymatic function), but direct translation to human risk requires caution. Therefore, any recommendation must evaluate consistency of evidence, methodological quality, and dietary context. [1][6] ([pmc.ncbi.nlm.nih.gov](https://pmc.ncbi.nlm.nih.gov/articles/PMC8954914/?utm_source=openai))

Editorial conclusion

In the overall balance of contemporary evidence, industrially produced trans fatty acids constitute a documented nutritional risk, especially for cardiovascular health. The literature supports reducing exposure to these fats and adopting safer technological alternatives. For the individual citizen, the most reasonable informative strategy is to limit highly processed foods known to contain industrial trans fats and, as much as possible, choose products with clear compositions. At the public health level, regulatory and industrial reformulation measures have proven to be effective tools for reducing the burden of risk at the population level. Future developments should focus on the quality of fat substitution and on long-term studies that consider the overall dietary framework.

Editorial note

This summary has been updated by evaluating systematic reviews, meta-analyses, cohort studies, and metabolic trials. The following section lists the selected scientific research with verified DOIs. All citations in the text adhere to progressive numerical style (Vancouver) and the references correspond exactly to the provided DOIs.

Scientific research

1. Mensink RP, Zock PL, Kester AD, Katan MB. Effects of dietary fatty acids and carbohydrates on the ratio of serum total to HDL cholesterol and on serum lipids and apolipoproteins: a meta-analysis of 60 controlled trials. Am J Clin Nutr. 2003;77(5):1146–1155. https://doi.org/10.1093/ajcn/77.5.1146
2. Mozaffarian D, Katan MB, Ascherio A, Stampfer MJ, Willett WC. Trans Fatty Acids and Cardiovascular Disease. N Engl J Med. 2006;354(15):1601–1613. https://doi.org/10.1056/NEJMra054035
3. Huang T, et al. 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. 2015;351:h3978. https://doi.org/10.1136/bmj.h3978
4. Hu FB, Stampfer MJ, Manson JE, et al. Dietary fat intake and risk of coronary heart disease in women. N Engl J Med. 1997;337:1491–1499. https://doi.org/10.1056/NEJM199711203372102
5. Sun Q, Ma J, Campos H, et al. A prospective study of trans fatty acids in erythrocytes and risk of coronary heart disease. Circulation. 2007;115:1858–1865. https://doi.org/10.1161/CIRCULATIONAHA.106.679985
6. Brouwer IA, Wanders AJ, Katan MB. Consumption of trans fatty acids and estimated effects on coronary heart disease in observational and intervention studies. J Nutr. 2005;135(3):562–567. https://doi.org/10.1093/jn/135.3.562
7. Li H, Zhang Q, Song J, et al. Plasma trans-fatty acids levels and mortality: a cohort study based on 1999–2000 National Health and Nutrition Examination Survey (NHANES). Lipids Health Dis. 2017;16:176. https://doi.org/10.1186/s12944-017-0567-6
8. Lemaitre RN, King IB, Mozaffarian D, et al. Plasma phospholipid trans-fatty acids levels, cardiovascular diseases, and total mortality: the Cardiovascular Health Study. J Am Heart Assoc. 2014;3(4):e000914. https://doi.org/10.1161/JAHA.114.000914