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Health Line
3 days ago
- Health
- Health Line
Are Vegetable and Seed Oils Bad for Your Health?
While these oils can be a healthy source of fat, some varieties are better choices than others. That said, the often-mentioned adverse effects of omega-6 fats may not be as clear as previously believed. The consumption of vegetable oils has increased dramatically in the past century. Most mainstream health professionals consider them healthy, but vegetable oils may cause health problems. Their health effects vary depending on what fatty acids they contain, what plants they are extracted from, and how they are processed. This article examines the evidence to determine whether vegetable and seed oils harm your health. What are they and how are they made? Edible oils extracted from plants are commonly known as vegetable oils. In addition to their use in cooking and baking, they're found in processed foods, including salad dressings, margarine, mayonnaise, and cookies. Common vegetable oils include safflower oil, soybean oil, and canola oil. Refined vegetable oils were not available until the 20th century, when the technology to extract them became available. These are extracted from plants using either a chemical solvent or an oil mill. Then they are often purified, refined, and sometimes chemically altered. Health-conscious consumers prefer oils made by crushing or pressing plants or seeds rather than those produced using chemicals. Consumption has increased drastically In the past century, vegetable oil consumption has increased at the expense of other fats like butter. They are often labeled 'heart-healthy' and recommended as an alternative to sources of saturated fat, such as butter, lard, and tallow. Vegetable oils are considered heart-healthy because studies consistently link polyunsaturated fat to a reduced risk of heart problems compared with saturated fat. Despite their potential health benefits, some scientists worry about how much of these oils people consume. As explained in the next chapter, these concerns mainly apply to oils that contain a high amount of omega-6 fats. What do we know about omega-6? It's important to note that not all plant oils are bad for your health. For example, avocado oil and olive oil are both excellent choices. Both omega-6 and omega-3 fatty acids are essential fatty acids, meaning that you need some of them in your diet because your body can't produce them. Throughout evolution, humans got omega-6 and omega-3 in a certain ratio. While this ratio differed between populations, it's estimated to have been about 1:1. However, in the past century or so, this ratio in the Western diet has shifted dramatically and may be as high as 20:1. Older research has hypothesized that too much omega-6 relative to omega-3 may contribute to chronic inflammation. On the other hand, a more recent study from 2025 did not show a connection between higher omega-6 consumption and inflammation. Chronic inflammation is an underlying factor in some of the most common Western diseases, such as heart disease, cancer, diabetes, and arthritis. Observational studies have also associated a high intake of omega-6 fat with an increased risk of heart disease. However, these associations don't necessarily imply a causal relationship. In fact, the evidence for omega-6 being detrimental to human health is mixed. Some studies investigating the effects of omega-6 fat consumption generally do not support the idea that these fats increase inflammation. For instance, eating a lot of linoleic acid, which is the most common omega-6 fat, doesn't appear to affect blood levels of inflammatory markers. Consider limiting plant oils high in omega-6, as well as processed foods that contain these plant oils, which include: soybean oil corn oil cottonseed oil sunflower oil peanut oil sesame oil rice bran oil Scientists do not fully understand the effects of omega-6 fats on the body, and more human studies are needed. However, if you are concerned, it is more important to limit processed foods high in omega-6 fats, such as baked treats, chips, deep-fried fast foods, or takeout meals, as these have a more direct and proven effect on health. Current studies remain inconclusive about the actual impact of avoiding vegetable oils when cooking at home on health. These oils are easily oxidized Saturated, monounsaturated, or polyunsaturated fats differ by the number of double bonds their chemical structures contain: Saturated fats: no double bonds Monounsaturated fats: one double bond Polyunsaturated fats: two or more double bonds The problem with polyunsaturated fats is that all these double bonds make them susceptible to oxidation. The fatty acids react with oxygen in the atmosphere and start deteriorating. The fat you eat isn't only stored as fat tissue or burned for energy ; it is also incorporated into cell membranes. If your body contains a lot of polyunsaturated fatty acids, your cell membranes are more sensitive to oxidation. In short, you have a very high level of fragile fatty acids that can easily be degraded to form harmful compounds called free radicals, which can cause cell damage. For this reason, it may be best to eat polyunsaturated fats in moderation. Vary your diet by eating a mix of healthy saturated, monounsaturated, and polyunsaturated fats. The USDA 2020-2025 Dietary Guidelines for Americans recommend aiming for 20-35% of total daily calories from fats, with no more than 10% of these calories coming from saturated fat. They are sometimes high in trans fats Commercial vegetable oils may also contain trans fats, which form when the oils are hydrogenated. Food producers use hydrogenation to harden vegetable oils, making them solid like butter at room temperature. Margarines are no longer full of trans fats since the FDA ban on trans fats in 2015, which went into effect in 2018, with an extended deadline of 2020 for some food manufacturers. However, some margarines may still contain a small amount of trans fat, so it's important to read the nutrition label. However, non-hydrogenated vegetable oils may also contain some trans fats. However, it's important to note that naturally occurring trans fats found in non-hydrogenated oils are less detrimental to health than industrial trans fats. Also, natural trans fats are found in very small amounts compared to hydrogenated oils. One 2015 study found extremely low amounts of trans fats (less than a quarter of 1%) in vegetable cooking oils. A high intake of trans fats is associated with all sorts of chronic diseases, including heart disease, obesity, cancer, and diabetes. If a product lists hydrogenated oil or partially hydrogenated oil as an ingredient, it likely contains trans fats. For optimal health, avoid these products, although with the trans fat ban, they are likely to be present only in very small amounts now. Vegetable oils and heart disease The reason is that vegetable oils are generally low in saturated fat and high in polyunsaturated fat. The benefits of reduced saturated fat intake are controversial. However, studies show that reducing saturated fat intake for at least 2 years reduces the risk of heart problems by 21%, but it has no significant effects on the risk of death from heart disease. Furthermore, omega-3 polyunsaturated fatty acids appear to have a greater benefit than omega-6 polyunsaturated fatty acids. The omega-6 linoleic acid has been associated with a lower risk of heart disease. However, it is important to be vigilant about avoiding highly refined vegetable oils and processed foods that contain these oils. Our food environment makes it very easy for us to get more than enough omega-6-rich vegetable oils. We can control how we prepare food at home, so in an effort to practice moderation, it may be a good idea to choose other oils that are lower in omega-6 content, like olive oil or avocado oil. There is a lot of evidence on the benefits of olive oil on heart health.
Yahoo
24-06-2025
- Health
- Yahoo
Dietitian Shares The 1 Cooking Oil Rule They Follow For A Healthy Heart
Some people worry that seed oils (like sunflower, peanut, and soybean oil) are bad for us because they contain an omega-6 fatty acid (linoleic acid). But this, experts claim, does not actually cause the inflammation it's accused of creating. Kerry Beeson, a qualified nutritional therapist at Prep Kitchen, previously told HuffPost UK: 'Seed oils are objectively quite healthy, in that they're typically low in saturated fats.' Writing for UC Davis Health, cardiovascular dietitian Margie Junker, who focuses on how our diets affect heart health, shared that she loved flax and peanut oil. 'Liquid plant oils are rich in unsaturated fats, which reduce low-density lipoprotein (LDL) cholesterol and heart disease risk,' she said. But, she added, she avoids one particular type of fat for cooking. 'I stay away from fats that are hard at room temperature, such as bacon grease, shortening and margarine,' she told the university. According to the World Cancer Research Fund, most cooking fats are higher in saturated fats. 'Too much fat in your diet, especially saturated fats, can raise your cholesterol, which increases the risk of heart disease,' the NHS added. Other solid cooking fats include ghee, lard, and butter. 'I also avoid tropical oils (coconut, palm, and palm kernel), animal fats (butter and lard), and partially hydrogenated fats,' Junker shared. Coconut oil has some of the highest saturated fat levels of all common cooking oils (86% to butter's 52%). So, while Junker said she 'occasionally' adds coconut oil or butter to a dish for flavour, she chooses not to cook with them. The British Heart Foundation recommends rapeseed oil as their best pick alongside olive oil, while Junker likes avocado oil most. But though some oils and fats are higher in saturated fats than others, fats of any kind should not make up more than 35% of our diet. 'Current UK government guidelines advise cutting down on all fats and replacing saturated fat with some unsaturated fat,' the NHS shared. Combining lower-saturated fats with moderation is key to better heart health. Are Seed Oils Really Bad For You? I Asked A Nutritional Therapist The Only 3 Cooking Oils Mary Berry Says We Need Sorry, Your Essential Oils Are Essentially Useless
BBC News
08-06-2025
- Health
- BBC News
Seed oils dey bad for your health?
E don dey fly upandan recently say seed oils like canola and sunflower oil get harmful effects. Dis na true? You fit get bottle of sunflower oil or canola (rapeseed) oil inside your kitchen cupboard. You fit use am cook, spray ontop salad, seed oils dey popular across di world. But dis seed oils don become centre of debate online. For recent years, seed oils don dey collect plenty attack from social media wia some pipo dey claim say e dey "toxic", "poisonous" and dey damage pipo health. Some critics don give some seed oils nickname as 'di hateful eight' - dis dey refer to di eight popular seed oils canola, corn, cottonseed, grapeseed, soy, rice bran, sunflower and safflower - and dey blame dem say na dem dey cause heart diseases and type 2 diabetes. Question be weda na true true say seed oils be di enemy, abi pipo just dey fight dem for no reason? Seed oils dey connected to heart issue? Some pipo wey dey tok against seed oil dey focus on di high omega 6 fatty acid wey dey inside am. Omega 6 fatty acid na essential fatty acid, wey mean say we need dem, but we no fit produce dem oursefs. For recent years, some scientists don argue say omega 6 fit cause chronic inflammation (e fit increase risk of developing diseases wey include heart disease and cancer). But trials wey dem do show say omega 6 fatty acid no dey increase inflammation, na so Dariush Mozaffarian tok. Im be professor and doctor for di Food is Medicine Institute for Tufts University for Massachusetts, US. "New research show say omega 6 fatty acids dey give rise to unique natural molecules like lipoxins, wey get powerful anti-inflammatory effects for body, na so Mozaffarian tok. For recent research wey cover over 200,000 pipo for US wey dey around age 30, di researchers find out say pipo wey dey chop more of plant oil (including seed oils) dey less likely to die from cardiovascular diseases or cancer. On di oda hand, pipo wey dey take in more of butter dey likely to die during di same period. Plenti observational studies about how omega 6 dey affect our hearts dey. Dem dey look into data of diet and health and find out say di two get relationship. But some observational studies dey rely on account of wetin di pipo tok say dem eat, na so Matti Marklund tok. Im be professor of human nutrition for Johns Hopkins Bloomberg School of Public Health for US. E add say dis fit be problem as pipo fit no remember wetin dem eat or dem fit no dey honest about dia diet. Anoda way to measure omega 6 intake na to measure how much di amount of omega 6 individual components and ingredients dey inside pesin diet. However Marklund add say e dey difficult to translate how much of food pesin chop into quantities. Plenty studies wey dey investigate di effects of omega 6 fatty acids on our health dey focus on linoleic acid. Dis na omega 6 fatty acid wey dey in high amounts inside seed oil. Dem don find out say e dey lower bad LDL cholesterol inside blood. For study wey dem do for 2019, Marklund focus on levels of fatty acid for blood of participants from 30 observational studies - wey some role for upto 30 years. E look at how many of dem develop cardiovascular disease and die from am. E find out say di ones wey get di highest levels of linoleic acid for blood, na dem get di lowest risk of developing cardiovascular disease. Anoda allegation dem sama seed oils be say e dey harmful to pipo wey dey eat plenty of omega 6 if you compare am wit pipo wey dey take plenti omega 3. Some confusion dey between omega 6 and health of di heart, na wetin Christopher Gardener tok, I'm be Director of nutrition studies for Stamford Prevention Research Centre for US. Dis na sake of role wey omega 6 dey play wen blood clots happun, Gradner say pipo dey relate am only to stroke and heart attack. E say Omega 3 dey do more of blood thinning. "If you get wound for your hand and you want make e clot, you gas need balance." Meanwhile, scientists conclude for analysis of 30 studies wey dem conduct for 2019 say pipo wey get higher amounts of linoleic acid for dia blood dey 7% less likely to develop heart disease. Linoleic (acid) fit improve cholesterol to reduce di risk of cardiovascular disease, and improve glucose metabolism wey dey reduces di risk of type 2 diabetes, na so Marklund tok. Seed oils and 3.6 ratio Anoda common accuse wey dem sama on seed oils be say to eat plenty omega 6 compared to eating omega 3 dey harmful. For western world, omega 6 fatty acid dey account for around 15% of our total energy intake. Average person ratio of omega 3 to omega 6 fit be upto 50:1. However e suppose be like 4:1 to reduce our risk of cardiovascular disease, according to one study like dat. Review and meta analysis wey World Health Organization do for 2022 report say higher omega 6:3 ratio dey associated wit greater risk of cognitive decline and ulcerative colitis, wey be chronic inflammatory bowel disease. For di oda side, dem link higher omega 3:6 ratio to reduced risk of depression. Di scientists wey conduct di WHO study conclude say higher omega intake of omega 6 fatty acid from sees oils dey unlikely to increase your risk of death and disease - but add say dem need more quality research. But while some scientists dey argue say you no suppose get too much omega 6 for your system pass omega 3, Marklund say e better to take more omega 3, dan to reduce your omega 6, as both get health benefits. How dem dey process seed oils Unlike oda oils, na from plant dem dey from extract seed oils. Some dey concerned say dem dey extract seed oils wit hexane - wey be chemical wey dem make from crude oil - but little evidence dey wey suggest say di process fit cause issue. Researchers don recently find out say omega 6 fit cause growth of one specific type of breast cancer. While some evidence suggest say hexane fit dey linked to plenty health conditions, after dem extract am, dem dey deodorise and bleach am to remove and additives. Scientists fit tok say hexane extract dey normal for food processing, and say di process of deodorizing and bleaching it Dey help remove potential harmful compounds," na so Gardener tok. Seed oils wey dem use cold-press method dey avoid di process completely, as di process involve to squeeze di seeds to extract di oil - but dis result dey more expensive. Seed oils for cause growth of tumours? Upon say plenty research dey wey show di potential benefits of omega 6 on our health, Researcher don recently find out say dis fatty acid fit fuel di growth of specific type of breast cancer. Di findings fit also get implications say di impact of omega 6 consumption on oda diseases. Cancer cells dey use nutrients as fuel to grow and multiply but till now, dem bin get limited research wey dey look at di role wey omega 6 fatty acid dey play. But study wey dem publish for March dis year find mechanism wey linoleic acid, wey be omega 6 fatty acid dey use grow and multiply inside patients wey get triple negative breast cancer (TNBC). Dis na di most aggressive sub-type of di disease and na one wey no dey respond to therapies. Studies wey dem carry out before suggest say nothing dey link omega 6 fatty acid or any small increase in risk, na so Nikolaos Koundouros tok, im be postdoctoral associate for Weill Cornell Medicine Research Centre for New York. But e add say di studies no take into account say multiple sub-types of breast cancer dey, and e dey different from patient to patient unto how dem dey survive or ontop wetin dey cause dem, plus how dem dey respond to therapy. TNBC be like e dey respond pass for linoleic acid, na so Koundouros tok. Koundouros and oda team of researchers discover for lab say wen pesin take omega 6, TNBC cells go activate protein complex wey dey linked to tumor growth and progression. E get anoda protein wey dey in large amount for TNBC tumours, e dey take fatty acids and lipids throughout di body and inside cells to wia dem suppose be. Koundouros explain say dese proteins, along wit omega 6 fit dey responsible for oda chronic diseases like obesity and diabetes. Dis research fit bring new info about how to treat TNBC patients, but e no get wider implications for everyone, na so Koundouros tok. E say "e dey important to remember say omega 6 fats dey essential for some reasons , if you cut dem off, you fit get bad side effects". Which seed oil? Some seed oils like canola and soya bin oil don get more studies pass odas and e get more balanced evidence base. "All dese dey provide balanced combination of healthy fats, including monounsaturated fats, omega 6 polyunsaturated fats, and omega 3 polyunsaturated fats," na wetin Mozaffarian tok. E add say Canola oil get similar anti inflammatory effects and dey produce better improvements for blood cholesterol levels dan olive oil wey dem dey hail as di healthiest of all oils. One meta analysis dem do 27 trials on show say canola oil dey significantly reduce LDL cholesterol wen you compare am to sunflower oil and saturated fat, while anoda one find out say e dey dramatically reduce body weight especially for pipo wey get type 2 diabetes. "Canola oil dey produce excellent benefits for blood cholesterol levels, and dey modestly reduce body weight. Healthy fats wey dey inside canola oil especially omega 6 polyunsaturated fat dey also improve blood glucose, insulin resistance and insulin production," na so Mozaffarian tok. Dem also find out say soya bean dey improve cholesterol levels when you compare am to saturated fat. One study find out say pipo wey dey consume more of soya bean oil get lower risk of death from all causes; 6% lower risk for every 5kg dem consume daily. Which seed oil be di healthiest? "Seeds na one of natures most nourishing gifts; package of beneficial healthy fats,"na wetin Mozaffarian tok. Why plenty pipo dey attack something like dis dey confuse scientists, some wey dey well studied inside nutrition science. But dis misunderstanding fit dey come from "misplaced combination of partial truths", na wetin Mozaffarian tok. For instance, some pipo dey link seed oils to ultra-processed foods (UPFs), we some times dey contain seed oils, like canola, corn, soyabean and sunflower oils. For recent years, huge focus dey on di health risk of consuming too many UPFs, including risk of developing type two diabetes and heart diseases. More like dis: "But dese dangers dey arise from too much starch, sugar and salt, loss of natural intact food structure and dozens or even hundreds of artificial additives," na so Mozaffarian tok. But if you wan draw line between pipo wey dey eat more seed oils and unhealthy outcomes, na unto say we too dey eat food wey get plenty sugar and sodium,"na wetin Gardner suggest. E say e get plenty ways to consume seed oils for house wey no involve UPFs, like to use salad or stir-fry. "I no dey happy to see pipo troway seed oils sake of dis seed oil war," na so Gardner tok. While some scientists want make dem do more rigorous trials to look into di effects of seed oil consumption ontop our health, odas like Marklund dey argue say already, plenty good quality trials dey ground wey dey show benefits on blood cholesterol, blood glucose and insulin levels for general population. "Omega 6 fatty acids dey excellent for health," na so Marklund tok. "E dey linked to lower onset of heart disease, stroke, diabetes and even death from all causes." For better insight into health and wellbeing matter wey Dey rooted in science, sign up for Health Fix newsletter, while di Essential List dey deliver handpicked selection of features and insights. For more science technology, environment and health stories from BBC, make you follow us for Facebook, X and Instagram.
BBC News
31-05-2025
- Health
- BBC News
Are seed oils really bad for you?
Seed oils like canola and sunflower oil have attracted controversial claims about harmful effects in recent times. Is there any truth to them? You might have a bottle of sunflower oil or canola (rapeseed) oil stashed away in a kitchen cupboard somewhere. Whether you cook with them or drizzle them over salads, seed oils are popular across the world. But these unassuming seed oils have become the centre of a heated debate online. In recent years, seed oils have become the target of countless social media posts, with people claiming that they are "toxic", "poisonous" and, ultimately, are damaging our health. Critics have nicknamed some seed oils 'the hateful eight' – referencing eight popular seed oils, canola, corn, cottonseed, grapeseed, soy, rice bran, sunflower and safflower – and blame them for causing heart disease and type 2 diabetes. Are seed oils really the enemy, or is the antagonism towards them unjustified? Are seed oils connected to heart health? Much of the recent criticism of seed oils focuses on their high omega-6 fatty acid content. Omega 6 fatty acids are essential fatty acids, which means we need them, but can't produce them ourselves. In recent years some scientists have argued that omega 6 can cause chronic inflammation (which can increase the risk of developing diseases including heart disease and cancer). But controlled trials have found that omega-6 fatty acids do not increase inflammation, says Dariush Mozaffarian, professor and director of the Food is Medicine Institute at Tufts University in Massachusetts in the US. "New research shows that omega-6 fatty acids give rise to unique natural molecules, like lipoxins, that have powerful anti-inflammatory effects in the body," says Mozaffarian. Recent research studied the diet and health of over 200,000 people in the US for around 30 years. The researchers found that people who consumed more plant oils (including seed oils) were less likely to die from cardiovascular disease or cancer over the course of the study. On the other hand, those with a higher intake of butter were more likely to die during the same period. There are numerous observational studies looking at how omega 6 effects our heart health – where scientists look at data on diet and health, and find associations between the two. But some observational studies rely on people's own accounts of what they eat, says Matti Marklund, assistant professor of human nutrition at Johns Hopkins Bloomberg School of Public Health in the US. And this, he adds, can be problematic because people may misremember, or even be dishonest, about their dietary habits. Another way to measure omega 6 intake is to measure the average amount in the individual components and ingredients in a person's diet. However, Marklund adds, it can be difficult to translate what people say they have eaten into certain quantities. Numerous studies investigating the effects of omega 6 on our health focus on linoleic acid, an omega 6 fatty acid found in high amounts in seed oil, that has been found to lower the 'bad' LDL cholesterol in our blood. In a 2019 study, Marklund instead focused on the levels of fatty acids in the blood of participants from around 30 observational studies – some which followed people for up to 30 years – and looked at how many developed cardiovascular disease and died from it. He found that those with the highest levels of linoleic acid in blood had the lowest risk of developing cardiovascular disease. There is some confusion regarding omega 6 and heart health, says Christopher Gardner, director of nutrition studies at the Stanford Prevention Research Center in the US. This partly stems from omega 6's role in the process of blood clotting, which Gardner says people mistakenly only associate with strokes and heart attacks. Omega 3, he says, tends to be more blood-thinning. "If you had a wound in your hand, you'd want it to clot," he says. "You need balance." Meanwhile, scientists concluded in a 2019 analysis of 30 studies that people with higher amounts of linoleic acid in their blood were 7% less likely to develop heart disease. "Linoleic [acid] might improve cholesterol to reduce the risk of cardiovascular disease, and also improve glucose metabolism, which reduces the risk of type 2 diabetes," Marklund says. Seed oils and the 3:6 ratio Another common accusation levelled at seed oils is that eating too much omega 6 compared to omega 3 is harmful. In the Western world, omega-6 fatty acids account for around 15% of our total energy intake. The average person's ratio of omega 3 to omega 6 can be up to 50:1. However, it should be more like 4:1 to reduce our risk of cardiovascular disease, according to one study. A 2022 World Health Organization review and meta-analysis reported that a higher omega 6:3 ratio was associated with a greater risk of cognitive decline and ulcerative colitis, a chronic inflammatory bowel disease. On the other hand, a higher omega 3:6 ratio was also linked to a 26% reduced risk of depression. Overall, the scientists involved in the WHO study concluded that a high intake of omega 6 fatty acids from seed oils is unlikely to increase your risk of death and disease – but say that more high-quality research is needed. But while some scientists argue that you shouldn't have too much omega 6 compared to omega 3, Marklund says it's better to up your intake of omega 3 rather than consume less omega 6, as both are associated with health benefits. How seed oils are processed Unlike other oils, seed oils are extracted from the seeds of plants. There are some concerns that seed oils are extracted with hexane – a chemical made from crude oil – but there is little evidence so far suggesting that this process can cause issues. While some evidence suggests hexane could be linked to several health conditions, after being extracted, the oil is then deodorised and bleached to remove and additives. "Scientists will say hexane extract is normal in food processing, and the deodorising and bleaching removes potentially harmful compounds," says Gardner. Cold-pressed seed oils avoid this process entirely, as it involves squeezing the seeds to extract the oil – but this results in a more expensive product. Can seed oils fuel tumour growth? Despite an abundance of research showing the potential benefits omega 6 might have to our health, researchers have recently found that this fatty acid can fuel the growth of a specific type of breast cancer. The findings may have implications for the impact of omega 6 consumption on other diseases, too. Cancer cells use nutrients as fuel to grow and multiply, but until now, there was limited research looking at the role omega 6 fatty acids play. But a study published in March this year found a mechanism by which linoleic acid, an omega 6 fatty acid, helps cancer cells to grow and multiply in patients with triple negative breast cancer (TNBC). This is the most aggressive sub-type of the disease, and one that doesn't respond well to targeted therapies. Previous studies suggest there is no association with omega 6 fatty acids, or a small increase in risk, says Nikolaos Koundouros, postdoctoral associate at Weill Cornell Medicine research centre in New York. But these studies, he says, haven't taken into account that there are multiple sub-types of breast cancer, and that they all differ in terms of a patient's survival and prognosis, and how they might respond to targeted therapy. TNBC seems to respond the most to omega 6 linoleic acid, Koundouros says. Along with a team of researchers, Koundouros discovered in the lab that, when fed omega 6, TNBC cells activate a protein complex linked to tumour growth and progression. Another protein, which is found in larger amounts in TNBC tumours compared to other breast cancer subtypes, is known to take fatty acids and lipids throughout the body and within cells to exactly where they need to be. Koundouros explains that these proteins, along with omega 6, may also be relevant in other chronic diseases, such as obesity and type 2 diabetes. This research could potentially inform treatment options for TNBC patients, but it doesn't necessarily have wider implications for everyone, Koundouros says. "It's important to remember omega 6 fats are essential for a reason; if you completely cut them out, you could have detrimental side effects," he says. Which seed oil? Some seed oils – such as canola oil and soybean oil – have been studied more than others, so have a more rigorous evidence base. "These each provide a balanced combination of healthy fats, including monounsaturated fats, omega-6 polyunsaturated fats, and omega-3 polyunsaturated fats," Mozaffarian says. Canola oil, Mozaffarian adds, has similar anti-inflammatory effects and produces better improvements in blood cholesterol levels than olive oil, which has long been hailed the healthiest of all oils. One meta-analysis of 27 trials found that canola oil was found to significantly reduce LDL cholesterol compared to sunflower oil and saturated fat, while another found that it dramatically reduced body weight, especially in in those with type 2 diabetes. "Canola oil produces excellent benefits for blood cholesterol levels, and also modestly reduces body weight. The healthy fats in canola oil, especially the omega 6 polyunsaturated fats, also improve blood glucose, insulin resistance, and insulin production," says Mozaffarian. Soybean oil has also been found to improve cholesterol levels compared to saturated fats. One study found that people who consumed more soybean oil had lower risk of death from all causes; a 6% lower risk for every 5g they consumed daily. Which seed oil is healthiest? "Seeds are one of nature's most nourishing gifts; a package of beneficial healthy fats," says Mozaffarian. That something so well studied within nutrition science has had such a backlash has been a source of confusion for some scientists. But this misunderstanding may come from a "misplaced combination of partial truths", Mozaffarian says. For instance, some people may link seed oils to ultra-processed foods (UPFs), which often contain seed oils, particularly canola, corn, soybean, and sunflower oils. In recent years there has been a huge focus on the health risks of consuming too many UPFs, including increased risk of developing type two diabetes and heart disease. More like this:• What is the healthiest cooking oil?• The truth about saturated fat• Cod liver oil: The fishy fix that was surprisingly healthy "But these dangers arise from too much starch, sugar, and salt, loss of natural intact food structure and dozens, or even hundreds, of artificial additives," Mozaffarian says. Some people have also drawn a correlation with increased consumption of seed oils in recent years and the rise in obesity and diabetes. "But if you want to draw parallels with people eating more seed oils and unhealthy outcomes, it's because we're eating food that tends to contain a lot of sugar and sodium," Gardner suggests. He says there are many ways to consume seed oils at home that don't involve UPFs, such as with a salad or stir-fry. "I'd hate to see people tossing out seed oils because of this seed oil war," says Gardner. Ultimately, while some scientists call for more rigorous trials looking into the effects of seed oil consumption on our health, others, including Marklund, argue that there is already a wealth of good quality trials showing benefits on blood cholesterol, blood glucose and insulin levels for the general population. "Omega-6 fatty acids are excellent for health," says Marklund. "They have been linked to lower onset of heart disease, stroke, diabetes, and even death from all causes." -- For trusted insights into better health and wellbeing rooted in science, sign up to the Health Fix newsletter, while The Essential List delivers a handpicked selection of features and insights. For more science, technology, environment and health stories from the BBC, follow us on Facebook, X and Instagram.
Daily Mail
21-05-2025
- Health
- Daily Mail
I'm a Harvard researcher who studies seed oils... here's the terrifying truth about their dangers
Online forums, influencers, US health officials and now, Harvard researchers - people in every facet of life are weighing in on seed oils. While some call them toxic and blame them for sky-high rates of obesity and other chronic diseases, some experts say there simply isn't enough information to make that conclusion. Researchers know very little about the benefits and harms of consuming seed oils, which include canola, corn, sunflower, and other refined oils made from the seeds of certain plants. Dr Jane Zhao, an expert in global and public health at Harvard University and a nutrition researcher focusing on seed oils, says evidence is multi-directional and inconclusive, marked by flawed studies and cherry-picked facts that fit a person's own narrative, whether that's for or against. The oils are mainly composed of unsaturated fat, primarily omega-6 fatty acids, which detractors claim drive up rates of inflammation in the body. 'The truth is,' Dr Zhao said, 'we don't fully understand what the causal effect of omega-6 fatty acids is, which dominate most seed oils, on disease risk.' The panic over seed oils has been fueled by a single meta-analysis published in 2016 that found seed oils to be harmful, increasing the risk of some measures of heart disease by 13 percent. This analysis, though, was an outlier. Dozens of other meta-analyses on the topic show mixed results, ranging from a very mild benefit to heart health and stroke prevention to having no association with increased risk of either. 'Taken together, these findings suggest that the case for seed oils as unequivocally 'heart-healthy' is not closed,' Dr Zhao wrote for Stat News. This lack of conclusive evidence, however, has not stopped HHS Secretary Robert F Kennedy, Jr from shunning seed oils and telling people to do the same - replacing them with saturated fats such as beef tallow. Many traditional studies have suggested eating more omega-6 fats, like those found in seed oils, is linked to better heart health, Dr Zhao said. But these types of studies have some problems: people who eat more of these oils might also be doing other healthy things, like exercising or eating more vegetables, that could influence the results. When it comes to omega-6 fats, the evidence is mixed. Meta-analyses vacillate between the findings that fats in seed oils are associated with a decreased risk of heart disease or that there is no link at all. Researchers behind the 2016 report that turbocharged the debate over seed oils analyzed data from the Minnesota Coronary Experiment in the 1970s and combined it with other studies. The Minnesota Coronary Survey from the late 1960s and early '70s involved over 9,000 people and tested whether swapping saturated fat for vegetable oil high in linoleic acid (an omega-6 fat) would reduce heart disease risk. Results showed they didn't. Authors of the 2016 report then revealed swapping out a saturated fat like butter for a seed oil lowered cholesterol but failed to reduce heart disease — and may have actually increased deaths and heart attacks. Consuming a diet full of seed oils has also been tied to prostate and colorectal cancer. Some research suggests they may increase inflammation, making it easier for cancer cells to replicate and spread. Chronic inflammation also suppresses the immune system's ability to destroy those abnormal cells. Despite links described in those studies, there are plenty that come to the opposite conclusion. A 2019 meta-analysis found higher levels of omega-6 in the blood were associated with a lower heart disease and stroke risk, as did an analysis released in 2023. But a report in 2024 found no association between omega-6s and heart disease, while a 2018 systematic Cochrane review of trials found no relationship between this type of fat and heart health. 'The scientific community should be honest about this uncertainty. It's OK to say: 'We don't yet have all the answers,'' Dr Zhao said. 'Doing so doesn't confuse the public; it respects them. It signals that we're still asking questions and are open to new evidence, even if it challenges longstanding beliefs.' Seed oils are everywhere in the Western diet, appearing in their unhealthiest form in ultra-processed foods, salad dressings, and fast food. Seed oils are also commonly used to cook healthy Mediterranean diet-style meals, however, which prioritize whole produce, minimally processed ingredients, omega-3 fatty acids in the form of salmon and nuts, and limited carbohydrates. Americans now get roughly eight percent of their daily calories from linoleic acid, the primary omega-6 in seed oils, up from about three percent at the turn of the 20th century. While seed oil critics draw a link between the ingredient and rocketing rates of obesity, diabetes, and other chronic diseases, given their omnipresence in the US food supply, it's impossible to blame one single ingredient in processed foods that contain hundreds. When all those ingredients, including seed oils, come together, they make ultra-palatable and calorie-dense snacks like chips, cookies, baked goods, and more, which, over time, degrade one's health. Sautéing vegetables in canola oil a few times per week or mixing a simple salad dressing with sunflower oil packs a different nutritional punch than a fast food meal, and, overall, any health risks linked to seed oils are outweighed by the benefits of eating fiber- and nutrient-rich vegetables. 'Until we know more, we should be cautious about making sweeping recommendations,' Dr Zhao said. 'In the meantime, the best advice may be this: favor balance over extremes. That means not fearing every bite of croissant, but also not assuming that loading every meal with seed oils is a surefire path to good health. 'The seed oil debate doesn't need more hype — it needs more humility. And more science.'
