We Agree: Here's Why the Latest ZOE Podcast Is Gaining Attention
History repeats itself.
During the 1980s, the Centre for Science in the Public Interest (CSPI), a self-described ‘food and health watchdog’, petitioned McDonald’s and other fast-food chains to replace their beef tallow with partially hydrogenated vegetable oils, which are loaded with trans fats, for frying. In their newsletter, the CSPI declared these new vegetable oils an improvement on nature whilst promising their readership that, based on scientific research, trans fats are harmless.[1] Sadly, they got their way, and fast food restaurants swapped a stable, heat-resistant fat for a highly processed one steeped in toxic by-products, including trans fats.
Vegetable oil manufacturers and trade associations aggressively sought to undermine scientific evidence highlighting the dangers of trans fats. They infiltrated the scientific community, strategically downplaying harmful findings through article reviews and letters to journal editors. In a more insidious turn, industry representatives allegedly resorted to personal intimidation tactics, targeting a scientist who revealed damning results about trans fats. Their efforts were a calculated attempt to protect their interests by distorting the scientific narrative and suppressing inconvenient truths about trans fat risks.[2] Trans fats have now been banned in many countries because the evidence showing they cause heart disease piled so high even corruption couldn’t bury it. History repeats itself, but this time, the cover-up concerns the toxicity of industrialised vegetable oils, also known as seed oils.
ZOE Seed Oils Podcast
We’re not backwards in coming forwards with our views on vegetable oils. So when some people got in touch with us about a recent ZOE podcast entitled, ‘Nutrition Doctor: Seed oils may lower your risk of heart disease | Prof. Sarah Berry,’ we decided to take a look.[3]
The episode begins with Sarah Berry, professor in the Department of Nutritional Sciences at King's College London and Chief Scientist at ZOE, saying, ‘It drives me insane that there is so much misinformation around the health effects of seed oils. It’s shocking!’ We agree; some still tout them as a healthy alternative to stable ancient fats, including those humans evolved eating! Sadly, Professor Berry is one of them.
If Berry wants to position herself as an expert on vegetable oils, it would be better to start the podcast with a fact, not an error: canola oil and rapeseed oil are not ‘exactly the same thing, but just with different labels.’ In the 1960s, Canadian farmers cross-pollinated rapeseed to create a new variety lower in erucic acid content, an undesirable fat. They named their invention Canola by combining ‘Can’ from Canada and ‘ola,’ meaning oil. In the 1990s, selective breeding became genetic modification (GM). Nowadays, 90% of canola oil in North America is genetically modified to withstand the herbicide glyphosate, most often sold as Roundup.[4] British farms do not grow this GM version or any GM crops, instead opting to develop their version of a low erucic acid rapeseed oil that retains an earthier flavour than its distant cousin, Canola. We’re not fans of either version.
Berry tells us three major arguments are being used against refined vegetable oils and then proceeds to list four. We’ll address the two most significant issues: the research used to defend these junk oils and the unquestionable oxidation problem. Also, we'll focus on refined oils because Berry doesn’t think there’s much difference between cold-pressed and refined oils.
Associations don’t show causations
Berry mentions that chronic diseases have increased in a ‘linear relationship’ with the industrialisation and consumption of vegetable oils. That’s true. It’s also true that you can’t blame vegetable oils for that correlation because it might just be a coincidence. ‘Associations don’t show causations,’ Berry reminds us.
There are countless examples of people defending their nutrition beliefs using epidemiological evidence, i.e. just associations, and then rubbishing the same evidence when disagreeing. Berry exemplifies this throughout and in her following few sentences when she blames the other ingredients in baked goods, as well as a lack of exercise, chronic stress, sleep issues and, ‘you know, et cetera, et cetera, et cetera, all these other issues.’ Anything but the vegetable oils. Generally, providing evidence other than the exact type you’re bashing at that moment is helpful.
The ZOE narrator says that epidemiological papers provide ‘really strong links’ between certain foods and ‘worse health outcomes’ to which Berry nods along. No, they don’t. That’s precisely the problem with nutritional epidemiological studies. But don’t take our word for it. Dr John Ioannidis, a professor of medicine and epidemiology at Stanford Medical School, admonishes this kind of research at every opportunity and believes it all belongs in the bin.[5] In an interview with his university, Ioannidis says:
‘The biggest problem is that the vast majority of studies are not experimental, randomised designs. Simply by observing what people eat — or even worse, what they recall they ate — and trying to link this to disease outcomes is moreover a waste of effort. These studies need to be largely abandoned. We’ve wasted enough resources and caused enough confusion, and now we need to refocus. Funds, resources and effort should be dispensed into fewer, better-designed, randomised trials.’[6]
The most damaging thing nutritional epidemiology has done is allow the cholesterol-heart disease hypothesis to exist perpetually. Approaching eighty years old now, the theory posits that a diet rich in saturated fat raises LDL cholesterol and, therefore, your risk of heart disease. Since the 1950s, high blood cholesterol levels have emerged as a risk factor. Since then, scientists and doctors have proclaimed that lowering ‘bad’ cholesterol (LDL) extends life and the quality of it. Whenever Berry mentions the benefits of reducing cholesterol, she’s spouting dogma as old as our grandparents.
Aware of the epidemiological weaknesses, Berry adds, ‘There's also many, many randomised control trials that show that if you increase your polyunsaturated fatty acid intake, you reduce your LDL cholesterol significantly, and it results in a 32% reduction in cardiovascular disease.’ The first part of the sentence is accurate; yes, you can lower your LDL cholesterol by eating PUFAs. But the second part is a cheap trick made up from epidemiological research and refers only to relative risks between groups in those papers, not absolute risks for the population. In other words, if you increase your PUFAs, you are categorically not reducing your risk of CVD by 32%.
Antioxidant treatments, like Vitamin E, which should protect against cholesterol oxidation, failed to lower heart disease risk.[7] Similarly, drugs designed to raise ‘good’ HDL cholesterol showed no benefit in reducing heart attacks or strokes despite significantly improving cholesterol levels.[8] Even statins, a go-to for cholesterol-lowering, only delayed death by a few days, according to some studies.[9] A large analysis of 44 RCTs of cholesterol-lowering therapies revealed that, despite reducing ‘bad’ LDL cholesterol by as much as 50%, these interventions didn’t consistently prevent heart attacks or extend life.[10] Furthermore, 30 of these studies showed no decrease in cardiovascular events. Another review and meta-analysis showed that 92% of people with high cholesterol lived longer than those with lower cholesterol.[11] Despite these repeated failures, the cholesterol-heart disease theory continues to dominate medical thinking, even as evidence against it grows.
Plant sterols, which Berry refers to positively throughout, are not the health panacea she believes them to be. A review of these plant-based fats writes of the ‘compelling evidence from recent genetic studies [that] have linked elevated plasma concentrations of circulating plant sterols with cardiovascular disease presence, thus raising concerns about the safety of phytosterol supplementation.’[12] Unilever PLC asked the European Food Safety Authority if they could label their plant sterol-enriched products with heart health claims via lowered cholesterol. The EFSA responded, ‘Plant sterols have been shown to lower/reduce blood cholesterol[...]However, there are no human intervention studies demonstrating that plant sterols reduce the risk of coronary heart disease.’[13]
PUFAs are prone to oxidation
The host asks Berry whether PUFAs are prone to oxidation when heated and thus start producing toxic compounds. Her answer is no, and then she tells us that these compounds are ‘very difficult’ to generate at home unless you repeatedly burn the oil and leave it outside. To back this up, she refers to her own unpublished study on 19 healthy men eating repeatedly heated vegetable oil muffins or fresh oil muffins before measuring markers of inflammation and cardiovascular response. So, rather than challenging her beliefs about repeatedly heating vegetable oils by looking at what the experts in this area say, she just reflects on her own lived experience fifteen years ago before offering advice to the public.[14]
Without access to the study, we’ll take an educated guess as to why those healthy young men may not have had a negative side effect from eating the repeatedly heated oil muffins. Here we go: Their robust, inbuilt antioxidant systems were able to quench the oxidative compounds in the muffins. Ta-da! If this was indeed what happened, the paper demonstrates the inability of short-term research to replicate long-term issues, like eating repeatedly heated vegetable oils daily for years, as so many of us do.
In 1960 a series of intervention trials on inpatients proved that the more PUFAs one eats, the more vitamin E they need.[15] Three times more, according to their data, compared with groups eating lard. Much more recent research tells us a bit about what’s happening. There’s a tipping point when the chronic consumption of PUFAs and the oxidative stress they create can no longer be quenched by the antioxidant vitamin E.[16] The cells begin breaking down, a marker of which can be measured.[17] Professor Stephen Guyenet, a neuroscientist and researcher, reviewed 46 studies spanning a fifty-year period which used biopsies, the gold standard, to measure cellular lipid fractions in subjects. He found that as dietary linoleic acid (the most common dietary PUFA) doubled in US diets, so too did the PUFAs in people’s cells. In 1959, people had an average of 9.1% cellular linoleic acid, by 2008 that had swollen to 21.5%.[18] Individual responses to these cellular levels of unstable fats are dependent on many factors based on their subjective ability to prevent all those PUFAs from oxidising. Let’s go back to see what the vegetable oil industry scientists are telling us about oxidative products in their vegetable oils.
For over a century, vegetable oil scientists have been trying to protect their cash cows from oxidative stress, a major cause of waste. Dr Martin Grootveld, a professor of bioanalytical chemistry and chemical pathology, is a leading expert on the toxic by-products formed in vegetable oils during heating. With over 200 journal articles, numerous book chapters, and several books to his name, he has extensively researched oxidation reactions using advanced techniques like nuclear magnetic resonance (NMR). His studies consistently reveal that heated vegetable oils are loaded with harmful oxidation products, unlike stable fats such as coconut oil and butter, which produce far fewer toxins.[19] Whilst researching for ‘Dark Calories’ a book about the damaging effects by vegetable oils, Catharine Shanahan MD read through vegetable oil industry group chats. She writes of a ‘a regular stream of scientists reporting on “extremely high levels” of seed-oil-degradation derivatives identified in common commercial products cooked in seed oils.’[20] In 2022, Dr Eric Decker, professor in the Department of Food Science at the University of Massachusetts, and world-renowned expert on the problem of oxidation was the keynote speaker at the American Oil Society’s annual conference. The title of his speech was, ‘Why Does Lipid Oxidation in Foods Continue to be Such a Challenge?’[21] Notice, he says ‘foods’, as in the end product, the things so many of us eat. Amongst other things, Decker says, these heated PUFAs contain aldehydes which are highly toxic.[22] Aldehydes can be causal in cancer[23] and heart disease.[24] And, contrary to what Berry tells us, you can easily generate these at home.[25]
Just in case this doesn’t age well, like a skin cell loaded with PUFAs, Berry makes several caveats during the show. Despite what she’s just said about not needing to worry about heated vegetable oils, Berry recommends people ‘use fresh oil where you can.’
Trans fats haven’t completely gone away
PUFA oils still contain trans fats despite a ban. That’s because the ban covers deliberately produced trans fats, not accidentally made ones. It’s important to note that industrialised trans fats are different from the natural trans fats found in meat and dairy. When oils are exposed to high heat during the deodorisation process, trans fats are unintentionally formed. Legally, oils can be labelled ‘zero grams of trans fats’ as long as they stay under 0.5 grams per 14-gram serving size; don’t get us started on teeny tiny serving sizes! Canola oil can still contain 3.6% trans fats.[26]
Wrap up
‘The purpose of scientific endeavour is to seek Truth, not proclaim it’ yet Berry does this constantly, presenting as if this is all settled science and therefore needs no discussion.[27] No, it’s a harmful narrative built on poor-quality research whilst simultaneously ignoring contrary, better-quality evidence. If you still think high PUFA vegetable oils are healthy, read our comprehensive article.
Remember this: If you decide to reduce seed oils and they turn out to be harmful, as we believe, you'll avoid oxidative stress and chronic inflammation, potentially adding years to your life. If we’re wrong and seed oils are harmless, what have you lost by cutting back on fried and processed foods? A few inches, most likely.
References
[1] Blume, E. (1987a). Hydrogenation: The food industry’s wild card. Nutrition Action Healthletter, 14(1), 8-9.
[2] Schleifer, D. (2011). We Spent a Million Bucks and Then We Had To Do Something. Bulletin of Science, Technology & Society. https://doi.org/10.1177/0270467611422837
[3] ZOE (2024) ‘Nutrition Doctor: Seed oils may lower your risk of heart disease | Prof. Sarah Berry. ZOE. Available: https://www.youtube.com/watch?v=VRlleOTBq7k Last accessed: 16th September 2024.
[4] Schafer, Meredith G et al. “The establishment of genetically engineered canola populations in the U.S.” PloS one vol. 6,10 (2011): e25736. doi:10.1371/journal.pone.0025736
[5]Crowe, K. (2018) University of Twitter? Scientists give impromptu lecture critiquing nutrition research. CBC News. Available at: https://www.cbc.ca/news/health/second-opinion-alcohol180505-1.4648331
[6] Armitage, H. (2018) 5 Questions: John Ioannidis calls for more rigorous nutrition research. Stanford Medicine. https://med.stanford.edu/news/all-news/2018/07/john-ioannidis-calls-for-more-rigorous-nutrition-research.html
[7] Vivekananthan, D. P., Penn, M. S., Sapp, S. K., Hsu, A., & Topol, E. J. (2003). Use of antioxidant vitamins for the prevention of cardiovascular disease: meta-analysis of randomised trials. Lancet (London, England), 361(9374), 2017–2023. https://doi.org/10.1016/S0140-6736(03)13637-9
[8] Eyvazian, V. A., & Frishman, W. H. (2017). Evacetrapib: Another CETP Inhibitor for Dyslipidemia With No Clinical Benefit. Cardiology in review, 25(2), 43–52. https://doi.org/10.1097/CRD.0000000000000137
[9] Kristensen, M. L., Christensen, P. M., & Hallas, J. (2015). The effect of statins on average survival in randomised trials, an analysis of end point postponement. BMJ open, 5(9), e007118. https://doi.org/10.1136/bmjopen-2014-007118
[10] DuBroff R. (2017). Cholesterol paradox: a correlate does not a surrogate make. Evidence-based medicine, 22(1), 15–19. https://doi.org/10.1136/ebmed-2016-110602
[11] Ravnskov U, Diamond DM, Hama R, et alLack of an association or an inverse association between low-density-lipoprotein cholesterol and mortality in the elderly: a systematic reviewBMJ Open 2016;6:e010401. doi: 10.1136/bmjopen-2015-010401
[12] Barkas, F., Bathrellou, E., Nomikos, T., Panagiotakos, D., Liberopoulos, E., & Kontogianni, M. D. (2022). Plant Sterols and Plant Stanols in Cholesterol Management and Cardiovascular Prevention. Nutrients, 15(13), 2845. https://doi.org/10.3390/nu15132845
[13] Bresson, Jean-Louis, et al. "Plant Sterols and Blood Cholesterol Scientific substantiation of a health claim related to plant sterols and lower/reduced blood cholesterol and reduced risk of (coronary) heart disease pursuant to Article 14 of Regulation (EC) No 1924/2006 Scientific Opinion of the Panel on Dietetic Products, Nutrition and Allergies." EFSA J 781 (2008): 1-12.
[14] Berry told us over email that the study was unpublished and was for her masters degree fifteen years ago.
[15] HORWITT, M. (1960). Vitamin E and Lipid Metabolism in Man. The American Journal of Clinical Nutrition, 8(4), 451-461. https://doi.org/10.1093/ajcn/8.4.451
[16] Traber M. G. (2014). Vitamin E inadequacy in humans: causes and consequences. Advances in nutrition (Bethesda, Md.), 5(5), 503–514. https://doi.org/10.3945/an.114.006254
[17] Bartolini, D., Marinelli, R., Giusepponi, D., Galarini, R., Barola, C., Stabile, A. M., Sebastiani, B., Paoletti, F., Betti, M., Rende, M., & Galli, F. (2021). Alpha-Tocopherol Metabolites (the Vitamin E Metabolome) and Their Interindividual Variability during Supplementation. Antioxidants (Basel, Switzerland), 10(2), 173. https://doi.org/10.3390/antiox10020173
[18] Guyenet, S. J., & Carlson, S. E. (2015). Increase in Adipose Tissue Linoleic Acid of US Adults in the Last Half Century. Advances in Nutrition, 6(6), 660-664. https://doi.org/10.3945/an.115.009944
[19] Shanahan, Catherine. Dark Calories: How Vegetable Oils Destroy Our Health and How We Can Get It Back (p. 20). Orion. Kindle Edition.
[20] Grootveld, Martin & Ruiz-Rodado, Victor & Silwood, Chris. (2014). Detection, monitoring, and deleterious health effects of lipid oxidation products generated in culinary oils during thermal stressing episodes. International News on Fats, Oils and Related Materials. 25. 614-624; Shanahan, Catherine. Dark Calories: How Vegetable Oils Destroy Our Health and How We Can Get It Back (p. 20). Orion. Kindle Edition.
[21] Decker, E. (2022) ‘Why Does Lipid Oxidation in Foods Continue to be Such a Challenge?’ AOCS. Available at: https://www.youtube.com/watch?v=B_U_9vvpDWo Last accessed: 18th September 2024.
[22] Moumtaz, Sarah et al. “Toxic aldehyde generation in and food uptake from culinary oils during frying practices: peroxidative resistance of a monounsaturate-rich algae oil.” Scientific reports vol. 9,1 4125. 11 Mar. 2019, doi:10.1038/s41598-019-39767-1
[23] Moumtaz, S., Percival, B.C., Parmar, D. et al. Toxic aldehyde generation in and food uptake from culinary oils during frying practices: peroxidative resistance of a monounsaturate-rich algae oil. Sci Rep 9, 4125 (2019). https://doi.org/10.1038/s41598-019-39767-1
[24] Uchida K. (2000). Role of reactive aldehyde in cardiovascular diseases. Free radical biology & medicine, 28(12), 1685–1696. https://doi.org/10.1016/s0891-5849(00)00226-4
[25] Zhang, Q., Qin, W., Lin, D., Shen, Q., & Saleh, A. S. (2015). The changes in the volatile aldehydes formed during the deep-fat frying process. Journal of food science and technology, 52(12), 7683–7696. https://doi.org/10.1007/s13197-015-1923-z
[26] Crosby, G. (2015) Ask the Expert. Harvard School of Chan. Available online: https://www.hsph.harvard.edu/nutritionsource/2015/04/13/ask-the-expert-concerns-about-canola-oil/ Last accessed: 16th May 2023.
[27] Marjoribanks, R. (2022) The Purpose of Science is to Seek the Truth, Not Proclaim it. Available at: https://rogermarjoribanks.info/purpose-science-seek-truth-proclaim/ Last accessed: 17th September 2024.
