Does eating fish or taking fish oil supplements reduce stroke risk?
Vegetarians and Stroke Risk Factors—Omega 3s?
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Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.
In my last video, we started to explore what might explain the higher stroke risk in vegetarians found in the EPIC-Oxford study. Lower risk of heart disease, and lower risk of cardiovascular disease overall, but higher risk of stroke. We looked into vitamin D levels as a potential mechanism, but that didn’t seem to be the case. What about long-chain omega 3s, the fish fats like EPA and DHA, found, not surprisingly, in markedly lower levels in vegetarians and vegans? About 30% lower in vegetarians, and more than half as low in vegans.
But according to the most extensive systematic assessment of effects of omega-3 fats on cardiovascular health to date, there is no benefit for stroke, combing 28 randomized controlled trials. In fact, there was evidence that taking fish oil didn’t help with heart disease or overall mortality. either. This may be because on one hand, the omega 3s may be helping, but the mercury in fish may be making things worse. That’s the constant challenge among public health professionals, balancing the benefits with the contaminant risks.
For example, dietary exposure to PCBs may be associated with increased risk of stroke. In this study, for instance, neither fish nor intake of PCBs was related to stroke risk. However, at the same fish intake, dietary PCBs were associated with an increased risk of stroke; so, the PCB pollutants may be masking the fish benefit. Thus, if we had a time machine and could go back before the industrial revolution and find fish in an unpolluted state, it might protect against stroke. But looking at the data, if fish really was protective, then we might expect the pescatarians, those who eat fish, but no other meat, to be down here or something, since they would have the fish benefit without the meat risk. But no, they’re stuck out here. So, it doesn’t seem to be the omega 3s, either. Let’s take a closer look at what the vegetarians were actually eating.
When it comes to plant-based diets for cardiovascular disease prevention, all plant foods are not created equal. There are basically two types of vegetarians: those that do it for their health, and those that do it for ethical reasons, like global warming, or animals. And they tend to eat different diets. For example, health vegans tend to eat more fruit and less sweets. You don’t tend to see those doing it for health chowing down on vegan doughnuts.
In the United States, the primary motivations for meat reduction are health and cost. A middle-class American family is four times more likely to reduce meat for health reasons compared to environmental or animal welfare concerns. But in the UK, where this stroke study was done, the #1 reason given for becoming vegetarian or vegan is ethics.
We know plant-based diets that emphasize higher intakes of plant foods and lower intakes of animal foods are associated with a lower risk of incident cardiovascular disease, a lower risk of dying from all causes put together––but that’s only for healthy plant foods. Eating lots of Wonder Bread, soda, and apple pie isn’t going to do you many favors. For all types of plant-based diets, it’s crucial that the choice of plant foods is given careful consideration. We should be choosing whole grains over refined grains, whole fruits, avoiding trans fats and added sugars. Could it be that the veggie Brits were just eating more chips? We’ll find out, next.
Please consider volunteering to help out on the site.
- Tong TYN, Appleby PN, Bradbury KE, et al. Risks of ischaemic heart disease and stroke in meat eaters, fish eaters, and vegetarians over 18 years of follow-up: results from the prospective EPIC-Oxford study. BMJ. 2019;366:l4897.
- Rosell MS, Lloyd-wright Z, Appleby PN, Sanders TA, Allen NE, Key TJ. Long-chain n-3 polyunsaturated fatty acids in plasma in British meat-eating, vegetarian, and vegan men. Am J Clin Nutr. 2005;82(2):327-34.
- Abdelhamid AS, Brown TJ, Brainard JS, et al. Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Database Syst Rev. 2018;7:CD003177.
- Moreira ELG, Farina M. An unsolved puzzle: the complex interplay between methylmercury and fish oil-derived fatty acids within the cardiovascular system. Toxicol Res. 2014;3:300-10.
- Bergkvist C, Kippler M, Larsson SC, et al. Dietary exposure to polychlorinated biphenyls is associated with increased risk of stroke in women. J Intern Med. 2014;276(3):248-59.
- Jacobs DR, Ruzzin J, Lee DH. Environmental pollutants: downgrading the fish food stock affects chronic disease risk. J Intern Med. 2014;276(3):240-2.
- Hemler EC, Hu FB. Plant-Based Diets for Cardiovascular Disease Prevention: All Plant Foods Are Not Created Equal. Curr Atheroscler Rep. 2019;21(5):18.
- Jabs J, Devine CM, Sobal J. Model of the process of adopting vegetarian diets: health vegetarians and ethical vegetarians. J Nutr Educ Behav. 1998;30(4):196-202.
- Radnitz C, Beezhold B, Dimatteo J. Investigation of lifestyle choices of individuals following a vegan diet for health and ethical reasons. Appetite. 2015;90:31-6.
- Neff RA, Edwards D, Palmer A, Ramsing R, Righter A, Wolfson J. Reducing meat consumption in the USA: a nationally representative survey of attitudes and behaviours. Public Health Nutr. 2018;21(10):1835-1844.
- Almost half of UK vegans made the change in the last year, according to new data. Vegan Trade Journal. Published November 19, 2018.
- Kim H, Caulfield LE, Garcia-larsen V, Steffen LM, Coresh J, Rebholz CM. Plant-Based Diets Are Associated With a Lower Risk of Incident Cardiovascular Disease, Cardiovascular Disease Mortality, and All-Cause Mortality in a General Population of Middle-Aged Adults. J Am Heart Assoc. 2019;8(16):e012865.
- Satija A, Hu FB. Plant-based diets and cardiovascular health. Trends Cardiovasc Med. 2018;28(7):437-441.
Video production by Glass Entertainment
Motion graphics by Avocado Video
Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.
In my last video, we started to explore what might explain the higher stroke risk in vegetarians found in the EPIC-Oxford study. Lower risk of heart disease, and lower risk of cardiovascular disease overall, but higher risk of stroke. We looked into vitamin D levels as a potential mechanism, but that didn’t seem to be the case. What about long-chain omega 3s, the fish fats like EPA and DHA, found, not surprisingly, in markedly lower levels in vegetarians and vegans? About 30% lower in vegetarians, and more than half as low in vegans.
But according to the most extensive systematic assessment of effects of omega-3 fats on cardiovascular health to date, there is no benefit for stroke, combing 28 randomized controlled trials. In fact, there was evidence that taking fish oil didn’t help with heart disease or overall mortality. either. This may be because on one hand, the omega 3s may be helping, but the mercury in fish may be making things worse. That’s the constant challenge among public health professionals, balancing the benefits with the contaminant risks.
For example, dietary exposure to PCBs may be associated with increased risk of stroke. In this study, for instance, neither fish nor intake of PCBs was related to stroke risk. However, at the same fish intake, dietary PCBs were associated with an increased risk of stroke; so, the PCB pollutants may be masking the fish benefit. Thus, if we had a time machine and could go back before the industrial revolution and find fish in an unpolluted state, it might protect against stroke. But looking at the data, if fish really was protective, then we might expect the pescatarians, those who eat fish, but no other meat, to be down here or something, since they would have the fish benefit without the meat risk. But no, they’re stuck out here. So, it doesn’t seem to be the omega 3s, either. Let’s take a closer look at what the vegetarians were actually eating.
When it comes to plant-based diets for cardiovascular disease prevention, all plant foods are not created equal. There are basically two types of vegetarians: those that do it for their health, and those that do it for ethical reasons, like global warming, or animals. And they tend to eat different diets. For example, health vegans tend to eat more fruit and less sweets. You don’t tend to see those doing it for health chowing down on vegan doughnuts.
In the United States, the primary motivations for meat reduction are health and cost. A middle-class American family is four times more likely to reduce meat for health reasons compared to environmental or animal welfare concerns. But in the UK, where this stroke study was done, the #1 reason given for becoming vegetarian or vegan is ethics.
We know plant-based diets that emphasize higher intakes of plant foods and lower intakes of animal foods are associated with a lower risk of incident cardiovascular disease, a lower risk of dying from all causes put together––but that’s only for healthy plant foods. Eating lots of Wonder Bread, soda, and apple pie isn’t going to do you many favors. For all types of plant-based diets, it’s crucial that the choice of plant foods is given careful consideration. We should be choosing whole grains over refined grains, whole fruits, avoiding trans fats and added sugars. Could it be that the veggie Brits were just eating more chips? We’ll find out, next.
Please consider volunteering to help out on the site.
- Tong TYN, Appleby PN, Bradbury KE, et al. Risks of ischaemic heart disease and stroke in meat eaters, fish eaters, and vegetarians over 18 years of follow-up: results from the prospective EPIC-Oxford study. BMJ. 2019;366:l4897.
- Rosell MS, Lloyd-wright Z, Appleby PN, Sanders TA, Allen NE, Key TJ. Long-chain n-3 polyunsaturated fatty acids in plasma in British meat-eating, vegetarian, and vegan men. Am J Clin Nutr. 2005;82(2):327-34.
- Abdelhamid AS, Brown TJ, Brainard JS, et al. Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Database Syst Rev. 2018;7:CD003177.
- Moreira ELG, Farina M. An unsolved puzzle: the complex interplay between methylmercury and fish oil-derived fatty acids within the cardiovascular system. Toxicol Res. 2014;3:300-10.
- Bergkvist C, Kippler M, Larsson SC, et al. Dietary exposure to polychlorinated biphenyls is associated with increased risk of stroke in women. J Intern Med. 2014;276(3):248-59.
- Jacobs DR, Ruzzin J, Lee DH. Environmental pollutants: downgrading the fish food stock affects chronic disease risk. J Intern Med. 2014;276(3):240-2.
- Hemler EC, Hu FB. Plant-Based Diets for Cardiovascular Disease Prevention: All Plant Foods Are Not Created Equal. Curr Atheroscler Rep. 2019;21(5):18.
- Jabs J, Devine CM, Sobal J. Model of the process of adopting vegetarian diets: health vegetarians and ethical vegetarians. J Nutr Educ Behav. 1998;30(4):196-202.
- Radnitz C, Beezhold B, Dimatteo J. Investigation of lifestyle choices of individuals following a vegan diet for health and ethical reasons. Appetite. 2015;90:31-6.
- Neff RA, Edwards D, Palmer A, Ramsing R, Righter A, Wolfson J. Reducing meat consumption in the USA: a nationally representative survey of attitudes and behaviours. Public Health Nutr. 2018;21(10):1835-1844.
- Almost half of UK vegans made the change in the last year, according to new data. Vegan Trade Journal. Published November 19, 2018.
- Kim H, Caulfield LE, Garcia-larsen V, Steffen LM, Coresh J, Rebholz CM. Plant-Based Diets Are Associated With a Lower Risk of Incident Cardiovascular Disease, Cardiovascular Disease Mortality, and All-Cause Mortality in a General Population of Middle-Aged Adults. J Am Heart Assoc. 2019;8(16):e012865.
- Satija A, Hu FB. Plant-based diets and cardiovascular health. Trends Cardiovasc Med. 2018;28(7):437-441.
Video production by Glass Entertainment
Motion graphics by Avocado Video
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Title
Vegetarians and Stroke Risk Factors—Omega 3s?
LicenseCreative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)
Content URLDoctor's Note
Okay, another strikeout trying to explain the increased risk. Could it be that the vegetarians were eating particularly unhealthy diets? Labels like vegetarian or vegan just tell me what you don’t eat, but there’s lots of unhealthy vegetarian foods––like French fries and potato chips and soda pop. That’s why, as a physician, I prefer the term whole food plant-based nutrition. That tells me what you do eat—oh, you actually eat vegetables, a diet centered around the healthiest foods out there. But is that what’s going on? We’ll find out in my next video:
- Vegetarians and Stroke Risk Factors—Vegan Junk Food?
- Vegetarians and Stroke Risk Factors—Saturated Fat?
- Vegetarians and Stroke Risk Factors—Animal Protein?
- Vegetarians and Stroke Risk Factors—Vitamin B12 & Homocysteine?
- How to Test for Functional Vitamin B12 Deficiency
- Should Vegetarians Take Creatine to Normalize Homocysteine?
- The Efficacy and Safety of Creatine for High Homocysteine
If you missed the first four, you can catch up here:
- What to Eat for Stroke Prevention
- What Not to Eat for Stroke Prevention
- Do Vegetarians Really Have Higher Stroke Risk?
- Vegetarians and Stroke Risk Factors—Vitamin D?
Surprised about the fishy oil findings? You wouldn’t be if you’ve been following the science. See, for example, Is Fish Oil Just Snake Oil? and Omega 3s and the Eskimo Fish Tale.
2023 Update: I recently put out a new video, Update on Vegetarian Stroke Risk.
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