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Vegetarian and vegan diets

This HEART UK Nutrition Academy webpage has been funded by Novartis Pharmaceuticals UK Ltd who have had no input into the content or development of this material.
 

The impact of vegetarian and vegan diets on cardiovascular health and metabolic risk factors has been extensively investigated. We review the evidence and provide a summary of key findings.

Take home messages

  • Vegetarian and vegan diets fall under the umbrella term of plant-based diets.
  • National and international cardiovascular disease prevention guidelines advocate diets mainly made up of nutrient-rich plant foods.
  • Randomised controlled and cohort studies have repeatedly shown that, compared to omnivorous and usual Western diets, vegetarian and vegan diets are associated with:
    • a 15-41% lower risk of CVD 
    • 21-32% lower risk of ischaemic heart disease 
    • reduced cardiovascular risk factors including total cholesterol, LDL cholesterol, overweight and obesity, and type 2 diabetes, and excess energy intakes.
  • The positive impacts of vegetarian and vegan diets are linked to their high content of nutrient-rich plant foods, such as whole grains, fruits, vegetables, nuts, seeds, beans, and pulses.
  • Vegan diets exclude all animal products while vegetarian diets exclude meat and reduce consumption of other animal products. 
  • Overall, healthy vegetarian or vegan diets tend to have a cardiovascular-protective nutrient profile, with low saturated fats and high levels of unsaturated fats, fibres, and antioxidant vitamins and minerals.

The impact of vegetarian diets on blood lipids and cardiovascular disease (CVD) has been the subject of a number of meta-analyses of both randomised controlled trials (RCT) and cohort studies. The evidence demonstrates that following healthy vegetarian or vegan diets is linked to a reduction in CVD risk1–6 and improved cardiometabolic risk factors, including blood lipids2,4,5,7–10, blood glucose control and diabetes2,5,7,11–13, and overweight and obesity7,14–16.

The strength of the evidence has influenced the current dietary guidelines from the European Society of Cardiology (ESC)17 and the American Heart Association (AHA)18 for primary and secondary CVD prevention. The ESC and AHA guidelines emphasise the importance of promoting higher intakes of healthy plant-based foods, specifically fruits, vegetables, whole grains, legumes, nuts, and seeds.

The cardioprotective benefits of vegetarian and vegan diets have been attributed to their inherently healthy nutrition profile and the avoidance of atherogenic compounds associated with high intakes of red and processed meat2,6,7,19,20.

Definitions  of vegetarian and vegan diets

Vegetarian and vegan diets fall within the broader category of plant-based diets. They include:

  • Lacto-vegetarian: Excludes meat, poultry and fish, but includes dairy products.
  • Ovo-vegetarian: Excludes meat, poultry, fish and dairy, but includes eggs.
  • Lacto-ovo-vegetarian: Excludes meat, poultry and fish, but includes both eggs and dairy.
  • Vegan: Excludes all animal products, relying exclusively on plant foods.

A handful of studies have included people who rarely eat animal products or fish in the vegetarian groups. 

Cardiovascular benefits of vegetarian and vegan diets

Numerous meta-analyses, predominantly from observational studies, consistently show a strong association between vegetarian and vegan diets and lower CVD risk compared to non-vegetarian diets1–6.

  • In a 2023 umbrella review of nine meta-analyses of prospective cohort studies, vegetarian diets were linked to significant reductions in CVD outcomes compared to non-vegetarian diets, including a 41% lower risk of overall CVD and a 32% lower risk of ischaemic heart disease (IHD)1.
  • Wang et al.'s 2023 review mirrored these findings, reporting a 32% lower risk of CHD and a 26-34% lower risk of CHD mortality for vegetarians and vegans compared to omnivores2.
  • A 2023 meta-analysis, incorporating 13 prospective cohort studies with up to 423,000 participants, reaffirmed the cardiovascular protective properties of vegetarian diets3. Over a period of five to 28 years, compared to non-vegetarians, those on a vegetarian diet had a 15% lower CVD risk and a 21% lower IHD risk, while vegans had an 18% reduction in IHD risk.
  • These findings align with a 2020 meta-analysis5 and are supported by two cohort studies of 12,1686 and over 94,0004 participants, indicating a consistent reduction in CVD risk.

Improved cardiometabolic risk factors

Vegetarian diets contribute to cardiovascular health by mitigating key cardiometabolic risk factors, including raised total cholesterol, low-density lipoprotein (LDL) cholesterol, type 2 diabetes, overweight and obesity, and blood pressure.

Lipid profile benefits

  • Two 2017 meta-analyses of RCTs and observational studies9,13, and a 2020 umbrella review of 20 meta-analyses5, consistently showed that  vegans and vegetarians had significantly lower total and LDL cholesterol levels compared to omnivores. Notably, no impact on triglycerides (TG) was observed.
  • A more recent meta-analysis of 20 RCTs with an average duration of 25 weeks, including 1,878 adults at risk of CVD aged 28-64 years, corroborated the earlier findings7. Those following vegetarian diets had significantly lower total and LDL cholesterol levels compared to their non-vegetarian counterparts. Importantly, the study highlighted that the cholesterol-lowering effect of vegetarian diets persisted irrespective of lipid-lowering drugs, calorie intake and physical activity levels.

Given the direct link between LDL cholesterol levels and the risk of atherosclerotic CVD21,22, the capacity of vegetarian diets to lower total and LDL cholesterol is key to their benefits for cardiovascular health.

Lower body weight

Overweight and, particularly, obesity raise the risk of CVD and other cardiometabolic factors such as dyslipidaemia, insulin resistance, type 2 diabetes and hypertension2.

Evidence from the Seventh-day Adventist study reveals that individuals adhering to vegetarian and vegan diets tend to maintain a lower body weight compared to those on standard Western and omnivorous diets15. Numerous reviews and meta-analyses of RCTs, and cross-sectional and prospective cohort studies, consistently report that vegetarians and vegans, compared to omnivores, have a lower body weight and are less likely to be obese5,13,16.

Potential to lower blood pressure

Results for hypertension have not been consistent. Hypertension is thought to be responsible for over half of deaths from CVD and IHD23

  • A pooled analysis of 15 RCTs involving 856 participants demonstrated that vegetarians, in comparison to omnivores, had significantly lower mean systolic (-2.66mmHg) and diastolic (-1.69mmHg) blood pressure24.  This benefit was most pronounced among those following a vegan diet.
  • These findings were similar to an earlier meta-analysis reporting reductions in systolic (-4.8 to -6.9 mm Hg) and diastolic (-2.2 to -4.7 mm Hg) blood pressure11.
  • However, more recent meta-analyses have not replicated these findings7,14.

Blood glucose control and type 2 diabetes

Healthy vegetarian diets consistently show an association with a lower incidence (18% to 50%) of type 2 diabetes12.

Reviews and meta-analyses of RCTs and prospective cohort studies affirm this reduction2,5. Healthy vegetarian diets are also linked to lower HbA1c and blood glucose levels, along with improved insulin sensitivity.

Mechanism of action

The benefits of vegetarian diets come from the greater amounts of cardiovascular-protective foods and nutrients, coupled with reduced consumption of foods linked to negative outcomes such as red and processed meat2,6,7,19,20.

Healthy vegetarian diets are high in fruits, vegetables, whole grains, nuts and seeds, with little or no meat, which creates a diet rich in polyunsaturated fats, fibre, antioxidant phytochemicals, and lower levels of salt and saturated fats.

In summary  

Healthy vegetarian and vegan diets yield comparable cardiovascular advantages to other healthy plant-based diets. Repeatedly validated through RCTs and cohort studies, vegetarian and vegan diets lead to a reduced risk of CVD incidence and mortality compared to omnivorous and typical Western diets. They also mitigate key cardiovascular risk factors such as total and LDL cholesterol, overweight and obesity and blood glucose control, and the risk of type 2 diabetes.

Like other healthy plant-based diets, it is not solely the adoption of vegetarian diets but their quality that results in better health. A vegetarian diet that’s high in refined carbohydrates or saturated fats, such as coconut and palm oils, may not have the same advantages. Find out more.

Our scientific review on plant-based diets & cardiovascular health

Read

References

  1. Ocagli H, Berti G, Rango D, et al. Association of Vegetarian and Vegan Diets with Cardiovascular Health: An Umbrella Review of Meta-Analysis of Observational Studies and Randomized Trials. Nutrients. 2023;15(19):4103. doi:10.3390/nu15194103
  2. Wang T, Masedunskas A, Willett WC, Fontana L. Vegetarian and vegan diets: benefits and drawbacks. European Heart Journal. 2023;44(36):3423-3439. doi:10.1093/eurheartj/ehad436
  3. Dybvik JS, Svendsen M, Aune D. Vegetarian and vegan diets and the risk of cardiovascular disease, ischemic heart disease and stroke: a systematic review and meta-analysis of prospective cohort studies. Eur J Nutr. 2023;62(1):51-69. doi:10.1007/s00394-022-02942-8
  4. Kjeldsen EW, Thomassen JQ, Rasmussen KL, Nordestgaard BG, Tybjærg-Hansen A, Frikke-Schmidt R. Impact of diet on ten-year absolute cardiovascular risk in a prospective cohort of 94 321 individuals: A tool for implementation of healthy diets. The Lancet Regional Health - Europe. 2022;19:100419. doi:10.1016/j.lanepe.2022.100419
  5. Oussalah A, Levy J, Berthezène C, Alpers DH, Guéant JL. Health outcomes associated with vegetarian diets: An umbrella review of systematic reviews and meta-analyses. Clinical Nutrition. 2020;39(11):3283-3307. doi:10.1016/j.clnu.2020.02.037
  6. 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. Journal of the American Heart Association. 2019;8(16):e012865. doi:10.1161/JAHA.119.012865
  7. Wang T, Kroeger CM, Cassidy S, et al. Vegetarian Dietary Patterns and Cardiometabolic Risk in People With or at High Risk of Cardiovascular Disease: A Systematic Review and Meta-analysis. JAMA Netw Open. 2023;6(7):e2325658. doi:10.1001/jamanetworkopen.2023.25658
  8. Koch CA, Kjeldsen EW, Frikke-Schmidt R. Vegetarian or vegan diets and blood lipids: a meta-analysis of randomized trials. Eur Heart J. 2023;44(28):2609-2622. doi:10.1093/eurheartj/ehad211
  9. Yokoyama Y, Levin SM, Barnard ND. Association between plant-based diets and plasma lipids: a systematic review and meta-analysis. Nutrition Reviews. 2017;75(9):683-698. doi:10.1093/nutrit/nux030
  10. Xu Y, Mo G, Yao Y, Li C. The effects of vegetarian diets on glycemia and lipid parameters in adult patients with overweight and obesity: a systematic review and meta-analysis. Eur J Clin Nutr. 2023;77(8):794-802. doi:10.1038/s41430-023-01283-x
  11. Yokoyama Y, Nishimura K, Barnard ND, et al. Vegetarian Diets and Blood Pressure: A Meta-analysis. JAMA Internal Medicine. 2014;174(4):577-587. doi:10.1001/jamainternmed.2013.14547
  12. Olfert MD, Wattick RA. Vegetarian Diets and the Risk of Diabetes. Curr Diab Rep. 2018;18(11):101. doi:10.1007/s11892-018-1070-9
  13. Dinu M, Abbate R, Gensini GF, Casini A, Sofi F. Vegetarian, vegan diets and multiple health outcomes: A systematic review with meta-analysis of observational studies. Critical Reviews in Food Science and Nutrition. 2017;57(17):3640-3649. doi:10.1080/10408398.2016.1138447
  14. Melgar B, Diaz-Arocutipa C, Huerta-Rengifo C, Piscoya A, Barboza JJ, Hernandez AV. Vegetarian diets on anthropometric, metabolic and blood pressure outcomes in people with overweight and obesity: a systematic review and meta-analysis of randomized controlled trials. Int J Obes. 2023;47(10):903-910. doi:10.1038/s41366-023-01357-7
  15. Orlich MJ, Fraser GE. Vegetarian diets in the Adventist Health Study 2: a review of initial published findings1234. The American Journal of Clinical Nutrition. 2014;100:353S-358S. doi:10.3945/ajcn.113.071233
  16. Fontes T, Rodrigues LM, Ferreira-Pêgo C. Comparison between Different Groups of Vegetarianism and Its Associations with Body Composition: A Literature Review from 2015 to 2021. Nutrients. 2022;14(9). doi:10.3390/nu14091853
  17. Visseren FLJ, Mach F, Smulders YM, et al. 2021 ESC Guidelines on cardiovascular disease prevention in clinical practice: Developed by the Task Force for cardiovascular disease prevention in clinical practice with representatives of the European Society of Cardiology and 12 medical societies With the special contribution of the European Association of Preventive Cardiology (EAPC). European Heart Journal. 2021;42(34):3227-3337. doi:10.1093/eurheartj/ehab484
  18. Arnett DK, Blumenthal RS, Albert MA, et al. 2019 ACC/AHA Guideline on the Primary Prevention of Cardiovascular Disease: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. Circulation. 2019;140(11):e596-e646. doi:10.1161/CIR.0000000000000678
  19. Bowman SA. A Vegetarian-Style Dietary Pattern Is Associated with Lower Energy, Saturated Fat, and Sodium Intakes; and Higher Whole Grains, Legumes, Nuts, and Soy Intakes by Adults: National Health and Nutrition Examination Surveys 2013–2016. Nutrients. 2020;12(9):2668. doi:10.3390/nu12092668
  20. Satija A, Hu FB. Plant-based diets and cardiovascular health. Trends Cardiovasc Med. 2018;28(7):437-441. doi:10.1016/j.tcm.2018.02.004
  21. Ference BA, Ginsberg HN, Graham I, et al. Low-density lipoproteins cause atherosclerotic cardiovascular disease. 1. Evidence from genetic, epidemiologic, and clinical studies. A consensus statement from the European Atherosclerosis Society Consensus Panel. European Heart Journal. 2017;38(32):2459-2472. doi:10.1093/eurheartj/ehx144
  22. Prospective Studies Collaborative. Blood cholesterol and vascular mortality by age, sex, and blood pressure: a meta-analysis of individual data from 61 prospective studies with 55 000 vascular deaths. The Lancet. 2007;370(9602):1829-1839. doi:10.1016/S0140-6736(07)61778-4
  23. Global Burden of Disease Collaborative Network. Global Burden of Disease Study 2019 (GBD 2019). Independent search results: high systolic blood pressure in adults as a risk factor for deaths and DALYs from cardiovascular disease, ischaemic heart disease and ischaemic stroke deaths in middle to high income countries. Institute for Health Metrics and Evaluation (IHME). Published 2023. Accessed January 2, 2024. https://vizhub.healthdata.org/gbd-results
  24. Lee KW, Loh HC, Ching SM, Devaraj NK, Hoo FK. Effects of Vegetarian Diets on Blood Pressure Lowering: A Systematic Review with Meta-Analysis and Trial Sequential Analysis. Nutrients. 2020;12(6):1604. doi:10.3390/nu12061604

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