Before we get into the science and evidence about plant-based diets, there’s one important point to make: there are healthy meat-eaters, and there are unhealthy meat-eaters. Just as there are healthy and unhealthy vegans. But, on average, vegans and vegetarians do live longer - they have lower mortality rates than meat-eaters, and grow old with fewer health issues (1). For example, those on a plant-based diet tend to have:
Healthier gut profiles - reduced abundance of pathogenic gut bacteria and greater abundance of protective species (2)
Lower blood pressure (3)
Lower incidence of heart disease (4)
Lower overall cancer incidence (5)
Lower risk of developing diabetes (6)
That’s a pretty impressive list of diseases you can be protected against by adopting a plant-based diet, and it includes two of the top killers in Western countries: heart disease and cancer.
So Why do Vegans and Vegetarians Live Longer?
The reasons why plant-based diets can be so protective can be broken down into two main categories:
1. Vegans and vegetarians don’t eat meat
Yes, this is stating the extremely obvious, but this is of course the main difference between meat-eaters and those on a plant-based diet. And it’s an important difference, because:
Replacing carcinogenic processed meats with healthful vegan foods like fruit, vegetables, grains, pulses, nuts and seeds comes with a vast array of health benefits.
All meat, including white meat like chicken (7), contain high levels of saturated fat and cholesterol, which is associated with cardiovascular risk (8). Dairy and eggs are also high in saturated fat, so vegans benefit even more from these effects.
Processed meat has been classified as a class-1 carcinogen (cancer-causing) by the World Health Organisation (9) – this means the evidence is just as strong as it is with smoking and asbestos, both also class-1 carcinogens! It's also classified all red meat (beef, lamb, pork, goat etc.) as class-2 carcinogens, meaning they are probably cancer-causing.
Meat and dairy contain hormones and antibiotics, given to livestock to increase rates of weight gain and feed efficiency, and these can impact human health in a number of ways (10).
2. Vegans and vegetarians tend to eat more healthful foods
This is almost by default – if you don’t eat meat, you tend to replace those calories with more vegetables, fruits, grains, pulses, beans, nuts and seeds. It may also be that vegetarians and vegans pay more attention to their health. Of course it isn’t always the case (some vegans live on junk food), but on average, consumption of these nutritious, whole plant-foods, tends to be higher. And this comes with a vast array of health benefits:
Fruit and vegetables contain protective bioactive compounds such as antioxidants, polyphenols, fibre, vitamins and minerals, which work through numerous complex mechanisms to reduce antioxidant stress, lower blood levels of VLDL and LDL cholesterol (the bad types), and help to maintain a healthy weight. So it's no surprise that higher consumption has been associated with reduced risk of type 2 diabetes (11), lower risk of developing several cancers (12), reduced risk of cardiovascular disease (13), and lower risk of becoming overweight (14). In fact, higher intake of fruit and vegetables is associated with a reduced overall mortality risk, by any cause (13).
Whole grains are also rich in phytochemicals, antioxidants, vitamins, trace minerals, fibre, and protein. In fact, because they’re so nutritious, increased intake of whole grains is associated with lower blood pressure, reduced risk of cardiovascular disease (15), reduced risk of some cancers (16,17), reduced risk of developing diabetes (18), and having a lower body weight (19). (More about the benefit of whole grains here).
Consuming your protein from plant-based sources such as beans, legumes, pulses, and soy can actually lower VLDL and LDL-cholesterol by specific mechanisms, as well as by displacing meat consumption (20,21). So while a high protein intake from animal sources increases cancer death risk and diabetes mortality, replacing it with plant-based protein sources eliminates these risks (22).
Nuts and seeds pack an impressive variety of vitamins and minerals, and are a great source of protein and fibre. High nut consumption has been shown to lower total cholesterol and LDL cholesterol and is associated with reduced risk of cardiovascular disease and cancer mortality (23,24).
You can get an abundance of protein from vegan sources such as pulses, whole grains, tofu, vegetables, nuts and seeds - plus they come with countless health benefits
So, by avoiding meat and instead replacing animal foods with more whole plant foods, it's possible to improve your health in a huge variety of ways (as well as the obvious benefits to the environment and animal welfare issues). Of course, you hear the occasional story about someone who tried a vegan diet and didn’t feel great, or of an avid meat-eater who had steak for lunch every day and lived to a ripe old age. Everyone is different and has different experiences, lifestyles, and genetics. But the growing body of high quality scientific evidence of the health benefits of a plant-based diet, as well as reports of so many vegan athletes surpassing their competitors, is a pretty compelling reason to at least give a plant-based diet a go.
References:
1. Song, M., Fung, T., Hu, F., Willett, W., Longo, V., Chan, A., & Giovannucci, E. (2016). Association of Animal and Plant Protein Intake With All-Cause and Cause-Specific Mortality. JAMA Internal Medicine, 176(10), 1453-1463.
2. Glick-Bauer, M. C., & Yeh, M. (2014). The health advantage of a vegan diet: Exploring the gut microbiota connection. Nutrients, 6(11), 4822-4838.
3. Yokoyama, Y. D., Takegami, M., Miyamoto, Y., Barnard, N., Nishimura, K., Watanabe, M., Okamura, T. (2014). Vegetarian diets and blood pressure a meta-analysis. JAMA Internal Medicine, 174(4), 577-587.
4. Huang, Tao, Yang, Bin, Zheng, Jusheng, Li, Guipu, Wahlqvist, Mark L., & Li, Duo. (2012). Cardiovascular Disease Mortality and Cancer Incidence in Vegetarians: A Meta-Analysis and Systematic Review. Annals of Nutrition and Metabolism, 60(4), 233-240.
5. Dinu, M., Abbate, R., Gensini, G., Casini, A., & Sofi, F. (2017). Vegetarian, vegan diets and multiple health outcomes: A systematic review with meta-analysis of observational studies. Critical Reviews in Food Science and Nutrition, 57(17), 3640-3649.
6. Vang, A., Singh, P., Lee, J., Haddad, E., & Brinegar, C. (2008). Meats, Processed Meats, Obesity, Weight Gain and Occurrence of Diabetes among Adults: Findings from Adventist Health Studies. Annals of Nutrition and Metabolism, 52(2), 96-104.
7. Wang, Y., Lehane, C., Ghebremeskel, K., & Crawford, M. (2010). Modern organic and broiler chickens sold for human consumption provide more energy from fat than protein. Public Health Nutrition, 13(3), 400-408.
8. Hooper, L., Martin, N., Abdelhamid, A., & Smith, G. (2015). Reduction in saturated fat intake for cardiovascular disease. Cochrane Database Of Systematic Reviews, (6), CD011737.
9. WHO International Agency for Research on Cancer (2015). Q&A on the carcinogenicity of the consumption of red meat and prcessed meat. Accessed 11.10.17 at: https://www.iarc.fr/en/media-centre/iarcnews/pdf/Monographs-Q&A_Vol114.pdf
10. Jeong, Sang-Hee, Kang, Daejin, Lim, Myung-Woon, Kang, Chang Soo, & Sung, Ha Jung. (2010). Risk assessment of growth hormones and antimicrobial residues in meat. Toxicological Research, 26(4), 301-13.
11. Carter, P., Gray, L., Troughton, J., Khunti, K., & Davies, M. (2010). Fruit and vegetable intake and incidence of type 2 diabetes mellitus: Systematic review and meta-analysis. BMJ, 341, BMJ, 19, 19 August August 2010, Vol.341.
12. Schwingshackl, L., & Hoffmann, G. (2014). Adherence to Mediterranean diet and risk of cancer: A systematic review and meta‐analysis of observational studies. International Journal of Cancer, 135(8), 1884-1897.
13. Wang, X., Ouyang, Y., Liu, J., Zhu, M., Zhao, G., Bao, W., & Hu, F. (2014). Fruit and vegetable consumption and mortality from all causes, cardiovascular disease, and cancer: Systematic review and dose-response meta-analysis of prospective cohort studies. BMJ, 349(7969), 9.
14. Mytton, O., Nnoaham, K., Eyles, H., Scarborough, P., & Mhurchu, C. (2014). Systematic review and meta-analysis of the effect of increased vegetable and fruit consumption on body weight and energy intake. Bmc Public Health, 14, Bmc Public Health, 2014 Aug 28, Vol.14.
15. Tighe, Paula, Duthie, Garry, Vaughan, Nicholas, Brittenden, Julie, Simpson, William G, Duthie, Susan, . . . Thies, Frank. (2010). Effect of increased consumption of whole-grain foods on blood pressure and other cardiovascular risk markers in healthy middle-aged persons: A randomized controlled trial. The American Journal of Clinical Nutrition, 92(4), 733-40.
16. Aune, D., Chan, D., Lau, R., Vieira, R., Greenwood, D., Kampman, E., & Norat, T. (2011). Dietary fibre, whole grains, and risk of colorectal cancer: Systematic review and dose-response meta-analysis of prospective studies. BMJ : British Medical Journal, 343, BMJ : British Medical Journal, 2011, Vol.343.
17. Skeie, G., Braaten, T., Olsen, A., Kyrø, C., Tjønneland, A., Landberg, R., . . . Lund, E. (2016). Intake of whole grains and incidence of oesophageal cancer in the HELGA Cohort. European Journal of Epidemiology, 31(4), 405-414.
18. Chanson-Rolle, A., Meynier, A., Aubin, F., Lappi, J., Poutanen, K., Vinoy, S., . . . Barengo, N. (2015). Systematic Review and Meta-Analysis of Human Studies to Support a Quantitative Recommendation for Whole Grain Intake in Relation to Type 2 Diabetes (Meta-Analysis to Recommend a Whole Grain Intake). 10(6), E0131377.
19. Giacco, Della Pepa, Luongo, & Riccardi. (2011). Whole grain intake in relation to body weight: From epidemiological evidence to clinical trials. Nutrition, Metabolism and Cardiovascular Diseases, 21(12), 901-908.
20. Jenkins, D., Mirrahimi, A., Srichaikul, K., Berryman, C., Wang, L., Carleton, A., . . . Kris-Etherton, P. (2010). Soy protein reduces serum cholesterol by both intrinsic and food displacement mechanisms. The Journal of Nutrition, 140(12), 2302S-2311S.
21. Ha, V., Sievenpiper, J., De Souza, R., Jayalath, V., Mirrahimi, A., Agarwal, A., . . . Jenkins, D. (2014). Effect of dietary pulse intake on established therapeutic lipid targets for cardiovascular risk reduction: A systematic review and meta-analysis of randomized controlled trials. Canadian Medical Association. Journal, 186(8), E252-62.
22. Levine, Suarez, Brandhorst, Balasubramanian, Cheng, Madia, . . . Longo. (2014). Low Protein Intake Is Associated with a Major Reduction in IGF-1, Cancer, and Overall Mortality in the 65 and Younger but Not Older Population. Cell Metabolism,19(3), 407-417.
23. Del Gobbo, L., Falk, M., Feldman, R., Lewis, K., & Mozaffarian, D. (2015). Effects of tree nuts on blood lipids, apolipoproteins, and blood pressure: Systematic review, meta-analysis, and dose-response of 61 controlled intervention trials. The American Journal of Clinical Nutrition, 102(6), 1347-56.
24. Grosso, G., Yang, J., Marventano, S., Micek, A., Galvano, F., & Kales, S. (2015). Nut consumption on all-cause, cardiovascular, and cancer mortality risk: A systematic review and meta-analysis of epidemiologic studies. The American Journal of Clinical Nutrition, 101(4), 783-793.