The Semi-Vegetarian Diet and Metabolic Syndrome: How Reducing Meat Intake Affects Disease Risk
Abstract
The typical Western diet promotes high consumption of simple carbohydrates, meat, sugar, and processed food products, and is associated with an increased risk of heart disease, type 2 diabetes, obesity, and cancer. Known as Metabolic Syndrome (MetS), these diseases can be reduced by adopting a plant-based diet; however, reducing meat intake may produce similar benefits. Studies show that adopting a semi-vegetarian diet will lower one’s risk of MetS compared to a non-vegetarian diet. For instance, the Mediterranean diet, which reduces but does not necessarily eliminate meat intake, has long been proven to reduce MetS risk. Also, South Asian non-vegetarians, who eat a limited amount of meat compared to US non-vegetarians, see a similarly low risk of diabetes and coronary heart disease compared to South Asian vegetarians. While vegetarian and vegan diets may produce the strongest benefits, placing an emphasis on decreasing rather than eliminating meat intake may produce a more sustainable approach to changing the Western diet and the diseases associated with it. The Semi-Vegetarian Diet and Metabolic Syndrome: How Reducing Meat Intake Affects Disease Risk.
Metabolic syndrome (MetS) refers to several diseases that have become more common with the typical Western diet. An increased consumption of simple carbohydrates, meat, sugar, and processed food products, combined with a largely sedentary lifestyle, is associated with the development of type 2 diabetes, obesity, hypertension, heart disease, and certain cancers (Pollan, 2008). Plant-based diets have long been proven to reduce the risk of MetS, however reducing meat intake may produce similar benefits.
There are several different categories of the vegetarian diet: vegan (consuming no animal products), lacto-ovo vegetarian (consuming eggs and dairy but no fish or meat), pesco-vegetarian (consuming fish but no meat), semi-vegetarian (limiting meat and fish intake), and non-vegetarian (no meat restriction). Semi-vegetarian is typically defined as consuming less than or equal to one serving of meat or fish per week.
Many people adopt an all-or-nothing approach to diet. Because high meat intake is seen as essential in the typical Western diet, most people find it impossible and unrealistic to cut out meat entirely. With the risk of MetS increasing in the US and abroad, decreasing meat consumption and promoting a semi-vegetarian diet is of great importance. This literature review will demonstrate that a semi-vegetarian diet reduces the risk of MetS compared to a non-vegetarian diet.
Results
In Michael Pollan’s book, In Defense of Food: An Eater’s Manifesto (2008), he promotes the slogan: “Eat food. Not too much. Mostly plants.” He stresses the importance of reducing consumption of processed food products and meat to improve one’s health and reduce the risk of MetS. Pollan states that while high meat intake will raise one’s risk of developing heart disease and cancer, eating less than one serving of meat a day (his definition of semi-vegetarian) does not appear to increase one’s risk. He finds that a semi-vegetarian diet will hold the same preventative health benefits as a vegetarian diet. The exact cause of this relationship is unclear; for instance, it could come from the reduction of saturated fat or the increased intake of vegetables and fruits. Pollan also explains that by eating more processed food products, the Western diet includes less wholesome foods and is thus less healthy than any number of traditional diets from around the world that include a wide variety of non-processed foods, including meat.
Similarly, Tonstad, Butler, Yan, and Fraser (2009) demonstrate that type 2 diabetes risk decreases with lower meat consumption. The study follows 22,434 men and 38,469 women over four years and compares type 2 diabetes risk and diet. The vegan and lacto-ovo vegetarian diets are associated with a reduced risk of type 2 diabetes by nearly one half. The vegan and vegetarian groups are found to consume the highest amount of fruits and vegetables, less saturated fat, and more foods with a low glycemic index. The study finds that all variations of the vegetarian diet are associated with a reduced risk of type 2 diabetes and lower BMI than non-vegetarian diets, however the strongest protection comes from the vegan and lacto-ovo vegetarian diets.
Sabaté and Wien (2015) also analyze vegetarian dietary patterns and risk of MetS. They find that a vegetarian diet is related to lower risk of type 2 diabetes, hypertension, specific cancers, and all-cause mortality. They also explore the relationship between childhood vegetable intake and MetS. They site a 27 year study that found a 14% decrease in MetS associated with a higher vegetable intake in childhood. Finally, they compare the Mediterranean diet to the vegetarian diet, showing similarities in the high consumption of fruits, vegetables, grains, legumes, and nuts; moderate intake of dairy products; and low intake of meat, cream, and sweets. They site a meta-analysis of fifty original research studies that associates the Mediterranean diet with a 31% reduced risk of MetS.
Williams and Patel (2017) discuss the health benefits of a plant-based diet and how it relates to cardiovascular disease (CVD). They state that a diet including whole grains, unsaturated fats, n-3 fatty acids, and plenty of fruits and vegetables will help to prevent CVD. They stress the importance of destroying the roots of CVD by making dietary changes, rather than merely treating its symptoms. They also delve into the idea of the “all-or-none” mindset that many people have with nutrition, emphasizing that “smaller dietary tweaks rather than major changes would be more encouraging and sustainable for those finding it difficult to make a complete and precipitous change in dietary habits.”
Finally, Jaacks et al. (2016) compare the differences between vegetarian South Asian and US adults in terms cardiometabolic disease risk. In the study, both South Asian and US vegetarians are found to be less likely to exhibit overweight and obesity than non-vegetarians, and thus experience lower risk of diabetes and coronary heart disease. However, this association is stronger in the US population studied. Vegetarians in South Asia are found to be only slightly less likely to be overweight or obese than non-vegetarians. This is likely because South Asian non-vegetarians are shown to eat less meat to begin with than American non-vegetarians, so the difference is not as noticeable. The reduced meat intake of South Asian non-vegetarians is found to be healthier than the high meat intake of US non-vegetarians, and vegetarians are healthier in both the US and South Asian populations.
Discussion
This evidence supports the thesis that a semi-vegetarian diet reduces the risk of MetS compared to a non-vegetarian diet. Studies show that reducing meat intake lowers the risk of diabetes, obesity, heart disease, and certain cancers. It appears that vegetarian or vegan diets may produce the strongest benefits, and a semi-vegetarian diet is beneficial to health and longevity compared to a non-vegetarian diet.
There are many possible reasons for this relationship. It could be due to a decrease in saturated fat intake, a reduction of calories, or an increase in fiber, to name a few. An important connection appears to be that by simply eating less meat, there is more room in each meal for plant-based foods and fruits and vegetables (Pollan, 2008). This will automatically increase vitamin, mineral, and fiber intake, and lower disease risk.
The studies referenced above find an increasingly positive relationship between reduced meat consumption and lower risk of MetS. Vegan diets are found to have stronger health benefits than either vegetarian or semi-vegetarian diets, implying that the less animal products a person consumes, the less likely they are to develop MetS (Tonstad et al., 2009). However, there are also dietary concerns to take into consideration when planning a vegan diet. Strictly plant-based diets are frequently deficient in vitamins and minerals such as calcium, vitamin D, vitamin B-12, iron, and zinc. A vegan diet can be a healthy option but it must be carefully planned in order to consume adequate amounts of macro- and micro-nutrients.
The health benefits of the Mediterranean diet are well known and it has many similarities with a semi-vegetarian diet (Sabaté & Wein, 2015). The Mediterranean diet typically limits meat consumption, but it does not necessarily eliminate it entirely. It is possible that reduced meat intake could be one reason that the Mediterranean diet lowers MetS risk. Reducing meat intake lowers the risk of CVD, and it does not need to be eliminated from the diet to see these benefits (Williams & Patel, 2017). An all-or-nothing mentality towards diet discourages people from reducing meat intake, and small dietary tweaks should be encouraged to gradually reduce meat consumption, increase intake of plant-based foods, and lower the overall risk of MetS.
Finally, the study by Jaacks et al. (2016) portrays telling and significant results for how reduced meat consumption and a more traditional diet affects MetS risk. South Asian non-vegetarians are found to have lower BMI and obesity risk than US non-vegetarians, likely because they consume less meat. While vegetarians produce an even lower risk, the difference is not significant between South Asian vegetarians and non-vegetarians. South Asian non-vegetarians are found to eat little meat to begin with, and also consume a more traditional and less processed diet. A reduced meat intake as seen in the South Asian non-vegetarian diet is shown to be much healthier than the high meat intake of the typical American diet, and not significantly different than the South Asian vegetarian diet in terms of disease risk factors. These findings agree with Pollan’s (2008) assertion that a semi-vegetarian diet produces the same reduced risk of MetS as a strictly vegetarian diet.
Conclusions and Future Study
As diets around the world are shifting from traditional to Western, MetS is affecting a greater number of people each year. MetS in the US is approximately 20% and increasing worldwide (Sabaté & Wein, 2015). As diabetes becomes increasingly normalized and CVD is a leading cause of death in the US, the need for change is imperative. Unfortunately, high meat intake is seen as essential in the typical Western diet, and most people find it impossible and unrealistic to cut out meat entirely. Placing an emphasis on decreasing rather than eliminating meat intake may produce a more sustainable approach to changing the Western diet and the diseases associated with it.
As Pollan (2008) demonstrates, the typical Western diet is markedly different than any of the various traditional diets around the world. If the Western diet is very high in processed foods, meat, and sugar, then perhaps a vegetarian diet will portray much greater differences from a semi-vegetarian diet. It would be beneficial if future research studied specific countries (as seen in the South Asia study referenced above) with more traditional, less processed diets, and see how MetS risk compares to vegetarians within their country. The differences may not be as great as seen in the US. Overall, reducing meat intake will reduce risk of MetS.
A preventative approach is essential to reducing disease risk, and this begins with our diet. Rather than searching for cures and treating diseases as they occur, our focus should be on eliminating the problem before it begins. This could lower the massive healthcare costs that are associated with these diseases and raise life expectancy. Reducing our meat intake could also lessen the environmental impact of the meat industry, creating a healthier planet for future generations. With more and more people shifting towards an increasingly vegetarian diet, hopefully we can lessen the occurrence of MetS and promote a healthier future.
References
Jaacks, L.M., Kapoor, D., Singh, K., Narayan, K.M.V., Ali, M.K., Kadir, M.M., … Prabhakaran, D. (2016). Vegetarianism and cardiometabolic disease risk factors: Differences between South Asian and US adults. Nutrition. Retrieved from: https://search-proquest-com.ezp-01.lirn.net/central/docview/1880039627/fulltext/E1039F3CC1604F1CPQ/5?accountid=158302
Pollan, M. (2008). In defense of food: An eater’s manifesto. New York, NY: Penguin Press.
Sabaté, J., & Wien, M. (2015). A perspective on vegetarian dietary patterns and risk of metabolic syndrome. The British Journal of Nutrition. Retrieved from: https://search-proquest-com.ezp-01.lirn.net/central/docview/1694456314/fulltext/15F24C5CA7C4646PQ/13?accountid=158302
Tonstad, S., Butler, T. Yan, R., & Fraser, G.E. (2009). Type of vegetarian diet, body weight, and prevalence of type 2 diabetes. Diabetes Care. Retrieved from: https://search-proquest-com.ezp-02.lirn.net/central/docview/223034883/fulltextPDF/E3922B892FF441D6PQ/1?accountid=158302
Williams, K.A., & Patel, H. (2017). Healthy plant-based diet: What does it really mean? Journal of the American College of Cardiology. Retrieved from: https://search-proquest-com.ezp-01.lirn.net/central/docview/1922853192/fulltext/15F24C5CA7C4646PQ/8?accountid=158302