Concerning the Efficacy of a Vegetarian Diet: A Review of Factors and Outcomes, Research Paper Example

Introduction: The health benefits of vegetarian diets have been much championed and widely touted, both in popular circles and in the literature. There is evidence indeed that adhering to a vegetarian diet results in improved health outcomes, including reduced weight, and lower risks of heart disease, diabetes, and certain cancers. However, a careful consideration of the literature provides room to doubt that at least some of the purported benefits of vegetarian diets are uniquely vegetarian, since the influence of other lifestyle factors, including physical exercise and the avoidance of smoking and excessive drinking, has been found to be significant for vegetarians and non-vegetarians alike.

Diet and Preference: Adherence and Outcomes

Vegetarian diets are particularly of interest for their widely-perceived efficacy in securing weight loss and control, in light of the quite serious prevalence of obesity in the United States and many other Western nations (Burke et al., 2008, p. 166). As Burke et al. explained, the use of vegetarian diets to achieve such improved health outcomes is well-supported in the literature. By adopting and maintaining vegetarian diets, overweight individuals can lose excess weight and maintain a healthy body weight long-term (p. 166). Indeed, the literature indicates better adherence and better results to vegetarian dietary regimens than many other, popular “fad diets” that have gained publicity and attention in recent times (p. 166).

The literature is also quite clear about the reasons for the efficacy of vegetarian diets in controlling weight: individuals who adhere to vegetarian diets and eliminate fish and meat benefit from reduced intake of calories and saturated fat, as well as more energy from carbohydrates (Burke et al., 2008, p. 167). This results in “leaner body mass and less weight regain” (p. 167). However, individual preference is an important factor in any consideration of the efficacy of diets in reducing weight, since preference may influence the degree to which the individual is committed to the dietary regimen in question (p. 167). Accordingly, Burke et al. (2008) tested two hypotheses: firstly, that giving participants the option to choose “either a standard calorie- and fat-restricted diet (STD-D) or a calorie- and fat-restricted LOV-D [lacto-ovo-vegetarian diet] would result in greater weight loss compared to having one of these diets randomly assigned”, and secondly, the hypothesis that those participants who adhered to the vegetarian diet, LOV-D, would lose more weight than those who adhered to the STD-D (p. 167). This is significant, inasmuch as it allows for the study results to examine both the effects of the vegetarian diet itself, and the effects of allowing the participants to choose for themselves versus randomly assigning them a diet to follow.

What Burke et al. (2008) found was that in fact, participants who were given the diet of their preference, or Preference-Yes, and who had chosen the LOV-D, had a change in weight of -9.9%, with a confidence interval of -11.9 to -7.6% (p. 170). On the other hand, Preference-Yes participants with the STD-D had a weight change of -7.4%, with a confidence interval of -9.2 to -5.5% (p. 171). For the Preference-No LOV-D group, that is, those individuals who were assigned the vegetarian diet, the results were -9.3% weight change, and a confidence interval of -11.1 to -7.3%; and for the Preference-No STD-D group, the results were -9.4% weight change, with a confidence interval of -11.0 to -7.3% (p. 171). Thus, the results were actually rather counterintuitive in some ways: though all groups lost weight and then regained some weight during the maintenance phase of the experiment, “the different diets produced no difference in percentage weight change… nor was there a preference x diet interaction” (p. 171). In fact, the irony is that those individuals who were assigned a diet did somewhat better than those who were allowed to choose (p. 173). There was a small effect of preference alone on predicting body mass index (BMI) change over time, but not for diet (p. 171). And regarding adherence, the main effect was by diet, not preference, with members of the LOV-D group generally more adherent than those of the STD-D group, although some members of the LOV-D group were remiss as well (p. 172).

The Importance of Lifestyle: A Consideration of Factors

In any discussion of the nutritional efficacy and health outcomes of vegetarian diets, care must be taken to distinguish between the strict effects of the vegetarian diet(s) in question as opposed to the omnivorous diet(s) in question, and the effects of other lifestyle decisions. As Deriemaker, Aerenhouts, Ridder, Hebbelinck, and Clarys (2011) observed, vegetarians are, on average, usually more health-conscious than omnivores, and as such are more likely to avoid smoking and excessive alcohol use, and to adopt other healthy practices, including physical exercise (p. 2). In order to ascertain the health effects of an institutionalized vegetarian diet, that is to say, a vegetarian diet to which the individual has long adhered, it is therefore imperative to obtain a comparable sample of omnivores (p. 2).

Accordingly, Deriemaker et al. (2011) compared samples of elderly vegetarians (V) and omnivores or non-vegetarians (NV), with participants in both groups all “’apparently healthy’” (p. 2). What they found was illuminating: vegetarian females did not meet the recommended daily intake (RDI) for energy, whilst non-vegetarian females did (p. 3). Vegetarian and non-vegetarian males, on the other hand, both met their own RDI for energy (p. 3). Mean protein intake was too high for female vegetarians, and for the non-vegetarians of both genders (p. 3). However, female vegetarians had a higher intake of carbohydrates than female non-vegetarians (p. 3). Non-vegetarian females and vegetarian males both had higher mono- and disaccharide intakes than the RDI, and polysaccharide intake was too low for all groups (p. 3). Interestingly, saturated fat intake was too high for the females of both groups and the male non-vegetarians (p. 4). What all of this suggests, in short, is a much more mixed picture: all groups were relatively healthy, but gender as well as diet was correlated with different dietary health outcomes (pp. 4-6). As the authors pointed out, however, in light of the fact that overall, vegetarian and non-vegetarian participants “did not substantially differ with respect to dietary intake and nutritional status,” caution should be taken in concluding that it is only the effects of diet that account for “different morbidity and mortality risks among V and NV” (p. 6). This again speaks to the point made by Burke et al. (2008), namely that other lifestyle factors may influence the health outcomes of vegetarians versus non-vegetarians.

Does Vegetarianism Improve Health?

For all that the preceding two studies provide ambiguous or mixed results at best regarding the efficacy of a vegetarian diet, there remains ample reason to believe that vegetarianism, if properly implemented, can lead to improved health outcomes. As Hart (2009) explained, vegetarian diets have been convincingly linked to “prevention of chronic diseases, including diabetes, heart disease, and obesity” (p. 64). Many of the plant foods that vegetarians rely on provide ample quantities of such important nutrients as “vitamins, minerals, fiber, phytochemicals,” and a variety of antioxidants, anti-inflammatory agents, anti-carcinogens, and more besides (p. 64). Moreover, many vegetarians also benefit from lower intake of saturated fat, cholesterol, and calories (p. 64). A healthy vegetarian diet, Hart explains, includes not only ample quantities of fruits and vegetables, but also “whole grains, legumes, and nuts” and, for ovo-lacto vegetarians, eggs and dairy (p. 64).

Diabetes is one health condition the risk of which may be ameliorated substantially by the adoption of a vegetarian diet (Hart, 2009, p. 65). Notwithstanding the undoubted impact of genetics and excess weight as risk factors for the development of type 2 diabetes, vegetarians appear to have a significantly lessened risk of developing this condition (p. 65). In fact, type 2 diabetics have been shown to improve their measures of glycemic and lipid control by adhering to a vegan diet low in fat (p. 65). Vegetarian diets low in both saturated fat and cholesterol, and high in the intake of fruits and vegetables, have also been shown to be efficacious in reducing an individual’s risk of developing ischemic heart disease (p. 65). Not only do such vegetarians tend to have lower weight, but they also tend to consume higher levels of antioxidants, and both are thought to be significant factors in reducing the incidence of ischemic heart disease (p. 65). One very large study, consisting of 84,251 women and 42,148 men, ascertained that the consumption of fruits, especially those rich in vitamin C, and vegetables, especially those that are green and leafy, reduces the risk of coronary heart disease (CHD) (p. 65). A number of other studies have also found that the consumption of whole grains, but not refined grains, reduce the risk of cardiovascular disease (p. 65). Other studies have found beneficial impacts of a vegetarian diet to include substantial weight control: vegetarians, especially lactovegetarians, have low rates of obesity and overweight status (pp. 65-66). Finally, emergent research indicates possible links between consumption of a vegetarian diet and reduced risk of certain cancers, including breast cancer and prostate cancer (p. 66).

According to Phillips (2005), vegetarians and especially vegans face one major nutritional issue: whether or not they can replace the nutrients that omnivores gain from meat and other animal products (depending upon diet) (p. 137). Vegetarians, including vegans, benefit from lower intakes of saturated fatty acids and cholesterol, as well as “more folate, fibre, antioxidants, phytochemicals and carotenoids”, but the trade-off is that they have to find energy-dense plant-based foods, including “vegetable oils, nuts, seeds” and the like (pp. 137-138). Although some vegetarians and vegans struggle with protein intake, according to Phillips the majority seem to find plenty of acceptable and healthy protein from cereals and legumes in particular (pp. 138-139). Vegetarians also tend to benefit from reduced consumption of fats, with such plant-based sources as canola and soybean oils providing sufficient fats from healthier sources than many of the sources used by omnivores (pp. 140-141).

And, too, vegetarians benefit from the consumption of ample carbohydrates, which are generally from more healthy sources than omnivorous diets: not only do vegetarians consume more carbohydrates than do omnivores, but they also tend to consume far more fiber, in no small part because of their reliance on unrefined cereals, fruits, vegetables, and pulses as major sources of carbohydrates (Phillips, 2005, p. 141). Thus, if vegetarians can overcome the nutrient problem associated with avoiding meat, and if they rely on high-quality sources of fiber, they tend to experience better health than their omnivorous counterparts (p. 141). Phillips found attestation of some improved health outcomes for vegetarians: some evidence indicates a decrease in all causes of mortality (p. 153). However, there is also evidence that non-vegetarians who adhere to comparably healthy lifestyle practices have similar health outcomes, including similar reductions in mortality (p. 154). Phillips also found that vegetarians had lower risks of cancer, especially colonic cancer, since vegetarian diets eliminate many of the relevant carcinogens (pp. 156-157).

Conclusion: The influence of vegetarian diets upon health outcomes is indeed significant, but only if other lifestyle considerations are accounted for. Many vegetarians are more health-conscious than the average omnivore, precisely because vegetarians tend to represent a cross-section of the population that is especially health-conscious. When compared with similarly healthy omnivores, the improved health outcomes of many vegetarians are often well-matched. However, it does seem clear that vegetarian diets are very efficacious in reducing the risks of many conditions, such as heart disease, certain cancers, and diabetes.

References & Annotations 

Burke, L. E., et al. (2008). A randomized clinical trial of a standard versus vegetarian diet for weight loss: the impact of treatment preference. International Journal of Obesity, 32, pp. 166-176. Retrieved from http://www.search.ebscohost.com/

In this innovative study, Burke et al. examined both whether or not a vegetarian diet would lead to improved weight loss outcomes as opposed to a non-vegetarian diet, and whether or not preference exerted any impact on the respective health outcomes. What they found was that those individuals who were assigned a diet did slightly better over time than those individuals who were allowed to choose for themselves, and that both diets were efficacious. This study was used to demonstrate that healthy non-vegetarian diets can produce similar outcomes.

Deriemaeker, P., Aerenhouts, D., Ridder, D. D., Hebbelinck, M., & Clarys, P. (2011). Health aspects, nutrition and physical characteristics in matched samples of institutionalized vegetarian and non-vegetarian elderly (> 65 yrs). Nutrition & Metabolism, 8(37), pp. 1-8. Retrieved from http://www.search.ebscohost.com/

Deriemaker et al. provided crucial insights on the importance of lifestyle factors other than diet, which may confound attempts to ascertain whether or not vegetarian diets are healthier. Comparing elderly vegetarians and non-vegetarians, all of whom were healthy, they found that the results were quite mixed, with health outcomes varying somewhat by diet but also by gender. Overall, both groups were found to be very healthy.

Hart, J. (2009). The health benefits of a vegetarian diet. Alternative and Complementary Therapies, 15(2), pp. 64-68. Retrieved from http://www.search.ebscohost.com/

Hart draws on a number of studies to provide convincing evidence that vegetarian diets, if properly formulated and adhered to, are associated with improved health outcomes. These improved health outcomes include reduced risks of ischemic heart disease, type 2 diabetes, and possibly certain cancers as well. This source is compelling and convincing, but as seen, lifestyle factors aside from diet must also be accounted for. Moreover, Hart admits that further research is needed to address the dietary challenges that confront vegetarians, as well as the benefits.

Phillips, F. (2005). Vegetarian nutrition. Nutrition Bulletin, 30, 132-167. Retrieved from http://www.search.ebscohost.com/

Phillips provides compelling evidence that there are many improved health outcomes associated with a vegetarian diet. While noting that vegetarians do face significant dietary challenges, Phillips also provides ample evidence that many vegetarians have mastered these, and experience positive health outcomes as a result. However, many of the improved health outcomes associated with vegetarian diets seem to be shared by healthy omnivores.