The topic of eating meat can often devolve into both sides of the debate making defensive, emotionally-charged arguments. This post will examine the health issues, and cut through the propaganda on both sides.
The big health debate
Fad diets are prevalent in Western society today, with people looking to lose weight quickly. They have, in many cases, become comparable to ideologies – science is regularly distorted so that businesses catering to a specific diet can continue to make money. Seeing as this post is about vegetarianism, I won’t look into these specific diets today, but many of the same arguments about what is good for one’s health and what is bad come up in the discussion of these diets as well.
I’ll start off by criticising the claims of some vegetarian and vegan activists. Firstly, an oft-cited study purporting to demonstrate that meat is responsible for a plethora of health issues is The China Study. Nevertheless, it has been subjected to many valid criticisms, in particular relating to its misrepresentation of data. Even more demonstrative of the tendency of some vegetarian activists to misrepresent science to show that animal products are responsible for any scary disease one can think of is the People for the Ethical Treatment of Animals’ (PETA) claim that dairy products cause autism. Dr. Steven Novella of the Skeptics’ Guide to the Universe convincingly demonstrates that they misrepresent the literature to suit their own ideology.
On the other hand, those who promote paleo-diets, which contain a lot of meat, as well as some meat-eaters in general, also misrepresent the science about a vegetarian diet to cater to their own views. For example, they may assert that a vegetarian or vegan diet invariably involves certain nutrient deficiencies, whether it’s of Vitamin B12, calcium, Vitamin D, protein or iron. What they often fail to mention is that protein, iron and calcium are present in plant-based foods, and that Vitamin D can be taken in with adequate amounts of sunlight. Moreover, Vitamin B12 is in many fortified vegetarian and vegan foods, and can also be taken in supplement form. Summarising the evidence, the American Dietetic Association has stated:
“It is the position of the American Dietetic Association that appropriately planned vegetarian diets, including total vegetarian or vegan diets, are healthful, nutritionally adequate, and may provide health benefits in the prevention and treatment of certain diseases. Well-planned vegetarian diets are appropriate for individuals during all stages of the life cycle, including pregnancy, lactation, infancy, childhood, and adolescence, and for athletes.”
The association then specifies further the diseases that vegetarianism may help to prevent, including heart disease, cancer and diabetes. I will now examine these diseases, in relation to the vegetarian diet, in more detail.
Heart disease and the vegetarian diet
The scientific literature as a whole demonstrates a sustained association with the vegetarian diet and a lower risk of cardiovascular disease compared with the average omnivorous diet in the West. Studies have repeatedly found that vegetarians have a lower risk of heart disease than meat-eaters. A particularly well-designed study was the EPIC-Oxford cohort study, the results of which were published in 2013, which included a sample size of 44,561 men and women, and a particularly high proportion – 34% – of vegetarians. Having controlled for age, smoking, alcohol intake, physical activity, educational level and socioeconomic background, as well as other risk factors for heart disease, the authors found that vegetarians had a 32% lower risk of heart disease than those who ate meat and fish.
This corroborates previous findings, such as this analysis of 5 prospective studies, which found a 24% lower risk of heart disease in vegetarians compared with non-vegetarians.
The mechanisms as to why vegetarians would have a lower risk of cardiovascular disease are also quite clear. As the authors of the 2013 EPIC-Oxford study stated:
“The lower risk of IHD among individuals consuming a vegetarian diet can be largely explained through reduced levels of well-established risk factors for IHD, such as non-HDL-cholesterol concentrations and systolic blood pressure. Vegetarians had a better lipid profile than did nonvegetarians, probably because of a higher ratio of polyunsaturated to saturated fat in their diet and a lower BMI.”
There is one caveat, however: the aforementioned analysis of 5 studies, when it looked in closer detail at the kinds of diets that were being studied, found:
“Further categorization of diets showed that, in comparison with regular meat eaters, mortality from ischemic heart disease was 20% lower in occasional meat eaters, 34% lower in people who ate fish but not meat, 34% lower in lactoovovegetarians, and 26% lower in vegans.”
While the association with lower risk of heart disease of both lacto-ovo vegetarianism and pescetarianism (people who eat fish but not meat) is clearly stronger than the association of occasional meat-eating, these results do suggest that it is still possible to reduce the risk of heart disease to some extent as a meat-eater. Despite this, these results, as well as the fact that meat in general is high in saturated fat, which causes an increase in levels of LDL cholesterol, also suggest that it is harder to reduce one’s risk of cardiovascular disease as a meat-eater than as a vegetarian, particularly if the saturated fat in meat is being replaced by polyunsaturated – and most likely monounsaturated – fats in a vegetarian diet. Indeed, as this detailed review of the evidence on healthy eating states:
“…the evidence from epidemiologic, clinical, and mechanistic studies is consistent in finding that the risk of CHD is reduced when SFAs are replaced with polyunsaturated fatty acids”
All of this means that every piece of meat being eaten is a wasted chance to replace some saturated fat in the diet with healthier unsaturated fats, thereby reducing one’s risk of cardiovascular disease.
Cancer and vegetarianism
Red meat, particularly processed meat such as bacon, salami, ham, and sausages, has been strongly linked with an increased risk of cancer. A 2012 study conducted by researchers at Harvard University, pooling the results from two large cohort studies, giving a total sample size of over 120,000 men and women who were followed for a number of years, found that both unprocessed and processed red meats increase the risk of cancer. This was after controlling for a number of factors, including body mass index, age, smoking status, consumption of grains, fruits and vegetables, family history of cancer, alcohol intake and physical activity level.
However, another study, published in 2013 by Oxford University, only found that processed meat increases the risk of cancer, not unprocessed meat. Therefore, it is reasonable to conclude that processed meat should be kept off the menu, and that further research into unprocessed red meat should be carried out.
In the meanwhile, various mechanisms by which red meat and processed meat could contribute to an increased risk of cancer have been proposed, meaning that these correlations can plausibly be instances of causation, particular as various other factors, particularly in the Harvard Study, were likely ruled out.
Do these associations of processed meat, and possibly red meat, with a higher risk of cancer have any real effect on the cancer risk of vegetarians as a group, though? There is conflicting evidence on this issue.
Some studies have found a decreased risk of overall cancer in vegetarians compared with non-vegetarians, although in the majority of studies which have found a link, it is only of certain cancers that there is a decreased risk. Some, meanwhile, have found no decreased risk. The literature taken as a whole, though, does support the hypothesis that there is a lower rate of cancer incidences in vegetarian populations.
If it is only red meat, or processed red meat, that causes cancer, and the evidence is somewhat misty when it comes to studying vegetarian and non-vegetarian populations in terms of cancer, then this once again suggests that health-conscious meat-eaters can reduce their cancer risk. Again, however, it may be harder for them to do so – vegetarians are much less likely to be tempted by the hot dog while at a restaurant and the bacon rasher that’s sitting in the freezer.
Diabetes, obesity and vegetarianism
Obesity is one of the key factors leading to diabetes, which is why obesity and diabetes have been grouped together in this section. Other factors include genetics, physical activity and diet.
A number of studies have shown that meat intake may be associated with obesity. This 2009 study, for example, found “positive associations between MC and risk for obesity and central obesity.” Meanwhile, this 2011 study of European adults similarly found that “protein from food items of animal origin, especially meat and poultry, seemed to be positively associated with long-term weight gain.”
More specifically, some studies have found that processed meat and red meat consumption in particular is linked to an increased risk of diabetes. A 2002 study of 42,504 males found that frequent consumption of processed meats may increase risk of type 2 diabetes. Meanwhile, even after adjusting for other variables, this 2011 Harvard study found that consumption of both unprocessed and processed red meat was linked with an increased risk of diabetes, and that replacing one serving of red meat per day with a serving of nuts, low-fat dairy and whole grains per day could decrease risk of Type 2 diabetes by up to 35%.
If meat is associated with an increased risk of obesity, which in turn leads to an increased risk of diabetes, as well as an independent increased risk of diabetes, particularly from processed meat, then we should see vegans and vegetarians contracting diabetes less. And this is precisely what this 2009 analysis of the Adventist Health Study-2 found, concluding:
all variants of vegetarian diets (vegan, lacto-ovo, and pesco- and semi-vegetarian) were associated with substantially lower risk of type 2 diabetes and lower BMI than nonvegetarian diets. The protection afforded by vegan and lacto-ovo vegetarian diets was strongest.
Indeed, prevalence of diabetes in vegans was 2.9%; in lacto-ovo vegetarians it was 3.2%; in pescetarians it was 4.8%; in semi-vegetarians it was 6.1%, while in non-vegetarians it was 7.6%. This appears to show a clear spectrum between amount of animal products eaten and prevalence of diabetes.
Another 2011 analysis of the Adventist Health Study-2 found broadly similar results, with a vegan diet offering the most protection against diabetes and diabetes being most prevalent amongst those eating a non-vegetarian diet. Specifically, cases of diabetes developed in 0.54% of vegans, 1.08% of lacto ovo vegetarians, 1.29% of pesco vegetarians, 0.92% of semi-vegetarians and 2.12% of non-vegetarians. Importantly, the study controlled for a number of factors, including age, gender, education, income, television watching, physical activity, sleep, alcohol use, smoking and BMI. It concluded that “vegetarian diets were associated with a substantial and independent lower incidence of diabetes [amongst] non-Black and Black participants, indicating the potential of these diets to stem the current diabetes epidemic.”
The literature, therefore, is consistent in finding that a vegetarian diet is highly likely to protect against obesity and diabetes.
Overall mortality and vegetarianism
As we would expect from the information above, studies have found that vegetarians have a lower total mortality than meat-eaters, with this 2013 study concluding: “vegetarian diets are associated with lower all-cause mortality and with some reductions in cause-specific mortality.”
It is worth noting that another study by Key et al. in 2003, which included “health-conscious” meat-eaters as well as vegetarians, found no significant difference in overall mortality between vegetarians and non-vegetarians. This, again, suggests that health-conscious meat-eating is a perfectly viable option, but that, without consciously thinking about health, a vegetarian diet is more suitable.
It is very likely that the average vegetarian is at lower risk of suffering from heart disease and diabetes compared with the average meat-eater. Concerning cancer, the weight of the evidence does suggest that vegetarians have a lower risk of contracting certain cancers compared with the average meat-eater, but more research should be done on this issue. As for morality, it is likely that the average vegetarian has a lower risk of premature mortality than the average meat-eater. But, for many of these issues, a health-conscious meat-eater would probably have the same risk as the average vegetarian.
Put simply, it is easier to be healthy on a vegetarian diet and, if you’re willing to keep away from sugary products such as sweets and soft drinks, but you’re not willing to do in-depth research into nutrition, a vegetarian diet will keep you healthier than an omnivorous diet. An average vegetarian like this will have a lower risk of contracting the above diseases than the average meat-eater, simply because saturated fat causes an increased risk of heart disease as well as the fact that red meat, particularly processed meat, has been linked to an increased risk of both cancer and diabetes.