Common fallacies and truths about vegetarian nutrition

Vegetarianism is defined as a practice when a person abstains from eating meat (including fish). There are four important objections against ‘common omnivorism’—nutritional, ethical, ecological, and economical. In this post, we shall discuss common fallacies and truths about vegetarian nutrition.

Many omnivores argue that one cannot stay healthy on a vegetarian (or vegan) diet, so let’s discuss first what vegetarians have to or don’t have to do to stay healthy. After that, we shall discuss some beneficial compounds found in meat and that eating poultry and fish can actually be healthy. Note: because many people consider this kind of discussion controversial, this article is based on reliable large-scale human studies; you can find numbered references at the end of the article.

Vegetarian nutrition can provide enough protein

Source: veganyumyum.com

A common misconception is that one cannot get enough protein from a veg(etari)an diet. However, there are great vegan sources of protein, such as legumes, tofu, seitan, tempeh, and many others (which can be can also be more delicious than most people can imagine—see the photo and the related website on the right). Vegetarians can furthermore eat eggs and dairy products (although it is not advisable to eat a lot of dairy products, which we will see later), which are again a source of protein.

There was a concern that isoflavones in soy may cause hormonal imbalance and lead to a lower quality of sperm in men or a greater risk of breast cancer in women. However, these worries were dismissed by recent meta-analyses^[1][2]. Also, even though soy is known to be a common allergen, soy allergy probably affects no more than 0.1% of population^[3] (there are actually more people born with more than 10 fingers than there are people allergic to soybeans). In these rare cases, obtaining enough protein from a vegetarian diet may prove quite problematic, and the affected person might have to rely on protein powder supplements in order to get enough protein (in case he or she doesn’t want to consume meat). However, for the majority of us, soy can even have some beneficial effects, such as improvement of memory in aging individuals^[4].

What is important to note is that, while vegans generally consume enough protein (if they consume a wide range of products, not only those derived from soy, but also legumes, whole grains and others), most omnivores in western countries consume more protein than is required, which causes unnecessary stress on kidneys and has been (in case of animal protein) linked to higher incidence of cancer^[6]. However, some people, such as athletes, may require higher than average protein intake; if they are vegetarian, using whey protein powder is a good alternative (as it may actually also lower the risk of cancer^[7]), or they can use a soy protein powder if they are vegan. One should also realize that it is not necessary to stay at drinking protein shakes; it is possible to buy a protein powder without artificial sweeteners and aromas and use it for baking, for example).

High consumption of casein (another milk protein) has been linked to an increased risk of cancer^[6] (at least in rodents), and since milk proteins consist of about 80% casein and cheese proteins of almost 100% casein, it is not advisable to rely on dairy products as one’s main source of protein. Nevertheless, casein doesn’t seem to be the most important issue when it comes to dairy (as people generally don’t consume it in excessive quantities); a more important issue is that milk contains mostly saturated fat, whose detrimental effects will be explained later.

Iron is not a problem

Another common argument is that vegetarians cannot get enough iron, because the main source of it is meat. While it is true that meat usually contains much more iron than vegetables per unit weight, many vegetable sources contain much more iron than meat per calorie^[5], which means, strictly speaking, that a vegetarian diet often contains even more iron than that of omnivores; however, the iron form found in vegetarian diet is less bioavailable (it cannot be absorbed as well as the heme iron present in meat), so the blood iron levels in vegetarians are generally lower than in omnivores. Nevertheless, it has been shown that incidence of iron deficiency (i.e. iron levels so low that it causes any physiological problem) is not significantly different in vegetarians than in omnivores^[8], and, in fact, iron has been shown to be carcinogenic in larger doses^[9], so the lower intake of iron appears to be actually healthier than the average intake.

Why not dairy?

A common argument against veganism is that without dairy, one wouldn’t be getting enough calcium, which would lead to osteoporosis. However, studies have shown that veganism doesn’t lead to lower bone mineral density^[10] (some studies have found lower mineral density in vegans, but the difference was insignificant in terms of the risk of fractures). However, once one gets enough calcium (and the necessary level appears to be below what is generally recommended by authorities^[11]), there seems to be no benefit from taking even more. On the contrary, the higher your calcium intake is, the more likely you will develop osteoporosis later in your life^[11]. There are two possible explanations for that: 1) all cells in our body have a limit in number of possible divisions, and higher calcium intake forces bone cells to operate at a greater rate, which reduces their lifespan, or 2) milk has a tendency to make blood more acid, which is counteracted by the body by using calcium that is already stored in the bones. So while there might be minor temporary benefits of high intake of dairy, in long term, it is actually detrimental for bone mineral density.

Furthermore, cheese and other dairy products contain large amounts of saturated fats. This kind of fat has many detrimental effects on human health; most importantly, it increases the risk of cancer^[12]. However, it should be noted that the label “vegetable oil” doesn’t necessarily mean “good oil”. There are two commonly used types of ‘vegetable’ oils—palm oil and coconut oil—which also contain great proportion of saturated fats.

Red meat and processed meat is bad

Finally, there is an overwhelming amount of evidence that eating red meat and processed meat significantly increases the risk of cancer, vascular diseases and diabetes (processed meat means meat that is not sold raw, e.g. sausages, bacon, salami etc.). For example, one meta-study from 2010, which included over 1.2 million individuals, concluded that eating just 50g of processed meat per day (which is only a fraction of what most people consume) was associated with 42% higher risk of heart disease and a 19% higher risk of type 2 diabetes^[13]. Red meat seems to contain compounds that become carcinogenic during cooking. For example, one study found that eating regularly grilled or well done red meat increases the risk of cancer by more than 50%^[14].

Beneficial compounds found in meat

It should be noted that although meat and dairy have many detrimental effects on human health (whereas vegan foods generally contain lots of antioxidants and other beneficial compounds), there are several nutrients found in meat that have also very beneficial effects. The most important of them is vitamin B₁₂, which should be taken as a supplement by both vegans and vegetarians, because long term B₁₂ deficiency can lead to impaired cognitive function, and there is no reliable natural plant source of it. It can take several years before B₁₂ stores in the body become depleted, and this is probably the reason why some vegetarians and vegans start to feel bad after several years on a meat-free diet, and their problems magically disappear after they start eating meat again.

Furthermore, red meat is the largest natural source of creatine, carnosine and carnitine; three compounds that are not essential, but at appropriate dosages (which would be hardly reachable just by eating meat) can have beneficial effects on cognition and life span. While many would argue that “you should eat a lot of meat if you want to be smart”, it is even smarter to avoid the detrimental effects of red meat consumption and simply take advantage of these compounds by taking them as supplements. (Some people object that taking a supplement is a form of saying “my diet is not good enough”. I would say the opposite: If you don’t take any supplements, then your diet is probably not good enough, because you are simply not getting many nutrients that would improve your health, cognition, and life span.)

Poultry and fish can actually be healthy

To end our discussion on meat consumption, there is one fact that should be noted. Poultry and fish have not been mentioned yet. There are also some risks connected with eating poultry and fish, but these are not inherent properties of the meats themselves. About 50% of poultry meat (in the U.S.) is contaminated with dangerous bacteria^[15] (if you check the reference, you will find that it is actually contaminated with feces), and improper cooking of meat is the most common source of bacterial gastrointestinal illnesses, and sea fish are usually contaminated with mercury and other toxic compounds^[16] (due to pollution in water), which in long term can lead to very serious health issues (however, the amount of contaminants depends on the habitat of the particular fish)

Nevertheless, if these factors are eliminated (which is possible), it seems that eating unprocessed poultry and fish in small amounts can be as healthy (as a source of protein), as tofu or other vegan sources (but the vitamin B₁₂ content in fish and poultry is also quite low, so B₁₂ supplementation for poultry-and-fish-eaters is also reasonable). However, this is in no way an argument for a common western diet, which consists mostly of processed meat, red meat, and dairy products. The conclusion is that from a purely nutritional viewpoint, a specific type of diet that includes meat can be healthy (but so could be argued, for example, about eating certain parts of the human body, so the nutritional viewpoint is certainly not the only one to consider). Nevertheless, if you choose not to eat poultry and fish, your diet can still be completely adequate in terms of nutritional needs.