Of Vegetarian Nuances


Diet and the Earth

In the face of climate change, animal abuse and malnutrition, vegetarianism is the trend. A way to contribute without making disproportionate efforts. Just what humanity needs. Yes, global warming is a reality and food of animal origin have a much greater impact on water consumption and greenhouse gas emissions than food of plant origin [9, 10]. Producing 1 kg of beef requires approximately 15 000 liters (L) of water, while 1 kg of rice requires 2 000 L [12, 13]. In turn, producing 100 grams (g) of beef protein produces approx. 50 kg CO2eq (CO2 equivalent of total greenhouse gases (GHG) produced), while 100g of grain protein produces 2.7 kg CO2eq [11, 13]. That’s just 5.4 % of the emissions that 100 g of beef protein produces! The difference is drastic. This does not necessarily mean that it is imperative to become vegetarian or vegan, but if we were to reduce meat consumption, in particular beef consumption by even 40%, a lot of land could be saved, 2x the size of India approximately and 168 billion tons of CO2eq [13].

Having clarified the undoubted impact of our diet on the environment, talking about what our species eats involves practically all aspects: social, political, economic, behavioral and nutritional, to name a few. But, so as not to extend this to infinity and beyond, let’s focus on the human body and its health. Let’s talk about diet.

It is common to find in many internet forums the debate on whether Homo sapiens is vegetarian, vegan, carnivore or omnivore. People seem to be waiting for a miraculous biological argument that will give the final verdict. From a comparison of intestine length, an anthropological evaluation of our eating habits or even the presence of our fangs, today obfuscated by braces… Many arguments, few answers. The truth is that today we are mostly omnivores and something that would contribute a lot to this discussion is to understand the effects on the body of a vegetarian or vegan diet. Understanding how an organism responds when deprived of a certain element is a good way to learn about the effects of that element on it. In fact, the logic behind this is used a lot in genetics. For example, gene knock-out (literally “knocking out genes”) is a technique in which they remove a gene from a mouse or other organism and study the consequences in order to understand the function of that gene. So, let’s leave genes aside and go back to our species: what happens when you take away meat from humans, or when you take away all food that comes from animals?

The first thing we need to understand is that it is a mistake to generalize (it mostly always is) about what we should or should not eat. Each person is unique and not only in terms of their DNA, but also in terms of what they need to be healthy. So nutritional requirements vary from person to person and also in terms of what food they can and cannot eat. There are some who get fat very easily, others do not; some eat a lot and others little; some are lactose intolerant, others are not; some cannot eat gluten, many can. And this list goes on forever, among different disorders, intolerances, syndromes and other diseases. The diversity of diets is gigantic. However, vitamins and minerals, carbohydrates, fats and proteins, we all need them to live.

Being vegetarian or vegan has many health benefits: lower risk of death from heart disease, lower cholesterol levels, lower blood pressure, decreased risk of hypertension and type 2 diabetes, lower body mass index and incidence of cancer [1, 5, 6]. The problem is that if done wrong, as most things, it can have negative effects; after all, a diet of cheese pizza, candy, milkshake and French fries is technically a vegetarian diet. And as the spanish saying goes, “in variety lies the pleasure” or in this case, well-being. That’s right, you have to know how to be vegetarian or vegan, but more importantly, you have to do it based on yourself, on your particular needs and characteristics.

In addition, there are certain nutrients in which vegetarian/vegan foods are deficient. Specifically, the nutrients you need to watch out for the most if you decide to follow a vegetarian or vegan diet are: vitamin B12, protein, calcium, iron, zinc, and n-3 fatty acids [1, 6]. Let’s look at them one by one.

Vitamin B12

Vitamin B12 is involved in cellular metabolism as it is necessary for the synthesis of DNA (cofactor) and the metabolism of fatty acids (fats) and amino acids (protein). In other words, without it, we would have serious problems. It is especially important in the maturation of red blood cells in the bone marrow (those little donut shaped swimmers that transport oxygen to all your body tissues) which is why a deficiency of it can cause megaloblastic anemia [2]. The issue is that only some bacteria and archaea* can produce it and there are no vegan or vegetarian sources that provide significant values of this vitamin [1, 6, 8]. Therefore, it would be necessary to take supplements or foods fortified in B12.

*One of the three domains of the tree of life: Bacteria, Archaea, and Eukaryotes. Archaea are similar to bacteria in that they both lack a nucleus. Eukaryotes are us.


Proteins are chains of amino acids and in the genetic code there are 20 of them. Amino acids are necessary to produce new proteins (Translation | RNA — -> Protein, yes?), other biomolecules or as a source of energy. Proteins perform an incredibly vast array of functions within organisms and are involved in virtually every process within the cell. Plant protein is in general less digestible than animal protein, so it is recommended that vegetarians and especially vegans consume more protein than others. In addition, there are certain compounds in vegetables that act as protein digestion inhibitors (tannins, phytates and others) that further reduce their digestibility. One solution is to soak the grains or sprout them. But relax, achieving a healthy protein intake as a vegan or vegetarian is perfectly achievable by eating a wide variety of vegetables (tofu, seitan, lentils, chickpeas and grains, quinoa, amaranth, among others).

Calcium, iron and zinc

The absorption of these minerals is also affected by the above mentioned phytates and polyphenolics present in tea, coffee and chocolate. But, as my mom always says, for every problem there is a solution, and in this case, consuming Vitamin C stimulates absorption, which offsets the effects of those nagging phytates and polyphenolics. No problem. Therefore, better to eat iron-rich food, drink that delicious morning orange juice and soak those grains. In general, there is not much difference in the levels of these minerals between vegans/vegetarians and non-vegetarians, but it is better for vegans/vegetarians to consume more of them.

Fats (fatty acids)

To conclude the topic of nutrients, we only have the n-3 fatty acids left [the what?]. They are the same as the Omega-3 type. Now a little chemistry review, voluntarily that is.

For those who want a little more chemistry, go ahead, those who don’t, skip to the next paragraph.

A fatty acid is a long chain of carbon and hydrogen atoms with one carboxylic acid end (-COOH) called alpha (α) and another methyl end (-CH3) called “omega” (ω) . Omega-3 has a double bond at the third carbon, counting from the omega end. Hence, n-3 or Omega-3.

The important thing is that they are absolutely necessary and few vegetables provide them properly, so it is crucialthat vegetarians and especially vegans consume good sources of these fatty acids such as nuts, chia seeds, hemp or flaxseed and their oils.

In conclusion, a well-planned vegetarian or vegan diet that includes a wide variety of plants and a sufficient source of vitamin B12 can provide an adequate intake of nutrients and bring many health benefits. Not to mention the good they do for the planet. The best advice is that if you want to be vegetarian or vegan, do it, but do it well, and preferably consult a nutritionist, please.


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  2. Chanarin, I., O’hea, A., Malkowska, V., Rinsler, M., & Price, A. (1985, 11). Megaloblastic Anaemia In A Vegetarian Hindu Community. The Lancet, 326(8465), 1168–1172. doi:10.1016/s0140–6736(85)92690-x
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  7. Schlemmer, U., Frølich, W., Prieto, R. M., & Grases, F. (2009, 09). Phytate in foods and significance for humans: Food sources, intake, processing, bioavailability, protective role and analysis. Molecular Nutrition & Food Research, 53(S2). doi:10.1002/mnfr.200900099
  8. Fang, Huan, Jie Kang, and Dawei Zhang. “Microbial production of vitamin B 12: a review and future perspectives.” Microbial cell factories 16.1 (2017): 15.
  9. Root, Terry L., et al. “Fingerprints of global warming on wild animals and plants.” Nature 421.6918 (2003): 57.
  10. Cox, Peter M., et al. “Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model.” Nature408.6809 (2000): 184.
  11. Poore, Joseph, and Thomas Nemecek. “Reducing food’s environmental impacts through producers and consumers.” Science 360.6392 (2018): 987–992.
  12. Fox, Tim, and Ceng Fimeche. “Global food: waste not, want not.” London: Institution of Mechanical Engineers (2013).
  13. Ranganathan, Janet, et al. “Shifting diets for a sustainable food future.” World Resources Institute (2016).

I am a science communicator, biologist, microbiologist, and musician. I like to learn, research and explain things.

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