Hi all,
Biochemist researcher here (PhD). Since I've seen this question "how do I start building my vegan diet in a healthy way?" repeating quite a lot here, I wanted to offer an easy go-to guide.
In short, the answer is poor people's diet.
Meat and other animal products were only at the reach of the wealthy for most of the time humanity existed. The majority, aka "the poor", had to find substitutes that will include the proteins and other nutrients needed to maintain a healthy diet.
"Poor people's diet" are rice+tofu, Pita+Humus, rice+lentils, rice+beans, cereals+soy milk, beans on toast, corn and frijoles... in any culture around the world, you'll find vegan dishes, so it's affordable, varied, and easy to achieve. (and recipes improved to perfection).
That also mean, that a vegan diet can be very sustainable and not expensive, if you just stick to the simple ingredients.
Why grains + legumes? The simple answer is, "the right combination of protein's building blocks"
In detail, in order to build proteins, our body needs their building blocks - amino acids. There are 20 most-common types of amino acids, and 9 of them, our body cannot synthesise by itself (from other sources) so they need to come from our food. Think about it this way - if you have bricks, but no metal and wood, you cannot build a full house - no matter how many bricks you have.
Different food sources offer different combinations of those essential amino acids. Some are rich in some types. others lack those but have others. We need a balanced diet, so we get all those 9 amino acids in the proportion our body requires to build proteins.
In which composition? For someone who bases their diet on animal products, it's quite easy to get all those essential amino acids in one go (eg meat). The further the protein source organism is from humans, the further away the combination of amino acids is from our needs. So legumes (beans, chickpeas, lentils etc), for example, are rich in the amino acid Lysine and lack amino acid Methionine, and vice versa for grains - they are rich in Methionine and lack Lysine. So a combination of those will give you the right proportion of amino acids your body needs.
To clarify, it's important to consume them at the same meal: if you have excess of one amino acid but not enough of the others, your body will most likely use it for energy or store it as fat. Our body doesn't know how to store amino acids "for later".
That to say, that if you see a plant-based product (e.g. soy yogurt) that promises it's rich in protein, it's true - only that you wouldn't be able to gain all the building blocks needed to build a human protein out of it, because it doesn't contain the right proportion of amino acids your body needs.
I hope it's clear now why we need a balanced diet, and what it means.
Just to clarify, our body doesn't take a protein (regardless of its source - a cow or soy beans...) and turns it directly into "a human protein". The correct thing is, that our body takes that protein (by eating), breaks it apart to its building blocks in the digestion system, absorbs those amino acids, and then uses them to build a new human protein.
That was biochemistry 101 for a balanced vegan diet, I'm very happy to answer more questions if you have any.
Keep in mind that protein is a major need of our diet, but it's not enough: we also need minerals and vitamins, so make sure to include a variety of nuts & seeds (also good sources of proteins), fresh fruits and vegetables.
And, unlike what someone might have told you - carbs and fats are not necessarily your enemies- depends on what type they are. I can write another post about those if people ask :)
Lastly, keep in mind that the best PR for veganism is a happy & healthy vegan, so look after yourself :)
