I wanted to make this post as a one-stop shop for responses when combated by others about your diet and its nutritional significance. I’m sure you’ve been told certain essential nutrients can only be found in meat. That is not the case. In fact, such a claim is absurd and goes against the well-established science of biology and chemistry. Let’s address the most common question vegans are asked by non-vegans:
“So where do you get your protein?”
All biomass on Earth is created by photosynthetic organisms (or chemotrophs). All the protein you have ever consumed in your life originated in plants, algae or bacteria. They are the primary producers (autotrophs). Anyone who asks, “where do vegans get their protein” needs to re-take biology.
The full essential amino acid profile can be obtained from plants. The 9 essential amino acids are: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Humans and animals (consumers, heterotrophs) lack the pathways to synthesize these protein building blocks.
1. Histidine – Not synthesized in humans or animals. Biosynthesis of L-histidine occurs in bacteria and plants from the biochemical intermediate phosphoribosyl pyrophosphate.
2. Isoleucine – Not synthesized in humans or animals. Biosynthesis occurs in microorganisms and plants (several step process) starting from pyruvic acid and alpha-ketoglutarate.
3. Leucine – Not synthesized in humans or animals. Biosynthesis occurs in plants and microorganisms from pyruvic acid.
4. Lysine – Not synthesized in humans or animals. Biosynthesis occurs in plants and microorganisms from aspartic acid.
5. Methionine – Not synthesized in humans or animals. Biosynthesis occurs in plants and microorganisms from aspartic acid, cysteine, methanethiol or hydrogen sulfide. with the help of several enzymes.
6. Phenylalanine – Not synthesized in humans or animals. Biosynthesis occurs in bacteria and plants via the shikimate pathway beginning with converting chorismate to prephenate.
7. Threonine – Not synthesized in humans or animals. Biosynthesis occurs in bacteria and plants from aspartic acid via α-aspartyl-semialdehyde and homoserine.
8. Tryptophan – Not synthesized in humans or animals. Biosynthesis occurs in bacteria and plants from shikimic acid or anthranilate.
9. Valine – Not synthesized in humans or animals. Biosynthesis occurs in bacteria and plants from pyruvic acid.
Once again, all organic material comes from our primary producers and not animals.
“What about heme iron?”
Heme iron can’t be regulated by the human body and thus excessive amounts leads to oxidative stress (-OH). Heme iron is not essential for humans and has been linked to metabolic syndrome, atherosclerosis, and others.
“What about vitamins?”
I’ve heard time and time again that certain vitamins can only be found in meat. Let’s tackle that, shall we?
Almost all vitamins initially come from bacteria. B1, B2, B3 and B6 are plant biostimulants and are produced by microorganisms as by-products. B6 is found in aleuron layer (outermost layer of endosperm) of grains.
Thiamine (B1) biosynthesis occurs in bacteria, fungi and plants. Riboflavin is made by various bacteria and fungi such as Bacillus subtilis. Niacin (B3) is best found in fungi. Mushrooms are the best natural source of niacin.
And as we all know, B12 (methylcobalamin) is also produced by bacteria.
Vitamin A (retinol) is synthesized from the breakdown of beta-carotene, which is a pigment found in plants and fruits.
Vitamin C (ascorbic acid) is an enzyme cofactor in plants. The richest sources are fruits and vegetables.
Vitamin D – D3 (calciferol): weather or not this is a true vitamin is debatable as it can be produced in the human body via exposure to UVB rays. Calciferol is produced in the skin from 7-dehydrocholesterol when an electrocyclic reaction occurs due to being stuck by UVB rays.
Vitamin E (tocopherols and tocotrienols) α-Tocopherol, the most common form is biosynthesized in plants and is most abundant in vegetable oils, nuts, seeds and whole grains.
Vitamin K1 (phylloquinone) functions as an electron receptor in plants during photosynthesis I. Thus it is most abundant in green plants. K1 gets converted to K2 in the testes, pancreas, and arterial walls.
To suggest that the biosynthesis of these nutrients occur so far up the food chain is absurd and makes absolutely no sense. Plants and fungi depend on these nutrients as well so they MUST be created by microorganisms or synthesized by systems within plants.
And let’s cover minerals real quick.
Zinc is crucial for plant development. Calcium is responsible for holding together cell walls in plants. Iron helps produce chlorophyll. Magnesium is a building block of chlorophyll. Phosphorus plays an important role in photosynthesis. Potassium has many roles in plants. It is essential for ATP production, photosynthesis and enzyme activation.
As you see, these minerals are just as essential to humans as they are plants.
Feel free to use this as a resource. Anytime someone asks me these questions, it’s very satisfying to bombard them with the science. Most of this is high school level biology and chemistry and it’s quite alarming how many grown adults don’t know some of this stuff.