Amino acids
The basic molecules that make up proteins (there are 20), assembled into chains in a precise order, 9 of which are essential (supplied by the diet).
Amino acids are the « letters » that make up the « words » that are proteins. There are 20 of them, combined in varied sequences to form tens of thousands of different proteins (enzymes, hormones, muscles, antibodies and so on).
They are classified as:
- Essential (9): the body cannot make them → they must come from food (histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine)
- Non-essential (11): the body synthesises them
- Conditionally essential: normally made by the body, but needed from food in certain situations (stress, illness, growth), for example glutamine and arginine
The original angle (much more than muscle building blocks): amino acids are often reduced to muscle. Yet many have fascinating specific roles beyond structure:
- Tryptophan → serotonin (mood) and melatonin (sleep)
- Tyrosine/phenylalanine → dopamine and noradrenaline (motivation, energy, attention)
- Glutamine → fuel for gut and immune cells, integrity of the gut barrier
- Glycine → a component of collagen, sleep quality, detoxification
- Arginine → precursor of nitric oxide (dilation of blood vessels, blood pressure)
- Cysteine → precursor of glutathione (a major antioxidant)
So dietary protein directly influences neurotransmitters, mood, sleep, immunity and gut health, not just muscles.
The concept of the limiting amino acid: in a protein, the essential amino acid present in the smallest proportion « limits » the use of all the others (like the weak link in a chain). This is why combining complementary plant sources (pulses rich in lysine + cereals rich in methionine) optimises intake.
The amino acid pool: the body maintains a dynamic reserve of amino acids (constantly recycled through protein turnover). Hence the importance of a regular intake spread across the day.