The best replacement for amino acid is protein.

The best alternatives to amino acid are rated as following:
★★★★★  protein
★★★★  bcaa
★★★  creatine
★★  glutamine
★★  nucleic acid
★  codon
★  nucleotide
★  peptide
★  soy sauce
★  polypeptide
★  fatty acid
  organic acid
  protein supplement
  imino acid
  residue
  keto acid
  l amino acid

Your alternative for amino acid is not listed? Suggest!
Speaking about amino acid, one probably shouldn't forget about sulfur.

Other search terms related to amino acid and their ratings are:
★★★★★ sulfur
★ more than one codon
ninhydrin
You have in mind a companion for amino acid and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of amino acid in all years. Click on graph for more.
amino acid
protein
bcaa