<Tr> <Th> Amino acid (s) </Th> <Th> WHO mg per kg body weight </Th> <Th> WHO mg per 70 kg </Th> <Th> US mg per kg body weight </Th> </Tr> <Tr> <Td> H Histidine </Td> <Td> 10 </Td> <Td> 700 </Td> <Td> 14 </Td> </Tr> <Tr> <Td> I Isoleucine </Td> <Td> 20 </Td> <Td> 1400 </Td> <Td> 19 </Td> </Tr> <Tr> <Td> L Leucine </Td> <Td> 39 </Td> <Td> 2730 </Td> <Td> 42 </Td> </Tr>

Why are eight out of twenty amino acids considered to be essential for humans