What happens to excess dietary amino acids?

Excess dietary amino acids are primarily converted into glucose or triglycerides through various metabolic pathways. When the body has more amino acids than it can use for protein synthesis or for other immediate purposes, it engages in a process called deamination, wherein the amino group is removed from the amino acid. This process leaves a carbon skeleton, which can then enter various metabolic pathways.

The carbon skeleton can be converted into glucose through gluconeogenesis, particularly if the body requires more glucose, such as during fasting or intense exercise. Alternatively, if the body's energy needs are met and there is a surplus, these carbon skeletons can also be turned into triglycerides for storage. This conversion process helps to maintain appropriate energy levels and ensures that excess proteins are not wasted but rather stored or converted into other useful forms of energy.

While some amino acids can indeed be excreted in urine after being metabolized, this happens primarily in relation to their nitrogen content rather than directly because of dietary intake. The transformation into fatty acids is a similar biochemical pathway but is less directly involved when considering the primary metabolic fates of amino acids. Immediate use for energy is also a possibility but generally occurs only when the body has an immediate need, rather than as a standard response to excess intake.