Pea.

Methionine is the limiting amino acid in pea protein, meaning it is the one that caps how much of the rest can be used for synthesis. Adding methionine, or a methionine-rich protein, lifts that cap. The effect is on the quality score of the protein blend, not on any separate physiological action.

Leucine crossing a threshold concentration is what initiates the anabolic signalling step after a protein feeding. Pea protein reaches that threshold at a larger serving than whey does. Adding free leucine is the standard formulation answer, and it changes the signal, not the total amino acid supply.

Whey is leucine-dense and rapidly absorbed, pea is lysine-rich and digests more slowly. Blending covers both the sulfur amino acid gap in pea and gives a wider absorption window than whey alone. Anyone avoiding dairy obviously cannot use this pairing.

Casein clots in the stomach and releases amino acids slowly. Pea sits between casein and whey in digestion rate. The combination broadens the amino acid delivery curve, which is the usual rationale for overnight formulations.

The iron in peas is non-heme and is held back by the phytate in the same food. Ascorbate reduces ferric iron to the ferrous form and competes with phytate for it, partly overriding the inhibition. Eating peas alongside a vitamin C source is the practical version of this.

Phytase hydrolyses phytic acid into lower inositol phosphates that bind minerals far less tightly. Soaking, sprouting and fermenting peas all work by activating or adding this enzyme. Added phytase does the same thing in a single step.

Zinc is more sensitive to phytate than iron is, and the phytate to zinc molar ratio of a meal predicts absorption reasonably well. A diet built heavily on whole legumes raises that ratio. Soaking, sprouting or fermenting the peas lowers it.

Calcium forms insoluble complexes with phytate and can worsen the phytate inhibition of other minerals rather than relieve it. High-calcium and high-phytate loads taken at the same time work against each other. Spacing them out is the practical response.

Humans lack alpha-galactosidase, so raffinose and stachyose from peas reach the colon undigested and are fermented into gas. Supplemental alpha-galactosidase splits them in the small intestine before that happens. This applies to whole peas and pea flour, not to protein isolate.

Cooked and cooled pea starch is itself partly resistant, and it is fermented in the colon to short-chain fatty acids including butyrate. Adding a separate resistant starch source stacks the same substrate class. For anyone already sensitive to fermentation, that stacks the discomfort too.

Pea alpha-galactosides and resistant starch are both substrates for colonic fermenters. Pairing them with a live culture is standard synbiotic reasoning. What follows depends on the strain, and no specific pea and strain combination has been established.

Creatine comes from meat and fish in the diet, so people building their protein intake around pea have lower baseline intake and generally lower muscle creatine stores. Supplemental creatine fills that gap. The two are independent, and the pairing is about the diet pattern rather than an interaction between them.

Pea protein contains no vitamin B12, since B12 is made by bacteria and reaches the diet through animal foods. Anyone using pea protein as part of a fully plant-based pattern needs a separate B12 source. This is a gap to cover, not a synergy in the usual sense.