AminoLens

The whole lifecycle, in order

Your body has never once absorbed a gram of protein.

You break down and rebuild roughly 250 g of your own protein every day. Diet tops up the losses; it does not supply the whole build.

Protein is the only macronutrient people track as a single number and then argue about. Fat and carbohydrate get discussed as types. Protein gets discussed as an amount, as though 30 g were 30 g wherever it came from.

It is not, and the reason is mechanical rather than ideological. Here is the whole lifecycle, in order.

  1. 1. Digestion

    Stomach acid and enzymes chop the protein you ate into individual amino acids and short peptides. Nothing you swallow arrives intact. Your body does not absorb chicken protein or whey protein or bean protein: it absorbs an amino acid soup, and the only thing that distinguishes one food from another by the time it crosses the gut wall is the recipe of that soup.

  2. 2. The pool

    Absorbed amino acids join a circulating free pool, mixed together with amino acids released by your body's own constant recycling. This is why the timing rules people worry about are mostly softer than they sound: the pool is a buffer, and it does not care which meal a given molecule arrived in.

  3. 3. Building

    Cells draw from the pool to synthesise muscle, enzymes, hormones, antibodies, skin and hair. Every protein has a fixed recipe. If one required amino acid is not available, that protein is not made. There are no substitutions and no partial builds. This is the fact everything else on this site follows from.

  4. 4. The overflow

    Amino acids beyond what synthesis can use are not stored as protein. There is no protein reserve. The nitrogen is stripped off and leaves as urea in your urine, and the carbon skeleton left behind is burned for energy or converted to glucose or fat. Surplus protein is not a muscle savings account. It is expensive calories.

  5. 5. The limiting principle

    Put those together. Recipes are fixed, so the scarcest essential amino acid in your pool sets a ceiling on how much protein synthesis can happen, regardless of how much of everything else is floating around. The rest of the surplus goes to step 4 and gets burned. That ceiling is the number no other tracker shows you, and it is the reason AminoLens exists.

What that looks like on a real plate

Rice and lentils, a genuinely sensible meal. The ribbons on the left are the food, the middle is the amino acid pool, and the right is what your body was asking for. One line runs out first, and everything above that line is the surplus from step four.

Where one meal's protein goes, amino acid by amino acid250 g white rice, cooked and 60 g lentils, cooked. Lysine runs out first, so this plate builds 11.62 g of body protein and every other amino acid has some left over.What you ateNine essentialsWhat it buildsWhite rice, cooked to Histidine: 137 mg, 79% of the lineWhite rice, cooked to Isoleucine: 252 mg, 72% of the lineWhite rice, cooked to Leucine: 485 mg, 71% of the lineWhite rice, cooked to Lysine: 213 mg, 41% of the lineWhite rice, cooked to Methionine + cysteine: 257 mg, 100% of the lineWhite rice, cooked to Phenylalanine + tyrosine: 502 mg, 114% of the lineWhite rice, cooked to Threonine: 209 mg, 78% of the lineWhite rice, cooked to Tryptophan: 67 mg, 97% of the lineWhite rice, cooked to Valine: 359 mg, 79% of the lineLentils, cooked to Histidine: 125 mg, 72% of the lineLentils, cooked to Isoleucine: 190 mg, 55% of the lineLentils, cooked to Leucine: 322 mg, 47% of the lineLentils, cooked to Lysine: 310 mg, 59% of the lineLentils, cooked to Methionine + cysteine: 97 mg, 38% of the lineLentils, cooked to Phenylalanine + tyrosine: 337 mg, 76% of the lineLentils, cooked to Threonine: 158 mg, 59% of the lineLentils, cooked to Tryptophan: 40 mg, 58% of the lineLentils, cooked to Valine: 220 mg, 49% of the lineHistidine: coveredHistidine: surplusIsoleucine: coveredIsoleucine: surplusLeucine: coveredLeucine: surplusLysine: coveredMethionine + cysteine: coveredMethionine + cysteine: surplusPhenylalanine + tyrosine: coveredPhenylalanine + tyrosine: surplusThreonine: coveredThreonine: surplusTryptophan: coveredTryptophan: surplusValine: coveredValine: surplusWhite rice, cooked250 gLentils, cooked60 gHisIleLeuLyslimiting - all 11.62 g usedSAAAAAThrTrpValBuilt into proteinSurplus, used for energy
Worked example: 250 g cooked rice with 60 g cooked lentils. Those 12.14 g of protein build 11.62 g of body protein, because lysine runs out first — the only line with nothing left over. AAA alone would have carried 22.08 g. Computed by the same engine the app runs on.
  • Histidine: supports 17.47 g
  • Isoleucine: supports 14.76 g
  • Leucine: supports 13.67 g
  • Lysine: supports 11.62 g (limiting - all of it is used)
  • Methionine + cysteine: supports 16.09 g
  • Phenylalanine + tyrosine: supports 22.08 g
  • Threonine: supports 15.94 g
  • Tryptophan: supports 17.96 g
  • Valine: supports 14.85 g

Read it for the person you actually are

This is not an argument that protein totals do not matter. They matter a great deal, and most of the pages below start by telling you to eat more protein, not less. It is an argument that the total is the first question rather than the only one.

Below, the same science told for the person you actually are.

Or start from the molecule

The other half of this site is organised by amino acid rather than by person: what each of the nine builds, how much you need, and which foods carry it. All nine are listed here, and if you only read one, make it lysine.

Stop guessing which one runs out first

Photograph a meal and find out in about ten seconds.

Analyse a meal

The amino acid camera.

AminoLens is an educational tool, not medical advice. Nothing here is guidance for any medical condition. Amino acid data from USDA FoodData Central; requirement patterns from WHO/FAO/UNU 2007.

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