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Soy Protein Isolate

Proteinoral · inferred

Complete plant protein from soybeans with all essential amino acids. Contains isoflavones with weak estrogenic activity. Intermediate digestion rate between whey and casein.

Projected serum levels — 25 g (≈ 25k mg), once daily

Soy Protein Isolate
Soy Protein Isolate modeled serum levels, 25 g (≈ 25k mg) once daily over 15 days Population-based pharmacokinetic estimate. Steady state reached after approximately 1 days. 0 5k 10k 15k 20k Day 0 Day 4 Day 8 Day 11 Day 15 Time on a regular schedule ≈ steady state · day 1

Maintenance schedule: 25 g (≈ 25k mg) once daily (oral).

Modeled steady state after ~1 days: peak ≈ 17.0k mg, trough ≈ 874 mg body load. Population-based estimate over 15 days for a reference dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.

Key facts

Category
Protein
Route modeled
Oral
Model confidence
inferred
Half-life
4.9 h
Common dose
25 g (≈ 25k mg)
Suggested maximum
75 g/day
Reference dose range
12.5–75 g (single dose)
Suggested cadence
once daily

Documented interactions

  • caution
    Iron (Bisglycinate) + Soy Protein Isolate Absorption

    Soy protein contains phytates that can reduce non-heme iron absorption by up to 80%. This is one of the strongest dietary inhibitors of iron absorption.

  • moderate
    Conjugated Estrogens (Premarin) + Soy Protein Isolate Stacked effects

    Conjugated Estrogens (Premarin) and Soy Protein Isolate both push the estrogen receptor alpha and estrogen receptor beta in the same direction.

  • moderate
    Estradiol Cypionate (Injection) + Soy Protein Isolate Stacked effects

    Estradiol Cypionate (Injection) and Soy Protein Isolate both push the estrogen receptor alpha and estrogen receptor beta in the same direction.

  • moderate
    Estradiol (Oral) + Soy Protein Isolate Stacked effects

    Estradiol (Oral) and Soy Protein Isolate both push the estrogen receptor alpha and estrogen receptor beta in the same direction.

  • moderate
    Estradiol (Transdermal Patch) + Soy Protein Isolate Stacked effects

    Estradiol (Transdermal Patch) and Soy Protein Isolate both push the estrogen receptor alpha and estrogen receptor beta in the same direction.

  • moderate
    Estradiol Valerate (Injection) + Soy Protein Isolate Stacked effects

    Estradiol Valerate (Injection) and Soy Protein Isolate both push the estrogen receptor alpha and estrogen receptor beta in the same direction.

Serum checks 42 modeled interaction pairings for soy protein isolate across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.

Research behind this entry

  1. Neither soy nor isoflavone intake affects male reproductive hormones: an expanded and updated meta-analysis of clinical studies Reed KE et al. · Reproductive Toxicology, 2021 DOI

    Meta-analysis of 41 clinical studies found soy protein and isoflavone supplementation does not significantly affect testosterone, estradiol, or sex hormone-binding globulin levels in men.

1 published study referenced in the app, each with a plain-language summary.