Soybeans (Dry)

Food · Legume · Food, Typed Supps

Soybeans pack complete protein like meat, plus special plant compounds — and no, eating them won't mess with your hormones.

Stage by stage

Cooking & Chewing (Mouth): Thorough cooking of dry soybeans deactivates trypsin inhibitors and lectins, and chewing then releases the protein and isoflavones packed within the bean's dense matrix.
Protein Breakdown (Stomach): In the stomach, pepsin and gastric acid begin breaking soy's protein down into peptides, work made possible by the earlier cooking process.
Isoflavone Conversion (Small Intestine): In the small intestine, pancreatic enzymes finish digesting protein into amino acids while gut bacteria convert isoflavone glycosides like genistin and daidzin into their active forms, genistein and daidzein.
Tissue Support (Bone & Vascular Tissue): Absorbed isoflavones travel through the bloodstream and bind weakly to estrogen receptors in bone and blood vessels, while soy's amino acids and iron support muscle repair and red blood cell production.

Timing

Pairing soy foods with vitamin C-rich foods can improve absorption of soy's non-heme iron, and spreading protein intake across meals helps maximize its muscle-building benefit.

Time to effect

Weeks to Months: Isoflavones appear in the bloodstream within one to two hours of eating soy, but clinically measurable effects on cholesterol, menopausal symptoms, or bone density typically require weeks to months of consistent intake.

Allergens

Contains: Soya. Derived from what this food is, not from a product label.

Eating patterns

Fits: Vegan, Vegetarian, Pescatarian, Halal, Kosher, Keto, Gluten-free. Depends on the product: Low-FODMAP.

Satiety

192 on the satiety index, where white bread is 100 — high. Modelled from the Holt et al. (1995) measurements.

Environmental footprint

3.2 kg CO2e and 149 litres of freshwater per kg, matched to "Tofu" in Poore & Nemecek (2018), Science 360.

Cost band

Cheap — roughly £2.5 per kg, as a band midpoint rather than a price.

Key nutrients

Complete plant protein
Isoflavones (genistein, daidzein)
Iron
Dietary fiber
Manganese

Nutrition per 100g

Calories: 146.7
Protein: 13.5g
Carbohydrate: 1.4g
of which sugars: 1.4g
Fat: 7.7g
of which saturated: 1.1g
Fibre: 7.2g
Sodium: 9mg

Food vs. supplement

Whole soybeans deliver isoflavones bound within a protein- and fiber-rich food matrix that gut bacteria must unlock, while isoflavone supplements provide a concentrated, rapidly absorbed dose without that matrix — a difference that may help explain why whole-soyfood studies show more consistent outcomes than supplement trials.

Kitchen tip

Soak and thoroughly cook dry soybeans (or ferment them into tempeh, miso, or natto) before eating — raw or undercooked soybeans contain trypsin inhibitors and lectins that impair digestion and can cause gastrointestinal upset.

Common myth

"Eating soy foods raises estrogen levels and feminizes men, or increases breast cancer risk." In reality: Soy isoflavones are weak phytoestrogens that bind mainly to estrogen receptor-beta; meta-analyses of clinical trials find no significant effect of soy protein or isoflavone intake on men's testosterone or estrogen levels, and human clinical evidence does not support the increased breast cancer risk suggested by early rodent and cell-culture studies — some cohort research instead links soy intake to improved survival after a breast cancer diagnosis.