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Amino acidsModerate evidence

Soy protein

Also known as: soy isolate, SPI

Soy protein is a plant protein with a complete essential amino-acid profile, mostly sold as an isolate with over 85–90% protein. It contains isoflavones and is one of the best-studied plant proteins.

What it is used for

  • muscle growth with training – moderate evidence, slightly smaller effect than whey
  • modest LDL cholesterol lowering – moderate evidence
  • complete protein on a plant-based diet – strong evidence

Forms and how they differ

isolate

highest protein, little fat and carbohydrate

concentrate

more fibre and carbs, cheaper

textured soy

a food, not a powder

When to take it

After training or between meals.

Pairs well with

Plant drinks, fruit; creatine on a plant-based diet.

Do not combine / separate

If you take thyroid medicine (levothyroxine), keep a gap of a few hours.

Watch out for

Not suitable with soy allergy. With hormone-sensitive conditions, thyroid or kidney disease, or when taking medicines, consult your doctor.

Safety

Safe for healthy people within normal total protein intake; do not exceed the label dose.

Practical tip

If you want a plant protein closest to whey in effect, soy is one of the best choices.

Products containing Soy protein 1

Soy protein isolateisolateMusclesHeart & vesselsRecovery
How to read the evidence rating
Strong evidenceModerate evidenceWeak evidenceNo evidence

Strong = several good human studies or official recommendations; moderate = promising but smaller studies; weak = few studies or mixed results; no evidence = claims not confirmed.

Combination check

Select the supplements you take and, if relevant, your medicines. We show what interferes, what needs a time gap and what to watch out for.

Check Soy protein with others

Which supplements do you actually need?

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From the same group

Acetyl-L-carnitineWeak evidenceAlmond proteinWeak evidenceAmino acid complexWeak evidenceBCAAWeak evidenceBeef proteinModerate evidenceCaseinStrong evidence
Important notice

This information is educational and does not replace advice from a doctor or pharmacist. We do not give medicine dosages. Supplements are no substitute for a varied diet; if pregnant, breastfeeding, ill or on medication, consult a doctor first.