Isoflavone content ranges 500-fold across soy foods
A US survey measured 1 microgram per gram in soy sauce and 540 in tempeh, or 0.1 mg and 54 mg per 100 g. A label saying soy says almost nothing about the amount.
What the study found
From soy sauce to tempeh, isoflavone content spans 500-fold
A national survey measuring United States retail soy foods directly found 1 microgram per gram in soy sauce and 540 in tempeh, which works out at 0.1 mg and 54 mg per 100 grams. A label saying it contains soy therefore says almost nothing about how much isoflavone anyone is getting.
The caveat · Soy foods measured back in 1999
The measurements are from 1999, and brands, formulations and processing have all changed since, so treat them as an order of magnitude rather than as current values. Composite samples were used, which averages out the brand-to-brand and batch-to-batch variation a shopper actually meets.