An in vitro method for estimation of iron availability from meals.

An in vitro method for estimating food iron availability is described. The method involves simulated gastrointestinal digestion followed by measurement of soluble, low molecular weight iron. Mixtures of foods (meals) were homogenized and exposed to pepsin at pH 2. Dialysis was used to adjust the pH to intestinal levels and digestion was continued after the addition of pancreatin and bile salts. Iron from the digestion mixture which diffused across a 6 to 8000 molecular weight cutoff semipermeable membrane was used as an indicator of available iron. Results were similar when intrinsic food iron or added extrinsic radioiron was measured. Availability estimates were made on meals formulated to contain known iron availability enhancing and inhibiting factors. Relative availabilities determined for a series of meals containing ascorbic acid, eggs, orange juice, tea, coffee, cola, or whole wheat bread show that the method accurately reflects actual food iron availability.