Bioavailability of iron from spinach using an in vitro/human Caco-2 cell bioassay model

Area of Science:

• Nutritional Science
• Biochemistry

Background:

• Spinach (Spinacia oleracea) is a common vegetable, but its iron bioavailability is often debated.
• Assessing iron bioavailability is crucial for understanding dietary iron absorption and preventing deficiencies.

Purpose of the Study:

• To evaluate the iron bioavailability of spinach (cv Whitney) using an established in vitro human intestinal cell culture ferritin bioassay.
• To determine the effect of supplemental ascorbic acid on iron bioavailability from spinach.

Main Methods:

• Spinach was grown, harvested, freeze-dried, and subjected to in vitro digestion simulating human gastrointestinal conditions.
• Caco-2 cell cultures were utilized to measure iron bioavailability via ferritin production.
• Ascorbic acid was added to some spinach digestion samples.

Main Results:

• Spinach contained an average of 71 micrograms of iron per gram of dry weight.
• Supplemental ascorbic acid significantly increased iron bioavailability from spinach, effectively doubling it.
• The in vitro/Caco-2 cell ferritin bioassay model demonstrated its utility in assessing iron bioavailability.

Conclusions:

• Fresh spinach is a relatively poor source of bioavailable iron when consumed alone.
• The addition of ascorbic acid substantially enhances iron absorption from spinach.
• Evaluating whole meals rather than single food items is important for accurate dietary iron assessment.
• The developed in vitro/Caco-2 cell ferritin bioassay is a valuable tool for prescreening diets, including space flight diets, for bioavailable iron.