Oxalic acid (found in vegetables like spinach), tannins (such as those found in coffee, tea, and red wine), phytates (which can be found in certain legumes and vegetables), certain polyphenols (e.g., flavonoids), and foods high in minerals like calcium, zinc, and magnesium may decrease iron absorption. This is why taking iron on an empty stomach, or at least in the absence of some of these compounds, will increase absorption. However, some people will experience increased side effects such as nausea when taking iron on an empty stomach. If choosing to take iron with food to in order minimize side effects, choose foods that contain compounds which can enhance iron uptake and/or counteract the actions of phytates, tannins and minerals, such as vitamin C, folic acid, citric acid, cysteine-rich peptides and vitamin A. Meat, poultry and fish can enhance uptake of heme iron; carotenes, retinoids, alcohol, citric, tartaric and malic acids can enhance uptake of non-heme iron.[1]
What dietary factors affect iron absorption?
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•Last Updated: May 16, 2025
Dietary factors that decrease iron absorption include oxalic acid, tannins, phytates, certain polyphenols, and high mineral foods, and taking iron on an empty stomach can enhance absorption. To minimize side effects when taking iron with food, it's beneficial to choose foods that contain vitamin C, folic acid, and other compounds that enhance iron uptake.