The mechanism the post describes is well established in nutrition science. Vitamin C, or ascorbic acid, acts as a potent enhancer of non-heme iron absorption, the type of iron found in plant-based foods like spinach, lentils, and fortified cereals . Vitamin C helps the body absorb non-heme iron by converting it into a more soluble and stable form. This chemical change allows the iron to pass through the intestinal wall and into the bloodstream more efficiently . Classic single-meal studies by Hallberg and colleagues concluded that ascorbic acid has a key physiologic role in facilitating the absorption of non-heme iron from the diet and that about 50 mg of the vitamin in each main meal is desirable for optimum effect , and that ascorbic acid promotes iron absorption from the diet by reducing the negative effect on iron absorption of certain ligands such as phytates and tannins present in the diet . Spinach itself does contain non-heme iron, and clinical guidance routinely recommends pairing it with vitamin C sources such as citrus. Cleveland Clinic notes that "Consuming foods that are high in vitamin C at the same meal with iron-rich plant foods boosts the bioavailability of iron." "This means you absorb more of it."