Tomatoes are a sweet, juicy fruit often misidentified as a vegetable. They are used in a wide variety of foods and preparations from sauces to fresh slices on sandwiches. The high sugar content in tomatoes requires them to receive plenty of sun and grow in good organically rich soil. In addition to nuts and leafy green vegetables, tomatoes are rich in iron. Toxicity can occur if soils are already iron rich.
Tomato plants that have been exposed to too much iron can look withered and have stunted growth. The leaves will develop brown spots at the tips, which will spread to the base of the leaves and eventually turn orangish brown. Leaves will dry up and some will fall off. Fruit production will be poor and in some instances the plant can die.
Toxic soils that have been overly saturated with fertilizers containing iron salts are the main culprit for plant toxicity of iron. The soils are primarily acidic or less than 5.0 pH. When combined with low manganese levels, the plant is unable to take up sufficient manganese and actually gets symptoms consistent with manganese deficiency. The excess iron inhibits the uptake of manganese and is therefore the underlying cause of the plants problems.
Tomato plants should always be planted in a neutral soil to avoid excess iron already in the earth. If necessary, add of manganese to the soil by liming the season before planting. Chelated limestone is readily mixed into soil and provides manganese and calcium to improve soil pH.
Toxicity related to eating iron charged tomatoes is extremely rare. Those that need to worry about toxicity are children and the aged. Those who take iron supplements could also be susceptible to food-derived toxicity. High doses of calcium is a common counter measure.
Iron Toxicity in Cooked Tomatoes
Foods that are high in acidity can absorb iron from the pots in which they are cooked. Tomato sauce is simmered for a long time in cookware. If the pot contains iron the acidity in the tomatoes will leech it out into the sauce,raising the iron levels to toxic. It is recommended cooking tomatoes in a non-iron pot to avoid any concerns.